TNP-470, an angiogenesis inhibitor, suppresses the progression of peritoneal fibrosis in mouse experimental model

BACKGROUND: In patients on long-term peritoneal dialysis (PD), angiogenesis and vasculopathy are observed in the peritoneum, and the degree of vascularization correlates with the area of fibrotic tissue, suggesting the involvement of angiogenesis in the progression of peritoneal fibrosis. The aim of the present study was to evaluate the effect of TNP-470, an anti-angiogenic compound, on the development of peritoneal fibrosis induced by chlorhexidine gluconate (CG). METHODS: Peritoneal fibrosis was induced by injection of CG into peritoneal cavity of Institute for Cancer Research (ICR) mice. TNP-470 was injected subcutaneously with CG. Mice were sacrificed, and peritoneal tissues were dissected out at days eight and 16 after CG and TNP-470 injection. The expression patterns of CD31 (as a marker of endothelial cells), vascular endothelial cell growth factor (VEGF), alpha-smooth muscle actin (as a marker of myofibroblasts), heat shock protein 47 (HSP47), type III collagen, F4/80 (as a marker of mice macrophages), proliferating cell nuclear antigen (PCNA), and cyclin-dependent kinase 2 (Cdk2) were examined by immunohistochemistry. RESULTS: CG-injected mice showed thickening of the submesothelial zone and increased number of vessels, myofibroblasts, and infiltrating macrophages. The expression levels of VEGF, type III collagen, and HSP47 were increased, and a large number of PCNA-positive cells and Cdk2-expressing cells were observed in the thickened submesothelial area. Treatment with TNP-470 suppressed the submesothelial zone thickening and reduced collagen III expression as well as angiogenesis. TNP-470 also decreased the number of VEGF-expressing cells, myofibroblasts, macrophages, PCNA-positive cells, and Cdk2-expressing cells. CONCLUSION: Our results indicate the involvement of angiogenesis in the progression of peritoneal fibrosis, and suggest that TNP-470 may be potentially useful for the prevention of peritoneal fibrosis through inhibition of angiogenesis and suppression of myofibroblast proliferation.