Development of novel in vitro human alveolar epithelial cell models to study distal lung biology and disease [scRNA-seq]
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ABSTRACT: To address the need for human alveolar epithelial cell (AEC)-derived lines to more suitably model distal lung diseases, we have generated and characterized novel immortalized cell lines derived from human AECs. We used a combination of the ROCK inhibitor, Y-27632, and lentiviral transduction of SV40 Large T antigen of previously cryopreserved isolated human alveolar epithelial type 2 (AT2) cells to generate immortalized AECs. These AEC lines proliferate well on standard tissue culture dishes forming an epithelial monolayer and express lung progenitor markers SOX9 and SOX2. When grown in 3D culture with lung fibroblasts, the cells form NKX2-1+ organoids expressing more mature alveolar lung markers, AQP5 and GPRC5A. Single cell RNA-sequencing of one AEC line comparing cells in 2D versus 3D revealed increased cellular heterogeneity and an induction of cytokine and lipoprotein signaling in 3D culture, reflecting interactions with the microenvironment during organoid formation. Taken together, these data show our novel progenitor-like AEC lines retain a genetic and structural memory of their alveolar cell lineage despite long-term expansion, providing a valuable new system to model the distal lung in vitro.
Project description:To address the need for human alveolar epithelial cell (AEC)-derived lines to more suitably model distal lung diseases, we have generated and characterized novel immortalized cell lines derived from human AECs. We used a combination of the ROCK inhibitor, Y-27632, and lentiviral transduction of SV40 Large T antigen of previously cryopreserved isolated human alveolar epithelial type 2 (AT2) cells to generate immortalized AECs. These AEC lines proliferate well on standard tissue culture dishes forming an epithelial monolayer and express lung progenitor markers SOX9 and SOX2. When grown in 3D culture with lung fibroblasts, the cells form NKX2-1+ organoids expressing more mature alveolar lung markers, AQP5 and GPRC5A. Single cell RNA-sequencing of one AEC line comparing cells in 2D versus 3D revealed increased cellular heterogeneity and an induction of cytokine and lipoprotein signaling in 3D culture, reflecting interactions with the microenvironment during organoid formation. Taken together, these data show our novel progenitor-like AEC lines retain a genetic and structural memory of their alveolar cell lineage despite long-term expansion, providing a valuable new system to model the distal lung in vitro.
Project description:Background: Disruption of alveolar epithelial cell (AEC) differentiation is implicated in 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. We 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. Enhancer 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.
Project description:Airway epithelial cells (AEC) are critical components of the inflammatory and immune response during exposure to pathogens. AECs in monolayer culture and differentiated epithelial cells in air-liquid interface (ALI) represent two distinct and commonly used in vitro models, yet differences in their response to pathogens have not been investigated. In this study, we compared the transcriptional effects of flagellin on AECs in monolayer culture versus ALI culture using exon microarrays and RNAsequencing. We found that AECs cultured in monolayer and ALI have strikingly different transcriptional states at baseline. When challenged with flagellin, monolayer AEC cultures greatly increased transcription of numerous genes mapping to wounding response, immunity and inflammatory response. In contrast, AECs in ALI culture had an unexpectedly muted response to flagellin, both in number of genes expressed and relative enrichment of inflammatory and immune pathways. In conclusion, In vitro culturing methods have a dramatic effect on the transcriptional profile of AECs at baseline and after stimulation with flagellin. These differences suggest that epithelial responses to pathogen challenges are distinctly different in culture models of intact and injured epithelium.
Project description:Airway epithelial cells (AEC) are critical components of the inflammatory and immune response during exposure to pathogens. AECs in monolayer culture and differentiated epithelial cells in air-liquid interface (ALI) represent two distinct and commonly used in vitro models, yet differences in their response to pathogens have not been investigated. In this study, we compared the transcriptional effects of flagellin on AECs in monolayer culture versus ALI culture using exon microarrays and RNAsequencing. We found that AECs cultured in monolayer and ALI have strikingly different transcriptional states at baseline. When challenged with flagellin, monolayer AEC cultures greatly increased transcription of numerous genes mapping to wounding response, immunity and inflammatory response. In contrast, AECs in ALI culture had an unexpectedly muted response to flagellin, both in number of genes expressed and relative enrichment of inflammatory and immune pathways. In conclusion, In vitro culturing methods have a dramatic effect on the transcriptional profile of AECs at baseline and after stimulation with flagellin. These differences suggest that epithelial responses to pathogen challenges are distinctly different in culture models of intact and injured epithelium.
Project description:The cAMP response element binding protein (Creb) is a member of a leucine zipper transcription factor family that regulates gene expression primarily in response to the intracellular cAMP signalling pathway. Previous studies have shown Creb1-null mice suffer respiratory failure with lung atelectasis and a large reduction in Sftpd mRNA. Using a new line of Creb1-null mice we have further investigated Creb function in the developing mouse lung, focussing on differentiation of the airway epithelium. The lungs of Creb1-null fetal mice showed normal respiratory development until E17.5 when proximal and distal airways fail to inflate. Subsequent ultrastructural analysis of the lungs of E17.5 Creb1-null fetal mice revealed a defect in AEC differentiation with a reduction in proportions of type-II AECs and in particular, a very large reduction in type-I AECs. Furthermore, immunostaining for the proximal epithelial cell markers Scgb1a1 (also known as CC10) (Clara cells), Foxj1 (Ciliated cells), and CGRP (Neuroendocrine cells) showed delayed or defective proximal epithelial differentiation in Creb1-null fetal lungs. Quantitative real time PCR (qRT-PCR) analysis at E17.5 in Creb1-null fetal lungs showed differential expression of mRNAs for Creb/Atf1 subfamily members, surfactant-associated proteins, type-I AEC markers and proximal epithelial markers. Furthermore, whole-genome microarray analysis at E17.5 in Creb1-null fetal lungs has provided novel genes which will prove useful to further investigate Creb-mediated signalling in lung development. Together these results demonstrate that Creb plays a key role in determining cell lineages and differentiation of the developing lung epithelium.
Project description:The structure of alveoli is critical for proper lung function, the extracellular matrix (ECM) that forms these delicate structures need to be maintained throughout life, when this fails, patients suffer from conditions such as emphysema or lung fibrosis. The alveolar walls are lined by alveolar epithelial cells (AEC), and we herein set out to examine their potential to contribute to ECM remodeling in a human three-dimensional in vitro model based on human lung ECM. Cryopreserved type 2 AEC (AEC2) isolated from healthy lungs and lungs of patients with chronic obstructive pulmonary disease (COPD) were cultured in decellularized human lung slices over a period of 13 days. AEC2 from healthy lungs were treated with transforming growth factor ß1 (TGF-ß1) to evaluate the plasticity of their ECM production. Evaluation of phenotypic markers and expression of matrisome genes and proteins were performed by RNA-sequencing, mass spectrometry and immunohistochemistry. AEC2 in our model displayed an AEC marker profile similar to freshly isolated AEC2. COPD-derived AEC2 retained expression of known disease markers such as HLA-A throughout the culture period. AEC2 matrisome expression was found not to be limited to basement membrane components but included a complex set of structural proteins found in interstitial ECM. With TGF-ß1 stimuli, AEC2 showed a change in ECM production resembling what have previously been documented in mesenchymal cells, without loss of AEC marker expression. A previously unexplored potential of AEC to directly contribute to ECM turnover is revealed, motivating a re-evaluation of the role of AEC2 in pathological lung remodeling.
Project description:A GFP-expressing recombinant A/Puerto Rico/8/1934 influenza virus was used to infect C57BL/6 wild type mice and on day 3 post infection, lung alveolar epithelial cells (AEC) were isolated and sorted based on GFP expression. GFP+ AEC represent the infected AEC and GFP- AEC represent the bystander AEC. AEC were also sorted from uninfected mice to serve as controls.
Project description:We applied next-generation sequencing to investigate the gene expression profiles in mouse alveolar epithelial cells (AECs). We identified a number of differentially regulated genes in the AECs of mice with bleomycin induced pulmonary fibrosis and LPS induced acute lung injury.
Project description:DNA methylation profiling of airway epithelial cells (AECs) and peripheral blood mononuclear cells (PBMCs) from normal, atopic and asthmatic subjects. The Illumina GoldenGate Methylation Cancer Panel I was used to obtain DNA methylation profiles across approximately 1505 CpGs in AECs and PBMCs. Samples included 7 healthy, 9 atopic, 4 atopic asthmatic and 5 non-atopic asthmatic subjects. Please note that only some of the samples are matched (i.e. AECs and PBMCs from the same individual) due to DNA quality or sample collection (i.e. only one sample (AEC or PBMC) was collected from the patient). Bisulphite converted DNA from the 41 samples were hybridised to the Illumina GoldenGate Methylation Beadchip
Project description:Alveolar epithelial regeneration is critical for normal lung function and becomes dysregulated in disease. While alveolar type 2 (AT2) and club cells are known distal lung epithelial progenitors, determining if alveolar epithelial type 1 (AT1) cells also contribute to alveolar regeneration has been hampered by lack of highly specific mouse models labeling AT1 cells. To address this, the Gramd2CreERT2 transgenic strain was generated and crossed to ROSAmTmG mice. Extensive cellular characterization, including distal lung immunofluorescence and cytospin staining, confirmed that GRAMD2+ AT1 cells are highly enriched for green fluoresecent protein (GFP). Interestingly, Gramd2CreERT2 GFP+ cells were able to form colonies in organoid co-culture with Mlg fibroblasts. Temporal scRNAseq revealed that Gramd2+ AT1 cells transition through numerous intermediate lung epithelial cell states including basal, secretory and AT2 cell in organoids while acquiring proliferative capacity. Our results indicate that Gramd2+ AT1 cells are highly plastic suggesting they may contribute to alveolar regeneration.