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RNA-Seq analysis of genes and pathways involved in the TGF-β-driven transformation of fibroblasts to myofibroblasts

ABSTRACT: Background: Asthma is the most common chronic lung disease in children and young adults worldwide. Airway remodelling (including increased fibroblasts and myofibroblasts in airway walls due to chronic inflammation) differentiates asthmatic from non-asthmatic airways. The increase in airway fibroblasts and myofibroblasts occurs via epithelial to mesenchymal transition (EMT) where epithelial cells lose their tight junctions and are transdifferentiated to mesenchymal cells, with further increases in myofibroblasts occurring via fibroblast-myofibroblast transition (FMT). Transforming growth factor (TGF)-β is the central EMT- and FMT-inducing cytokine. In this study, we have used next generation sequencing to delineate the changes in the fibroblast transcriptome induced by TGF-β treatment in both the short term and after differentiation into myofibroblasts, to gain an understanding of the contribution of TGF-b induced transdifferentiation to the asthmatic phenotype. The data obtained from RNAseq analysis was confirmed by quantitative PCR (qPCR). Results: As expected, we found that genes coding for intermediates in the TGF-β signalling pathways (SMADs) were differentially expressed after treatment, and genes involved in cytoskeletal pathways (FN1, LAMA, ITGB1) were differentially expressed in myofibroblasts compared to fibroblasts. Importantly, genes that were previously shown to be changed in asthmatic lungs (ADAMTS1, DSP, TIMPs, MMPs) were differentially expressed in myofibroblasts, strongly suggesting that TGF-β mediated differentiation of fibroblasts to myofibroblasts may underlie important changes in the asthmatic airway. We also identified new signalling pathways (AKT, PTEN) that are changed in myofibroblasts compared to fibroblasts. Conclusion: We have found a significant number of genes that are altered after differentiation of fibroblasts into myofibroblasts by TGF-β treatment, many of which were expected or predicted. However, we also identified novel genes and pathways that were affected after treatment of fibroblasts with TGF-β, which suggests additional pathways that that are activated during the transition between fibroblasts and myofibroblasts, and may contribute to the asthma phenotype.

ORGANISM(S): Homo sapiens

PROVIDER: GSE110021 | GEO | 2020/01/28

REPOSITORIES: GEO

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Project description:Tumor microenvironment contains various components including cancer cells, tumor vessels, and cancer associated fibroblasts (CAFs), comprising of tumor-promoting myofibroblasts and tumor-suppressing fibroblasts. Multiple lines of evidence indicated that transforming growth factor-β (TGF-β) induces the formation of myofibroblasts and other types of mesenchymal (non-myofibroblastic) cells from endothelial cells. Recent reports showed that fibroblast growth factor 2 (FGF2) modulates TGF-β-induced mesenchymal transition of endothelial cells, but the molecular mechanisms regarding the signals that control the transcriptional networks during the formation of different groups of fibroblasts remain largely unclear. Here, we studied the roles of FGF2 during the regulation of TGF-β-induced mesenchymal transition of tumor endothelial cells (TECs). We demonstrated that auto/paracrine FGF signals in TECs inhibit TGF-β-induced endothelial-to-myofibroblast transition (End-MyoT), leading to suppressed formation of contractile myofibroblast cells, but on the other hand can also collaborate with TGF-β in promoting the formation of active fibroblastic cells which have migratory and proliferative properties. FGF2 modulated TGF-β-induced formation of myofibroblastic and non-myofibroblastic cells from TECs via transcriptional regulation of the array of various mesenchymal markers and growth factors. Furthermore, we observed that TECs treated with TGF-β were more competent in promoting in vivo tumor growth than TECs treated with TGF-β and FGF2. Mechanistically, we showed that Elk1 mediated this FGF2-induced inhibition of End-MyoT via inhibition of TGF-β-induced transcriptional activation of α-SMA promoter by myocardin-related transcription factor (MRTF)-A. Our data suggest that TGF-β and FGF2 oppose and cooperate with each other during the formation of myofibroblastic and non-myofibroblastic cells from TECs to determine the characteristics of the mesenchymal cells in tumor microenvironment. Identification of marker genes for TGF-β-induced endothelial-to-myofibroblast transition

Project description:ABSTRACT Background: Primary human distal lung/parenchymal fibroblasts (DLF) exhibit a different phenotype from airway fibroblasts (AF), including the expression of high levels of alpha-SMA. The scope of the differences and the mechanisms driving them are unknown. We hypothesized that the distinct fibroblast characteristics based on lung region predicted a broad range of genomic differences which contribute to distinctly different functional pathway activation in AF and DLF. Methods and Findings: To investigate whether comprehensive gene expression patterns vary between AF and DLF, we compared global gene expression profiles of 3 matched pairs of primary human fibroblasts isolated from proximal and distal lung. 194 transcripts were upregulated in AF, and 290 transcripts upregulated in DLF. Quantitative real-time PCR (qRT-PCR) from both asthmatic and normal subjects confirmed the validity of microarray data (n = 8). Further analysis identified distinct pathway activation patterns, including the identification of the TGF-β receptor/SMAD3 signaling pathway as critical to the phenotypic differences in AF and DLF. The functional impact of these molecular differences on AF and DLF was then analyzed using Western blot, qRT-PCR, ELISA and gene knock-down approaches. TGF-β receptor/SMAD2-3 pathway analysis confirmed the contribution of higher TGF-β1 expression and accompanying SMAD3 and JNK activation to the increased alpha-SMA level seen in DLF. There are two limitations associated with our work. First, the microarray sample size was small. Second, for ethical reasons, a large majority of our data were from asthmatic subjects, only one pair of airway and distal lung tissues from a subject without knowing preexisting lung disease matched for age and smoking status was available. In this single normal subject, the same pattern of differences existed, supporting the concept that these genomic differences are regional, rather than disease-related. Conclusions: These findings demonstrated marked molecular and functional differences for these two lung regional fibroblast populations. These results suggest that airway and parenchymal fibroblasts differ in their responses to injury, repair, and remodeling in the lungs. There are likely profound implications of these observations for understanding mechanisms of development of fibrotic lung diseases as well as approaching therapy. In order to identify the underlying molecular differences between airway- and distal lung fibroblasts, microarray analysis was performed on 3 different matched pairs of fibroblasts.

Project description:Signalling pathways regulate all major cellular events in health and disease, including asthma development and progression. Complexity of human intracellular signalization can be explored using novel systemic approaches that exploit whole-transcriptome analysis. Cap-analysis-of-gene-expression (CAGE) is a method of choice for generating transcriptome libraries, as it interrogates only terminally capped mRNAs that have the highest probability to be translated into protein. In this study we for the first time systematically profiled differentially activated Intracellular Signalling Pathways (ISPs) in cultured primary human airway smooth muscle (ASM) cells from asthmatic (n=8) and non-asthmatic (n=6) subjects in a high-throughput assay, highlighting asthma-specific co-regulatory patterns. CAGE-libraries from primary human ASM cells were subject to massive parallel next generation sequencing, and a comprehensive analysis of ISP activation was performed using a recently developed technique OncoFinder. Analysis of 270 ISPs led to discovery of multiple pathways clearly distinguishing asthmatic from normal cells. In particular, we found 146 (p<0.05) and 103 (p<0.01) signalling pathways differentially active in asthmatic vs non-asthmatic samples. We identified seven clusters of coherently acting pathways functionally related to the disease. Pathways down-regulated in asthma mostly represented cell death-promoting pathways, whereas the up-regulated ones were mainly involved in cell growth and proliferation, inflammatory response and some specific reactions, including smooth muscle contraction and hypoxia - related signalization. Most of interactions uncovered in this study were not previously associated with asthma, suggesting that these results may be pivotal to development of novel therapeutic strategies that specifically address the ISP signature linked with asthma pathophysiology. Capped mRNA profiles of primary bronchial smooth muscle cells from 8 asthmatic and 6 healthy donors were generated by deep sequencing using Illumina HiSeq1500.

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RNA-Seq analysis of genes and pathways involved in the TGF-β-driven transformation of fibroblasts to myofibroblasts

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