Preventive Effects of Erythropoietin on Peritoneal Hypoxia and Fibrosis in Rats with Chlorhexidine Gluconate-induced Peritoneal Fibrosis

Abstract

Background: Vasculopathy is one of the characteristic findings in long-term peritoneal dialysis (PD) patients. Erythropoietin (Epo) used to treat renal anemia may promote angiogenesis. The present study evaluated anti-fibrotic effects of Epo in the rat with chlorhexidine gluconate (CG) -induced peritoneal sclerosis. Methods: Twenty-four Sprague-Dawley rats at 8 weeks of age were divided into four groups. The rats were intraperitoneally administered CG and Epo (CG+Epo group), CG alone (CG group) or Epo alone (Epo group) for 28 days. A control group was administered ethanol and vehicle. Expressions of hypoxia-inducible factor-1a (HIF-1a), erythropoietin receptor (EpoR) and pimonidazole were evaluated by immunohistochemistry. HIF-1a, vascular endothelial growth factor (VEGF), angiopoietin-1 (Ang-1), angiopoietin-2 (Ang-2) and connective tissue growth factor (CTGF) were examined by real-time PCR. Double staining was performed for CD34 and a-smooth muscle actin, and the microvessel density (MVD) and microvessel pericyte coverage index (MPI) were calculated. Results: Peritoneal fibrosis stimulated by CG was suppressed by Epo administration, and hematocrit in the CG+Epo group was significantly higher than that in the CG group. The numbers of HIF-1a, EpoR and pimonidazole expressing cells in the CG+Epo group were lower than those in the CG group. The expressions of HIF-1a, VEGF, Ang-2 and CTGF mRNA were increased in the CG group although they were reduced in the CG+Epo group. The Ang-1 mRNA expression in the CG group was lower than that in the CG+Epo group. Since MVD and MPI were significantly higher in the CG+Epo group than in the CG group, a sufficient vascular network may be established in the CG+Epo group. Conclusions: Epo may play an important role in preventing peritoneal fibrosis via improvement of hypoxia by elevation of hematocrit, establishment of a sufficient microcirculatory network and decrease of CTGF production by inhibition of HIF-1a expression in this rat model.