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Abstract Background Bronchopulmonary dysplasia (BPD) is a chronic lung condition of premature neonates, yet without an established pharmacological treatment. The BPD rabbit model exposed to 95% oxygen has been used in recent years for drug testing. However, the toxicity of the strong hyperoxic hit precludes a longer-term follow-up due to high mortality after the first week of life. This study aimed to extend the preterm rabbit model to postnatal day (PND) 14 to mimic the evolving phase of BPD and enable the investigation of therapeutic interventions at later and more relevant time points. Methods Preterm rabbit pups delivered on the 28th day of gestation were either exposed to room air or different degrees of hyperoxia (50% and 70% O2) for 14 days. Single (immediately after birth) or double (at birth and at PND5) intratracheal lipopolysaccharide (LPS) administrations were also tested in combination with 50% O2. Age-matched rabbits delivered vaginally at term were used as controls. Survival, weight gain, lung function, pulmonary artery micro-ultrasound Doppler analysis, lung histology (alveolarization, lung injury score, and design-based stereology), and longitudinal micro-CT imaging were used to compare the outcomes at PND14. Results Premature birth itself, without any other BPD hit, was associated with lung function deficits, delayed lung development, and cardiovascular abnormalities. The BPD-like lung phenotype was enhanced by 70% O2 but not by 50% O2 hyperoxia. Intratracheal LPS delivered immediately after birth was associated with significantly higher lung injury scores at PND14 and increased tissue damping, a marker of parenchymal air resistance. Conclusion Several strategies are feasible to extend the preterm rabbit model of BPD to PND14. Preterm birth at the saccular phase itself, even in the absence of other postnatal BPD hits, was associated with lung function deficits, delayed lung development, and cardiovascular abnormalities compared with age-matched term rabbit pups. Enhanced BPD-like phenotypes can be further achieved by continued exposure to moderate hyperoxia (70% O2) and the intratracheal administration of LPS.

Abstract Background Drug discovery strongly relies on the thorough evaluation of preclinical experimental studies. In the context of pulmonary fibrosis, micro-computed tomography (µCT) and histology are well-established and complementary tools for assessing, in animal models, disease progression and response to treatment. µCT offers dynamic, real-time insights into disease evolution and the effects of therapies, while histology provides a detailed microscopic examination of lung tissue. Here, we present a semi-automatic pipeline that integrates these readouts by matching individual µCT volume slices with the corresponding histological sections, effectively linking densitometric data with Ashcroft score measurements. Methods The tool first geometrically aligns the vertical axis of the µCT volume with the cutting plane used to prepare the histological sample. Then, focusing on the left lung, it computes the affine registration that identifies the µCT coronal slice that best matches the histological section. Finally, quantitative µCT imaging parameters are extracted from the selected slice. In a proof-of-concept test, the tool was applied to a bleomycin-induced mouse model of lung fibrosis. Results The proposed approach demonstrated high accuracy and time effectiveness in matching µCT and histological sections minimizing manual intervention, with an overall success rate of 95%, and reduced time required to align µCT and histological data from 40 to 5 min. Significant correlations were found between quantitative data derived from µCT and histology data. Conclusions The precise combination of microscopic ex-vivo information with 3D in-vivo data enhances the accuracy and representativeness of tissue analysis and provides a structural context for omic studies, serving as the foundation for a multi-layer platform. By facilitating a detailed and objective view of disease progression and treatment response, this approach has the potential to accelerate the development of effective therapies for lung fibrosis.

Abstract Background Idiopathic Pulmonary Fibrosis (IPF), prevalently affecting individuals over 60 years of age, has been mainly studied in young mouse models. The limited efficacy of current treatments underscores the need for animal models that better mimic an aged patient population. We addressed this by inducing pulmonary fibrosis in aged mice, using longitudinal micro-CT imaging as primary readout, with special attention to animal welfare. Methods A double bleomycin dose was administered to 18–24 months-old male C57Bl/6j mice to induce pulmonary fibrosis. Bleomycin dosage was reduced to as low as 75% compared to that commonly administered to young (8–12 weeks-old) mice, resulting in long-term lung fibrosis without mortality, complying with animal welfare guidelines. After fibrosis induction, animals received Nintedanib once-daily for two weeks and longitudinally monitored by micro-CT, which provided structural and functional biomarkers, followed by post-mortem histological analysis as terminal endpoint. Results Compared to young mice, aged animals displayed increased volume, reduced tissue density and function, and marked inflammation. This increased vulnerability imposed a bleomycin dosage reduction to the lowest tested level (2.5 µg/mouse), inducing a milder, yet persistent, fibrosis, while preserving animal welfare. Nintedanib treatment reduced fibrotic lesions and improved pulmonary function. Conclusions Our data identify a downsized bleomycin treatment that allows to achieve the best trade-off between fibrosis induction and animal welfare, a requirement for antifibrotic drug testing in aged lungs. Nintedanib displayed significant efficacy in this lower-severity disease model, suggesting potential patient stratification strategies. Lung pathology was quantitatively assessed by micro-CT, pointing to the value of longitudinal endpoints in clinical trials.

Abstract Micro-computed tomography (µCT)-based imaging plays a key role in monitoring disease progression and response to candidate drugs in various animal models of human disease, but manual image processing is still highly time-consuming and prone to operator bias. Focusing on an established mouse model of bleomycin (BLM)-induced lung fibrosis we document, here, the ability of a fully automated deep-learning (DL)-based model to improve and speed-up lung segmentation and the precise measurement of morphological and functional biomarkers in both the whole lung and in individual lobes. µCT-DL whose results were overall highly consistent with those of more conventional, especially histological, analyses, allowed to cut down by approximately 45-fold the time required to analyze the entire dataset and to longitudinally follow fibrosis evolution and response to the human-use-approved drug Nintedanib, using both inspiratory and expiratory μCT. Particularly significant advantages of this µCT-DL approach, are: (i) its reduced experimental variability, due to the fact that each animal acts as its own control and the measured, operator bias-free biomarkers can be quantitatively compared across experiments; (ii) its ability to monitor longitudinally the spatial distribution of fibrotic lesions, thus eliminating potential confounding effects associated with the more severe fibrosis observed in the apical region of the left lung and the compensatory effects taking place in the right lung; (iii) the animal sparing afforded by its non-invasive nature and high reliability; and (iv) the fact that it can be integrated into different drug discovery pipelines with a substantial increase in both the speed and robustness of the evaluation of new candidate drugs. The µCT-DL approach thus lends itself as a powerful new tool for the precision preclinical monitoring of BLM-induced lung fibrosis and other disease models as well. Its ease of operation and use of standard imaging instrumentation make it easily transferable to other laboratories and to other experimental settings, including clinical diagnostic applications.

Abstract Background Premature birth, perinatal inflammation, and life-saving therapies such as postnatal oxygen and mechanical ventilation are strongly associated with the development of bronchopulmonary dysplasia (BPD); these risk factors, alone or combined, cause lung inflammation and alter programmed molecular patterns of normal lung development. The current knowledge on the molecular regulation of lung development mainly derives from mechanistic studies conducted in newborn rodents exposed to postnatal hyperoxia, which have been proven useful but have some limitations. Methods Here, we used the rabbit model of BPD as a cost-effective alternative model that mirrors human lung development and, in addition, enables investigating the impact of premature birth per se on the pathophysiology of BPD without further perinatal insults (e.g., hyperoxia, LPS-induced inflammation). First, we characterized the rabbit’s normal lung development along the distinct stages (i.e., pseudoglandular, canalicular, saccular, and alveolar phases) using histological, transcriptomic and proteomic analyses. Then, the impact of premature birth was investigated, comparing the sequential transcriptomic profiles of preterm rabbits obtained at different time intervals during their first week of postnatal life with those from age-matched term pups. Results Histological findings showed stage-specific morphological features of the developing rabbit’s lung and validated the selected time intervals for the transcriptomic profiling. Cell cycle and embryo development, oxidative phosphorylation, and WNT signaling, among others, showed high gene expression in the pseudoglandular phase. Autophagy, epithelial morphogenesis, response to transforming growth factor β, angiogenesis, epithelium/endothelial cells development, and epithelium/endothelial cells migration pathways appeared upregulated from the 28th day of gestation (early saccular phase), which represents the starting point of the premature rabbit model. Premature birth caused a significant dysregulation of the inflammatory response. TNF-responsive, NF-κB regulated genes were significantly upregulated at premature delivery and triggered downstream inflammatory pathways such as leukocyte activation and cytokine signaling, which persisted upregulated during the first week of life. Preterm birth also dysregulated relevant pathways for normal lung development, such as blood vessel morphogenesis and epithelial-mesenchymal transition. Conclusion These findings establish the 28-day gestation premature rabbit as a suitable model for mechanistic and pharmacological studies in the context of BPD.

Abstract Background Tanimilast is a novel and selective inhaled inhibitor of phosphodiesterase-4 in advanced clinical development for chronic obstructive pulmonary disease (COPD). Tanimilast is known to exert prominent anti-inflammatory activity when tested in preclinical experimental models as well as in human clinical studies. Recently, we have demonstrated that it also finely tunes, rather than suppressing, the cytokine network secreted by activated dendritic cells (DCs). This study was designed to characterize the effects of tanimilast on T-cell polarizing properties of DCs and to investigate additional functional and phenotypical features induced by tanimilast. Methods DCs at day 6 of culture were stimulated with LPS in the presence or absence of tanimilast or the control drug budesonide. After 24 h, DCs were analyzed for the expression of surface markers of maturation and activation by flow cytometry and cocultured with T cells to investigate cell proliferation and activation/polarization. The regulation of type 2-skewing mediators was investigated by real-time PCR in DCs and compared to results obtained in vivo in a randomized placebo-controlled trial on COPD patients treated with tanimilast. Results Our results show that both tanimilast and budesonide reduced the production of the immunostimulatory cytokine IFN-γ by CD4+ T cells. However, the two drugs acted at different levels since budesonide mainly blocked T cell proliferation, while tanimilast skewed T cells towards a Th2 phenotype without affecting cell proliferation. In addition, only DCs matured in the presence of tanimilast displayed increased CD86/CD80 ratio and CD141 expression, which correlated with Th2 T cell induction and dead cell uptake respectively. These cells also upregulated cAMP-dependent immunosuppressive molecules such as IDO1, TSP1, VEGF-A and Amphiregulin. Notably, the translational value of these data was confirmed by the finding that these same genes were upregulated also in sputum cells of COPD patients treated with tanimilast as add-on to inhaled glucocorticoids and bronchodilators. Conclusion Taken together, these findings demonstrate distinct immunomodulatory properties of tanimilast associated with a type 2 endotype and CD141 upregulation in DCs and provide a mechanistic rationale for the administration of tanimilast on top of inhaled corticosteroids.