Alveolar Epithelial Differentiation Research Articles

PRDM3/16 regulate chromatin accessibility required for NKX2-1 mediated alveolar epithelial differentiation and function

While the critical role of NKX2-1 and its transcriptional targets in lung morphogenesis and pulmonary epithelial cell differentiation is increasingly known, mechanisms by which chromatin accessibility alters the epigenetic landscape and how NKX2-1 interacts with other co-activators required for alveolar epithelial cell differentiation and function are not well understood. Combined deletion of the histone methyl transferases Prdm3 and Prdm16 in early lung endoderm causes perinatal lethality due to respiratory failure from loss of AT2 cells and the accumulation of partially differentiated AT1 cells. Combination of single-cell RNA-seq, bulk ATAC-seq, and CUT&RUN data demonstrate that PRDM3 and PRDM16 regulate chromatin accessibility at NKX2-1 transcriptional targets critical for perinatal AT2 cell differentiation and surfactant homeostasis. Lineage specific deletion of PRDM3/16 in AT2 cells leads to lineage infidelity, with PRDM3/16 null cells acquiring partial AT1 fate. Together, these data demonstrate that NKX2-1-dependent regulation of alveolar epithelial cell differentiation is mediated by epigenomic modulation via PRDM3/16.

Fgf9 promotes incisor dental epithelial stem cell survival and enamel formation

BackgroundUnderstanding the role of cytokines in tooth development is critical for advancing dental tissue engineering. Fibroblast growth factor 9 (FGF9) is the only FGF consistently expressed throughout dental epithelial tissue, from the initiation of tooth bud formation to tooth maturation. However, mice lacking Fgf9 (Fgf9−/−) surprisingly show no obvious abnormalities in tooth development, suggesting potential compensation by other FGFs. Here we report findings from an Fgf9S99N mutation mouse model, a loss-of-function mutation with a dominant negative effect. Our study reveals that Fgf9 is crucial for dental epithelial stem cell (DESC) survival and enamel formation.MethodsTo dissect the role of Fgf9 in tooth development, we performed the micro-CT, histomorphological analysis and gene expression assay in mice and embryos with S99N mutation. In addition, we assessed the effect of FGF9 on the DESC survival and dental epithelial differentiation by DESC sphere formation assay and tooth explant culture. Cell/tissue culture methods, gene expression analysis, specific inhibitors, and antibody blockage analysis were employed to explore how Fgf9 regulates enamel differentiation and DESC survival through both direct and indirect mechanisms.ResultsThe Fgf9S99N mutation in mice led to reduced ameloblasts, impaired enamel formation, and increased apoptosis in the cervical loop (CL). DESC sphere culture experiments revealed that FGF9 facilitated DESC survival via activating ERK/CREB signaling, without affecting cell proliferation. Furthermore, in vitro tissue culture experiments demonstrated that FGF9 promoted enamel formation in a manner dependent on the presence of mesenchyme. Interestingly, FGF9 stimulation inhibited enamel formation in isolated enamel epithelia and DESC spheres. Further investigation revealed that FGF9 supports DESC survival and promotes amelogenesis by stimulating the secretion of FGF3 and FGF10 in dental mesenchymal cells via the MAPK/ERK signaling pathway.ConclusionsOur study demonstrates that Fgf9 is essential for DESC survival and enamel formation. Fgf9 performs as a dual-directional regulator of the dental enamel epithelium, not only inhibiting DESC differentiation into ameloblasts to preserve the stemness of DESC, but also promoting ameloblast differentiation through epithelial-mesenchymal interactions.

Single-Cell Transcriptome Analysis Reveals 2 Subtypes of Tumor Cells of Sclerosing Pneumocytoma With Distinct Molecular Features and Clinical Implications

Pulmonary sclerosing pneumocytoma (PSP) is a rare, distinctive benign lung adenoma of pneumocyte origin. Despite its rarity, the tumor’s unique cellular morphology has sparked ongoing debates regarding the origin of its constituent cells. This study aimed to elucidate the molecular features of PSP tumor cells and enhance our understanding of the cellular processes contributing to PSP formation and biological behavior. Tissue samples from PSP and corresponding normal lung tissues (n = 4) were collected. We employed single-cell RNA sequencing and microarray-based spatial transcriptomic analyses to identify cell types and investigate their transcriptomes, with a focus on transcription factors, enriched gene expression, and single-cell trajectory evaluations. Our analysis identified 2 types of tumor cells: mesenchymal-epithelial dual-phenotype (MEDP) cells and a distinct subpopulation of type II alveolar epithelial cells exhibiting characteristics slightly reminiscent of type I alveolar epithelial cells (AT2Cs) corresponding to histologic round stromal cells and surface cuboidal cells, respectively. MEDP cells displayed weak alveolar epithelial differentiation but strong collagen production capabilities, as indicated by the expression of both TTF-1 and vimentin. These cells played a pivotal role in forming the solid and sclerotic areas of PSP. Moreover, MEDP cells exhibited a pronounced propensity for epithelial-mesenchymal transition, suggesting a greater potential for metastasis compared with AT2Cs. The capillary endothelial cells of PSP displayed notable diversity. Overall, this study provides, for the first time, a comprehensive mapping of the single-cell transcriptome profile of PSP. Our findings delineate 2 distinct subtypes of tumor cells, MEDP cells and AT2Cs, each with its own biological characteristics and spatial distribution. A deeper understanding of these cell types promises insights into the histology and biological behaviors of this rare tumor.

Generation of human alveolar epithelial type I cells from pluripotent stem cells

Alveolar epithelial type I cells (AT1s) line the gas exchange barrier of the distal lung and have been historically challenging to isolate or maintain in cell culture. Here, we engineer a human invitro AT1 model system via directed differentiation of induced pluripotent stem cells (iPSCs). We use primary adult AT1 global transcriptomes to suggest benchmarks and pathways, such as Hippo-LATS-YAP/TAZ signaling, enriched in these cells. Next, we generate iPSC-derived alveolar epithelial type II cells (AT2s) and find that nuclear YAP signaling is sufficient to promote a broad transcriptomic shift from AT2 to AT1 gene programs. The resulting cells express a molecular, morphologic, and functional phenotype reminiscent of human AT1 cells, including the capacity to form a flat epithelial barrier producing characteristic extracellular matrix molecules and secreted ligands. Our results provide an invitro model of human alveolar epithelial differentiation and a potential source of human AT1s.

Role of DCLK1/Hippo pathway in type II alveolar epithelial cells differentiation in acute respiratory distress syndrome

BackgroundDelay in type II alveolar epithelial cell (AECII) regeneration has been linked to higher mortality in patients with acute respiratory distress syndrome (ARDS). However, the interaction between Doublecortin-like kinase 1 (DCLK1) and the Hippo signaling pathway in ARDS-associated AECII differentiation remains unclear. Therefore, the objective of this study was to understand the role of the DCLK1/Hippo pathway in mediating AECII differentiation in ARDS.Materials and methodsAECII MLE-12 cells were exposed to 0, 0.1, or 1 μg/mL of lipopolysaccharide (LPS) for 6 and 12 h. In the mouse model, C57BL/6JNarl mice were intratracheally (i.t.) injected with 0 (control) or 5 mg/kg LPS and were euthanized for lung collection on days 3 and 7.ResultsWe found that LPS induced AECII markers of differentiation by reducing surfactant protein C (SPC) and p53 while increasing T1α (podoplanin) and E-cadherin at 12 h. Concurrently, nuclear YAP dynamic regulation and increased TAZ levels were observed in LPS-exposed AECII within 12 h. Inhibition of YAP consistently decreased cell levels of SPC, claudin 4 (CLDN-4), galectin 3 (LGALS-3), and p53 while increasing transepithelial electrical resistance (TEER) at 6 h. Furthermore, DCLK1 expression was reduced in isolated human AECII of ARDS, consistent with the results in LPS-exposed AECII at 6 h and mouse SPC-positive (SPC+) cells after 3-day LPS exposure. We observed that downregulated DCLK1 increased p-YAP/YAP, while DCLK1 overexpression slightly reduced p-YAP/YAP, indicating an association between DCLK1 and Hippo-YAP pathway.ConclusionsWe conclude that DCLK1-mediated Hippo signaling components of YAP/TAZ regulated markers of AECII-to-AECI differentiation in an LPS-induced ARDS model.Graphical

Prenatal FGFR2 Signaling via PI3K/AKT Specifies the PDGFRA+ Myofibroblast.

It is well known that FGFR2 (fibroblast growth factor receptor 2) signaling is critical for proper lung development. Recent studies demonstrate that epithelial FGFR2 signaling during the saccular phase of lung development (sacculation) regulates alveolar type 1 (AT1) and AT2 cell differentiation. During sacculation, PDGFRA (platelet-derived growth factor receptor-α)-positive lung fibroblasts exist as three functional subtypes: contractile myofibroblasts, extracellular matrix-producing matrix fibroblasts, and lipofibroblasts. All three subtypes are required during alveolarization to establish a niche that supports AT2 epithelial cell self-renewal and AT1 epithelial cell differentiation. FGFR2 signaling directs myofibroblast differentiation in PDGFRA+ fibroblasts during alveolar reseptation after pneumonectomy. However, it remains unknown if FGFR2 signaling regulates PDGFRA+ myo-, matrix, or lipofibroblast differentiation during sacculation. In this study, FGFR2 signaling was inhibited by temporal expression of a secreted dominant-negative FGFR2b (dnFGFR2) by AT2 cells from embryonic day (E) 16.5 to E18.5. Fibroblast and epithelial differentiation were analyzed at E18.5 and postnatal days 7 and 21. At all time points, the number of myofibroblasts was reduced and the number of lipo-/matrix fibroblasts was increased. AT2 cells are increased and AT1 cells are reduced postnatally, but not at E18.5. Similarly, in organoids made with PDGFRA+ fibroblasts from dnFGFR2 lungs, increased AT2 cells and reduced AT1 cells were observed. In vitro treatment of primary wild-type E16.5 adherent saccular lung fibroblasts with recombinant dnFGFR2b/c resulted in reduced myofibroblast contraction. Treatment with the PI3K/AKT activator 740 Y-P rescued the lack of myofibroblast differentiation caused by dnFGFR2b/2c. Moreover, treatment with the PI3K/AKT activator 740 Y-P rescued myofibroblast differentiation in E18.5 fibroblasts isolated from dnFGFR2 lungs.

The impact of the immune system on lung injury and regeneration in chronic obstructive pulmonary disease.

Chronic obstructive pulmonary disease (COPD) is a devastating respiratory condition that manifests via persistent inflammation, emphysema development and small airway remodeling. Lung regeneration is defined as the ability of the lung to repair itself after injury by the proliferation and differentiation of progenitor cell populations and becomes impaired in the COPD lung as a consequence of cell intrinsic epithelial stem cell defects and signals from the microenvironment. Although the loss of structural integrity and lung regenerative capacity are critical for disease progression, our understanding of the cellular players and molecular pathways that hamper regeneration in COPD remains limited. Intriguingly, despite being a key driver of COPD pathogenesis, the role of the immune system in regulating lung regenerative mechanisms is understudied. In this review, we summarize recent evidence on the contribution of immune cells to lung injury and regeneration. We focus on four main axes; the mechanisms via which myeloid cells cause alveolar degradation, the consequences of inefficient apoptotic cell removal, the formation of tertiary lymphoid structures and the production of autoreactive antibodies and the effects of innate and adaptive immune cell signaling on alveolar epithelial proliferation and differentiation. We finally provide insight on how recent technological advances in omics technologies and human ex vivo lung models can delineate immune cell-epithelium crosstalk and expedite precision pro-regenerative approaches toward reprogramming the alveolar immune niche to treat COPD.

Activation of α7nAChR in AT2 promotes alveolar regeneration through WNT7B signaling in acute lung injury.

Reducing inflammatory damage and improving alveolar epithelium regeneration are two key approaches to promoting lung repair in acute lung injury (ALI)/acute respiratory distress syndrome (ARDS). Stimulation of cholinergic-α7nAChR (α7 nicotinic acetylcholine receptor, coded by Chrna7) signaling could dampen lung inflammatory injury. However, whether activation of α7nAChR in alveolar type II (AT2) cells promotes alveolar epithelial injury repair and underlying mechanisms are elusive. Here, we found that α7nAChR was expressed on AT2 cells and was upregulated in response to LPS-induced ALI. Meanwhile, deletion of Chrna7 in AT2 cells impeded lung repair process and worsened lung inflammation in ALI. Using in vivo AT2 lineage-labeled mice and ex vivo AT2-derived alveolar organoids, we demonstrated that activation of α7nAChR expressed on AT2 cells improved alveolar regeneration by promoting AT2 cells to proliferate and subsequently differentiate toward alveolar type I (AT1) cells. Then we screened out the WNT7B signaling pathway by the RNA sequencing analysis of in vivo AT2 lineage-labeled cells, and further confirmed its indispensability for α7nAChR activation-mediated alveolar epithelial proliferation and differentiation. Thus, we have identified an unrecognized pathway that cholinergic-α7nAChR signaling determines alveolar regeneration and repair, which might provide us a novel therapeutic target for combating ALI.

Alveolar repair following LPS-induced injury requires cell-ECM interactions.

During alveolar repair, alveolar type 2 (AT2) epithelial cell progenitors rapidly proliferate and differentiate into flat AT1 epithelial cells. Failure of normal alveolar repair mechanisms can lead to loss of alveolar structure (emphysema) or development of fibrosis, depending on the type and severity of injury. To test if β1-containing integrins are required during repair following acute injury, we administered E. coli lipopolysaccharide (LPS) by intratracheal injection to mice with a postdevelopmental deletion of β1 integrin in AT2 cells. While control mice recovered from LPS injury without structural abnormalities, β1-deficient mice had more severe inflammation and developed emphysema. In addition, recovering alveoli were repopulated with an abundance of rounded epithelial cells coexpressing AT2 epithelial, AT1 epithelial, and mixed intermediate cell state markers, with few mature type 1 cells. AT2 cells deficient in β1 showed persistently increased proliferation after injury, which was blocked by inhibiting NF-κB activation in these cells. Lineage tracing experiments revealed that β1-deficient AT2 cells failed to differentiate into mature AT1 epithelial cells. Together, these findings demonstrate that functional alveolar repair after injury with terminal alveolar epithelial differentiation requires β1-containing integrins.

Incorporating GSE4 peptide in PEG/hyaluronic acid hydrogels to promote the alveolar epithelial differentiation of mesenchymal stem cells

Because of the shortage of donors, alveolar stem cells transplantation is under development as an important and promising treatment for end-stage lung disease. Currently, the acquisition of functional lung cells is mostly performed by two dimensional (2D) culture and suffers from low directed differentiation efficiency. It is particularly critical to replicate the three dimensional (3D) growth of lung cells, as cells grow in 3D microenvironment in vivo. In this work, we develop a 3D biomimetic composite hydrogel system based on the in situ crosslinking of the synthetic polymer 4 arm acrylated-poly(ethylene glycol) (4PEG-AC), the thiolated natural polymer hyaluronic acid (HA-SH), and the thiolated polypeptide (GSE4-SH) via a Michael-type “click” reaction under physiological conditions at pH 7.8. The PEG/HA/GSE4 hydrogel with a sheer modulus of 104.1 ± 9.9 Pa was used for 3D growth of bone marrow mesenchymal stem cells (BMSCs), displaying excellent biocompatibility. Covalent conjugation of GSE4 peptide in hydrogel promoted the differentiation of BMSCs into alveolar epithelial type 2 cells (AEC2s) with a AEC2s-differentiation rate of 58.6 ± 3.3%. Overall, this study provides a suitable 3D biomimetic platform to enable the efficient differentiation of stem cells into lung cells for lung tissue engineering.

Cellular metabolic basis of altered immunity in the lungs of patients with COVID-19.

Metabolic pathways drive cellular behavior. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection causes lung tissue damage directly by targeting cells or indirectly by producing inflammatory cytokines. However, whether functional alterations are related to metabolic changes in lung cells after SARS-CoV-2 infection remains unknown. Here, we analyzed the lung single-nucleus RNA-sequencing (snRNA-seq) data of several deceased COVID-19 patients and focused on changes in transcripts associated with cellular metabolism. We observed upregulated glycolysis and oxidative phosphorylation in alveolar type 2 progenitor cells, which may block alveolar epithelial differentiation and surfactant secretion. Elevated inositol phosphate metabolism in airway progenitor cells may promote neutrophil infiltration and damage the lung barrier. Further, multiple metabolic alterations in the airway goblet cells are associated with impaired muco-ciliary clearance. Increased glycolysis, oxidative phosphorylation, and inositol phosphate metabolism not only enhance macrophage activation but also contribute to SARS-CoV-2 induced lung injury. The cytotoxicity of natural killer cells and CD8+ T cells may be enhanced by glycerolipid and inositol phosphate metabolism. Glycolytic activation in fibroblasts is related to myofibroblast differentiation and fibrogenesis. Glycolysis, oxidative phosphorylation, and glutathione metabolism may also boost the aging, apoptosis and proliferation of vascular smooth muscle cells, resulting in pulmonary arterial hypertension. In conclusion, this preliminary study revealed a possible cellular metabolic basis for the altered innate immunity, adaptive immunity, and niche cell function in the lung after SARS-CoV-2 infection. Therefore, patients with COVID-19 may benefit from therapeutic strategies targeting cellular metabolism in future.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00430-021-00727-0.

Polyphenols from Chinese Herbal Medicine: Molecular Mechanisms and Therapeutic Targets in Pulmonary Fibrosis.

Pulmonary fibrosis (PF) is a highly confounding and fatal pathological process with finite treatment options. Multiple factors such as oxidative and immune/inflammation involve key pathological processes in chronic lung disease, and their intimate interactions mediate chronic lung damage, denudation of the alveolar epithelium, hyperproliferation of type II alveolar epithelial cells (AECIIs), proliferation and differentiation of fibroblasts, and the permeability of microvessels. We reviewed the classic mechanism of PF and highlighted a few emerging mechanisms for studying complex networks in lung disease pathology. Polyphenols, as a multi-target drug, has excellent potential in the treatment of pulmonary fibrosis. We then reviewed recent advances in discovering phenolic compounds from fruits, tea, and medical herbs with the bioactivities of simultaneously regulating multiple factors (e.g., oxidative stress, inflammation, autophagy, apoptosis, pyroptosis) for minimizing pulmonary fibrosis injury. These compounds include resveratrol, curcumin, salvianolic acid B, epigallocatechin-3-gallate, gallic acid, corilagin. Each phenolic compound can exert its anti-PF effect through various mechanisms, and the signaling pathways involved in different phenolic compounds are not the same. This review summarized the available evidence on phenolic compounds' effectiveness in pulmonary diseases and explored the molecular mechanisms and therapeutic targets of phenolic compounds from Chinese herbal medicine with the properties of inhibition of ongoing fibrogenesis and resolution of existing fibrosis.

Comprehensive epigenomic profiling of human alveolar epithelial differentiation identifies key epigenetic states and transcription factor co-regulatory networks for maintenance of distal lung identity

BackgroundDisruption of alveolar epithelial cell (AEC) differentiation is implicated in distal lung diseases such as chronic obstructive pulmonary disease, idiopathic pulmonary fibrosis, and lung adenocarcinoma that impact morbidity and mortality worldwide. Elucidating underlying disease pathogenesis requires a mechanistic molecular understanding of AEC differentiation. Previous studies have focused on changes of individual transcription factors, and to date no study has comprehensively characterized the dynamic, global epigenomic alterations that facilitate this critical differentiation process in humans.ResultsWe comprehensively profiled the epigenomic states of human AECs during type 2 to type 1-like cell differentiation, including the methylome and chromatin functional domains, and integrated this with transcriptome-wide RNA expression data. Enhancer regions were drastically altered during AEC differentiation. Transcription factor binding analysis within enhancer regions revealed diverse interactive networks with enrichment for many transcription factors, including NKX2–1 and FOXA family members, as well as transcription factors with less well characterized roles in AEC differentiation, such as members of the MEF2, TEAD, and AP1 families. Additionally, associations among transcription factors changed during differentiation, implicating a complex network of heterotrimeric complex switching in driving differentiation. Integration of AEC enhancer states with the catalog of enhancer elements in the Roadmap Epigenomics Mapping Consortium and Encyclopedia of DNA Elements (ENCODE) revealed that AECs have similar epigenomic structures to other profiled epithelial cell types, including human mammary epithelial cells (HMECs), with NKX2–1 serving as a distinguishing feature of distal lung differentiation.ConclusionsEnhancer regions are hotspots of epigenomic alteration that regulate AEC differentiation. Furthermore, the differentiation process is regulated by dynamic networks of transcription factors acting in concert, rather than individually. These findings provide a roadmap for understanding the relationship between disruption of the epigenetic state during AEC differentiation and development of lung diseases that may be therapeutically amenable.

YAP regulates alveolar epithelial cell differentiation and AGER via NFIB/KLF5/NKX2-1

SummaryVentilation is dependent upon pulmonary alveoli lined by two major epithelial cell types, alveolar type-1 (AT1) and 2 (AT2) cells. AT1 cells mediate gas exchange while AT2 cells synthesize and secrete pulmonary surfactants and serve as progenitor cells which repair the alveoli. We developed transgenic mice in which YAP was activated or deleted to determine its roles in alveolar epithelial cell differentiation. Postnatal YAP activation increased epithelial cell proliferation, increased AT1 cell numbers, and caused indeterminate differentiation of subsets of alveolar cells expressing atypical genes normally restricted to airway epithelial cells. YAP deletion increased expression of genes associated with mature AT2 cells. YAP activation enhanced DNA accessibility in promoters of transcription factors and motif enrichment analysis predicted target genes associated with alveolar cell differentiation. YAP participated with KLF5, NFIB, and NKX2-1 to regulate AGER. YAP plays a central role in a transcriptional network that regulates alveolar epithelial differentiation.

Pretreatment of aged mice with retinoic acid supports alveolar regeneration via upregulation of reciprocal PDGFA signalling

ObjectivesIdiopathic pulmonary fibrosis (IPF) primarily affects the aged population and is characterised by failure of alveolar regeneration, leading to loss of alveolar type 1 (AT1) cells. Aged mouse models of...

YAP Regulates NFI/KLF5 Transcriptional and Epigenetic Networks Directing Alveolar Epithelial Cell Differentiation

Ventilation is dependent upon the pulmonary alveoli which are lined by two major epithelial cell types, alveolar type 1 and 2 (AT1) and (AT2) cells. AT1 cells are located in close apposition to alveolar capillary endothelial cells to mediate gas exchange. AT2 cells synthesize and secrete pulmonary surfactant lipids and protein and serve as progenitor cells which proliferate and differentiate to repair the alveoli after injury. Herein, we developed transgenic mice in which YAP was activated or deleted to determine its roles in alveolar epithelial cell differentiation. Organoids from YAPactive mice selectively differentiated into AT1 cells demonstrating that YAP may be required for AT1 cell differentiation in-vitro . Activation of YAP in the postnatal lung increased epithelial cell proliferation, increased numbers of AT1 cells, and caused indeterminate differentiation of subsets of alveolar cells in-vivo, inducing atypical expression of genes normally restricted to conducting airway epithelial cells. Deletion of YAP increased expression of genes associated with mature AT2 cells. In combination with altered gene expression, YAP activation caused widespread changes in chromatin accessibility and ATAC sequencing demonstrated enhanced DNA accessibility in promoters of transcription factors and predicted target genes associated with alveolar cell differentiation. YAP participated with KLF5, NFIB, and NKX2-1 to regulate alveolar epithelial cell gene expression, together activating AGER, an AT1 signature gene. YAP plays a central role in a transcriptional network regulating alveolar epithelial differentiation.

A critical role for miR-142 in alveolar epithelial lineage formation in mouse lung development.

The respiratory epithelium arises from alveolar epithelial progenitors which differentiate into alveolar epithelial type 1 (AT1) and type 2 (AT2) cells. AT2 cells are stem cells in the lung critical for the repair process after injury. Mechanisms regulating AT1 and AT2 cell maturation are poorly defined. We report that the activation of the glucocorticoid pathway in an in vitro alveolar epithelial lineage differentiation assay led to increased AT2 marker Sftpc and decreased miR-142 expression. Using miR-142 KO mice, we demonstrate an increase in the AT2/AT1 cell number ratio. Overexpression of miR-142 in alveolar progenitor cells in vivo led to the opposite effect. Examination of the KO lungs at E18.5 revealed enhanced expression of miR-142 targets Apc, Ep300 and Kras associated with increased β-catenin and p-Erk signaling. Silencing of miR-142 expression in lung explants grown in vitro triggers enhanced Sftpc expression as well as increased AT2/AT1 cell number ratio. Pharmacological inhibition of Ep300-β-catenin but not Erk in vitro prevented the increase in Sftpc expression triggered by loss of miR-142. These results suggest that the glucocorticoid-miR-142-Ep300-β-catenin signaling axis controls pneumocyte maturation.

39 - Close neighbors in the niche: Paracrine signals from endothelial cells promote alveolar epithelial differentiation of induced pluripotent stem cell-derived lung progenitors

39 - Close neighbors in the niche: Paracrine signals from endothelial cells promote alveolar epithelial differentiation of induced pluripotent stem cell-derived lung progenitors

CCN5 in alveolar epithelial proliferation and differentiation during neonatal lung oxygen injury.

Lung immaturity is the major cause of morbidity and mortality in premature infants, especially those born <28weeks of gestation. These infants are at high risk of developing respiratory distress syndrome (RDS), a lung disease caused by insufficient surfactant production and immaturity of saccular/alveolar type II epithelial cells in the lung. RDS treatment includes oxygen and respiratory support that improve survival but also increase the risk for bronchopulmonary dysplasia (BPD), a chronic lung disease characterized by arrested alveolarization, airway hyperreactivity, and pulmonary hypertension. The mechanisms regulating normal alveolar development and how injury disrupts normal development to cause BPD are not well understood. We examined the role of the matricellular protein CCN5 (Cysteine-rich protein 61/Connective tissue growth factor/Nephroblastoma-overexpressed protein) in the development of BPD. Cultured non-proliferating alveolar type II cells expressed low levels of CCN5 protein, and displayed higher levels during proliferation. siRNA targeting of CCN5 reduced alveolar type II cell proliferation and migration in cell culture. In a mouse model of hyperoxia-induced BPD, CCN5 protein was increased only in proliferating alveolar type I cells. Alveolar epithelial cells co-expressing markers of type II cells and type I cells also appeared. The results suggest that hyperoxic injury in immature lungs induces proliferation of type I cells and trans-differentiation of type II cells into type I cells. We propose that the mechanism of the injury response in BPD includes CCN5 expression. Study of CCN5 in neonatal alveolar injury will further our understanding of BPD pathophysiology while providing a mechanistic foundation for therapeutic approaches.

To Evaluate The Synergistic Effects of Dexamethasone and TGF-beta Inhibitors for Alveolar Epithelial Cells Differentiation

To Evaluate The Synergistic Effects of Dexamethasone and TGF-beta Inhibitors for Alveolar Epithelial Cells Differentiation