Proliferation Of Epithelial Progenitor Cells Research Articles

Thymic epithelial organoids mediate T cell development.

Although the advent of organoids opened unprecedented perspectives for basic and translational research, immune system-related organoids remain largely underdeveloped. Here we established organoids from the thymus, the lymphoid organ responsible for T cell development. We identified conditions enabling thymic epithelial progenitor cell proliferation and development into organoids with diverse cell populations and transcriptional profiles resembling in vivo thymic epithelial cells (TECs) more closely than traditional TEC cultures. Contrary to these two-dimensional cultures, thymic epithelial organoids maintained thymus functionality in vitro and mediated physiological T cell development upon reaggregation with T cell progenitors. The reaggregates showed in vivo-like epithelial diversity and ability to attract T cell progenitors. Thymic epithelial organoids are the first organoids originating from the stromal compartment of a lymphoid organ. They provide new opportunities to study TEC biology and T cell development in vitro, paving the way for future thymic regeneration strategies in ageing or acute injuries.

Foxn1 overexpression promotes thymic epithelial progenitor cell proliferation and mTEC maintenance, but does not prevent thymic involution.

The transcription factor FOXN1 is essential for fetal thymic epithelial cell (TEC) differentiation and proliferation. Postnatally, Foxn1 levels vary widely between TEC subsets, from low/undetectable in putative TEC progenitors to highest in differentiated TEC subsets. Correct Foxn1 expression is required to maintain the postnatal microenvironment; premature downregulation of Foxn1 causes a rapid involution-like phenotype, and transgenic overexpression can cause thymic hyperplasia and/or delayed involution. We investigated a K5.Foxn1 transgene that drives overexpression in mouse TECs, but causes neither hyperplasia nor delay or prevention of aging-related involution. Similarly, this transgene cannot rescue thymus size in Foxn1lacZ/lacZ mice, which undergo premature involution as a result of reduced Foxn1 levels. However, TEC differentiation and cortico-medullary organization are maintained with aging in both K5.Foxn1 and Foxn1lacZ/lacZ mice. Analysis of candidate TEC markers showed co-expression of progenitor and differentiation markers as well as increased proliferation in Plet1+ TECs associated with Foxn1 expression. These results demonstrate that the functions of FOXN1 in promoting TEC proliferation and differentiation are separable and context dependent, and suggest that modulating Foxn1 levels can regulate the balance of proliferation and differentiation in TEC progenitors.

MICU1-dependent mitochondrial calcium uptake regulates lung alveolar type 2 cell plasticity and lung regeneration.

Lung alveolar type 2 (AT2) cells are progenitors for alveolar type 1 (AT1) cells. Although many factors regulate AT2 cell plasticity, the role of mitochondrial calcium (mCa2+) uptake in controlling AT2 cells remains unclear. We previously identified that the miR-302 family supports lung epithelial progenitor cell proliferation and less differentiated phenotypes during development. Here, we report that a sustained elevation of miR-302 in adult AT2 cells decreases AT2-to-AT1 cell differentiation during the Streptococcus pneumoniae–induced lung injury repair. We identified that miR-302 targets and represses the expression of mitochondrial Ca2+ uptake 1 (MICU1), which regulates mCa2+ uptake through the mCa2+ uniporter channel by acting as a gatekeeper at low cytosolic Ca2+ levels. Our results reveal a marked increase in MICU1 protein expression and decreased mCa2+ uptake during AT2-to-AT1 cell differentiation in the adult lung. Deletion of Micu1 in AT2 cells reduces AT2-to-AT1 cell differentiation during steady-state tissue maintenance and alveolar epithelial regeneration after bacterial pneumonia. These studies indicate that mCa2+ uptake is extensively modulated during AT2-to-AT1 cell differentiation and that MICU1-dependent mCa2+ uniporter channel gating is a prominent mechanism modulating AT2-to-AT1 cell differentiation.

ANKRD22 Drives Rapid Proliferation of Lgr5+ Cells and Acts as a Promising Therapeutic Target in Gastric Mucosal Injury.

Background & AimsRapid gastric epithelial progenitor cell (EPC) proliferation and inflammatory response inhibition play key roles in promoting the repair of gastric mucosal damage. However, specific targets inducing these effects are unknown. In this study, we explored the effects of a potential target, Ankyrin repeat domain 22 (ANKRD22).MethodsAn acute gastric mucosal injury model was established with Ankrd22-/- and Ankrd22+/+ mice by intragastric administration of acidified ethanol. Organoid culture and flow cytometry were performed to evaluate the effects of ANKRD22 on leucine-rich repeat-containing G-protein–coupled receptor 5–positive (Lgr5+) gastric EPC proliferation. The mechanisms by which ANKRD22 affects gastric EPC proliferation and inflammatory responses were explored by mitochondrial Ca2+ influx and immunoblotting. Candidate ANKRD22 inhibitors then were screened virtually and validated in vitro and in vivo.ResultsAfter acute gastric mucosal injury, the number of Lgr5+ gastric EPCs was increased significantly in Ankrd22-/- mice compared with that in Ankrd22+/+ mice. Moreover, Ankrd22 knockout attenuated inflammatory cell infiltration into damaged gastric tissues. ANKRD22 deletion also reduced mitochondrial Ca2+ influx and cytoplasmic nuclear factor of activated T cells in gastric epithelial cells and macrophages, which further induced Lgr5+ gastric EPC proliferation and decreased macrophage release of tumor necrosis factor-α and interleukin 1α. In addition, a small molecule, AV023, was found to show similar effects to those produced by ANKRD22 deletion in vitro. Intraperitoneal injection of AV023 into the mouse model promoted the repair of gastric mucosal damage, with increased proliferation of Lgr5+ gastric EPCs and visible relief of inflammation.ConclusionsANKRD22 inhibition is a potential target-based therapeutic approach for promoting the repair of gastric mucosal damage.

Cell cycle-related kinase is a crucial regulator for ciliogenesis and Hedgehog signaling in embryonic mouse lung development

Cell cycle-related kinase (CCRK) has a conserved role in ciliogenesis, and Ccrk defects in mice lead to developmental defects, including exencephaly, preaxial polydactyly, skeletal abnormalities, retinal degeneration, and polycystic kidney. Here, we found that Ccrk is highly expressed in mouse trachea and bronchioles. Ccrk mutants exhibited pulmonary hypoplasia and abnormal branching morphogenesis in respiratory organ development. Furthermore, we demonstrated that Ccrk mutant lungs exhibit not only impaired branching morphogenesis but also a significant sacculation deficiency in alveoli associated with reduced epithelial progenitor cell proliferation. In pseudoglandular stages, Ccrk mutant lungs showed a downregulation of Hedgehog (Hh) signaling and defects in cilia morphology and frequency during progenitor-cell proliferation. Interestingly, we observed that activation of the Hh signaling pathway by small-molecule smoothened agonist (SAG) partially rescued bud morphology during branch bifurcation in explants from Ccrk mutant lungs. Therefore, CCRK properly regulates respiratory airway architecture in part through Hh-signal transduction and ciliogenesis.

Abstract P4-03-11: Fibroblasts isolated from the “normal-like” tissue adjacent to breast tumours suppress healthy epithelial progenitor cell proliferation while supporting tumour cell growth

Abstract The tissue adjacent to breast tumors has been referred to as “normal-like” tissue despite exhibiting many alterations at epigenetic and gene expression levels consistent with enhanced proliferation and wound healing signatures. However, the influence of such alterations on the proliferation and differentiation of healthy breast progenitors is currently unknown. Fibroblasts are a major component of microenvironment for the healthy and malignant breast cells. We therefore, isolate fibroblast from primary breast tumors, tissue adjacent to tumors (TAT) and the healthy breast tissue and examine their ability to support proliferation of healthy and malignant breast cells. To characterize the TAT samples we first utilized clonal co-culture assays using breast cells obtained from the healthy breast tissue (reduction mammoplasty sample, RM) and the healthy fibroblasts. Our results suggested that the TAT samples surprisingly contained significantly decreased pool of progenitors compared to the RM samples. In order to study the underlying mechanism, we characterized fibroblasts derived from either the breast tumours (TAFs) or the TAT samples (TATF) or the RM normal samples (NAFs) and assessed their role on breast progenitor cell functions. Fibroblasts were isolated from the ER+ and ER- breast tumours and their adjacent breast tissue. We observed that matrigel co-cultures consisting of RM samples and NAFs led to a 5.5-fold expansion of the progenitors, whereas the co-cultures of TAT or the RM samples with either TAFs or TATFs failed to show expansion of epithelial progenitors. The comparative secretome analysis of the NAFs and the TATFs identified TGFβ as a candidate molecule primarily secreted only by the TATFs and not by NAFs. Interestingly, blocking TGFβ signaling restored both TAFs' and TATFs' ability to support the expansion of healthy progenitors in matrigel cultures. Lastly, we found that TAFs were able to enhanced breast cancer cell proliferation in vivo and in vitro but to a lesser extent than the TAFs. Our observations suggest that the tissues adjacent to breast tumours are transformed into a TGFβ-enriched environment that is supportive of breast tumour growth while suppressing the proliferation and differentiation potentials of the healthy breast progenitors. Our data also suggest that the use of TGFβ blockers may be important in reducing risk of local breast tumour recurrence. Citation Format: Chatterjee S, Berdnikov A, Lee-Wing V, Safneck J, Buchel E, Raouf A. Fibroblasts isolated from the “normal-like” tissue adjacent to breast tumours suppress healthy epithelial progenitor cell proliferation while supporting tumour cell growth [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P4-03-11.

A Dynamic WNT/β-CATENIN Signaling Environment Leads to WNT-Independent and WNT-Dependent Proliferation of Embryonic Intestinal Progenitor Cells.

SummaryMuch of our understanding about how intestinal stem and progenitor cells are regulated comes from studying the late fetal stages of development and the adult intestine. In this light, little is known about intestine development prior to the formation of stereotypical villus structures with columnar epithelium, a stage when the epithelium is pseudostratified and appears to be a relatively uniform population of progenitor cells with high proliferative capacity. Here, we investigated a role for WNT/β-CATENIN signaling during the pseudostratified stages of development (E13.5, E14.5) and following villus formation (E15.5) in mice. In contrast to the well-described role for WNT/β-CATENIN signaling as a regulator of stem/progenitor cells in the late fetal and adult gut, conditional epithelial deletion of β-catenin or the Frizzled co-receptors Lrp5 and Lrp6 had no effect on epithelial progenitor cell proliferation in the pseudostratified epithelium. Mutant embryos displayed obvious developmental defects, including loss of proliferation and disruptions in villus formation starting only at E15.5. Mechanistically, our data suggest that WNT signaling-mediated proliferation at the time of villus formation is driven by mesenchymal, but not epithelial, WNT ligand secretion.

YAP regulates the expression of Hoxa1 and Hoxc13 in mouse and human oral and skin epithelial tissues.

Yes-associated protein (YAP) is a Hippo signaling transcriptional coactivator that plays pivotal roles in stem cell proliferation, organ size control, and tumor development. The downstream targets of YAP have been shown to be highly context dependent. In this study, we used the embryonic mouse tooth germ as a tool to search for the downstream targets of YAP in ectoderm-derived tissues. Yap deficiency in the dental epithelium resulted in a small tooth germ with reduced epithelial cell proliferation. We compared the gene expression profiles of embryonic day 14.5 (E14.5) Yap conditional knockout and YAP transgenic mouse tooth germs using transcriptome sequencing (RNA-Seq) and further confirmed the differentially expressed genes using real-time PCR and in situ hybridization. We found that YAP regulates the expression of Hoxa1 and Hoxc13 in oral and dental epithelial tissues as well as in the epidermis of skin during embryonic and adult stages. Sphere formation assay suggested that Hoxa1 and Hoxc13 are functionally involved in YAP-regulated epithelial progenitor cell proliferation, and chromatin immunoprecipitation (ChIP) assay implies that YAP may regulate Hoxa1 and Hoxc13 expression through TEAD transcription factors. These results provide mechanistic insights into abnormal YAP activities in mice and humans.

Hippo/Yap signaling controls epithelial progenitor cell proliferation and differentiation in the embryonic and adult lung.

The Hippo/Yap pathway is a well-conserved signaling cascade that regulates cell proliferation and differentiation to control organ size and stem/progenitor cell behavior. Following airway injury, Yap was dynamically regulated in regenerating airway epithelial cells. To determine the role of Hippo signaling in the lung, the mammalian Hippo kinases, Mst1 and Mst2, were deleted in epithelial cells of the embryonic and mature mouse lung. Mst1/2 deletion in the fetal lung enhanced proliferation and inhibited sacculation and epithelial cell differentiation. The transcriptional inhibition of cell proliferation and activation of differentiation during normal perinatal lung maturation were inversely regulated following embryonic Mst1/2 deletion. Ablation of Mst1/2 from bronchiolar epithelial cells in the adult lung caused airway hyperplasia and altered differentiation. Inhibitory Yap phosphorylation was decreased and Yap nuclear localization and transcriptional targets were increased after Mst1/2 deletion, consistent with canonical Hippo/Yap signaling. YAP potentiated cell proliferation and inhibited differentiation of human bronchial epithelial cells in vitro. Loss of Mst1/2 and expression of YAP regulated transcriptional targets controlling cell proliferation and differentiation, including Ajuba LIM protein. Ajuba was required for the effects of YAP on cell proliferation in vitro. Hippo/Yap signaling regulates Ajuba and controls proliferation and differentiation of lung epithelial progenitor cells.

The Stromal Vascular Fraction of Autologous Fat Graft Induces Proliferation of Epithelial Progenitor Cells in Healthy and Cancer-Containing Breast Tissue In Vitro

BACKGROUND: Autologous fat grafting is widely used for managing contour asymmetries in breast reconstruction. Adipose tissue contains a rich population of both multipotent mesenchymal stem cells and vascular progenitor cells (collectively referred to as adipose-derived stem cells, or ASCs).1 When isolated, the cellular fraction of adipose tissue containing ASCs is referred to as stromal vascular fraction (SVF). Despite widespread clinical use, interactions between the SVF of lipoaspirate and breast parenchyma remain poorly understood. Our study investigated the effect of progenitor-rich SVF on the behavior of mammary epithelial progenitor cells derived from two sources: (i) healthy breast tissue and (ii) cancer adjacent breast tissue. METHODS: Healthy breast tissue and abdominal lipoaspirate were obtained from patients undergoing elective reduction mammoplasty and liposuction. Breast tissue from outside the tumor-free margins of mastectomy specimens (termed ‘cancer-adjacent breast tissue’) was obtained from patients undergoing primary free-flap reconstruction. Samples of SVF (from lipoaspirate) and breast parenchymal cells were then isolated using established cell digestion protocols. ASCs within the SVF were characterized using established differentiation, colony-forming unit-fibroblast (CFU-f), and cell surface marker assays.1 Finally, SVF cells were co-cultured with breast parenchymal cells from (i) healthy and (ii) cancer-adjacent sources were co-cultured using a three-dimensional matrix called Matrigel. Control cultures consisted of breast cells from (i) healthy and (ii) cancer-adjacent tissue in the absence of SVF. After 14 days, the total cell numbers and mammary epithelial progenitor cell populations from each culture group were quantified using colony forming cell (CFC) assays. RESULTS: Differentiation, CFU-f, and surface marker assays demonstrated the presence of ASCs in SVF samples. Co-cultures of cancer-adjacent breast parenchymal cells with SVF showed a 9-fold expansion of mammary epithelial progenitor cells (control = 3-fold) compared to a 5.5-fold expansion in co-cultures of healthy breast parenchymal cells (control = 2-fold) with SVF based on CFC assays. CONCLUSIONS: SVF is capable of increasing the proliferation of mammary epithelial progenitor cells in both healthy and cancer-adjacent breast tissue. As a result, this study demonstrates the potential for interaction between the SVF within autologous fat graft and progenitor cells contained within breast parenchymal tissue.

Expanding the Pool of Stem Cell Therapy for Lung Growth and Repair

The lung’s regenerative capacity resides within long-lived stem cells that can divide, self-renew, and differentiate to repair injured tissue or cell loss and maintain normal homeostasis. The ability to enhance endogenous stem cell capacity to regenerate lung tissue is the key to the treatment of a multitude of debilitating lung diseases such as bronchopulmonary dysplasia (BPD), idiopathic pulmonary fibrosis, chronic obstructive pulmonary disease, pulmonary arterial hypertension, and other acute and chronic ailments of the lung. The challenge lies in identifying the progenitors of a tissue and, in the case of the lung, understanding the complex interactions lung progenitors have with the unique environment of an air–liquid interphase, proximal and distal airways, the intricate vascular tree, and the innate immune response. Indeed, many different lung stem/progenitor cells have been described, and their identity and role in lung regeneration continue to be debated. Article see p 2144 In the past decade, endothelial progenitor cells (EPCs) have been isolated from the lungs of animals and shown to have vasculogenic activity. Vasculogenesis was thought to occur only in the yolk sac of the developing embryo, but this dogma was challenged in 1997 by Asahara and coworkers1 who first reported the isolation and characterization of putative endothelial progenitor cells from human peripheral blood, showing they can differentiate into mature endothelial cells and be incorporated in the vessels of animal models of disease. Lung vascular development is closely linked with and may drive lung growth and airway development through the release of endothelial-derived angiogenic factors that induce the proliferation of epithelial progenitor cells to support lung alveolization.2 Hence, lung EPCs may play a critical role not only in normal lung development, but also in lung injury and repair to restore endothelial cell function and maintain homeostasis. By extension, the inability of lung EPCs to …

Endothelial-Derived Angiocrine Signals Induce and Sustain Regenerative Lung Alveolarization

To identify pathways involved in adult lung regeneration, we employ a unilateral pneumonectomy (PNX) model that promotes regenerative alveolarization in the remaining intact lung. We show that PNX stimulates pulmonary capillary endothelial cells (PCECs) to produce angiocrine growth factors that induce proliferation of epithelial progenitor cells supporting alveologenesis. Endothelial cells trigger expansion of cocultured epithelial cells, forming three-dimensional angiospheres reminiscent of alveolar-capillary sacs. After PNX, endothelial-specific inducible genetic ablation of Vegfr2 and Fgfr1 in mice inhibits production of MMP14, impairing alveolarization. MMP14 promotes expansion of epithelial progenitor cells by unmasking cryptic EGF-like ectodomains that activate the EGF receptor (EGFR). Consistent with this, neutralization of MMP14 impairs EGFR-mediated alveolar regeneration, whereas administration of EGF or intravascular transplantation of MMP14(+) PCECs into pneumonectomized Vegfr2/Fgfr1-deficient mice restores alveologenesis and lung inspiratory volume and compliance function. VEGFR2 and FGFR1 activation in PCECs therefore increases MMP14-dependent bioavailability of EGFR ligands to initiate and sustain alveologenesis.

The E3 ubiquitin ligase WWP1 regulates ΔNp63-dependent transcription through Lys63 linkages

The transcription factor p63, a member of the p53 family, plays a crucial role in epithelial development and tumorigenesis through the regulation of epithelial progenitor cell proliferation, differentiation and apoptosis. Similarly to p53, p63 activity is regulated by post-translational modifications, including ubiquitylation. Here, we report that the WWP1 E3 ubiquitin ligase binds specifically to ΔNp63 isoform but it does not trigger ΔNp63 proteasome-dependent degradation. Accordingly, we found that WWP1-dependent ubiquitylation of ΔNp63 occurs through the formation of Lys63-linked poly-ubiquitin chains. Importantly, we found that WWP1 is able to increase ΔNp63-dependent transcription and depletion of WWP1 in human primary keratinocytes induces cell cycle arrest. All together these results indicate that WWP1 regulates ΔNp63 transcriptional activity, acting thus as a potential regulator of the proliferation and survival of epithelial-derived cells.

Epithelial Progenitor Cells of the Embryonic Lung and the Role of MicroRNAs in Their Proliferation

The entire epithelium of the lung is generated from a small pool of undifferentiated progenitor cells. At least during the early stages of development these reside in the distal tips of the embryonic lung. They respond to multiple signals from the surrounding mesenchyme and play a critical role as morphogenetic organizing centers. In addition, they proliferate rapidly and give rise to daughter cells that differentiate into all the specialized epithelial cells types of the newborn lung. Despite the importance of the progenitor cells, we still know relatively little about the mechanisms controlling their proliferation, morphogenesis, and developmental fate. Here, we discuss new data on the potential role of microRNAs in co-coordinately regulating multiple signaling pathways in embryonic progenitor cells. In particular, our recent transgenic experiments suggest that microRNAs encoded by the miR-17-92 cluster positively promote proliferation of epithelial progenitor cells and inhibit their differentiation. We speculate on how this information might be exploited therapeutically in the long term.

Fgf10 dosage is critical for the amplification of epithelial cell progenitors and for the formation of multiple mesenchymal lineages during lung development

The key role played by Fgf10 during early lung development is clearly illustrated in Fgf10 knockout mice, which exhibit lung agenesis. However, Fgf10 is continuously expressed throughout lung development suggesting extended as well as additional roles for FGF10 at later stages of lung organogenesis. We previously reported that the enhancer trap Mlcv1v-nLacZ-24 transgenic mouse strain functions as a reporter for Fgf10 expression and displays decreased endogenous Fgf10 expression. In this paper, we have generated an allelic series to determine the impact of Fgf10 dosage on lung development. We report that 80% of the newborn Fgf10 hypomorphic mice die within 24 h of birth due to respiratory failure. These mutant mouse lungs display severe hypoplasia, dilation of the distal airways and large hemorrhagic areas. Epithelial differentiation and proliferation studies indicate a specific decrease in TTF1 and SP-B expressing cells correlating with reduced epithelial cell proliferation and associated with a decrease in activation of the canonical Wnt signaling in the epithelium. Analysis of vascular development shows a reduction in PECAM expression at E14.5, which is associated with a simplification of the vascular tree at E18.5. We also show a decrease in α-SMA expression in the respiratory airway suggesting defective smooth muscle cell formation. At the molecular level, these defects are associated with decrease in Vegfa and Pdgfa expression likely resulting from the decrease of the epithelial/mesenchymal ratio in the Fgf10 hypomorphic lungs. Thus, our results indicate that FGF10 plays a pivotal role in maintaining epithelial progenitor cell proliferation as well as coordinating alveolar smooth muscle cell formation and vascular development.

Bombesin ingestion stimulates epithelial digestive cell proliferation in suckling rats.

The characterization of a bombesin-like peptide in the breast milk of some mammals might suggest that this peptide may influence, in part, the postnatal development of the digestive tract. To test this hypothesis, our experiments investigated whether oral administration of bombesin affects epithelial progenitor cell proliferation in digestive organs of suckling and weaned rats. Four series of pups were given bombesin diluted in milk (20 micrograms/kg, 3 times daily) or milk alone, for 5 days during either the first, second, third, or fourth week of life. Pups were killed after [3H]thymidine pulse labeling. DNA labeling and mitotic indices were estimated in the oxyntic, antral, colonic mucosae, and exocrine pancreas. In all tissues examined, oral bombesin significantly increased over control values the two cell proliferative parameters studied during the suckling period (P less than 0.05 to P less than 0.001). In bombesin-treated rats, maximal stimulation of these parameters occurred in the second week of life. This effect of oral bombesin on the cell kinetics disappeared in all tissues after weaning. This study confirms the growth-promoting effect of bombesin observed on the digestive system of the neonatal rat after subcutaneous administration of the peptide and shows that bombesin, when given orally to suckling rats, is sufficiently resistant to proteolysis to enable it to exert a stimulatory effect on digestive cell proliferation. However, our findings as such do not prove that milk bombesin-like peptide has a physiological influence on the developing gastrointestinal tract and pancreas.