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Cytokeratin 15 (CK15) has been described as a stem cell marker in human organs and its expression is seen in breast tissue. CK15 expression is associated with aggressive features in endometrial and oesophageal cancers, but data on the breast are lacking. This study aims to investigate the clinicopathological associations and prognostic significance of CK15 in breast carcinomas. A multi-institute cohort of breast carcinomas were retrieved. Clinicopathological and outcome data were obtained and compared with immunohistochemical expression CK15 and a panel of biomarkers. In total, 1,476 cases were included, with an expression rate of 3.5%, preferentially expressed in luminal subtypes (p=0.024), with luminal B carcinomas being the highest (4.7%), as opposed to basal-like (1%) and HER2-overexpressed carcinomas (0%). Except for nodal stage (p=0.013) and nodal metastasis (p=0.048), oestrogen (p=0.035) and progesterone receptor (p=0.001) positivity, there were no associations with other clinicopathological parameters. A trend was observed with shorter breast cancer specific survival (BCSS) in CK15-positive luminal B carcinomas (p=0.062). On further subgroup multivariate analysis of luminal B HER2-negative carcinomas, CK15 expression exhibited robust correlation with shorter BCSS (HR=9.004, p=0.001) and disease-free survival (HR=7.085, p<0.001). Restricted to luminal breast carcinomas, specifically luminal B HER2-negative, CK15 is demonstrated to be a robust independent predictor of higher risk of recurrence and shorter survival, with potential as a clinical prognostic marker and an exclusive stem cell marker for this subgroup of carcinomas., (Copyright © 2024 Royal College of Pathologists of Australasia. Published by Elsevier B.V. All rights reserved.)

Objective: Keratin 15 (KRT15) exhibits inconsistent prognostic roles in different cancers, and its prognostic value in early cervical cancer patients who receive tumor resection remains unknown. This study aimed to assess the relationship of KRT15 expression with prognosis in these patients., Methods: Totally, 147 early cervical cancer patients who received tumor resection were reviewed in this retrospective study. KRT15 was detected in formalin-fixed paraffin-embedded tumor tissue by immunohistochemistry (IHC). KRT15 IHC scores were computed by multiplying the percentage of positively stained cells (scored as 0-4) and corresponding staining intensity (scored as 0-3), ranging from 0 to 12., Results: Elevated KRT15 IHC score was linked with moderate to well differentiation (P = 0.005), tumor size ≤ 4 cm (P = 0.017), and International Federation of Gynecology and Obstetrics (FIGO) stage Ia/Ib (P < 0.001). KRT15 IHC score was inversely associated with adjuvant radiotherapy (P = 0.025) and adjuvant chemotherapy (P = 0.016). KRT15 IHC score ≥ 1 was linked with increased disease-free survival (DFS) (P = 0.003) and overall survival (OS) (P = 0.049). Meanwhile, KRT15 IHC score ≥ 1 independently predicted increased DFS (hazard ratio = 0.213, P = 0.017), but not OS (P > 0.05). KRT15 IHC score ≥ 3 and KRT15 IHC score ≥ 6 could not predict DFS or OS (all P > 0.05). By subgroup analyses, KRT15 IHC score ≥ 1 forecasted favorable DFS in patients with age > 45 years, human papillomavirus-positive, squamous carcinoma, and tumor size ≤ 4 cm (all P < 0.05). KRT15 IHC score ≥ 1 and KRT15 IHC score ≥ 3 predicted ascended DFS in patients without adjuvant radiotherapy or adjuvant chemotherapy (all P < 0.05)., Conclusion: High KRT15 expression reflects favorable tumor features and longer survival in early cervical cancer patients who receive tumor resection., (© 2024. The Author(s), under exclusive licence to Royal Academy of Medicine in Ireland.)

Lichen planopilaris (LPP) and frontal fibrosing alopecia (FFA) are primary cicatricial alopecia that cause a major impact on quality of life due to irreversible hair loss and symptoms as itching, burning and pain. They are characterized by permanent loss of hair follicle stem cells (HFSCs) by pathomechanisms still poorly understood, resulting in poor efficacy of currently available treatments. Caveolae are flask-shaped lipid rafts invaginated within the plasma membrane of multiple cell types. Although their role in the HF physiology and pathophysiology is relatively unknown, we have previously demonstrated that the primary structural component of caveolae (caveolin-1 or Cav1) is upregulated in FFA. Thus, we propose to investigate the expression and localization of caveolae-associated structural proteins (Cav1, Cav2, and Cavin-1) and HFSCs (identified by K15) in both LPP and FFA. We analyzed 4 patients with LPP biopsied in affected and non-affected (NA) scalp, 4 patients with FFA biopsied in affected scalp and 4 healthy controls. Affected scalp of LPP and FFA demonstrated increased levels of Cav1 and Cavin-1 compared with HC and LPP-NA. Moreover, Cav1, Cav2 and Cavin1 all exhibit high colocalization with K15 and their expression appears to be negatively correlated, supporting the hypothesis that these proteins are important players in LPP/FFA and may serve as therapeutic targets in future treatments., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The vomeronasal organ (VNO) is a part of the accessory olfactory system, which detects pheromones and chemical factors that trigger a spectrum of sexual and social behaviors. The vomeronasal epithelium (VNE) shares several features with the epithelium of the main olfactory epithelium (MOE). However, it is a distinct neuroepithelium populated by chemosensory neurons that differ from the olfactory sensory neurons in cellular structure, receptor expression, and connectivity. The vomeronasal organ of rodents comprises a sensory epithelium (SE) and a thin non-sensory epithelium (NSE) that morphologically resembles the respiratory epithelium. Sox2-positive cells have been previously identified as the stem cell population that gives rise to neuronal progenitors in MOE and VNE. In addition, the MOE also comprises p63 positive horizontal basal cells, a second pool of quiescent stem cells that become active in response to injury. Immunolabeling against the transcription factor p63, Keratin-5 (Krt5), Krt14, NrCAM, and Krt5Cre tracing experiments highlighted the existence of horizontal basal cells distributed along the basal lamina of SE of the VNO. Single cell sequencing and genetic lineage tracing suggest that the vomeronasal horizontal basal cells arise from basal progenitors at the boundary between the SE and NSE proximal to the marginal zones. Moreover, our experiments revealed that the NSE of rodents is, like the respiratory epithelium, a stratified epithelium where the p63/Krt5+ basal progenitor cells self-replicate and give rise to the apical columnar cells facing the lumen of the VNO., (© 2024 Wiley Periodicals LLC.)

Background: Chronic obstructive pulmonary disease (COPD), a chronic inflammatory lung disease, is a leading cause of morbidity and mortality worldwide. Prolonged cigarette smoking (CS) that causes irreversible airway remodeling and significantly reduces lung function is a major risk factor for COPD. Keratin15 + (Krt15 + ) cells with the potential of self-renewal and differentiation properties have been implicated in the maintenance, proliferation, and differentiation of airway basal cells; however, the role of Krt15 in COPD is not clear., Methods: Krt15 knockout (Krt15 -/- ) and wild-type (WT) mice of C57BL/6 background were exposed to CS for six months to establish COPD models. Krt15-CrePGR;Rosa26-LSL-tdTomato mice were used to trace the fate of the Krt15 + cells. Hematoxylin and eosin (H&E) and Masson stainings were performed to assess histopathology and fibrosis, respectively. Furthermore, lentivirus-delivered short hairpin RNA (shRNA) was used to knock down KRT15 in human bronchial epithelial (HBE) cells stimulated with cigarette smoke extract (CSE). The protein expression was assessed using western blot, immunohistochemistry, and enzyme-linked immunosorbent assay., Results: Krt15 -/- CS mice developed severe inflammatory cell infiltration, airway remodeling, and emphysema. Moreover, Krt15 knockout aggravated CS-induced secretion of matrix metalloproteinase-9 (MMP-9) and epithelial-mesenchymal transformation (EMT), which was reversed by SB-3CT, an MMP-9 inhibitor. Consistent with this finding, KRT15 knockdown promoted MMP-9 expression and EMT progression in vitro. Furthermore, Krt15 + cells gradually increased in the bronchial epithelial cells and were transformed into alveolar type II (AT2) cells., Conclusion: Krt15 regulates the EMT process by promoting MMP-9 expression and protects the lung tissue from CS-induced injury, inflammatory infiltration, and apoptosis. Furthermore, Krt15 + cells transformed into AT2 cells to protect alveoli. These results suggest Krt15 as a potential therapeutic target for COPD., (© 2023. The Author(s).)

Keratin 15 (KRT15) overexpression links with tumor initiation, metastasis, and poor survival in several solid carcinomas. While its clinical relevance is scarcely reported in endometrial cancer (EC). Therefore, the current study aimed to investigate the abnormal expression of KRT15 and its correlation with clinical characteristics, survival in EC patients. Totally, 135 surgical EC patients were enrolled. KRT15 protein expression in formalin-fixed and paraffin-embedded tumor and adjuvant tissues was detected by immunohistochemical staining; meanwhile, KRT15 mRNA expression in fresh-frozen tumor and adjacent tissues was detected by reverse transcription-quantitative polymerase chain reaction. KRT15 protein and mRNA expressions were higher in tumor tissue compared with adjacent tissue (both P < .001). Elevated KRT15 protein expression was correlated with the occurrence of lymphovascular invasion (P = .010) and more advanced International Federation of Gynecology and Obstetrics stage (P = .018); meanwhile, elevated KRT15 mRNA expression was linked with more advanced International Federation of Gynecology and Obstetrics stage (P = .038) and marginally associated with the occurrence of stromal cervical invasion (P = .052). Besides, KRT15 protein and mRNA expressions were not correlated with other clinical features (all P > .05). KRT15 protein high was marginally correlated with poor accumulating disease-free survival (DFS) (P = .091) and overall survival (OS) (P = .059); meanwhile, the correlation of KRT15 mRNA expression with accumulating DFS (P = .212) and OS (P = .092) was even weaker. However, multivariate Cox's regressions showed that tumor KRT15 protein (high vs low) was independently correlated with poor DFS (P = .045) and OS (P = .043). KRT15 is abnormally increased in EC tissue, meanwhile, its upregulation links to the occurrence of lymphovascular invasion, stromal cervical invasion, and poor prognosis in EC patients., Competing Interests: The authors have no funding and conflicts of interest to disclose., (Copyright © 2022 the Author(s). Published by Wolters Kluwer Health, Inc.)

KRT15 has been reported to act as an oncogene in colorectal cancer. However, whether KRT15 promotes colorectal cancer migration and invasion remain unclear. In this study, western blot and qRT-PCR assay were used to determine the expression of KRT15 in colorectal cancer cells. Wound-healing and transwell migration assay were performed to assess the migration of colorectal cancer cells. Matrigel transwell invasion assay was employed to examine the invasion of colorectal cancer cells. We found that KRT15 was highly expressed in colorectal cancer cells. Ectopic expression of KRT15 dramatically promoted colorectal cancer cell migration and invasion. Conversely, silencing KRT15 remarkably suppressed the migration and invasion of colorectal cancer cells. Importantly, we found that MMP-7 was crucial for KRT15-induced migration and invasion of colorectal cancer cells. Knockdown of MMP-7 significantly diminished the migration and invasion induced by KRT15; overexpression of MMP-7 almost completely rescued the inhibitory effects of KRT15 shRNAs on colorectal cancer cell migration and invasion. In addition, by gain- and loss-of function, we confirmed that β-catenin was responsible for the increased expression of MMP-7 induced by KRT15 colorectal cancer cell lines. In conclusion, KRT15 promotes migration and invasion of colorectal cancer cell at least partly through β-catenin/MMP7 signaling pathway, suggesting KRT15 is a potential therapeutic target for patients with metastatic colorectal cancer., (© 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Manipulation of adrenergic signaling has been shown experimentally and clinically to affect hair follicle growth. In this study, we provide direct evidence that canonical cAMP/CRE-binding protein signaling through adrenergic receptors can regulate hair follicle stem cell (HFSC) activation and hair cycle. We found that CRE-binding protein activation is regulated through the hair cycle and coincides with HFSC activation. Both isoproterenol and procaterol, agonists of adrenergic receptors, show the capacity to activate the hair cycle in mice. Furthermore, deletion of ADRB2 receptor, which is thought to mediate sympathetic nervous system regulation of HFSCs, was sufficient to block HFSC activation. Downstream, stimulation of adenylyl cyclase with forskolin or inhibition of phosphodiesterase to increase cAMP accumulation or direct application of cAMP was each sufficient to promote HFSC activation and accelerate initiation of hair cycle. Genetic induction of a Designer Receptors Exclusively Activated by Designer Drug allele showed that G-protein coupled receptor/GαS stimulation, specifically in HFSCs, promoted the activation of the hair cycle. Finally, we provide evidence that G-protein coupled receptor/CRE-binding protein signaling can potentially act on HFSCs by promoting glycolytic metabolism, which was previously shown to stimulate HFSC activation. Together, these data provide mechanistic insights into the role of sympathetic innervation on HFSC function., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Vertebrate organs are arranged in a stereotypic, species-specific position along the animal body plan. Substantial morphological variation exists between related species, especially so in the vastly diversified teleost clade. It is still unclear how tissues, organs and systems can accommodate such diverse scaffolds. Here, we use the distinctive arrangement of neuromasts in the posterior lateral line (pLL) system of medaka fish to address the tissue-interactions defining a pattern. We show that patterning in this peripheral nervous system is established by autonomous organ precursors independent of neuronal wiring. In addition, we target the keratin 15 gene to generate stuck-in-the-midline (siml) mutants, which display epithelial lesions and a disrupted pLL patterning. By using siml/wt chimeras, we determine that the aberrant siml pLL pattern depends on the mutant epithelium, since a wild type epithelium can rescue the siml phenotype. Inducing epithelial lesions by 2-photon laser ablation during pLL morphogenesis phenocopies siml genetic mutants and reveals that epithelial integrity defines the final position of the embryonic pLL neuromasts. Our results using the medaka pLL disentangle intrinsic from extrinsic properties during the establishment of a sensory system. We speculate that intrinsic programs guarantee proper organ morphogenesis, while instructive interactions from surrounding tissues facilitates the accommodation of sensory organs to the diverse body plans found among teleosts., Competing Interests: Declaration of competing interest The authors declare that they have no competing interests., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Abstract: Pseudocarcinomatous desmoplastic trichoepithelioma (PDTE) features verrucous squamous epidermal hyperplasia with a jagged undersurface overlying cords of follicular germinative cells in a fibrotic stroma. To date, only 5 cases have been reported. We identified 7 new PDTEs from 2 institutions and reviewed their clinical manifestations and immunohistochemical profile. The median age was 14 years (range 8-34 years). New findings included vacuolization of the basal layer of the pseudocarcinomatous surface epithelium, and the frequent presence of singly distributed sebocytes within the cords of basaloid cells. The immunohistochemical profile resembles desmoplastic trichoepithelioma, with expression of TDAG51, CK15, and Ber-Ep4. Colonizing CK20+ Merkel cells were present in all cases. PDTE needs to be differentiated from malignant neoplasms such as squamous cell carcinoma, morphoeic basal cell carcinoma, and microcystic adnexal carcinoma. Recognizing the features of this sclerosing folliculosebaceous neoplasm facilitates accurate diagnosis and avoids overtreatment., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Gene knockout of the master regulator of mitochondrial fission, Drp1, prevents neoplastic transformation. Also, mitochondrial fission and its opposing process of mitochondrial fusion are emerging as crucial regulators of stemness. Intriguingly, stem/progenitor cells maintaining repressed mitochondrial fission are primed for self-renewal and proliferation. Using our newly derived carcinogen transformed human cell model, we demonstrate that fine-tuned Drp1 repression primes a slow cycling 'stem/progenitor-like state', which is characterized by small networks of fused mitochondria and a gene-expression profile with elevated functional stem/progenitor markers (Krt15, Sox2 etc) and their regulators (Cyclin E). Fine tuning Drp1 protein by reducing its activating phosphorylation sustains the neoplastic stem/progenitor cell markers. Whereas, fine-tuned reduction of Drp1 protein maintains the characteristic mitochondrial shape and gene-expression of the primed 'stem/progenitor-like state' to accelerate neoplastic transformation, and more complete reduction of Drp1 protein prevents it. Therefore, our data highlights a 'goldilocks' level of Drp1 repression supporting stem/progenitor state dependent neoplastic transformation., Competing Interests: BS, DP, MB, AH, SG, SL, GS, AG, AM, KM No competing interests declared, (© 2021, Spurlock et al.)

Background: Electrostimulation (ES) therapy for wound healing is limited in clinical use due to barriers such as cumbersome equipment and intermittent delivery of therapy., Methods: We adapted a human skin xenograft model that can be used to directly examine the nanogenerator-driven ES (NG-ES) effects on human skin in vivo-an essential translational step toward clinical application of the NG-ES technique for wound healing., Results: We show that NG-ES leads to rapid wound closure with complete restoration of normal skin architecture within 7 days compared to more than 30 days in the literature. NG-ES accelerates the inflammatory phase of wound healing with more rapid resolution of neutrophils and macrophages and enhances wound bed perfusion with more robust neovascularization., Conclusion: Our results support the translational evaluation and optimization of the NG-ES technology to deliver convenient, efficient wound healing therapy for use in human wounds., (© 2021. The Author(s).)

The cornea is an anterior eye structure specialized for vision. The corneal endothelium and stroma are derived from the periocular mesenchyme (POM), which originates from neural crest cells (NCCs), while the stratified corneal epithelium develops from the surface ectoderm. Activating protein-2β (AP-2β) is highly expressed in the POM and important for anterior segment development. Using a mouse model in which AP-2β is conditionally deleted in the NCCs (AP-2β NCC KO), we investigated resulting corneal epithelial abnormalities. Through PAS and IHC staining, we observed structural and phenotypic changes to the epithelium associated with AP-2β deletion. In addition to failure of the mutant epithelium to stratify, we also observed that Keratin-12, a marker of the differentiated epithelium, was absent, and Keratin-15, a limbal and conjunctival marker, was expanded across the central epithelium. Transcription factors PAX6 and P63 were not observed to be differentially expressed between WT and mutant. However, growth factor BMP4 was suppressed in the mutant epithelium. Given the non-NCC origin of the epithelium, we hypothesize that the abnormalities in the AP-2β NCC KO mouse result from changes to regulatory signaling from the POM-derived stroma. Our findings suggest that stromal pathways such as Wnt/β-Catenin signaling may regulate BMP4 expression, which influences cell fate and stratification.

The upper gastrointestinal tract, consisting of the esophagus, stomach, and duodenum, controls food transport, digestion, nutrient uptake, and hormone production. By single-cell analysis of healthy epithelia of these human organs, we molecularly define their distinct cell types. We identify a quiescent COL17A1 high KRT15 high stem/progenitor cell population in the most basal cell layer of the esophagus and detect substantial gene expression differences between identical cell types of the human and mouse stomach. Selective expression of BEST4, CFTR, guanylin, and uroguanylin identifies a rare duodenal cell type, referred to as BCHE cell, which likely mediates high-volume fluid secretion because of continual activation of the CFTR channel by guanylin/uroguanylin-mediated autocrine signaling. Serotonin-producing enterochromaffin cells in the antral stomach significantly differ in gene expression from duodenal enterochromaffin cells. We, furthermore, discover that the histamine-producing enterochromaffin-like cells in the oxyntic stomach express the luteinizing hormone, yet another member of the enteroendocrine hormone family., Competing Interests: Declaration of interests H.C. is an inventor on several patents related to organoid technology; his full disclosure is given at https://www.uu.nl/staff/JCClevers/., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Lung cancer is the leading cause of cancer-related deaths, and squamous cell carcinoma (SCC) is one of the most common types of lung cancer. Chemoprevention of lung cancer has gained increasing popularity as an alternative to treatment in reducing the burden of lung cancer. Pterostilbene (PS) may be developed as a chemopreventive agent due to its pharmacological activities, such as anti-proliferative, anti-inflammatory and antioxidant properties. This study aimed to investigate the effect of PS on the development of lung SCC in the mouse model., Methods: A total of 24 seven-week-old female Balb/C mice were randomly categorised into four groups, including two control groups comprising the N-nitroso-trischloroethylurea (NTCU)-induced lung SCC and vehicle control (VC) groups and two treatment groups comprising the 10mg/kg PS (PS10) and 50mg/kg PS (PS50) groups. All lung organs were harvested at week 26 for histopathological analysis., Results: All PS treatment groups showed chemopreventive activity by inhibiting the progression of lung SCC formation with PS10, resulting in mild hyperplasia, and PS50 was completely reversed in the normal bronchial epithelium layer compared with the VC group. PS treatment also reduced the expression of cytokeratin 5/6 in the bronchial epithelium layer. Both PS10 and PS50 significantly reduced the epithelium thickness compared to the NTCU group (p<0.05). PS is a potential chemopreventive agent against lung SCC growth by suppressing the progression of pre-malignant lesions and reducing the thickness of the bronchial epithelium., Conclusions: The underlying molecular mechanisms of PS in lung SCC should be further studied.

Squamous cell carcinoma (SCC) is the second commonest type of skin cancer, and SCCs make up about 90% of head and neck cancers (HNSCCs). HNSCCs harbor two frequent molecular alterations, namely, gain-of-function alterations of phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha ( PIK3CA) and loss-of-function mutations of tumor protein p53 ( TP53 ). However, it remains poorly understood whether HNSCCs harboring different genetic alterations exhibit differential immune tumor microenvironments (TME). It also remains unknown whether PIK3CA hyperactivation and TP53 deletion can lead to SCC development spontaneously. Here, we analyzed the Cancer Genome Atlas (TCGA) datasets of HNSCCs and found that patients with both PIK3CA and TP53 alterations exhibited worse survival, significantly lower CD8 tumor infiltrating lymphocytes (TILs) and higher M0 macrophages than other controls. To better model human tumorigenesis, we deleted TP53 and constitutively activated PIK3CA in mouse keratin-15-expressing stem cells, which leads to the spontaneous development of multilineage tumors including SCCs, termed Keratin-15-p53-PIK3CA (KPPA) tumors. KPPA tumors were heavily infiltrated with myeloid-derived suppressor cells (MDSCs), with a drastically increased ratio of polymorphonuclear-MDSC (PMN-MDSC) versus monocytic-MDSC (M-MDSC). CD8 TILs expressed more PD-1 and reduced their polyfunctionality. Overall, we established a genetic model to mimic human HNSCC pathogenesis, manifested with an immunosuppressive TME, which may help further elucidate immune evasion mechanisms and develop more effective immunotherapies for HNSCCs.

Aim: To investigate the expression and prognostic value of KRT 15 in esophageal carcinoma. Materials & methods: The expression levels of KRT 15 were measured in 128 cases of esophageal carcinoma and matched adjacent normal tissues by immunohistochemistry and Western blot assays. Results & conclusion: Western blot analysis shown the expression levels of KRT 15 in esophageal carcinoma were significantly higher compared with those in matched adjacent normal tissues (p < 0.001). immunohistochemistry result shown the high-expression rate of KRT 15 in esophageal carcinoma were 56.3%, which was significantly higher than those in normal tissues (35.9%; p = 0.002). KRT 15 high-expression correlated with T stage, lymph node metastasis, tumor node metastasis stage and prognosis (p < 0.05). These data indicate KRT 15 as a prognostic biomarker is highly expressed in esophageal carcinoma.

Limbal stem cells (LSCs), a subpopulation of limbal epithelial basal cells, are crucial to the homeostasis and wound healing of corneal epithelium. The identification and isolation of LSCs remains a challenge due to lack of specific LSCs biomarkers. In this study, Haematoxylin-eosin (HE), 4', 6-diamidino-2-phenylindole (DAPI), and immunohistochemistry (IHC) stains were performed on the pre- and post-natal limbus tissues of mice which has the advantage of more controllable in term of sampling age relative to human origin. By morphological analysis, we supported that there is an absence of the Palisades of Vogt (POV) in the mouse. The development of prenatal and neonatal cornea was dominated by its stroma, whereas after eyelids opened at P14, the corneal epithelial cells (CECs) quickly go stratification in response to the liquid-air interface. Based on IHC staining, we found that the expression of LSCs putative biomarkers in limbal epithelial basal cells appeared in chronological order as follows: Vim = p63 > CK14 > CK15 (where = represents same time; > represents earlier), and in corneal epithelial basal cells were weakened in chronological order as follows: Vim > p63 > CK15 > CK14, which might also represent the stemness degree. Furthermore, the dynamic spatial expression of the examined LSCs putative biomarkers during mouse development also implied a temporal restriction. The expression of Vim in epithelial cells of mouse ocular surface occurred during E12-E19 only. The expression of CK15 was completely undetectable in CECs after P14, whereas the others putative molecular markers of LSCs, such as p63 and CK14, still remained weak expression, suggesting that CK15 was suitable to serve as the mouse LSCs biomarkers after P14. In this study, our data demonstrated the dynamic spatiotemporal expression pattern of LSCs putative biomarkers in mouse was age-related and revealed the time spectrum of the expression of LSCs in mouse, which adds in our knowledge by understanding the dynamic expression pattern of biomarkers of stem cells relate to maintenance of their stemness., Competing Interests: Declaration of competing interest None., (Copyright © 2020 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Background: An antibody panel is needed to definitively differentiate between adenocarcinoma (AC) and squamous cell carcinoma (SCC) in order to meet more stringent requirements for the histologic classification of lung cancers. Staining of desmosomal plaque-related proteins may be useful in the diagnosis of lung SCC. Materials and methods: We compared the usefulness of six conventional (CK5/6, p40, p63, CK7, TTF1, and Napsin A) and three novel (PKP1, KRT15, and DSG3) markers to distinguish between lung SCC and AC in 85 small biopsy specimens (41 ACs and 44 SCCs). Correlations were examined between expression of the markers and patients' histologic and clinical data. Results: The specificity for SCC of membrane staining for PKP1, KRT15, and DSG3 was 97.4%, 94.6%, and 100%, respectively, and it was 100% when the markers were used together and in combination with the conventional markers (AUCs of 0.7619 for Panel 1 SCC, 0.7375 for Panel 2 SCC, 0.8552 for Panel 1 AC, and 0.8088 for Panel 2 AC). In a stepwise multivariate logistic regression model, the combination of CK5/6, p63, and PKP1 in membrane was the optimal panel to differentiate between SCC and AC, with a percentage correct classification of 96.2% overall (94.6% of ACs and 97.6% of SCCs). PKP1 and DSG3 are related to the prognosis. Conclusions: PKP1, KRT15, and DSG3 are highly specific for SCC, but they were more useful to differentiate between SCC and AC when used together and in combination with conventional markers. PKP1 and DSG3 expressions may have prognostic value.

Congenital urinary tract obstruction (UTO) is the leading cause of chronic kidney disease in children; however, current management strategies do not safeguard against progression to end-stage renal disease, highlighting the need for interventions to limit or reverse obstructive nephropathy. Experimental UTO triggers renal urothelial remodeling that culminates in the redistribution of basal keratin 5-positive (Krt5 + ) renal urothelial cells (RUCs) and the generation of uroplakin-positive (Upk) + RUCs that synthesize a protective apical urothelial plaque. The cellular source of Upk + RUCs is currently unknown, limiting the development of strategies to promote renal urothelial remodeling as a therapeutic approach. In the present study, we traced the origins of adult Upk + RUCs during normal development and in response to UTO. Fate mapping analysis demonstrated that adult Upk + RUCs derive from embryonic and neonatal Krt5 + RUCs, whereas Krt5 + RUCs lose this progenitor capacity and become lineage restricted by postnatal day 14 . However, in response to UTO, postnatal day 14 -labeled adult Krt5 + RUCs break their lineage restriction and robustly differentiate into Upk + RUCs. Thus, Krt5 + RUCs drive renal urothelial formation during normal ontogeny and after UTO by differentiating into Upk + RUCs in a temporally restricted manner.

During influenza pneumonia, the alveolar epithelial cells of the lungs are targeted by the influenza virus. The distal airway stem cells (DASCs) and proliferating alveolar type II (AT2) cells are reported to be putative lung repair cells. However, their relative spatial and temporal distribution is still unknown during influenza-induced acute lung injury. Here, we investigated the distribution of these cells, and concurrently performed global proteomic analysis of the infected lungs to elucidate and link the cellular and molecular events during influenza pneumonia recovery. BALB/c mice were infected with a sub-lethal dose of influenza H1N1 virus. From 5 to 25 days post-infection (dpi), mouse lungs were subjected to histopathologic and immunofluorescence analysis to probe for global distribution of lung repair cells (using P63 and KRT5 markers for DASCs; SPC and PCNA markers for AT2 cells). At 7 and 15 dpi, infected mouse lungs were also subjected to protein mass spectrometry for relative protein quantification. DASCs appeared only in the damaged area of the lung from 7 dpi onwards, reaching a peak at 21 dpi, and persisted until 25 dpi. However, no differentiation of DASCs to AT2 cells was observed by 25 dpi. In contrast, AT2 cells began proliferating from 7 dpi to replenish their population, especially within the boundary area between damaged and undamaged areas of the infected lungs. Mass spectrometry and gene ontology analysis revealed prominent innate immune responses at 7 dpi, which shifted towards adaptive immune responses by 15 dpi. Hence, proliferating AT2 cells but not DASCs contribute to AT2 cell regeneration following transition from innate to adaptive immune responses during the early phase of recovery from influenza pneumonia up to 25 dpi., Competing Interests: The authors declare no conflict of interest.

The effective prevention of tumor initiation, especially for potentially inoperable tumors, will be beneficial to obtain an overall higher quality of our health and life. Hence, thorough understanding of the pathophysiological mechanisms of early tumor formation arising from identifiable cellular origins is required to develop efficient preventative and early treatment options for each tumor type. Here, using genetically engineered mouse models, we provide preclinical experimental evidence for a long-standing open question regarding the pathophysiological potential of a microenvironmental and physiological stressor in tumor development, gastric acid-mediated regional microscopic injury in foregut squamous epithelia. This study demonstrates the association of gastric acid stress with Cyclooxygenase-2-dependent tumor formation originating from tumor-competent Krt5 + /Krt15 + foregut basal progenitor cells. Our findings suggest that clinical management of microenvironmental stressor-mediated microscopic injury may be important in delaying tumor initiation from foregut basal progenitor cells expressing pre-existing tumorigenic mutation(s) and genetic alteration(s).

Background: Hair follicle (HF) cycling is dependent upon activation and differentiation of an epithelial subpopulation of cells with stem-like characteristics. These cells express cytokeratin 15 (CK15) and are sequestered within a specialized niche termed the follicular bulge. The pathways that mediate bulge activation are poorly understood, although growing evidence suggests a role for epigenetic events., Methods: Here we investigated murine and human HFs to determine whether a recently described epigenetic hydroxymethylation marker, 5-hmC, known to mediate cell growth and differentiation, may play a role in bulge activation., Results: We found the bulge region of murine HFs to show variable 5-hmC distribution within the nuclei of CK15-positive stem cells during early anagen, a pattern that was not associated with resting stem cells of telogen follicles, which did not express 5-hmC. Moreover, during phases of early anagen that were induced in an organ culture model, spatial alterations in bulge stem cell 5-hmC reactivity, as assessed by dual labeling, were noted., Conclusions: These preliminary findings suggest that 5-hmC may play a dynamic role in bulge activation during anagen growth, and provide a foundation for further experimental inquiry into epigenomic regulation of HF stem cells., (© 2019 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Keratin 15 (K15), a type I keratin, which pairs with K5 in epidermis, has been used extensively as a biomarker for stem cells. Two commercial antibodies, LHK15, a mouse monoclonal and EPR1614Y, a rabbit monoclonal, have been widely employed to study K15 expression. Here we report differential reactivity of these antibodies on epithelial cells and tissue sections. Although the two antibodies specifically recognised K15 on western blot, they reacted differently on skin sections and cell lines. LHK15 reacted in patches, whereas EPR1614Y reacted homogenously with the basal keratinocytes in skin sections. In cultured cells, LHK15 did not react with K15 deficient NEB-1, KEB-11, MCF-7 and SW13 cells expressing only exogenous K8 and K18 but reacted when these cells were transduced with K15. On the other hand, EPR1614Y reacted with these cells even though they were devoid of K15. Taken together these results suggest that EPR1614Y recognises a conformational epitope on keratin filaments which can be reconstituted by other keratins as well as by K15. In conclusion, this report highlights that all commercially available antibodies may not be equally specific in identifying the K15 positive stem cell.

Objective: To investigate the expression of Ki-67, phosphohistone H-3 (PHH3), and cytokeratin 15 (CK15) proteins in the cells of the oral mucosa (OM) according to the degree of its malignant transformation., Material and Methods: OM biopsy specimens from 69 patients diagnosed with focal epithelial hyperplasia, intraepithelial squamous cell neoplasia, cancer in situ, and squamous cell carcinoma were examined. Tissue antigens were determined using mouse Ki-67 monoclonal antibodies, rabbit PHH3 polyclonal antibodies, and mouse CK15 monoclonal antibodies., Results: There was an increase in epithelial proliferative and mitotic activities in squamous cell carcinoma and a sharp decrease in the expression of CK15 in the cytoplasm in cancer in situ and squamous cell carcinoma of the OM., Conclusion: The protein CK15 can be used for the differential diagnosis between high-grade dysplasia and OM epithelial malignancy at the stage of carcinoma in situ and squamous cell carcinoma.

Hair follicle stem cells (HFSC) are localized in the bulge region of the hair follicle and play a role in producing hair. Recently, it has been shown that the number of HFSC decreases with age, which is thought to be a cause of senile alopecia. Therefore, maintaining HFSC may be key for the prevention of age-related hair loss, but the regulatory mechanisms of HFSC and the effects of aging on them are largely unknown. In general, stem cells are known to require regulatory factors in the pericellular microenvironment, termed the stem cell niche, to maintain their cell function. In this study, we focused on the extracellular matrix proteoglycan decorin (DCN) as a candidate factor for maintaining the human HFSC niche. Gene expression analysis showed that DCN was highly expressed in the bulge region. We observed decreases in DCN expression as well as the number of KRT15-positive HFSC with age. In vitro experiments with human plucked hair-derived HFSC revealed that HFSC lost their undifferentiated state with increasing passages, and prior to this change a decrease in DCN expression was observed. Furthermore, knockdown of DCN promoted HFSC differentiation. In contrast, when HFSC were cultured on DCN-coated plates, they showed an even more undifferentiated state. From these results, as a novel mechanism for maintaining HFSC, it was suggested that DCN functions as a stem cell niche component, and that the deficit of HFSC maintenance caused by a reduction in DCN expression could be a cause of age-related hair loss., (© 2018 Japanese Dermatological Association.)

Transplantation of cultivated limbal epithelial transplantation has been proven to restore the corneal surface in limbal stem cell deficiency (LSCD). Here we comparatively investigated the optimized conditions and the efficiency of limbal epithelial sheet growth in three media conditions as well as with substrate free (transwell), human amniotic membrane (HAM) sutured onto transwell inserts (HAMTW), and HAM slide scaffold (HAMS). Outcomes evaluated were outgrowth sheet size from limbal explants, expression of stem/progenitor cell markers p63α, ABCG2 and CK15, and colony formation efficiency (CFE). Additionally, limbal epithelial sheets on HAMS were transplanted into corneas of LSCD rabbit models. Limbal epithelial sheets with 5% human AB serum showed the greatest increase in ABCG2 efflux activity (JC1 low ), p63α expression, and CFE compared in both conditions without HAM and with HAM, respectively. The outgrowth sheet size, cell yield, and Ki67 expression were increased in limbal epithelial sheets on HAMS compared to transwell and HAMTW. ABCG2 efflux activity, p63α and CK15 expressions, and CFE were also increased in limbal epithelial sheets on HAMS as well. In corneas of transplanted rabbit LSCD models, p63α expressions were noted in the basal layers and CK12 expressions were observed in superficial layers. Cultivation of limbal epithelial sheet on HAMS with xeno-free medium enhances the growth and stemness of limbal epithelial sheets.

Two principal stem cell pools orchestrate the rapid cell turnover in the intestinal epithelium. Rapidly cycling Lgr5+ stem cells are intercalated between the Paneth cells at the crypt base (CBCs) and injury-resistant reserve stem cells reside above the crypt base. The intermediate filament Keratin 15 (Krt15) marks either stem cells or long-lived progenitor cells that contribute to tissue repair in the hair follicle or the esophageal epithelium. Herein, we demonstrate that Krt15 labels long-lived and multipotent cells in the small intestinal crypt by lineage tracing. Krt15+ crypt cells display self-renewal potential in vivo and in 3D organoid cultures. Krt15+ crypt cells are resistant to high-dose radiation and contribute to epithelial regeneration following injury. Notably, loss of the tumor suppressor Apc in Krt15+ cells leads to adenoma and adenocarcinoma formation. These results indicate that Krt15 marks long-lived, multipotent, and injury-resistant crypt cells that may function as a cell of origin in intestinal cancer., (Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.)

We have previously reported characteristics of canine corneal epithelial cells in vitro and found that canine corneal epithelial cells could maintain their proliferative capacity even after continuous culture without the use of feeder cells and growth promoting additives. The objective of this study was to elucidate proliferative characteristics of canine corneal epithelial cells independent of feeder cells and growth promoting additives, with the aim of developing a spontaneously derived corneal epithelial cell line. Canine and rabbit corneal epithelial cells were harvested from the limbus and cultured with, or without, feeder cells and growth promoting additives, and both were passaged continuously until growth arrest. Canine corneal epithelial cells could proliferate independently, and could be passaged more times than rabbit cells. A canine corneal epithelial cell line, cCEpi, which could be passaged more than 100 times without using feeder cells and growth promoting additives, was established. cCEpi cells maintained a cell morphology close to the primary culture and expressed p63, cytokeratin 15 (K15), and K3. Although changes in colony morphology, shortening of the population doubling time and a heteroploid karyotype were observed, cCEpi was not tumorigenic. Stratified cell sheets cultured from cCEpi were morphologically and immunohistologically similar to sheets cultivated from early passage cells. In conclusion, canine corneal epithelial cells can proliferate independent of feeder cells and growth promoting additives. cCEpi maintains properties similar to normal corneal epithelial cells and could be a useful source for studies in cellular biology and for developing novel therapies., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

High-risk human papillomaviruses (HPVs) have been shown in vitro to impinge on telomere homeostasis in a number of ways. However, the in vivo interaction of viruses with the telomere homeostasis apparatus has not been previously explored. Since E6 and E7 are the main viral oncogenes and key for viral replication, we have explored here the short-term phenotypes of the genes in the context of defective telomere homeostasis. We examined the short-term phenotypes of E6 and E7 in a context where the Terc component of the telomerase holoenzyme was knocked out. We determined that Terc was dispensable for most oncogene-mediated phenotypes. Surprisingly, E7-mediated reduction of label retaining cells was found to be in part dependent on the presence of Terc. Under the conditions examined here, there appears to be no compelling evidence Terc is required for most short-term viral oncogene mediated phenotypes. Further studies will elucidate its role in longer-term phenotypes.

We previously reported that vimentin, GFAP, and desmin (type III intermediate filament [IF] proteins) are mitotically phosphorylated by CDK1, Aurora-B, and Rho-kinase. This phosphorylation is critical for efficient separation of these IFs and completion of cytokinesis. Keratin 5 (K5) and K14 form a heterodimer, which constitutes IF network in basal layer cells of stratified squamous epithelia. Here, we report that the solubility of K5/K14 increased in mitosis. The in vitro assays revealed that three mitotic kinases phosphorylate K5 more than K14. We then identified Thr23/Thr144, Ser30, and Thr159 on murine K5 as major phosphorylation sites for CDK1, Aurora-B, and Rho-kinase, respectively. Using site- and phosphorylation-state-specific antibodies, we demonstrated that K5-Thr23 was phosphorylated in entire cytoplasm from prometaphase to metaphase, whereas K5-Ser30 phosphorylation occurred specifically at the cleavage furrow from anaphase to telophase. Efficient K5/K14-IF separation was impaired by K5 mutations at the sites phosphorylated by these mitotic kinases. K5-Thr23 phosphorylation was widely detected in dividing K5-positive cells of murine individuals. These results suggested that mitotic reorganization of K5/K14-IF network is governed largely through K5 phosphorylation by CDK1, Aurora-B, and Rho-kinase., (Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.)

The Stat6VT mouse model of atopic dermatitis (AD) is induced by T-cell-specific expression of a constitutively active form of the protein signal transducer and activator of transcription 6 (STAT6). Although AD-like lesions are known to develop in Stat6VT mice, this study was designed to determine if these mice develop acute and chronic phases of disease similar to humans. To address this, AD-like lesions from Stat6VT mice were harvested at two different timepoints relative to their onset. Lesions harvested within 1 week after development were defined as acute lesions, and those present for 1 month or more were defined as chronic lesions. Acute and chronic AD-like lesions from Stat6VT mice exhibited histologic findings and cytokine expression patterns similar to acute and chronic AD lesions in humans. Further analysis revealed increased levels of interleukin (IL)-33 transcripts in AD-like lesions compared to Stat6VT nonlesional and wild-type skin controls. Immunofluorescence also revealed increased numbers of IL-33 + keratinocytes in Stat6VT lesional skin and localized IL-33 + keratinocytes to a keratin 5 + subset. Furthermore, AD-like disease was more severe in IL-33-deficient Stat6VT mice compared to IL-33-sufficient Stat6VT mice. These studies suggest that Stat6VT mice can serve as a model of acute and chronic AD and that IL-33 may attenuate inflammation in this system.

The middle ear epithelium is derived from neural crest and endoderm, which line distinct regions of the middle ear cavity. Here, we investigate the distribution of putative stem cell markers in the middle ear, combined with an analysis of the location of label-retaining cells (LRCs) to create a map of the middle ear mucosa. We show that proliferating cells and LRCs were associated with specific regions of the ear epithelium, concentrated in the hypotympanum at the base of the auditory bulla and around the ear drum. Sox2 was widely expressed in the endodermally derived ciliated pseudostratified epithelium of the hypotympanum. This part of the middle ear showed high levels of Wnt activity, as indicated by the expression of Axin2, a readout of Wnt signalling. Keratin 5 showed a more restricted expression within the basal cells of this region, with very little overlap between the Sox2- and keratin 5-positive epithelium, indicating that these genes mark distinct populations. Little expression of Sox2 or keratin 5 was observed in the neural crest-derived middle ear epithelium that lined the promontory, except in cases of otitis media when this epithelium underwent hyperplasia. This study lays the foundation for furthering our understanding of homeostasis and repair in the middle ear., Competing Interests: Competing interestsThe authors declare no competing or financial interests., (© 2018. Published by The Company of Biologists Ltd.)

Background/aims: Little is known how miR-203 is involved in epidermal stem cells (ESCs) differentiation and scar formation., Methods: We first used luciferase assay to determine the interaction of miR-203 with the 3'-UTR in regulation of Hes1 expression. We then used flow cytometry to analyze the effects of miR-203 expression on the differentiation of ESCs to MFB by determination of CK15 ratio and α-SMA. To confirm the results of flow cytometry analysis, we used Western blot to examine the expression of α-SMA, Collagen I (Col I), and Collagen III (Col III), as well as the expression of Notch1, Jagged1, and Hes1 in ESCs after the treatment of pre-miR-203 or anti-miR-203. Finally, we examined the effects local anti-miR-203 treatment on would closure and scar formation using a mouse skin wound model., Results: Pre-miR-203 treatment increased ESCs differentiation to MFB cells, as indicated by decreased CK15 ratio and increased MFB biomarkers. This phenomenon was reversed by overexpression of Hes1 in ESCs. In addition, skin incision increased expression of miR-203 in wound tissue. Local treatment of anti-miR-203 could accelerate wound closure and reduce scar formation in vivo, which was associated with increased re-epithelialization, skin attachment regeneration, and collagen reassignment. Finally, we confirmed that anti-miR-203 treatment could inhibit ESCs differentiation in vivo via increasing Hesl expression., Conclusion: Taken together, our results suggested that overexpression of miR-203 in ESCs after skin wound may be a critical mechanism underlying the scar formation., (© 2018 The Author(s). Published by S. Karger AG, Basel.)

Background: This article concerns the identification of gene pairs or combinations of gene pairs associated with biological phenotype or clinical outcome, allowing for building predictive models that are not only robust to normalization but also easily validated and measured by qPCR techniques. However, given a small number of biological samples yet a large number of genes, this problem suffers from the difficulty of high computational complexity and imposes challenges to the accuracy of identification statistically., Results: In this paper, we propose a parsimonious model representation and develop efficient algorithms for identification. Particularly, we derive an equivalent model subject to a sum-to-zero constraint in penalized linear regression, where the correspondence between nonzero coefficients in these models is established. Most importantly, it reduces the model complexity of the traditional approach from the quadratic order to the linear order in the number of candidate genes, while overcoming the difficulty of model nonidentifiablity. Computationally, we develop an algorithm using the alternating direction method of multipliers (ADMM) to deal with the constraint. Numerically, we demonstrate that the proposed method outperforms the traditional method in terms of the statistical accuracy. Moreover, we demonstrate that our ADMM algorithm is more computationally efficient than a coordinate descent algorithm with a local search. Finally, we illustrate the proposed method on a prostate cancer dataset to identify gene pairs that are associated with pre-operative prostate-specific antigen., Conclusion: Our findings demonstrate the feasibility and utility of using gene pairs as biomarkers.

Mammalian epidermis is composed of four morphologically and functionally distinct layers of keratinocytes. The innermost basal layer consists of proliferating self-renewing keratinocytes, which also undergo asymmetric cell division to differentiate into postmitotic suprabasal cells throughout life. Control of the balance between growth and differentiation of basal cells is important for epidermal homeostasis to prevent skin disorders including malignancies; however, the underlying mechanism remains to be elucidated. Recently, MafB was identified as one of the transcription factors that regulate epidermal keratinocyte differentiation. MafB is expressed in postmitotic differentiating keratinocytes, and epidermal differentiation is partially impaired in MafB-deficient mice. To further establish the roles of MafB in the epidermis in vivo, we generated mice transgenic for MafB under the control of the basal cell-specific keratin (Krt) 14 promoter. In the epidermis of transgenic mice at embryonic day 18.5, the number of proliferating Krt14-positive basal-like cells was increased, and the granular and cornified layers were thickened. Furthermore, these MafB transgenic mice developed papillomas spontaneously with age. Therefore, MafB promotes differentiation in postmitotic keratinocytes and simultaneously has potential to promote growth when ectopically expressed in undifferentiated basal keratinocytes., (© 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

The basal, intermediate, and superficial cell layers of the urothelium undergo rapid and complete recovery following acute injury; however, the effects of chronic injury on urothelial regeneration have not been well defined. To address this discrepancy, we employed a mouse model to explore urothelial changes in response to spinal cord injury (SCI), a condition characterized by life-long bladder dysfunction. One day post SCI there was a focal loss of umbrella cells, which are large cells that populate the superficial cell layer and normally express uroplakins (UPKs) and KRT20, but not KRT5, KRT14, or TP63. In response to SCI, regions of urothelium devoid of umbrella cells were replaced with small superficial cells that lacked KRT20 expression and appeared to be derived in part from the underlying intermediate cell layer, including cells positive for KRT5 and TP63. We also observed KRT14-positive basal cells that extended thin cytoplasmic extensions, which terminated in the bladder lumen. Both KRT14-positive and KRT14-negative urothelial cells proliferated 1 day post SCI, and by 7 days, cells in the underlying lamina propria, detrusor, and adventitia were also dividing. At 28 days post SCI, the urothelium appeared morphologically patent, and the number of proliferative cells decreased to baseline levels; however, patches of small superficial cells were detected that coexpressed UPKs, KRT5, KRT14, and TP63, but failed to express KRT20. Thus, unlike the rapid and complete restoration of the urothelium that occurs in response to acute injuries, regions of incompletely differentiated urothelium were observed even 28 days post SCI., (Copyright © 2017 the American Physiological Society.)

The esophageal lumen is lined by a stratified squamous epithelium comprised of proliferative basal cells that differentiate while migrating toward the luminal surface and eventually desquamate. Rapid epithelial renewal occurs, but the specific cell of origin that supports this high proliferative demand remains unknown. Herein, we have described a long-lived progenitor cell population in the mouse esophageal epithelium that is characterized by expression of keratin 15 (Krt15). Genetic in vivo lineage tracing revealed that the Krt15 promoter marks a long-lived basal cell population able to self-renew, proliferate, and generate differentiated cells, consistent with a progenitor/stem cell population. Transcriptional profiling demonstrated that Krt15+ basal cells are molecularly distinct from Krt15- basal cells. Depletion of Krt15-derived cells resulted in decreased proliferation, thereby leading to atrophy of the esophageal epithelium. Further, Krt15+ cells were radioresistant and contributed to esophageal epithelial regeneration following radiation-induced injury. These results establish the presence of a long-lived and indispensable Krt15+ progenitor cell population that provides additional perspective on esophageal epithelial biology and the widely prevalent diseases that afflict this epithelium.

Cultures of epithelial cells are limited by the proliferative capacity of primary cells and cell senescence. Herein we show that primary human epithelial cell sheets cultured without dermal equivalents maintained homeostasis in vitro for at least 1 year. Transparency of these sheets enabled live observation of pigmented melanocytes and Fluorescent Ubiquitination-based Cell Cycle Indicator (FUCCI) labeled epithelial cells during wound healing. Cell turn over and KRT15 expression pattern stabilized within 3 months, when KRT15 bright clusters often associated with niche-like melanocytes became apparent. EdU labels were retained in a subset of epithelial cells and melanocytes after 6 months chasing, suggesting their slow cell cycling property. FUCCI-labeling demonstrated robust cell migration and proliferation following wounding. Transparency and long-term (1 year) homeostasis of this model will be a powerful tool for the study of wound healing and cell linage tracing.

Atopic dermatitis is increasing worldwide in correlation with air pollution. Various organic components of pollutants activate the transcription factor AhR (aryl hydrocarbon receptor). Through the use of AhR-CA mice, whose keratinocytes express constitutively active AhR and that develop atopic-dermatitis-like phenotypes, we identified Artn as a keratinocyte-specific AhR target gene whose product (the neurotrophic factor artemin) was responsible for epidermal hyper-innervation that led to hypersensitivity to pruritus. The activation of AhR via air pollutants induced expression of artemin, alloknesis, epidermal hyper-innervation and inflammation. AhR activation and ARTN expression were positively correlated in the epidermis of patients with atopic dermatitis. Thus, AhR in keratinocytes senses environmental stimuli and elicits an atopic-dermatitis pathology. We propose a mechanism of air-pollution-induced atopic dermatitis via activation of AhR.

Hair follicle stem cells (HFSCs) are considered one of the useful donor cell types for skin regenerative medicine owing to their robust proliferative capacity and multipotency. However, methods for easily and effectively obtaining HFSCs from a limited skin biopsy are still lacking. Here we report a novel approach for obtaining a subpopulation of HFSCs from a small skin sample from the rat tail, which uses the sebaceous glands (SGs) to capture the adjacent HFSCs. By means of organ culture, keratinocytes were expanded from the detached SGs, which also included adherent HFSCs from the hair follicle that could be passaged at the single-cell level. These SG-captured keratinocytes strongly expressed the basal layer markers K14, integrin α6, and p63; the bulge stem cell marker K15; and the upper isthmus stem cell marker Plet1. Furthermore, we reconstituted new epidermis, hair follicles, and SGs from the SG-captured keratinocytes using an easily operated, modified skin reconstitution assay based on silicone gel sheeting. This study suggests that the SGs could be an accessible capturer to harvest the adjacent HFSC subpopulation, particularly when the donor tissue is limited.

Background: Epidermal stem cells are multipotent cells that maintain the skin epidermis. Potential markers for stem cells have been identified in mammalian skin from mouse experiments; however, it is unclear if stem cells also contribute to tumour formation in human skin., Objectives: To investigate the expression of potential stem cell markers, such as leucine-rich repeat-containing G protein-coupled receptor (Lgr) 5, Lgr6, leucine-rich repeats and immunoglobulin-like domain protein 1 (Lrig1) and cytokeratin 15 (CK15) in basal cell carcinomas and tumours of the skin appendages., Methods: We tested 45 human basal cell carcinomas (BCCs), including superficial, nodular, adenoid, infiltrating and sclerosing types, and 38 human tumours of skin appendages, including 13 sebaceous adenomas and carcinomas, 20 eccrine sweat gland tumours and five pilomatricomas, for the expression of hair follicle stem cell markers such as Lgr5, Lrig1, CK15, β-catenin and SRY (sex determining region Y)-box 9 (SOX9), and compared these findings with those of healthy age-matched human epidermis., Results: We detected the expression of stem cell markers in all tumours tested. Regarding Lgr5, Lrig1, CK15 and SOX9, expression seemed to be lower in more aggressive tumour types, such as in the most advanced parts of infiltrating BCC, in sebaceous carcinoma and late-stage porocarcinoma, compared with less aggressive superficial or nodular BCC or early-stage porocarcinoma and sebaceous gland tumours. In aggressive, sclerosing BCC, Lrig1 and Lgr5 were downregulated but CK15, SOX9 and nuclear β-catenin were upregulated., Conclusions: Expression of potential stem cell markers of the epidermis and hair follicles was observed in skin tumours of appendages and BCCs. However, during tumour progression, many of these markers seemed to be downregulated., (© 2016 British Association of Dermatologists.)

The epidermis is continuously renewed by stem cell proliferation and differentiation. Basal keratinocytes append the dermal-epidermal junction, a cell surface-associated, extracellular matrix that provides structural support and influences their behaviour. It consists of laminins, type IV collagen, nidogens, and perlecan, which are necessary for tissue organization and structural integrity. Perlecan is a heparan sulfate proteoglycan known to be involved in keratinocyte survival and differentiation. Aging affects the dermal epidermal junction resulting in decreased contact with keratinocytes, thus impacting epidermal renewal and homeostasis. We found that perlecan expression decreased during chronological skin aging. Our in vitro studies revealed reduced perlecan transcript levels in aged keratinocytes. The production of in vitro skin models revealed that aged keratinocytes formed a thin and poorly organized epidermis. Supplementing these models with purified perlecan reversed the phenomenon allowing restoration of a well-differentiated multi-layered epithelium. Perlecan down-regulation in cultured keratinocytes caused depletion of the cell population that expressed keratin 15. This phenomenon depended on the perlecan heparan sulphate moieties, which suggested the involvement of a growth factor. Finally, we found defects in keratin 15 expression in the epidermis of aging skin. This study highlighted a new role for perlecan in maintaining the self-renewal capacity of basal keratinocytes.

Background: Keratin 5 (K5) is a cytoskeletal tissue-specific protein expressed in the epithelial cells of skin and esophagus and ectopic K5 expression in lymphocytes has never been reported., Objective: Here we demonstrate an ectopic epidermal self-protein expression in B-1 B cell by fate mapping of K5-expressing cells., Methods: K5-Cre×CAG-CAT-loxP-EGFP double Tg (K5×GFP) mice that express enhanced GFP under the control of the K5 promoter were employed., Results: Unexpectedly, B220(+)GFP(+) cells were found in LN, spleen, peripheral blood and peritoneal cavity. These cells were IgM(+)IgD(low)CD23(-)CD43(+)CD19(+)CD93(-), indicating that they were B-1 B cells. The number of B220(+)GFP(+) cells was significantly larger in spleen than in the other tissues tested. Although GFP(+) B-1 cells did not express K5 in the periphery, Lin(-)CD93(+)B220(low-neg)CD19(+) B-1 B cell progenitors expressed GFP and B220(+)CD93(+) progenitor cells expressed K5 and MHC-class II in BM, indicating that GFP(+) B-1 cells transiently expressed K5 and the progenitor cells were potential APC. GFP(+) B-1 cells in the periphery continued expressing MHC class II and had exogenous antigen-presenting capacity comparable to non-follicular B cells. GFP(+) B-1 cells spontaneously secreted more IgM than GFP(-) B-1 cells in vitro., Conclusion: These results indicate that B-1 B cells transiently and partially express K5 in BM and are potent for both natural antibody production and antigen presentation., (Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.)