An experimental model of the epithelial to mesenchymal transition and pro-fibrogenesis in urothelial cells related to bladder pain syndrome/interstitial cystitis

Background

Suitable in vitro models are needed to investigate urothelial epithelial to mesenchymal transition (EMT) and pro-fibrogenesis phenotype in bladder pain syndrome/interstitial cystitis (BPS/IC). This study is to establish a novel experimental BPS/IC cell model and explore how different concentrations of tumor necrosis factor (TNF)-α influence the EMT and pro-fibrogenesis phenotype of urothelial cells.

Methods

SV-HUC-1 urothelial cells were cultured with 2, 10, or 50 ng/mL TNF-α to mimic chronic inflammatory stimulation. The EMT and pro-fibrogenesis phenotype, including production of collagen I and pro-fibrosis cytokines, were estimated after 72 h of culture.

Results

The bladder urothelial cells of BPS/IC exhibited upregulated vimentin, TNF-α and TNF receptor, downregulated E-cadherin, and increased collagen I. Higher concentrations of TNF-α (10 and 50 ng/mL) produced an obvious mesenchymal morphology, enhanced invasion and migratory capacity, increased expression of vimentin, and decreased expression of E-cadherin. Collagen I was increased in cells treated with 2 and 10 ng/mL TNF-α after 72 h. Secretion of interleukin (IL)-6 and IL-8 was promoted with 10 and 50 ng/mL TNF-α, while that of IL-1β or transforming growth factor-β was unaffected. Slug and Smad2 were upregulated by TNF-α after 72 h. The Smad pathway was activated most strongly with 10 ng/mL TNF-α and Slug pathway activation was positively correlated with the concentration of TNF-α.

Conclusions

Sustained 10 ng/mL TNF-α stimulation induced the EMT and pro-fibrogenesis phenotype resembling BPS/IC in SV-HUC-1 cells. Minor inflammatory stimulation induced the pro-fibrogenesis phenotype while severe inflammatory stimulation was more likely to produce significant EMT changes. Different degrees of activation of the Slug and Smad pathways may underlie this phenomenon.