Human adipose stem cell conditioned medium has a pro-fibrotic and EMT-stimulating effect on urethral fibroblasts in vitro

Fibrosis, characterized by excessive deposition of scar tissue, leads to the dysfunction of various organs. An urethral stricture, or pathological narrowing of the urethra, is an example of such scarring. The use of human adipose stem cell conditioned medium (HASC-CM) has shown promise as an anti-fibrotic treatment in vivo , as molecules produced by HASCs exhibit anti-inflammatory and fibrosis-modulating properties. However, HASC-CM has also been demonstrated to activate epithelial-to-mesenchymal transition (EMT) in cancer-associated cells. To elucidate whether HASC-CM promotes EMT or myofibroblast activation, we investigated its effects on primary human urethral fibroblasts (HUFs) and prostatic fibroblasts of the WPMY-1 line. We showed that HASC-CM promotes migration speed in HUFs but not in WPMY-1 cells while also increasing vimentin levels in the cells, both markers of EMT. Moreover, HASC-CM suppressed SMAD5 signalling in HUFs without altering SMAD3 signalling in either cell type. In addition, HASC-CM treatment induced myocardin-related transcription factor A (MRTF-A) nuclear translocation and increased amount of alpha smooth muscle actin (αSMA) in HUFs, indicating a shift towards the myofibroblast phenotype. We conclude that the effect of HASC-CM on WPMY-1 cells is negligible, however, this type of treatment has a pro-fibrotic and EMT-stimulating effect on HUFs. • PDGFB, IL-1a, IL-2 and IL-6 were identified in human adipose stem cell conditioned medium (HASC-CM) • HASC-CM reduced SMAD5 phosphorylation in human urethral fibroblasts, but not WPMY-1 cells • Reduced SMAD5 phosphorylation in urethral fibroblasts influenced MRTF-A nuclear translocation and subsequent appearance of EMT markers • HASC-CM also provided pro-fibrotic stimuli, manifesting as the appearance of alpha smooth muscle actin fibers in urethral fibroblasts