RNAi-mediated Rab5a suppression inhibits proliferation and migration of vascular smooth muscle cells

Objective — The migration and proliferation of vascular smooth muscle cells (VSMC) are early and crucial events in the pathogenesis of intimal hyperplasia, the primary cause of restenosis after vascular reconstruction. We tested the hypothesis that down-regulation of Rab5a, a prototypical member of the Rab family of GTPases, leads to inhibition of VSMC proliferation and migration in the rat model. Methods — The intimal hyperplasia rat model was established and was used to test the expression of Rab5a at the vascular anastomoses at 7, 14 and 28 days post-operatively. The VSMCs were isolated from the thoracic aorta of SD rats and the expression of Rab5a was tested before and after exposure to RNAi by real-time PCR and Western blot.VSMC migration and proliferation were detected by flow cytometry using standard commercially available techniques and a Transwell chamber. Results — The rat models had significant stenosis at the anastomoses and the intima/media ratio was higher than that of the rat vessels. The expression of Rab5a was higher at the anastomotic site and peaked at 14 days after operation. The expression of Rab5a increased in the cultured VSMCs and decreased after RNAi. Proliferation and migration of VSMCs had been inhibited by down-regulating the expression of Rab5a. Conclusion — Aberrant expression of Rab5a can be found after vascular reconstruction and the proliferation and migration of VSMCs can be inhibited by RNAi silencing of Rab5a. This suggests the critical role for Rab5a in VSMCs proliferation and migration, and thus intimal hyperplasia and restenosis. Rab5a suppression might be a potential molecular therapeutic strategy to inhibit intimal hyperplasia.