Protective Effect of Tonsil-Derived Mesenchymal Stem Cells on Peritoneal Fibrosis by Inhibiting Oxidative Stress

Background: Mesenchymal stem cells (MSCs) have regenerative capability and exert paracrine actions on damaged tissues and have recently received a new attention due to its preventive effect on organ fibrosis by inhibiting epithelial-to-mesenchymal transition (EMT). The EMT of mesothelial cells (MCs) is an early mechanism of peritoneal dysfunction in peritoneal dialysis (PD). This study was undertaken to investigate the role of Tonsil-derived MSCs (T-MSCs) in TGFβ-induced EMT of human peritoneal mesothelial cells (HPMCs) and its mechanism. Methods: Transwell co-culture system was used in which MCs were cultured with T-MSCs or T-MSC-conditioned medium (CM). EMT was evaluated by the changes in morphology and markers of epithelial and mesenchymal cells. ROS generation was assessed by DCF-DA and MitoSoxR staining. The effects of T-MSC on the expression of antioxidant enzymes and anti-fibrotic proteins were compared with adipose (AD)-derived MSCs and bone marrow (BM)-derived MSCs. Animal model of PD was established by daily infusion of 4.25% glucose-based dialysate with MGO for 3 weeks via intraperitoneal catheter in Sprague-Dawley rats. T-MSC (5.0x106 cells, i.p.) was injected at 14 days, and peritoneal tissue was isolated in 7 days of T-MSC injection. Markers of oxidative stress and anti-fibrotic were evaluated with peritoneal equilibrium test and histologic analysis. Results: T-MSC or T-MSC-CM inhibited TGFβ-induced EMT (increased ZO-1 and E-cadherin, decreased αSMA) and oxidative stress (decreased ROS generation). Compared to AD- and BM-MSCs, T-MSCs exhibited higher expression of antioxidant enzymes (catalase, GPx, and SOD) and anti-fibrotic proteins (HGF and BMP-7). T-MSC-CM also restored TGF-β-induced suppression of antioxidant enzymes and anti-fibrotic factors in HPMCs. T-MSC-treated rats had a higher D2/D0 glucose and a lower D2/P2 creatinine. Anti-human nuclei staining confirmed T-MSC engraftment along the mesothelial layer. T-MSCs alleviated EMT and peritoneal fibrosis with an amelioration of oxidative stress, as evidenced by decreased expression of 8-OHdG, NT, and HNE, along with increased GSH and SOD2. Conclusion: T-MSCs represent a promising approach to prevent peritoneal fibrosis by providing anti-fibrosis and anti-oxidant effects in the peritoneal cavity and ameliorating the phenotype transition of peritoneal mesothelial cells. Funding: Government Support – Non-U.S.