['CCN1 (Cyr61) is an extracellular matrix-associated protein involved in cell proliferation and survival. CCN1 is bound to vascular smooth muscle cells (VSMCs) via integrins and is expressed in VSMCs in atherosclerotic lesions, suggesting involvement in the regulation of vascular smooth muscle cell (VSMC) proliferation and atherosclerosis. We hypothesized that knockdown of CCN1 may inhibit VSMC proliferation and suppress neointimal hyperplasia.', "We examined the effect of the knockdown of CCN1 using rat cultured VSMCs and a rat balloon injury model. CCN1 stimulated adhesion and migration of VSMCs in a dose-dependent manner, and this was blocked by an antibody for integrin alpha(6)beta(1). Moreover, knockdown of endogenous CCN1 by lentiviral delivery of siRNA significantly inhibited proliferation of VSMCs and the uptake of 5-bromo-2'-deoxyuridine (BrdU). Replenishment with recombinant CCN1 reversed the effect of siRNA knockdown. Interestingly, knockdown of CCN1 significantly suppressed neointimal hyperplasia in a rat carotid artery balloon injury model at days 14 and 28 after injury. Gene transfer of CCN1 to smooth muscle reversed the effect of CCN1 knockdown on neointimal formation. These results suggest that endogenous CCN1 regulates proliferation of VSMCs and neointimal hyperplasia."] Does cCN1 knockdown suppress neointimal hyperplasia in a rat artery balloon injury model?