Original Article Smad7 gene transfer attenuates angiogenesis in peritoneal dialysis rats WEISHENG PENG, 1 XIANRUI DOU, 2 WENKE HAO, 2 QIAOLING ZHOU, 1 RONG TANG, 1 JING NIE, 2 HUI Y LAN 3 and XUEQING YU 2 1 Department of Nephrology, Xiangya Hospital, Central South University, Changsha, 2 Department of Nephrology, The First Affiliated Hospital, Sun Yat-Sen University, Guangzhou, and 3 Department of Medicine, University of Hong Kong, Hong Kong, China KEY WORDS: angiogenesis, peritoneal dialysis, Smad7, transforming growth factor-b. Correspondence: Professor Qiaoling Zhou, Department of Nephrology, Xiangya hospital, Central South University, Changsha 410008, China. Email: zhouqling1@yahoo.com.cn Accepted for publication 25 November 2012. Accepted manuscript online 7 December 2012. doi:10.1111/nep.12017 SUMMARY AT A GLANCE This is an animal study that demonstrated reduced peritoneal angiogenesis through the blockade of transforming growth factor-b, through signalling with Smad7. This presents a novel therapeutic approach to decrease ultrafiltration failure and hence increase peritoneal dialysis technique longevity. ABSTRACT: Aim: Transforming growth factor-b (TGF-b) has been shown to play a role in peritoneal angiogenesis associated with peritoneal dialysis (PD). The present study investigated whether blockade of TGF-b signalling with Smad7 has a therapeutic effect on PD induced-peritoneal angiogenesis. Methods: A rat model of peritoneal dialysis was induced by a daily intra- peritoneal injection of 4.25% Dianeal and lipopolysaccharides. PD rats were transfected with a doxycycline regulated, Smad7-expressing plasmid using an ultrasound-microbubble-mediated system on day 0 and day 14 after initiation of PD and an empty vector was used as control. Peritoneal micro- vessel density (MVD) in peritoneal tissue was assessed by anti-CD31 immu- nohistochemistry after 4 weeks of PD and peritoneal angiogenic growth factors, including vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF) and platelet-derived growth factor (PDGF) was also examined by immunofluorescence, western blot and reverse transcription- polymerase chain reaction. Results: In contrast to the normal control group, at 4 weeks after PD, PD rats displayed peritoneal lesions, peritoneal angiogenesis and increased mRNA and protein expression of VEGF, bFGF and PDGF. Smad7 gene transfer significantly attenuated the peritoneal MVD and inhibited the upregulation of VEGF, bFGF and PDGF. Moreover, inhibition of peritoneal angiogenesis by overexpression of Smad7 was associated with inhibition of phosphorylation of Smad3 and downregulation of TGF-b expression. Conclusion: Smad7 gene transfer via an ultrasound-microbubble-mediated system is able to attenuate peritoneal angiogenesis in a rat model of PD. Those results suggest that blockade of the TGF-b/Smad signalling pathway may represent a novel therapeutic approach to prevent PD-induced perito- neal angiogenesis. Peritoneal dialysis (PD) is now a standard therapeutic option for chronic renal failure. However, long-term exposure to peritoneal dialysis fluid can induce peritoneal tissue remod- elling and angiogenesis, which can lead to a loss of ultrafil- tration (UF) capacity. Functional studies have shown that peritoneal angiogenesis associated with PD progressively increases the effective peritoneal surface area (EPSA) and increased EPSA causes an increase in small solute transport and results in UF loss and finally leads to peritoneal dysfunction. 1–3 Margetts et al. demonstrated that inhibiting angiogenesis was more important than inhibiting the process of peritoneal fibrosis in protecting the peritoneal membrane function. 4 Peritoneal angiogenesis is a multi-step process that involves the activation, proliferation and migration of endothelial cells. It has been reported that a lot of angiogenic factors such as vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), tumour necrosis factor-a (TNF-a), interleukin-1 (IL-1), platelet-derived growth factor (PDGF) is significantly increased in the perito- neal membrane of a PD model and those factors can potently induced peritoneal angiogenesis and function changes. 5–9 Nephrology 18 (2013) 138–147 © 2012 The Authors Nephrology © 2012 Asian Pacific Society of Nephrology 138