Inhibition of intimal hyperplasia after stenting by over-expression of p15: A member of the INK4 family of cyclin-dependent kinase inhibitors

We evaluated the role of p15^Ink4, a member of the INK4 family of CDK inhibitors on vascular smooth muscle cells (VSMCs) proliferation, cell cycle progression and intimal hyperplasia after stenting. Aortic VSMCs transduced with either adenovirus encoding for p15^Ink4 or β-galactosidase were assessed for DNA synthesis, cell cycle progression, and pRb phosphorylation. Rabbit carotid arteries were stented and treated with peri-adventitial delivery of saline or adenovirus encoding for p15^Ink4 or β-galactosidase. p15^Ink4 transgene and protein expression were evaluated at 24 h and 72 h, respectively. In-stent cell proliferation was evaluated by BrdU at day 7. Histomorphometric analysis of in-stent intimal hyperplasia was performed at 10weeks. Human p15^Ink4 DNA was detected in transduced VSMCs at 24h. p15^Ink4 over-expression reduced VSMCs DNA synthesis by 60%. Cell cycle progression was inhibited, with a 30% increase in G1 population accompanied by inhibition of pRb phosphorylation. Human p15^Ink4 transgene was identified in transduced stented arteries but not in control arteries. p15^Ink4 immunostaining was increased and cell proliferation significantly reduced by 50% in p15^Ink4 transduced arteries. Intimal cross-sectional area (CSA) of p15^Ink4-treated group was significantly lower than the β-gal treated and non-transduced groups (p=0.008). There were no differences in the intimal or medial inflammatory response between groups. p15^Ink4 over-expression blocks cell cycle progression leading to inhibition of VSMCs proliferation. Peri-adventitial delivery of p15^Ink4 significantly inhibits in-stent intimal hyperplasia.