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Disrupted neonatal lung alveologenesis often leads to bronchopulmonary dysplasia (BPD), the most common chronic lung disease in children. The inhibition of type 2 alveolar (AT2) cell proliferation plays an important role in the arrest of alveologenesis. However, the mechanism of AT2 cell proliferation retardation in BPD is still not fully elucidated. The purpose of the present study was to explore the effects of cyclin G1 (CCNG1) on AT2 cell proliferation in hyperoxia-induced lung injury in neonatal mice. Our findings revealed that hyperoxia significantly reduced the proportion of AT2 cells in the lungs of neonatal mice and coincided with an upregulation of CCNG1 expression. Notably, this upregulation of CCNG1 was accompanied by an increase in Wnt signaling. We observed colocalization of CCNG1 and Wnt3a within AT2 cells in the hyperoxia group. Further analysis showed that inhibiting CCNG1 expression regressed the expression of Wnt signaling and enhanced cell proliferation. These results suggest that CCNG1 plays a pivotal role in suppressing AT2 cell proliferation, at least partly by counteracting the effects of Wnt signaling to modulate AT2 cell growth in the BPD model. Our findings contribute to a better understanding of the mechanisms underlying BPD.

Bronchopulmonary dysplasia (BPD) affects patients' quality of life. Circular RNAs participated in BPD. However, circ-ECH1's role in BPD has not been reported yet. This study aimed to explore the role and mechanism of circ-ECH1 in BPD. Hyperoxia-treated type II alveolar epithelial cells (L2 cells) were used as the in vitro BPD model. CCK-8, flow cytometry, and reactive oxygen species (ROS) were used to evaluate cell viability. Fluorescence in situ hybridization confirmed the subcellular localization. Circ-ECH1 overexpression (or inhibited) and miR-708-5p mimics were used to investigate the roles of circ-ECH1 and miR-708-5p in BPD. Quantitative reverse-transcription polymerase reaction (qRT-PCR) detected the expressions of circ-ECH1, miR-708-5p, and neurotrophic receptor tyrosine kinase 2 (Ntrk2). Ntrk2 expression was evaluated by Western blot analysis. Changes in lung tissues were evaluated by hematoxylin and eosin staining. Pulmonary fibrosis was examined by Mason staining. TUNEL staining was performed to evaluate cell apoptosis in lung tissues. RNA sequencing was performed in the lung tissues of BPD rats. The binding between circ-ECH1 and miR-708-5p was confirmed through dual luciferase activity. Hyperoxia reduced cell viability and increased cell apoptosis and ROS accumulation. In addition, hyperoxia decreased the expression levels of circ-ECH1, which is mainly located in the cytoplasm. Circ-ECH1 overexpression increased cell viability but reduced cell apoptosis and ROS accumulation. On the contrary, interference with circ-ECH1 further promoted cell apoptosis and reduced cell activity. Furthermore, circ-ECH1 overexpression reduced the incidence of pulmonary fibrosis and lung cell apoptosis. RNA sequencing, followed by qRT-PCR, confirmed that the expressions of Ntrk2 and miR-708-5p were affected by circ-ECH1. miR-708-5p mimics reversed the role of circ-ECH1 in the BPD. Mechanistically, circ-ECH1 may bind with miR-708-5p to regulate Ntrk2 expression. Circ-ECH1 may compet with miR-708-5p to regulate Ntrk2 expression in BPD. The findings provided a new target for BPD treatment., (© 2024 Wiley Periodicals LLC.)

Intrauterine inflammation from chorioamnionitis (CA) is associated with placental dysfunction and increased risk of bronchopulmonary dysplasia (BPD), the chronic lung disease of prematurity. Antenatal steroid (ANS) treatment improves early respiratory outcomes for premature infants. However, it remains unclear whether ANS improves long-term respiratory outcomes, and whether these effects are mediated through the improvement of placental dysfunction and/or direct impact on the fetal lung. We hypothesized that maternal ANS therapy preserves long-term lung development and impacts placental structural changes and gene expression in experimental CA with features of BPD. Pregnant rat dams were administered either saline (CTL), intra-amniotic (IA) endotoxin (ETX), ETX plus intramuscular (IM) betamethasone (ETX + BETA), or IM BM alone (BETA) on embryonic day 20 (E20). We collected placental tissue at delivery (E22) and infant lung tissue on the day of life (DOL) 14 . In comparison with controls, IA ETX had impaired infant lung growth and function. Maternal BM treatment of ETX-exposed pregnant dams reduced infant total lung resistance by 15.3% ( P < 0.05), improved infant lung compliance by 9.5% ( P < 0.05), preserved alveolar and vascular growth ( P < 0.05), and improved right ventricular hypertrophy (RVH) by 42.4% ( P < 0.05). ETX + BETA pregnancies were also associated with normalization of placental spiral artery modification and altered placental gene expression. These included the upregulation of placental prolactin, which has regulatory effects on pregnancy homeostasis and has been clinically associated with decreased BPD risk. The current study identifies parallel lung and placental changes associated with ANS treatment, providing a foundation for future studies to identify alternate antenatal therapies with more specific efficacy for BPD prevention. NEW & NOTEWORTHY We performed parallel neonatal lung and placental analyses in a preclinical model to characterize the impact of antenatal betamethasone in experimental chorioamnionitis. Antenatal steroids improved long-term respiratory outcomes and were associated with concurrent structural and molecular changes in the placenta. This study establishes an important model system for future analyses to evaluate mechanistic links determining whether the long-term impact of antenatal steroids on lung development may be through alteration of placental function.

Bronchopulmonary dysplasia (BPD) is one of the most prevalent complication in preterm infants, primarily characterized by arrested alveolar growth. The involvement of epithelial-mesenchymal transition (EMT) of AECII cells is proposed to have a crucial role in the pathogenesis of BPD; however, the underlying mechanism remains unclear. The present study reveals a significant reduction of WHAMM (WASP homolog associated with actin, membranes, and microtubules) in hyperoxia-induced BPD mice, highlighting its crucial role in suppressing the progression of BPD through the inhibition of EMT in AECIIs. We demonstrated that hyperoxia-induced downregulation of WHAMM leads to the accumulation of TGF-β1 primarily through its mediation of the autophagic degradation pathway. Mechanistically, WHAMM enhanced the autophagosomal localization of TGF-β1 and concurrently promoted the process of autophagy, thereby comprehensively facilitating the autophagic degradation of TGF-β1. These findings reveal the important role of WHAMM in the development of BPD, and the proposed WHAMM/autophagy/TGF-β1/EMT pathway may represent a potential therapeutic strategy for BPD treatment., (© 2024 Wiley Periodicals LLC.)

Bronchopulmonary dysplasia (BPD) manifests in premature neonates with aberrant pulmonary function. Numerous long non-coding RNAs (lncRNAs) have been implicated in the pathogenesis of BPD. This study aims to elucidate the impact of the lncRNA myocardial infarction-associated transcript (MIAT) on the initiation and progression of BPD. Initially, BPD murine models were established through hyperoxia induction in newborn mice. Subsequently, MIAT and GATA binding protein 3 (GATA3) expression levels were assessed, and intravenous administration of short hairpin RNAs (shRNAs) targeting MIAT and GATA3 was performed. Pulmonary histological alterations were examined through histological staining. Levels of inflammatory mediators were quantified using enzyme-linked immunosorbent assay (ELISA) kits. The interaction between MIAT and GATA3 was scrutinized through RNA immunoprecipitation, RNA pull-down, and fluorescence in situ hybridization. The downstream mechanisms of GATA3 were explored using bioinformatics analysis. In summary, lncRNA MIAT exhibited elevated expression in the lung tissues of BPD-afflicted mice. MIAT localized to the nucleus and interacted with GATA3, thereby activating the mitogen-activated protein kinase (MAPK) pathway. Knockdown of MIAT or silencing of GATA3 attenuated the inflammatory response, deactivated the MAPK pathway, and ameliorated BPD symptoms in mice, on the other hand, p-Cresyl sulfate potassium can activate the MAPK signaling pathway and attenuates the effects of si-MIAT or si-GAT3. These improvements were characterized by enhanced alveolar differentiation and reduced glycogen and collagen deposition. In conclusion, lncRNA MIAT plays a pivotal role in activating the MAPK pathway and exacerbating hyperoxia-induced BPD in mice through the binding to GATA3. It's an important discovery for the pathogenesis of BPD and may provide some new treatment for infants diagnosed with BPD., Competing Interests: Declaration of competing interest Bo Tao reports financial support was provided by National Natural Science Foundation of China (82300068, 82300340). If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Bronchopulmonary dysplasia (BPD) is a serious complication in premature infants. This study aimed to investigate the mechanism of mitogen-activated protein 3 kinase 7 (Map3k7) affecting BPD by regulating caspase-1 mediated pyroptosis. The morphology of the lung tissue was observed using hematoxylin-eosin staining. TUNEL staining was performed to detect tissue apoptosis. RNA-seq and protein-protein interaction (PPI) network were performed to identify hub genes. Cell viability and apoptosis was analyzed using the CCK-8 assay and flow cytometry, respectively. Pyroptosis-related factors, inflammatory factors, oxidative stress indicators, and pathway-related proteins were detected using ELISA, qRT-PCR, and Western blotting. Hyperoxia-induced neonatal rats showed alveolar simplification with increased alveolar lumen, and decreased density of secondary alveolar cristae, demonstrating the successful BPD model. Map3k7 was identified as the crucial gene that was upregulated in BPD. Silencing Map3k7 promoted cell proliferation and suppressed apoptosis, inflammation, oxidative stress, and pyroptosis in hyperoxia-induced AEC-II, and alleviated BPD progression in hyperoxia-induced rats. Furthermore, silencing Map3k7 inhibited the TGF-β1/Smad3 pathway, and SRI-011381, the TGF-β pathway activator, weakened the inhibitory effects of silencing Map3k7 on hyperoxia-induced AEC-II. Silencing Map3k7 suppressed pyroptosis to alleviate BPD through inhibiting the TGF-β1/Smad3 pathway, providing a direction for the treatment of BPD in premature infants.

Background: Bronchopulmonary dysplasia (BPD), a chronic lung disease prevalent among premature infants, significantly impacts lifelong respiratory health. Macrophages, as key components of the innate immune system, play a role in lung tissue inflammation and injury, exhibiting diverse and dynamic functionalities. The M4 macrophage, a distinctive subtype primarily triggered by chemokine (C-X-C motif) ligand 4 (CXCL4), has been implicated in pulmonary inflammatory and fibrotic processes. Nonetheless, its contribution to the pathophysiology of BPD remains uncertain., Objective: This study aimed to elucidate the involvement of CXCL4 in hyperoxia-induced neonatal lung injury and fibrosis, with a particular focus on its influence on M4 macrophages., Methods: A BPD model in neonatal mice was established through continuous exposure to 95% O 2 for 7 days. Comparative analyses of lung damage and subsequent regeneration were conducted between wild-type (WT) and CXCL4 knockout (KO) mice. Lung tissue inflammation and fibrosis were assessed using histological and immunofluorescence staining, enzyme-linked immunosorbent assay, Western blot, and real-time quantitative polymerase chain reaction. Differentiation of M0 and M4 macrophages was performed in vitro using macrophage colony-stimulating factor and CXCL4, while expressions of S100A8 and MMP7, along with migration assays, were evaluated., Results: Elevated CXCL4 levels and M4 macrophage activation were identified in the lung tissue of BPD model mice. CXCL4 deficiency conferred protection to alveolar type 2 epithelial cells, reduced sphingosine-1-phosphate metabolic activity, mitigated pulmonary fibrosis, and limited M4 macrophage progression. This deletion further enhanced lung matrix remodeling during recovery. In vitro, CXCL4 promoted M4 macrophage differentiation and increased macrophage migration via chemokine (C-C motif) receptor 1., Conclusion: CXCL4 contributes to hyperoxia-induced lung injury and fibrosis through modulation of cytokine release, alveolar cell proliferation, lipid metabolism, and the regulation of macrophage phenotype and function., Competing Interests: Declarations. Ethical approval and consent to participate: This experiment was approved by the ethics committee of The Affiliated Huaian No. 1 People’s Hospital of Nanjing Medical University (approval number. DW-P-2023-001-10). Consent for publication: Not applicable. Competing interests: The authors declare no competing interests., (© 2024. The Author(s).)

Aim: Bronchopulmonary dysplasia (BPD) is a common morbidity in extremely premature infants. Previous studies demonstrated the important role of lysophosphatidic acid (LPA) in inflammation in BPD. However, the role of LPA and its receptors in hyperoxia-induced vascular malformations in BPD remains to be elucidated., Methods and Results: Elevated plasma LPA levels were observed in mice with BPD compared to controls (792 vs. 607 ng/mL, p < 0.05). Inhibition of LPA signaling protected against hyperoxia-induced lung injury in neonatal mice, demonstrated by a 2.8-fold increase in pulmonary vascular density and a 14% reduction in alveolar enlargement. In vitro studies showed that LPA suppressed tube formation in human umbilical vein endothelial cells (HUVECs) by approximately 50%. LPA receptor 2 (LPA 2 ) was identified as a functional LPA receptor in primary endothelial cells from the lungs of hyperoxic mice and in HUVECs under hyperoxic conditions. The LPA 2 antagonist H2L5186303 enhanced the tube formation ability of HUVECs exposed to LPA, both under normoxia (4-fold) and hyperoxia (5-fold). Moreover, H2L5186303 significantly protected against hyperoxia-induced vascular malformation (2-fold) and improved alveolarization in neonatal mice (12% decrease in mean linear intercept, MLI). Early growth response 1 (EGR1) was characterized as a downstream target of LPA 2 , silencing EGR1 restored tube formation in HUVECs exposed to LPA and hyperoxia., Conclusions: Our in vitro and in vivo findings demonstrate that the inhibition of LPA/LPA 2 signaling mitigates hyperoxia-induced pulmonary vascular malformations, suggesting the LPA/LPA 2 -dependent signaling pathway has therapeutic potential for extremely premature infants with BPD., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Premature infants with bronchopulmonary dysplasia (BPD) have impaired alveolar gas exchange due to alveolar simplification and dysmorphic pulmonary vasculature. Advances in clinical care have improved survival for infants with BPD, but the overall incidence of BPD remains unchanged because we lack specific therapies to prevent this disease. Recent work has suggested a role for increased transforming growth factor-beta (TGFβ) signaling and myofibroblast populations in BPD pathogenesis, but the functional significance of each remains unclear. Here, we utilize multiple murine models of alveolar simplification and comparative single-cell RNA sequencing to identify shared mechanisms that could contribute to BPD pathogenesis. Single-cell RNA sequencing reveals a profound loss of myofibroblasts in two models of BPD and identifies gene expression signatures of increased TGFβ signaling, cell cycle arrest, and impaired proliferation in myofibroblasts. Using pharmacologic and genetic approaches, we find no evidence that increased TGFβ signaling in the lung mesenchyme contributes to alveolar simplification. In contrast, this is likely a failed compensatory response, since none of our approaches to inhibit TGFβ signaling protect mice from alveolar simplification due to hyperoxia while several make simplification worse. In contrast, we find that impaired myofibroblast proliferation is a central feature in several murine models of BPD, and we show that inhibiting myofibroblast proliferation is sufficient to cause pathologic alveolar simplification. Our results underscore the importance of impaired myofibroblast proliferation as a central feature of alveolar simplification and suggest that efforts to reverse this process could have therapeutic value in BPD., Competing Interests: IK, CM, XR, VA, MC, TT, AA, DS No competing interests declared, (© 2024, Khan et al.)

N 6 -methyladenosine (m6A) regulates gene expression and governs many important biological processes. However, the function of m6A in the development of bronchopulmonary dysplasia (BPD) remains poorly characterized. Thus, the purpose of this investigation was to evaluate the effects of m6A RNA methylation regulators on the development of BPD. BPD-related transcriptome data were downloaded from the GEO database. Differentially expressed m6A methylation regulators between BPD and control group were identified. Consensus clustering was conducted for the classification of BPD and association between clusters and BPD phenotypes were explored. Analysis of differentially expressed genes (DEGs) and immune-related DEGs was performed. The GSEA, GO and KEGG analyses were used to interpret the functional enrichments. The composition of immune cell subtypes in BPD subsets was predicted by CIBERSORT analysis. Compared with the control group, expression of most m6A regulators showed significant alteration, especially for IGF2BP1/2/3. BPD was classified into 2 subsets, and cluster 1 was correlated with severe BPD. Furthermore, the results of functional enrichment analyses showed a disturbed immune-related signaling pathway. Based on CIBERSORT analysis, we found that the proportion of immune cell subsets changed between cluster 1 and cluster 2. Our study revealed the implication of m6A methylation regulators in the development of BPD, which might provide a novel insight for the diagnosis and treatment of BPD., Competing Interests: Declarations. Conflict of interest: The authors declare no conflict of interest. Ethical Approval: This article does not contain any studies with human participants or animals performed by any of the authors. Consent for Publication: All contributors have read and approved the submission to the Journal. Informed Consent: This article does not contain any study with human participants., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Purpose: Lung injury associated with bronchopulmonary dysplasia (BPD) and its related neurodevelopmental disorders have garnered increasing attention in the context of premature infants. Establishing a reliable animal model is essential for delving into the underlying mechanisms of these conditions., Methods: Newborn rats were randomly assigned to two groups: the hyperoxia-induced BPD group and the normoxia (NO) group. For the BPD group, they were nurtured in a hyperoxic environment with a high oxygen inspired fraction (0.85) from birth until day 14 within 28 days postnatally. In contrast, the NO group consisted of newborn rats that were nurtured in a normoxic environment with a standard oxygen inspired fraction (0.21) for 28 days postnatally. Various pathological sections of both lung and brain tissues were examined. TUNEL staining, immunofluorescence assays, and functional tests were performed, and the results were meticulously analyzed to assess the impact of hyperoxia environments on the developing organs., Results: In the newborn rats of the BPD group, a significant reduction in alveolar number coupled with enlargement was observed, alongside severe fibrosis, collagen deposition, and constriction of bronchi and vascular lumens. This was accompanied by an accumulation of inflammatory cells and a marked deterioration in lung function compared to the NO group (P < 0.05). Additionally, a decrease in neuronal count, an increase in neuronal apoptosis, proliferation of neuroglia cells, and demyelination were noted, and poorer performance in the Morris water maze test within the BPD group (P < 0.05)., Conclusion: The BPD-rats model was established successfully. Lung injury in the BPD group evident across the bronchi to the alveoli and pulmonary vessels, which was associated with deteriorated lung function at postnatal day 14. Concurrently, brain injury extended from the cerebral cortex to the hippocampus, which was associated with impaired performance in orientation navigation and spatial probe tests at postnatal day 28., Competing Interests: Declarations. Ethics approval and consent to participate: All the operations followed the National Institutes of Health Guidelines for the Care and Use of Laboratory Animals and ARRIVE Guidelines pertaining to animal experimentation. The protocol for all animal experiments was approved (2023074) by the Experimental Animal Management and Ethics Committee of the West China Second University Hospital, Sichuan University (Sichuan, China). Consent for publication: Not applicable. Availability of data and material. Competing interests: The authors declare no competing interests., (© 2024. The Author(s).)

Background: Abnormal pulmonary vascular development poses significant clinical challenges for infants with bronchopulmonary dysplasia (BPD). Although numerous factors have been suggested to control the development of pulmonary blood vessels, the mechanisms underlying the role of long noncoding RNAs (lncRNAs) in this process remain unclear., Methods: A lncRNA array was used to measure the differential expression of lncRNAs in premature infants with and without BPD. The expression of lncRNA-VSIG2-1:1 in patients with BPD and hyperoxia-induced human pulmonary microvascular endothelial cells (HPMECs) was assessed using quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Fluorescence in situ hybridization (FISH) assay was performed to detect the subcellular localization of lncRNA-VSIG2-1:1. Pulmonary microvascular endothelial cells were stably transfected with adenoviral vectors to silence or overexpress lncRNA-VSIG2-1:1. The effects of lncRNA-VSIG2-1:1 on the proliferation, migration, and tube formation abilities of HPMECs subjected to hyperoxia were examined by performing Cell Counting Kit-8 (CCK-8), cell migration, and tubule formation assays. RNA sequencing (RNA-seq) was performed to determine the correlation between lncRNA-VSIG2-1:1 and phosphoinositide-3-kinase (PI3K)/protein kinase B (AKT). The protein levels of vascular endothelial growth factor (VEGF), p-PI3K, PI3K, p-AKT, and AKT were determined using western blotting., Results: The expression of lncRNA-VSIG2-1:1 was upregulated in patients with BPD and hyperoxia-treated HPMECs. Inhibiting lncRNA-VSIG2-1:1 expression promoted the proliferation, migration, and tube-formation abilities of HPMECs, while significantly increasing VEGF, p-PI3K, and p-AKT levels., Conclusion: Our findings reveal that the suppression of lncRNA-VSIG2-1:1 expression stimulates angiogenesis in vitro by inducing the initiation of the VEGF/PI3K/AKT signaling pathway. This observation may aid the development of novel therapeutic targets for treating BPD., Competing Interests: Declarations. Ethics approval and consent to participate: This study was approved by the Research Ethics Committee of the Second Affiliated Hospital and Yuying Children’s Hospital of Wenzhou Medical University, China (Approval No.LS 2021-K-311-03), and it was performed in accordance with the Declaration of Helsinki. The patients/participants provided written informed consent to participate in this study. Consent to publish: Not applicable. Competing interests: The authors declare no competing interests., (© 2024. The Author(s).)

Background and Purposes: Liver X receptors (LXRs) are specialized nuclear receptors essential for maintaining cholesterol homeostasis, modulating LXR activity could have therapeutic potential in lung diseases. Bronchopulmonary dysplasia (BPD) is a chronic lung disease characterized by impaired alveolar development, in which apoptosis of alveolar epithelial cells is a key contributing factor. The current research focuses on exploring the potential mechanism by which the LXR pathway regulating alveolar epithelial type II cell apoptosis in response to hyperoxia exposure., Methods: BPD infants and non-BPD preterm infants were enrolled to measure serum total cholesterol (TC) levels. To further investigate the role of cholesterol metabolism in BPD, a neonatal rat model of BPD was established, and in vitro studies were conducted using mouse lung epithelial cells (MLE12). These experiments aimed to explore the impact of hyperoxia on cholesterol metabolism and assess the effects of LXR agonist intervention., Results: Elevated serum TC levels in BPD infants were observed, accompanied by lung cholesterol overload in BPD rats. Hyperoxia exposure also led to intracellular cholesterol accumulation in MLE12 cells, which may be attributed to the downregulated LXR signaling pathway. Activation of the LXR pathway prevented apoptosis and mitochondrial dysfunction in MLE12 cell. In BPD rats, intervention with the LXR agonist restored alveolar architecture and reduced alveolar epithelial type II cell apoptosis, which was associated with decreased oxidative stress and lung cholesterol accumulation., Conclusions: Disrupted cholesterol metabolism and impaired homeostasis in premature infants may contribute to the development of BPD. Targeting LXR signaling may provide potential therapeutic targets in BPD., Clinical Trial Number: Not applicable., (© 2024. The Author(s).)

Phenotype distortion of lung resident mesenchymal stem cells (MSC) in preterm infants is a hallmark event in the pathogenesis of bronchopulmonary dysplasia (BPD). Here, we evaluated the impact of cyclic mechanical stretch (CMS) and hyperoxia (HOX). The negative action of HOX on proliferation and cell death was more pronounced at 80% than at 40%. Although the impact of CMS alone was modest, CMS plus HOX displayed the strongest effect sizes. Exposure to CMS and/or HOX induced the downregulation of PDGFRα, and cellular senescence preceded by p21 accumulation. p21 interference interfered with cellular senescence and resulted in aggravated cell death, arguing for a prosurvival mechanism. HOX 40% and limited exposure to HOX 80% prevailed in a reversible phenotype with reuptake of proliferation, while prolonged exposure to HOX 80% resulted in definite MSC growth arrest. Our mechanistic data explain how HOX and CMS induce the effects on MSC phenotype disruption. The results are congruent with the clinical observation that preterm infants requiring supplemental oxygen plus mechanical ventilation are at particular risk for BPD. Although inhibiting p21 is not a feasible approach, limiting the duration and magnitude of the exposures is promising. NEW & NOTEWORTHY Rarefication of lung mesenchymal stem cells (MSC) due to exposure to cyclic mechanical stretch (CMS) during mechanical ventilation with oxygen-rich gas is a hallmark of bronchopulmonary dysplasia in preterm infants, but the pathomechanistic understanding is incomplete. Our studies identify a common signaling mechanism mediated by p21 accumulation, leading to cellular senescence and cell death, most pronounced during the combined exposure with in principle reversible phenotype change depending on strength and duration of exposures.

Bronchopulmonary dysplasia (BPD) is a severe lung disease in preterm infants, the abnormal proliferate and differentiate ability of type II epithelial cells (AEC II) is the key to the pathological basis of BPD. Mechanisms regarding abnormal AEC II in BPD remain unclear. The present work investigated the role and mechanisms of invariant natural killer T (iNKT) cells in lung disorder in BPD using public datasets, clinical samples, a hyperoxia-induced BPD mouse model and AEC II-iNKT cells transwell co-culture system. Firstly, we found that the NKT cells development factor IL-15 increased over time in patients with BPD in public databases, and clinically collected peripheral blood NKT cells in patients with BPD were increased. Subsequently, the percentage of iNKT cells increased in hyperoxia group compared with normoxia group, with the highest at P7, accompanied by increased activation with abnormal lung development. The administration of anti-CD1d neutralizing antibody to inhibit iNKT cells could alleviate the abnormal lung development of hyperoxia group mice, while α-GalCer administration could aggravate lung injury in hyperoxia group mice, and adoptive transfer of iNKT cells could aggravate the abnormal lung development in hyperoxia group mice. In addition, to further verify the role of iNKT cells on AEC II, AEC II-iNKT cells co-culture system was established. The presence of iNKT cells could aggravate the abnormal expression of SP-C and T1α under hyperoxia. Meanwhile, RNA-seq analysis showed that ferroptosis-related genes were highly expressed in AEC II co-cultured with iNKT cells under hyperoxia. We further validated the effect of the presence of iNKT cells under hyperoxia environment on AEC II ferroptosis levels, suggested that iNKT cells promote AEC II ferroptosis under hyperoxia, accompanied by decreased expression of SP-C and T1α. Our study found that the recruitment of iNKT cells in the lung may be an important cause of alveolarization disorder in BPD., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Bronchopulmonary dysplasia (BPD) is the most common chronic lung disease of preterm infants that is associated with life-long morbidities. Inflammatory insults contribute to BPD pathogenesis. Although the proinflammatory cytokine, IL-17a, plays a role in various neonatal inflammatory disorders, its role in BPD pathogenesis is unclear. To test the hypothesis that blocking IL-17a signaling decreases lipopolysaccharide (LPS)-mediated experimental BPD in neonatal mice, wild-type mice were injected intraperitoneally with phosphate-buffered saline or LPS during the saccular lung developmental phase. Pulmonary IL-17a expression was determined by enzyme-linked immunosorbent assay and by flow cytometry. LPS-injected mice had higher pulmonary IL-17a protein levels and IL-17a + and IL-22 + cells. γδ T cells, followed by non-T lymphoid cells, were the primary producers of IL-17a. Wild-type mice were then injected intraperitoneally with isotype antibody (Ab) or IL-17a Ab, while they were treated with phosphate-buffered saline or LPS, followed by quantification of lung inflammatory markers, alveolarization, vascularization, cell proliferation, and apoptosis. LPS-mediated alveolar simplification, apoptosis, and cell proliferation inhibition were significantly greater in mice treated with isotype Ab than in those treated with IL-17a Ab. Furthermore, STAT1 activation and IL-6 levels were significantly greater in LPS-exposed mice treated with isotype Ab than in those treated with IL-17a Ab. The study results indicate that blocking IL-17a signaling decreases LPS-mediated experimental BPD., Competing Interests: Disclosure Statement None declared., (Copyright © 2024 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.)

Bronchopulmonary dysplasia (BPD) is the most common complication of prematurity. Oxidative stress (OS) and inflammation are the major contributors to BPD. Despite aggressive treatments, BPD prevalence remains unchanged, which underscores the urgent need to explore more potential therapies. The endoplasmic reticulum (ER) plays crucial roles in surfactant and protein synthesis, assisting mitochondrial function, and maintaining metabolic homeostasis. Under OS, disturbed metabolism and protein folding transform the ER structure to refold proteins and help degrade non-essential proteins to resume cell homeostasis. When OS becomes excessive, the endogenous chaperone will leave the three ER stress sensors to allow subsequent changes, including cell death and senescence, impairing the growth potential of organs. The contributing role of ER stress in BPD is confirmed by reproducing the BPD phenotype in rat pups by ER stress inducers. Although chemical chaperones attenuate BPD, ER stress is still associated with cellular senescence. N -acetyl-lysyltyrosylcysteine amide (KYC) is a myeloperoxidase inhibitor that attenuates ER stress and senescence as a systems pharmacology agent. In this review, we describe the role of ER stress in BPD and discuss the therapeutic potentials of chemical chaperones and KYC, highlighting their promising role in future therapeutic interventions.

Bronchopulmonary dysplasia (BPD) and neurodevelopmental impairment are among the most common morbidities affecting preterm infants. Although BPD is a predictor of poor neurodevelopmental outcomes, it is currently uncertain how BPD contributes to brain injury in preterm infants. Extracellular vesicles (EVs) are involved in interorgan communication in diverse pathological processes. ASC (apoptosis-associated speck-like protein containing a caspase recruitment domain) is pivotal in inflammasome assembly and activation of inflammatory response. We assessed expression profiles of the alveolar macrophage (AM) markers CD11b, CD11c, and CD206 as well as ASC in EVs isolated from the plasma of preterm infants at risk for BPD at 1 week of age. We found that infants on higher fraction of inspired oxygen therapy (HO 2 ⩾30%) had increased concentrations of AM-derived EV-ASC compared with infants on lower fraction of inspired oxygen (LO 2 <30%). To assess the function of these EVs, we performed adoptive transfer experiments by injecting them into the circulation of newborn mice. We discovered that mice that received EVs from infants on HO 2 had increased lung inflammation, decreased alveolarization, and disrupted vascular development, the hallmarks of BPD. Importantly, these EVs crossed the blood-brain barrier, and the EVs from infants on HO 2 caused inflammation, reduced cell survival, and increased cell death, with features of pyroptosis and necroptosis in the hippocampus. These results highlight a novel role for AM-derived EV-ASC in mediating the lung-to-brain cross-talk that is critical in the pathogenesis of BPD and brain injury and identify potential novel targets for preventing and treating BPD and brain injury in preterm infants.

Bronchopulmonary dysplasia (BPD) is characterized by impaired lung alveolar and vascular growth. We investigated the hypothesis that neonatal exposure to hyperoxia leads to persistent BPD phenotype caused by decreased expression of liver kinase B1 (LKB1), a key regulator of mitochondrial function. We exposed mouse pups from Postnatal Day (P)1 through P10 to 21% or 75% oxygen. Half of the pups in each group received metformin or saline intraperitoneally from P1 to P10. Pups were killed at P4 or P10 or recovered in 21% O 2 until euthanasia at P21. Lung histology and morphometry, immunofluorescence, and immunoblots were performed to detect changes in lung structure and expression of LKB1; downstream targets AMPK, PGC-1α, and electron transport chain (ETC) complexes; and Notch ligands Jagged 1 and delta-like 4. LKB1 signaling and in vitro angiogenesis were assessed in human pulmonary artery endothelial cells (exposed to 21% or 95% O 2 for 36 hours. Levels of LKB1, phosphorylated AMPK, PGC-1α, and ETC complexes were decreased in lungs at P10 and P21 in hyperoxia. Metformin increased LKB1, phosphorylated AMPK, PGC-1α, and ETC complexes at P10 and P21 in pups exposed to hyperoxia. Radial alveolar count was decreased, and mean linear intercept increased in pups exposed to hyperoxia at P10 and P21; these were improved by metformin. Lung capillary density was decreased in hyperoxia at P10 and P21 and was increased by metformin. In vitro angiogenesis was decreased in human pulmonary artery endothelial cells by 95% O 2 and was improved by metformin. Decreased LKB1 signaling may contribute to decreased alveolar and vascular growth in a mouse model of BPD.

Bronchopulmonary dysplasia (BPD) is the most common lung complication of prematurity. Despite extensive research, our understanding of its pathophysiology remains limited, as reflected by the stable prevalence of BPD. Prematurity is the primary risk factor for BPD, with oxidative stress (OS) and inflammation playing significant roles and being closely linked to premature birth. Understanding the interplay and temporal relationship between OS and inflammation is crucial for developing new treatments for BPD. Animal studies suggest that OS and inflammation can exacerbate each other. Clinical trials focusing solely on antioxidants or anti-inflammatory therapies have been unsuccessful. In contrast, vitamin A and caffeine, with antioxidant and anti-inflammatory properties, have shown some efficacy, reducing BPD by about 10%. However, more than one-third of very preterm infants still suffer from BPD. New therapeutic agents are needed. A novel tripeptide, N-acetyl-lysyltyrosylcysteine amide (KYC), is a reversible myeloperoxidase inhibitor and a systems pharmacology agent. It reduces BPD severity by inhibiting MPO, enhancing antioxidative proteins, and alleviating endoplasmic reticulum stress and cellular senescence in a hyperoxia rat model. KYC represents a promising new approach to BPD treatment.

Bronchopulmonary dysplasia (BPD) is a common complication of preterm birth. Despite this, genetic drivers of BPD are poorly understood. The objective of this study is to better understand the impact of single nucleotide polymorphisms (SNPs) previously associated with BPD by examining associations with other phenotypes. We drew pediatric subjects from the biorepository at the Center for Applied Genomics to identify associations between these SNPs and 2,146 imputed phenotypes. Methylation data, external cohorts, and in silico validation methods were used to corroborate significant associations. We identified 60 SNPs that were previously associated with BPD. We found a significant association between rs3771150 and rs3771171 and mean eosinophil percentage in a European cohort of 6,999 patients and replicated this in external cohorts. Both SNPs were also associated with asthma, COPD and FEV1/FVC ratio. These SNPs displayed associations with methylation probes and were functionally linked to ST2 (IL1RL1) levels in blood and lung tissue. Our findings support a genetic justification for the epidemiological link between BPD and asthma. Given the well-established link between ST2 and type 2 inflammation in asthma, these findings provide a rationale for future studies exploring the role of type 2 inflammation in the pathogenesis of BPD., (© 2024. The Author(s).)

Background: Premature infants requiring mechanical ventilation and supplemental oxygen for respiratory support are at increased risk for bronchopulmonary dysplasia (BPD), wherein inflammation have been proposed as a driver of hyperoxia-induced injuries, including persistent loss of endothelial progenitor cells (EPCs), impaired vascularization and eventual alveolar simplification in BPD lungs. However, the underlying mechanisms linking these phenomena remain poorly defined., Methods: We used clodronate liposomes to deplete macrophages in a mouse model of neonatal hyperoxia-induced lung injury to evaluate if EPC loss in BPD lungs could be an effect of macrophage infiltration. We further generated in vitro culture systems initiated with cord blood (CB)-derived CD34 + EPCs and neonatal macrophages either polarized from CB-derived monocytes or isolated from tracheal aspirates of human preterm infants requiring mechanical ventilation and oxygen supplementation, to identify EV-transmitted molecular mechanism that is critical for inhibitory actions of hyperoxic macrophages on EPCs., Results: Initial experiments using mouse model identified the crucial role of macrophage infiltration in eliciting significant reduction of c-Kit + EPCs in BPD lungs. Further examination of this concept in human system, we found that hyperoxia-exposed neonatal macrophages hamper human CD34 + EPC maintenance and impair endothelial function in the differentiated progeny via the EV transmission of miR-23a-3p. Notably, treatment with antagomiR-23a-3p to silence miR-23a-3p in vivo enhances c-Kit + EPC maintenance, and increases capillary density, and consequently mitigates simplified alveolarization in BPD lungs., Conclusion: Our findings highlight the importance of pulmonary intercellular communication in the pathophysiology of BPD, by identifying a linkage through vesicle transfer of miR-23a-3p from hyperoxic macrophages to EPCs, and thus demonstrating potential for novel therapeutic target in BPD., (© 2024. The Author(s).)

Bronchopulmonary dysplasia (BPD) is a common chronic lung disease in infants and the most frequent adverse outcome of premature birth, despite major efforts to minimize injury. It is thought to result from aberrant repair response triggered by either prenatal or recurrent postnatal injury to the lungs during development. Intrauterine inflammation is an important risk factor for prenatal lung injury, which is also increasingly linked to BPD. However, the specific mechanisms remain unclear. This review summarizes clinical and animal research linking intrauterine inflammation to BPD. We assess how intrauterine inflammation affects lung alveolarization and vascular development. In addition, we discuss prenatal therapeutic strategies targeting intrauterine inflammation to prevent or treat BPD., (© 2024. The Author(s).)

Background: BPD is a refractory disease affecting preterm infants with alveolar dysplasia and declined pulmonary function. However, the molecular mechanism underlying BPD is largely unknown. To explore the pathogenic mechanism of BPD and to facilitate better diagnosis and treatment of this disease., Method: The DEMs and DEGs in BPD vs. Control samples from the miRNA expression data in GSE108754 and mRNA expression data in the GSE108755 were screened, followed by the construction of the miRNA-mRNA regulatory network. DEGs PPI network and hub DEGs analysis were constructed by using the STRING database and Cytoscape software. Functional and pathway enrichment analyses were then performed for these DEGs and DEMs based on the ClusterProfiler package in the R and the miRWalk database. The k-mean algorithm is used to perform clustering analysis of DEGs. Cellular experiments (flow cytometry, western blot, RT-PCR, dual-luciferase reporter assay) were used to validate the results of bioinformatics., Results: We obtained 20 DEMs and 262 DEGs. A 15 DEMs-11 DEGs regulatory network was constructed. miR-3202-RAG1 is a core sub-network. Hyperoxia induced a cell model of BPD. The upregulation of RAG1 and downregulation of miR-3202 were observed in BPD cells. Furthermore, siRNA targeting RAG1 was transfected into BEAS-2B cells to inhibit its expression and miR-3202 mimics was transfected into the cells to increase its expression. Inhibition of RAG1 and elevation of miR-3202 inhibit cell apoptosis and reduce ROS level caused by hyperoxia. A double-luciferase reporter assay revealed that miR-3202 directly targets RAG1., Conclusion: The miRNA-3202/RAG1 axis contributes into BPD-induced cell apoptosis and ROS production. The present study provides a probable target for the treatment of BPD., Competing Interests: Declaration of Competing Interest there is no conflict of interest., (Copyright © 2024 The Authors. Published by Elsevier GmbH.. All rights reserved.)

Bronchopulmonary dysplasia (BPD) is a chronic lung disease, associated with premature birth, that arises during the infantile period. It is an evolving disease process with an unchanged incidence due to advancements in neonatal care which allow for the survival of premature infants of lower gestational ages and birth weights. Currently, there are few effective interventions to prevent BPD. However, careful attention to BPD phenotypes and comprehensive care provided by an interdisciplinary team have improved care. Interventions early in the disease course hold promise for improving long-term survival and outcomes in adulthood for this high-risk population., Competing Interests: Disclosure The authors have no financial or commercial conflicts of interests to disclose., (Copyright © 2024 Elsevier Inc. All rights reserved.)

The lung macrophages play a crucial role in health and disease. Sexual dimorphism significantly impacts the phenotype and function of tissue-resident macrophages. The primary mechanisms responsible for sexually dimorphic outcomes in bronchopulmonary dysplasia (BPD) remain unidentified. We tested the hypothesis that biological sex plays a crucial role in the transcriptional state of alveolar macrophages, using neonatal murine hyperoxia-induced lung injury as a relevant model for human BPD. The effects of neonatal hyperoxia exposure (95 % FiO 2 , PND1-5: saccular stage) on the lung myeloid cells acutely after injury and during normoxic recovery were measured. Alveolar macrophages (AM) from room air- and hyperoxia exposed from male and female neonatal murine lungs were subjected to bulk-RNA Sequencing. AMs are significantly depleted in the hyperoxia-exposed lung acutely after injury, with subsequent recovery in both sexes. The transcriptome of the alveolar macrophages is impacted by neonatal hyperoxia exposure and by sex as a biological variable. Pathways related to DNA damage and interferon-signaling were positively enriched in female AMs. Metabolic pathways related to glucose and carbohydrate metabolism were positively enriched in the male AMs, while oxidative phosphorylation was negatively enriched. These pathways were shared with monocytes and airway macrophages from intubated male and female human premature neonates., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Bronchopulmonary dysplasia (BPD), caused by hyperoxia exposure, is the most common complication affecting preterm infants. The C-X-C motif chemokine ligand 17 (CXCL17) belongs to the chemokine family that plays important roles in various processes, but the function in BPD is unknown. Elevated serum CXCL17 levels were observed in human premature infants with hyperoxia-induced lung injury, suggesting that CXCL17 might be involved in BPD. To further validate our speculation, studies were conducted in a hyperoxia-induced lung injury mouse model and primary murine alveolar epithelial cells Type II (T2AEC) cells exposed to hyperoxia. RT-qPCR and western blot were used to validate CXCL17 expression in newborn mice. Hyperoxia exposure-induced lung injury was determined by assessing the lung wet-weight/dry-weight ratio and histological changes. Oxidative stress and inflammatory factors were examined by ELISA assay and RT-qPCR. Reactive oxygen species (ROS) level was evaluated by DHE staining. Apoptosis was assessed by TUNEL staining and western blot. The results showed that hyperoxia exposure increased CXCL17 levels in newborn mice pups. Hyperoxia exposure increased lung wet-weight/dry-weight ratio, increased alveolar diameter and enlarged alveoli, and reduced surfactant protein C expression. However, recombinant CXCL17 (rCXCL17) treatment alleviated hyperoxia-induced lung injury. rCXCL17 treatment inhibited hyperoxia-induced inflammation, oxidative stress, and apoptosis in neonatal mice. These results were further verified in T2AEC cells. Additionally, rCXCL17 treatment activated the AKT pathway, which is a protective pathway in BPD. Collectively, rCXCL17 alleviates hyperoxia-induced lung injury in neonatal mice by activating the AKT pathway, indicating that CXCL17 may be a promising target for BPD therapy., (© 2023. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Bronchopulmonary dysplasia (BPD) is the most common sequela of prematurity and is characterized by alveolar simplification and lung angiogenesis failure. The aim of this study was to explore the immune signatures of BPD. Differentially expressed gene analysis and immune infiltration analysis were conducted to identify key immune cell types and related genes by using the mRNA-seq dataset GSE25286. The expression patterns of key genes were validated in the scRNA-seq dataset GSE209664 and in experiments. The cell-cell crosstalk of key immune cells was explored with CellChat. We found that differentially expressed genes between BPD mice and controls were mostly enriched in leukocyte migration and M1 macrophages were highly enriched in BPD lungs. Hub genes (Cybb, Papss2, F7 and Fpr2) were validated at the single-cell level, among which the downregulation of Cybb was most closely related to macrophage infiltration. The reduced mRNA and protein levels of Cybb were further validated in animal experiments. Colocalization analysis of Cybb and macrophage markers demonstrated a significant decrease of Cybb in M1 macrophages. Cell-cell crosstalk found that alveolar epithelial cells interacted actively with macrophages through MIF-(CD74 + CD44) signalling. In conclusion, M1 macrophages played important roles in promoting BPD-like lung injury, which was correlated with a specific reduction of Cybb in macrophages and the potential activation of MIF signalling., (© 2024. The Author(s).)

To study a new method for establishing animal models of prenatal bronchopulmonary dysplasia (BPD), we used lung ultrasound score (LUS) to semi-quantitatively assess the severity of lung lesions in model rats. Lipopolysaccharide (LPS) was injected into the right lung of the fetus of the rat under ultrasound-guided, and the right lung of the neonates were scanning for LUS. Specimens were collected for pathological scoring and detection of pulmonary surfactant-associated glycoprotein (SP)-C and vascular endothelial growth factor (VEGF) expression quantity. The correlation between LUS and pathological scores was analyzed. (1) The animal models were consistent with the pathological manifestations of BPD. (2) It showed a strong positive correlation between LUS and pathological scores in animal models (r = 0.84, P < 0.005), and the expression quantity of SP-C and VEGF in lung tissue were decreased (both P < 0.05). Animal models established by ultrasound-guided puncture of the lung of rats and injection of LPS were consistent with the manifestation of BPD. This method could be used to establish animal models of BPD before birth, and the severity of BPD could be assessed by using LUS., (© 2024. The Author(s).)

miR-146b-5p has been studied to be highly expressed in bronchopulmonary dysplasia (BPD), but whether it is involved in regulating the process of BPD in premature infants remains unclear. This study was to explore miR-146b-5p in premature BPD and reveal its molecular mechanism. BPD mouse model and high-oxygen MLE-12 cell model were established. HE staining, TUNEL staining, and IF staining were conducted to evaluate the pathological injury and protein expression in mouse lung tissue. LDH assay, MMT assay, and flow cytometry were achieved to evaluate cytotoxicity, cell viability, and apoptosis. ELISA and immunoblotting were performed to evaluate inflammatory cytokines and Wnt pathway proteins in lung tissues and cells. Dual-luciferase reporter assay and RIP assay were needed to examine the targeting relationship between miR-146b-5p and KDM6B. miR-146b-5p was abundantly expressed in BPD and KDM6B was lowly expressed. miR-146b-5p knockdown improved hyperoxia-induced lung epithelial cell inflammation and apoptosis in both models. miR-146b-6p upregulation or KDM6B downregulation aggravated hyperoxia-induced inflammation and apoptosis of lung epithelial cells. This effect of overexpressing miR-146b-5p was rescued by forcing KDM6B. MiR-146b-5p activated Wnt signaling by regulating KDM6B. miR-146b-5p activates the Wnt pathway through targeted regulation of KDM6B, thereby aggravating hyperoxia-induced inflammation and apoptosis of lung epithelial cells., (© 2023. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Objectives: To investigate the role and mechanism of epithelial-mesenchymal transition (EMT) in a rat model of bronchopulmonary dysplasia (BPD)., Methods: The experiment consisted of two parts. (1) Forty-eight preterm rats were randomly divided into a normoxia group and a hyperoxia group, with 24 rats in each group. The hyperoxia group was exposed to 85% oxygen to establish a BPD model, while the normoxia group was kept in room air at normal pressure. Lung tissue samples were collected on days 1, 4, 7, and 14 of the experiment. (2) Rat type II alveolar epithelial cells (RLE-6TN) were randomly divided into a normoxia group (cultured in air) and a hyperoxia group (cultured in 95% oxygen), and cell samples were collected 12, 24, and 48 hours after hyperoxia exposure. Hematoxylin-eosin staining was used to observe alveolarization in preterm rat lungs, and immunofluorescence was used to detect the co-localization of surfactant protein C (SPC) and α-smooth muscle actin (α-SMA) in preterm rat lung tissue and RLE-6TN cells. Quantitative real-time polymerase chain reaction and protein immunoblotting were used to detect the expression levels of EMT-related mRNA and proteins in preterm rat lung tissue and RLE-6TN cells., Results: (1) Compared with the normoxia group, the hyperoxia group showed blocked alveolarization and simplified alveolar structure after 7 days of hyperoxia exposure. Co-localization of SPC and α-SMA was observed in lung tissue, with decreased SPC expression and increased α-SMA expression in the hyperoxia group at 7 and 14 days of hyperoxia exposure compared to the normoxia group. In the hyperoxia group, the mRNA and protein levels of TGF-β1, α-SMA, and N-cadherin were increased, while the mRNA and protein levels of SPC and E-cadherin were decreased at 7 and 14 days of hyperoxia exposure compared to the normoxia group ( P <0.05). (2) SPC and α-SMA was observed in RLE-6TN cells, with decreased SPC expression and increased α-SMA expression in the hyperoxia group at 24 and 48 hours of hyperoxia exposure compared to the normoxia group. Compared to the normoxia group, the mRNA and protein levels of SPC and E-cadherin in the hyperoxia group were decreased, while the mRNA and protein levels of TGF-β1, α-SMA, and E-cadherin in the hyperoxia group increased at 48 hours of hyperoxia exposure ( P <0.05)., Conclusions: EMT disrupts the tight connections between alveolar epithelial cells in a preterm rat model of BPD, leading to simplified alveolar structure and abnormal development, and is involved in the development of BPD. Citation:Chinese Journal of Contemporary Pediatrics, 2024, 26(7): 765-773 .

Bronchopulmonary dysplasia (BPD) is a severe complication of preterm births, which develops due to exposure to supplemental oxygen and mechanical ventilation. Published studies demonstrated that the number of endothelial progenitor cells (EPC) is decreased in mouse and human BPD lungs and that adoptive transfer of EPC is an effective approach in reversing the hyperoxia-induced lung damage in mouse model of BPD. Recent advancements in macrophage biology identified the specific subtypes of circulating and resident macrophages mediating the developmental and regenerative functions in the lungs. Several studies reported the successful application of macrophage therapy in accelerating the regenerative capacity of damaged tissues and enhancing the therapeutic efficacy of other transplantable progenitor cells. In the present study, we explored the efficacy of combined cell therapy with EPC and resident alveolar macrophages (rAM) in hyperoxia-induced BPD mouse model. rAM and EPC were purified from neonatal mouse lungs and were used for adoptive transfer to the recipient neonatal mice exposed to hyperoxia. Adoptive transfer of rAM alone did not result in engraftment of donor rAM into the lung tissue but increased the mRNA level and protein concentration of proangiogenic CXCL12 chemokine in recipient mouse lungs. Depletion of rAM by chlodronate-liposomes decreased the retention of donor EPC after their transplantation into hyperoxia-injured lungs. Adoptive transfer of rAM in combination with EPC enhanced the therapeutic efficacy of EPC as evidenced by increased retention of EPC, increased capillary density, improved arterial oxygenation, and alveolarization in hyperoxia-injured lungs. Dual therapy with EPC and rAM has promise in human BPD. NEW & NOTEWORTHY Recent studies demonstrated that transplantation of lung-resident endothelial progenitor cells (EPC) is an effective therapy in mouse model of bronchopulmonary dysplasia (BPD). However, key factors regulating the efficacy of EPC are unknown. Herein, we demonstrate that transplantation of tissue-resident alveolar macrophages (rAM) increases CXCL12 expression in neonatal mouse lungs. rAM are required for retention of donor EPC in hyperoxia-injured lungs. Co-transplantation of rAM and EPC improves the efficacy of EPC therapy in mouse BPD model.

Bronchopulmonary dysplasia (BPD) remains a significant challenge in neonatal care, the pathogenesis of which potentially involves altered lipid metabolism. Given the critical role of lipids in lung development and the injury response, we hypothesized that specific lipid species could serve as therapeutic agents in BPD. This study aimed to investigate the role of the lipid Phosphatidylcholine (PC) (16:0/14:0) in modulating BPD pathology and to elucidate its underlying mechanisms of action. Our approach integrated in vitro and in vivo methodologies to assess the effects of PC (16:0/14:0) on the histopathology, cellular proliferation, apoptosis, and molecular markers in lung tissue. In a hyperoxia-induced BPD rat model, we observed a reduction in alveolar number and an enlargement in alveolar size, which were ameliorated by PC (16:0/14:0) treatment. Correspondingly, in BPD cell models, PC (16:0/14:0) intervention led to increased cell viability, enhanced proliferation, reduced apoptosis, and elevated surfactant protein C (SPC) expression. RNA sequencing revealed significant gene expression differences between BPD and PC (16:0/14:0) treated groups, with a particular focus on Cldn1 (encoding claudin 1), which was significantly enriched in our analysis. Our findings suggest that PC (16:0/14:0) might protect against hyperoxia-induced alveolar type II cell damage by upregulating CLDN1 expression, potentially serving as a novel therapeutic target for BPD. This study not only advances our understanding of the role of lipids in BPD pathogenesis, but also highlights the significance of PC (16:0/14:0) in the prevention and treatment of BPD, offering new avenues for future research and therapeutic development., Competing Interests: Declaration of Competing Interest All authors declare no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Bronchopulmonary dysplasia (BPD) is a chronic lung disease commonly affecting premature infants, with limited therapeutic options and increased long-term consequences. Adrenomedullin ( Adm ), a proangiogenic peptide hormone, has been found to protect rodents against experimental BPD. This study aims to elucidate the molecular and cellular mechanisms through which Adm influences BPD pathogenesis using a lipopolysaccharide (LPS)-induced model of experimental BPD in mice. Bulk RNA sequencing of Adm -sufficient (wild-type or Adm +/+ ) and Adm -haplodeficient ( Adm +/- ) mice lungs, integrated with single-cell RNA sequencing data, revealed distinct gene expression patterns and cell type alterations associated with Adm deficiency and LPS exposure. Notably, computational integration with cell atlas data revealed that Adm -haplodeficient mouse lungs exhibited gene expression signatures characteristic of increased inflammation, natural killer (NK) cell frequency, and decreased endothelial cell and type II pneumocyte frequency. Furthermore, in silico human BPD patient data analysis supported our cell type frequency finding, highlighting elevated NK cells in BPD infants. These results underscore the protective role of Adm in experimental BPD and emphasize that it is a potential therapeutic target for BPD infants with an inflammatory phenotype.

Objective: We aimed to study the involvement of ferroptosis in the pathogenesis of bronchopulmonary dysplasia (BPD) by conducting bioinformatics analyses and identifying and validating the associated ferroptosis-related genes to explore new directions for treating BPD., Methods: The dataset GSE32472 on BPD was downloaded from the public genome database. Using R language, differentially expressed genes (DEGs) between the BPD and normal group were screened. In the present study, we adopted weighted gene correlation network analysis (WGCNA) for identifying BPD-related gene modules and ferroptosis-related genes were extracted from FerrDb. Their results were intersected to obtain the hub genes. After that, to explore the hub gene-related signaling pathways, the hub genes were exposed to gene ontology enrichment analysis. With the purpose of verifying the mRNA expression of the hub genes, a single-gene gene set enrichment analysis and quantitative reverse transcription polymerase chain reaction were conducted. Immune cell infiltration in BPD was analyzed using the CIBERSORT inverse fold product algorithm., Results: A total of 606 DEGs were screened. WGCNA provided the BPD-related gene module darkgreen4. The intersection of DEGs, intramodular genes, and ferroptosis-related genes revealed six ferroptosis-associated hub genes (ACSL1, GALNT14, WIPI1, MAPK14, PROK2, and CREB5). Receiver operating characteristic curve analysis demonstrated that the hub genes screened for BPD were of good diagnostic significance. According to the results of immune infiltration analysis, the proportions of CD8, CD4 naive, and memory resting T cells and M2 macrophage were elevated in the normal group, and the proportions of M0 macrophage, resting mast cell, and neutrophils were increased in the BPD group., Conclusions: A total of six ferroptosis-associated hub genes in BPD were identified in this study, and they may be potential new therapeutic targets for BPD., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Luo et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Background: Premature infants often require oxygen supplementation, which can elicit bronchopulmonary dysplasia (BPD) and lead to mitochondrial dysfunction. Mitochondria play important roles in lung development, in both normal metabolism and apoptosis. Enhancing our comprehension of the underlying mechanisms in BPD development can facilitate the effective treatments., Methods: Plasma samples from BPD and non-BPD infants were collected at 36 weeks post-menstrual age and used for metabolomic analysis. Based on hyperoxia-induced animal and cell models, changes in mitophagy and apoptosis were evaluated following treatment with itaconic acid (ITA). Finally, the mechanism of action of ITA in lung development was comprehensively demonstrated through rescue strategies and administration of corresponding inhibitors., Results: An imbalance in the tricarboxylic acid (TCA) cycle significantly affected lung development, with ITA serving as a significant metabolic marker for the outcomes of lung development. ITA improved the morphological changes in BPD rats, promoted SP-C expression, and inhibited the degree of alveolar type II epithelial cells (AEC II) apoptosis. Mechanistically, ITA mainly promotes the nuclear translocation of transcription factor EB (TFEB) to facilitate dysfunctional mitochondrial clearance and reduces apoptosis in AEC II cells by regulating autophagic flux., Conclusion: The metabolic imbalance in the TCA cycle is closely related to lung development. ITA can improve lung development by regulating autophagic flux and promote the nuclear translocation of TFEB, implying its potential therapeutic utility in the treatment of BPD., Competing Interests: Declaration of competing interest The authors have indicated they have no potential conflicts of interest to disclose., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Novel therapies are needed for bronchopulmonary dysplasia (BPD) because no effective treatment exists. Mesenchymal stromal cell extracellular vesicles (MSC-sEVs) have therapeutic efficacy in a mouse pup neonatal hyperoxia BPD model. We tested the hypothesis that MSC-sEVs will improve lung functional and structural development in mechanically ventilated preterm lambs. Preterm lambs (∼129 days; equivalent to human lung development at ∼28 wk gestation) were exposed to antenatal steroids, surfactant, caffeine, and supported by mechanical ventilation for 6-7 days. Lambs were randomized to blinded treatment with either MSC-sEVs (human bone marrow MSC-derived; 2 × 10 11 particles iv; n = 8; 4 F/4 M) or vehicle control (saline iv; 4 F/4 M) at 6 and 78 h post delivery. Physiological targets were pulse oximetry O 2 saturation 90-94% ([Formula: see text] 60-90 mmHg), [Formula: see text] 45-60 mmHg (pH 7.25-7.35), and tidal volume 5-7 mL/kg. MSC-sEVs-treated preterm lambs tolerated enteral feedings compared with vehicle control preterm lambs. Differences in weight patterns were statistically significant. Respiratory severity score, oxygenation index, A-a gradient, distal airspace wall thickness, and smooth muscle thickness around terminal bronchioles and pulmonary arterioles were significantly lower for the MSC-sEVs group. S/F ratio, radial alveolar count, secondary septal volume density, alveolar capillary surface density, and protein abundance of VEGF-R2 were significantly higher for the MSC-sEVs group. MSC-sEVs improved respiratory system physiology and alveolar formation in mechanically ventilated preterm lambs. MSC-sEVs may be an effective and safe therapy for appropriate functional and structural development of the lung in preterm infants who require mechanical ventilation and are at risk of developing BPD. NEW & NOTEWORTHY This study focused on potential treatment of preterm infants at risk of developing bronchopulmonary dysplasia (BPD), for which no effective treatment exists. We tested treatment of mechanically ventilated preterm lambs with human mesenchymal stromal cell extracellular vesicles (MSC-sEVs). The results show improved respiratory gas exchange and parenchymal growth of capillaries and epithelium that are necessary for alveolar formation. Our study provides new mechanistic insight into potential efficacy of MSC-sEVs for preterm infants at risk of developing BPD.

Extracellular vesicle (EV) biology in neonatal lung development and disease is a rapidly growing area of investigation. Although EV research in the neonatal population lags behind EV research in adult lung diseases, recent discoveries demonstrate promise in furthering our understanding of the pathophysiology of bronchopulmonary dysplasia and the potential use of EVs in the clinical setting, as both biomarkers and therapeutic agents. This review article explores some of the recent advances in this field and our evolving knowledge of the role of EVs in bronchopulmonary dysplasia.

Bronchopulmonary dysplasia (BPD), the chronic lung disease of prematurity, is characterized by impaired lung development with sustained functional abnormalities due to alterations of airways and the distal lung. Although clinical studies have shown striking associations between antenatal stress and BPD, little is known about the underlying pathogenetic mechanisms. Whether dysanapsis, the concept of discordant growth of the airways and parenchyma, contributes to late respiratory disease as a result of antenatal stress is unknown. We hypothesized that antenatal endotoxin (ETX) impairs juvenile lung function as a result of altered central airway and distal lung structure, suggesting the presence of dysanapsis in this preclinical BPD model. Fetal rats were exposed to intraamniotic ETX (10 μg) or saline solution (control) 2 days before term. We performed extensive structural and functional evaluation of the proximal airways and distal lung in 2-week-old rats. Distal lung structure was quantified by stereology. Conducting airway diameters were measured using micro-computed tomography. Lung function was assessed during invasive ventilation to quantify baseline mechanics, response to methacholine challenge, and spirometry. ETX-exposed pups exhibited distal lung simplification, decreased alveolar surface area, and decreased parenchyma-airway attachments. ETX-exposed pups exhibited decreased tracheal and second- and third-generation airway diameters. ETX increased respiratory system resistance and decreased lung compliance at baseline. Only Newtonian resistance, specific to large airways, exhibited increased methacholine reactivity in ETX-exposed pups compared with controls. ETX-exposed pups had a decreased ratio of FEV in 0.1 second to FVC and a normal FEV in 0.1 second, paralleling the clinical definition of dysanapsis. Antenatal ETX causes abnormalities of the central airways and distal lung growth, suggesting that dysanapsis contributes to abnormal lung function in juvenile rats.

Bronchopulmonary dysplasia (BPD) is a chronic lung disease common in extreme preterm infants and is characterized by alveolar simplification. Current BPD research mainly focuses on alveolar type 2 (AT2) cells, myofibroblasts, and the endothelium. However, a notable gap exists in the involvement of AT1 cells, which constitute a majority of the alveolar surface area. In this issue of the JCI, Callaway and colleagues explored the role of TGF-β signaling in AT1 cells for managing the AT1-to-AT2 transition and its involvement in the integration of mechanical forces with the pulmonary matrisome during development. The findings implicate AT1 cells in the pathogenesis of BPD.

Background: Despite advances in neonatal care, the incidence of Bronchopulmonary Dysplasia (BPD) remains high among preterm infants. Human induced pluripotent stem cells (hiPSCs) have shown promise in repairing injury in animal BPD models. Evidence suggests they exert their effects via paracrine mechanisms. We aim herein to assess the effectiveness of extracellular vesicles (EVs) derived from hiPSCs and their alveolar progenies (diPSCs) in attenuating hyperoxic injury in a preterm lung explant model., Methods: Murine lung lobes were harvested on embryonic day 17.5 and maintained in air-liquid interface. Following exposure to 95% O 2 for 24 h, media was supplemented with 5 × 10 6 particles/mL of EVs isolated from hiPSCs or diPSCs by size-exclusion chromatography. On day 3, explants were assessed using Hematoxylin-Eosin staining with mean linear intercept (MLI) measurements, immunohistochemistry, VEGFa and antioxidant gene expression. Statistical analysis was conducted using one-way ANOVA and Multiple Comparison Test. EV proteomic profiling was performed, and annotations focused on alveolarization and angiogenesis signaling pathways, as well as anti-inflammatory, anti-oxidant, and regenerative pathways., Results: Exposure of fetal lung explants to hyperoxia induced airspace enlargement, increased MLI, upregulation of anti-oxidants Prdx5 and Nfe2l2 with decreased VEGFa expression. Treatment with hiPSC-EVs improved parenchymal histologic changes. No overt changes in vasculature structure were observed on immunohistochemistry in our in vitro model. However, VEGFa and anti-oxidant genes were upregulated with diPSC-EVs, suggesting a pro-angiogenic and cytoprotective potential. EV proteomic analysis provided new insights in regard to potential pathways influencing lung regeneration., Conclusion: This proof-of-concept in vitro study reveals a potential role for hiPSC- and diPSC-EVs in attenuating lung changes associated with prematurity and oxygen exposure. Our findings pave the way for a novel cell free approach to prevent and/or treat BPD, and ultimately reduce the global burden of the disease., (© 2024. The Author(s).)

Oxidative stress, inflammation, and endoplasmic reticulum (ER) stress sequentially occur in bronchopulmonary dysplasia (BPD), and all result in DNA damage. When DNA damage becomes irreparable, tumor suppressors increase, followed by apoptosis or senescence. Although cellular senescence contributes to wound healing, its persistence inhibits growth. Therefore, we hypothesized that cellular senescence contributes to BPD progression. Human autopsy lungs were obtained. Sprague-Dawley rat pups exposed to 95% oxygen between Postnatal Day 1 (P1) and P10 were used as the BPD phenotype. N -acetyl-lysyltyrosylcysteine-amide (KYC), tauroursodeoxycholic acid (TUDCA), and Foxo4 dri were administered intraperitoneally to mitigate myeloperoxidase oxidant generation, ER stress, and cellular senescence, respectively. Lungs were examined by histology, transcriptomics, and immunoblotting. Cellular senescence increased in rat and human BPD lungs, as evidenced by increased oxidative DNA damage, tumor suppressors, GL-13 stain, and inflammatory cytokines with decreased cell proliferation and lamin B expression. Cellular senescence-related transcripts in BPD rat lungs were enriched at P10 and P21. Single-cell RNA sequencing showed increased cellular senescence in several cell types, including type 2 alveolar cells. In addition, Foxo4-p53 binding increased in BPD rat lungs. Daily TUDCA or KYC, administered intraperitoneally, effectively decreased cellular senescence, improved alveolar complexity, and partially maintained the numbers of type 2 alveolar cells. Foxo4 dri administered at P4, P6, P8, and P10 led to outcomes similar to TUDCA and KYC. Our data suggest that cellular senescence plays an essential role in BPD after initial inducement by hyperoxia. Reducing myeloperoxidase toxic oxidant production, ER stress, and attenuating cellular senescence are potential therapeutic strategies for halting BPD progression.

Premature birth disrupts normal lung development and places infants at risk for bronchopulmonary dysplasia (BPD), a disease disrupting lung health throughout the life of an individual and that is increasing in incidence. The TGF-β superfamily has been implicated in BPD pathogenesis, however, what cell lineage it impacts remains unclear. We show that TGFbr2 is critical for alveolar epithelial (AT1) cell fate maintenance and function. Loss of TGFbr2 in AT1 cells during late lung development leads to AT1-AT2 cell reprogramming and altered pulmonary architecture, which persists into adulthood. Restriction of fetal lung stretch and associated AT1 cell spreading through a model of oligohydramnios enhances AT1-AT2 reprogramming. Transcriptomic and proteomic analyses reveal the necessity of TGFbr2 expression in AT1 cells for extracellular matrix production. Moreover, TGF-β signaling regulates integrin transcription to alter AT1 cell morphology, which further impacts ECM expression through changes in mechanotransduction. These data reveal the cell intrinsic necessity of TGF-β signaling in maintaining AT1 cell fate and reveal this cell lineage as a major orchestrator of the alveolar matrisome.

Bronchopulmonary dysplasia (BPD), also called chronic lung disease of immaturity, afflicts approximately one third of all extremely premature infants, causing lifelong lung damage. There is no effective treatment other than supportive care. Retinopathy of prematurity (ROP), which impairs vision irreversibly, is common in BPD, suggesting a related pathogenesis. However, specific mechanisms of BPD and ROP are not known. Herein, a neonatal mouse hyperoxic model of coincident BPD and retinopathy was used to screen for candidate mediators, which revealed that granulocyte colony-stimulating factor (G-CSF), also known as colony-stimulating factor 3, was up-regulated significantly in mouse lung lavage fluid and plasma at postnatal day 14 in response to hyperoxia. Preterm infants with more severe BPD had increased plasma G-CSF. G-CSF-deficient neonatal pups showed significantly reduced alveolar simplification, normalized alveolar and airway resistance, and normalized weight gain compared with wild-type pups after hyperoxic lung injury. This was associated with a marked reduction in the intensity, and activation state, of neutrophilic and monocytic inflammation and its attendant oxidative stress response, and protection of lung endothelial cells. G-CSF deficiency also provided partial protection against ROP. The findings in this study implicate G-CSF as a pathogenic mediator of BPD and ROP, and suggest the therapeutic utility of targeting G-CSF biology to treat these conditions., (Copyright © 2023 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.)

Bronchopulmonary dysplasia, a common complication of premature infants, is mainly characterized by blocked alveolarization. Proverbially, the injury of alveolar type II epithelial cells is regarded as the pathologic basis of occurrence and development of bronchopulmonary dysplasia. In the case of alveolar epithelial damage, alveolar type II epithelial cells can also differentiate to alveolar type I epithelial cells as progenitor cells. During bronchopulmonary dysplasia, the differentiation of alveolar type II epithelial cells becomes abnormal. Group 2 innate lymphoid cells can produce type 2 cytokines in response to a variety of stimuli, including the epithelial cytokines IL-25, IL-33, and thymic stromal lymphopoietin. Previous studies have shown that group 2 innate lymphoid cells can inhibit the alveolarization process of bronchopulmonary dysplasia by secreting IL-13. However, whether group 2 innate lymphoid cells can affect the differentiation of alveolar type II epithelial cells in the pathologic process of bronchopulmonary dysplasia remains unclear. In this study, we have shown that IL-13 secreted by group 2 innate lymphoid cells increased during bronchopulmonary dysplasia, which was related to the release of large amounts of IL-33 by impaired alveolar type II epithelial cells. This led to abnormal differentiation of alveolar type II epithelial cells, reduced differentiation to alveolar type I epithelial cells, and increased transdifferentiation to mesenchymal cells through the epithelial-mesenchymal transition. Taken together, our study provides a complementary understanding of the development of bronchopulmonary dysplasia and highlights a novel immune mechanism in the pathogenesis of bronchopulmonary dysplasia., Competing Interests: Conflict of interest statement. The authors have no fiancial conflicts of interest., (© The Author(s) 2023. Published by Oxford University Press on behalf of Society for Leukocyte Biology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Bronchopulmonary dysplasia (BPD) is a multifactorial disease with many associated co-morbidities, responsible for most cases of chronic lung disease in childhood. The use of imaging exams is pivotal for the clinical care of BPD and the identification of candidates for experimental therapies and a closer follow-up. Imaging is also useful to improve communication with the family and objectively evaluate the clinical evolution of the patient's disease. BPD imaging has been classically performed using only chest X-rays, but several modern techniques are currently available, such as lung ultrasound, thoracic tomography, magnetic resonance imaging and electrical impedance tomography. These techniques are more accurate and provide clinically meaningful information. We reviewed the most recent evidence published in the last five years regarding these techniques and analyzed their advantages and disadvantages., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Bronchopulmonary dysplasia (BPD) is a disease of prematurity related to the arrest of normal lung development. The objective of this study was to better understand how proteome modulation and cell-type shifts are noted in BPD pathology. Pediatric human donors aged 1-3 yr were classified based on history of prematurity and histopathology consistent with "healed" BPD (hBPD, n = 3) and "established" BPD (eBPD, n = 3) compared with respective full-term born ( n = 6) age-matched term controls. Proteins were quantified by tandem mass spectroscopy with selected Western blot validations. Multiplexed immunofluorescence (MxIF) microscopy was performed on lung sections to enumerate cell types. Protein abundances and MxIF cell frequencies were compared among groups using ANOVA. Cell type and ontology enrichment were performed using an in-house tool and/or EnrichR. Proteomics detected 5,746 unique proteins, 186 upregulated and 534 downregulated, in eBPD versus control with fewer proteins differentially abundant in hBPD as compared with age-matched term controls. Cell-type enrichment suggested a loss of alveolar type I, alveolar type II, endothelial/capillary, and lymphatics, and an increase in smooth muscle and fibroblasts consistent with MxIF. Histochemistry and Western analysis also supported predictions of upregulated ferroptosis in eBPD versus control. Finally, several extracellular matrix components mapping to angiogenesis signaling pathways were altered in eBPD. Despite clear parsing by protein abundance, comparative MxIF analysis confirms phenotypic variability in BPD. This work provides the first demonstration of tandem mass spectrometry and multiplexed molecular analysis of human lung tissue for critical elucidation of BPD trajectory-defining factors into early childhood. NEW & NOTEWORTHY We provide new insights into the natural history of bronchopulmonary dysplasia in donor human lungs after the neonatal intensive care unit hospitalization. This study provides new insights into how the proteome and histopathology of BPD changes in early childhood, uncovering novel pathways for future study.

Worldwide, the incidence of both preterm births and chronic lung disease of infancy, or bronchopulmonary dysplasia, remains high. Infants with bronchopulmonary dysplasia have larger and fewer alveoli, a lung pathology that can persist into adulthood. Although recent data point to a role for hypoxia-inducible factor-1α (HIF-1α) in mediating pulmonary angiogenesis and alveolarization, the cell-specific role of HIF-1α remains incompletely understood. Thus, we hypothesized that HIF-1α, in a distinct subset of mesenchymal cells, mediates postnatal alveolarization. To test the hypothesis, we generated mice with a cell-specific deletion of HIF-1α by crossing SM22α promoter-driven Cre mice with HIF-1α flox/flox mice (SM22α-HIF-1α -/- ), determined SM-22α-expressing cell identity using single-cell RNA sequencing, and interrogated samples from preterm infants. Deletion of HIF-1α in SM22α-expressing cells had no effect on lung structure at day 3 of life. However, at 8 days, there were fewer and larger alveoli, a difference that persisted into adulthood. Microvascular density, elastin organization, and peripheral branching of the lung vasculature were decreased in SM22α-HIF-1α -/- mice, compared with control mice. Single-cell RNA sequencing demonstrated that three mesenchymal cell subtypes express SM22α: myofibroblasts, airway smooth muscle cells, and vascular smooth muscle cells. Pulmonary vascular smooth muscle cells from SM22α-HIF-1α -/- mice had decreased angiopoietin-2 expression and, in coculture experiments, a diminished capacity to promote angiogenesis that was rescued by angiopoietin-2. Angiopoietin-2 expression in tracheal aspirates of preterm infants was inversely correlated with overall mechanical ventilation time, a marker of disease severity. We conclude that SM22α-specific HIF-1α expression drives peripheral angiogenesis and alveolarization in the lung, perhaps by promoting angiopoietin-2 expression.

We report the case of a preterm infant who died at 10 months of age with severe bronchopulmonary dysplasia (sBPD) with refractory pulmonary hypertension and respiratory failure who had striking histologic features compatible with the diagnosis of alveolar capillary dysplasia with misalignment of pulmonary veins (ACDMPV) but without genetic confirmation of the diagnosis. We further demonstrate dramatic reductions in lung FOXF1 and TMEM100 content in sBPD, suggesting common mechanistic links between ACDMPV and sBPD with impaired FOXF1 signaling., (© 2023 Wiley Periodicals LLC.)

Bronchopulmonary dysplasia (BPD) is a chronic lung disease commonly seen in preterm infants, and is triggered by infection, mechanical ventilation, and oxygen toxicity. Among other problems, lifelong limitations in lung function and impaired psychomotor development may result. Despite major advances in understanding the disease pathologies, successful interventions are still limited to only a few drug therapies with a restricted therapeutic benefit, and which sometimes have significant side effects. As a more promising therapeutic option, mesenchymal stem cells (MSCs) have been in focus for several years due to their anti-inflammatory effects and their secretion of growth and development promoting factors. Preclinical studies provide evidence in that MSCs have the potential to contribute to the repair of lung injuries. This review provides an overview of MSCs, and other stem/progenitor cells present in the lung, their identifying characteristics, and their differentiation potential, including cytokine/growth factor involvement. Furthermore, animal studies and clinical trials using stem cells or their secretome are reviewed. To bring MSC-based therapeutic options further to clinical use, standardized protocols are needed, and upcoming side effects must be critically evaluated. To fill these gaps of knowledge, the MSCs' behavior and the effects of their secretome have to be examined in more (pre-) clinical studies, from which only few have been designed to date.