TGFβ mediates collagen production in human CRSsNP nasal mucosa‐derived fibroblasts through Smad2/3‐dependent pathway and CTGF induction and secretion

Chronic rhinosinusitis without nasal polyp (CRSsNP) is characterized by tissue remodeling and fibrosis. Transforming growth factor-β (TGF-β) is considered a master switch in the induction of the profibrotic program which can induce fibroblasts to synthesize and contract extracellular matrix (ECM) proteins. A previous study has shown TGF-β1 signaling and collagen overproduction in the CRSsNP, but the responsible cells and mechanism of action remain unclear. Therefore, this study was aimed to investigate the relationship between TGF-β1 stimulation and collagen expression and to explore the role of connective tissue growth factor (CTGF) during the remodeling process using human CRSsNP nasal mucosa tissues and mucosa-derived fibroblasts as main materials. We found that TGF-β1 and its isoforms could promote collagen protein expression. Concomitantly, TGF-β1 caused CTGF expression and secretion. An addition of exogenous CTGF to fibroblasts also caused collagen expression. In accordance with these observations, TGF-β1, CTGF, and collagen were highly expressed in the subepithelial stroma region of CRSsNP nasal mucosa, as determined by immunohistochemistry. The TGF-β1-mediated collagen expression could be blocked by actinomycin D and SIS3, suggesting that the induction was through transcriptional regulation and Smad2/3-dependent pathway. Finally, we demonstrated that CTGF small interfering RNA knockdown led to a substantial decrease in TGF-β1-mediated collagen expression. Collectively, our results provide first and further evidence that TGF-β1 mediates collagen expression-production through a canonical Smad2/3-dependent pathway and CTGF induction and secretion in human nasal fibroblasts. Moreover, TGF-β1, CTGF, and collagen are highly expressed in human CRSsNP nasal mucosa specimens, suggesting their roles in tissue remodeling during CRSsNP progression.