Adipose-derived mesenchymal stromal cells alleviate intestinal fibrosis: The role of tumor necrosis factor-stimulated gene 6 protein.

ABSTRACT

BACKGROUND: The therapeutic potential of adipose-derived mesenchymal stromal cells (AMSCs) in the treatment of intestinal fibrosis occured in patients with Crohn's disease (CD) remains unclear. Tumor necrosis factor-stimulated gene 6 (TSG6) protein plays a critical role in inflammation regulation and tissue repair. This study aimed to determine if AMSCs attenuate intestinal fibrosis by secreting paracrine TSG6 protein and explore the underlying mechanisms. METHODS: Two murine models for intestinal fibrosis were established using 2,4,6-trinitrobenzene sulfonic acid in BALB/c mice and dextran sulfate sodium in C57BL/6 mice. Primary human fibroblasts and CCD-18co cells were incubated with transforming growth factor (TGF)-ß1 to build two fibrosis cell models in vitro. RESULTS: Intraperitoneally administered AMSCs attenuated intestinal fibrosis in the two murine models, as evidenced by significant alleviation of colon shortening, collagen protein deposits, and submucosal thickening, and also decrease in the endoscopic and fibrosis scores (P < 0.001). Although intraperitoneally injected AMSCs did not migrate to the colon lesions, high levels of TSG6 expression and secretion were noticed both in vivo and in vitro. Similar to the role of AMSCs, injection of recombinant human TSG6 attenuated intestinal fibrosis in the mouse models, which was not observed with the administration of AMSCs with TSG6 knockdown or TSG6 neutralizing antibody. Mechanistically, TSG6 alleviates TGF-ß1-stimulated upregulation of α-smooth muscle actin (αSMA) and collagen I by inhibiting Smad2 phosphorylation. Furthermore, the expression of TSG6 is lower in intestinal fibrosis tissue of patients with Crohn's disease and can reduce pro-fibrotic protein (αSMA) secretion from primary ileal fibrotic tissue. CONCLUSIONS: AMSCs attenuate intestinal fibrosis by secreting paracrine TSG6 protein, which inhibits Smad2 phosphorylation. TSG6, a novel anti-fibrotic factor, could potentially improve intestinal fibrosis treatments.