The Effect of P27 on Luminal Narrowing in Rats After Aortic Balloon Withdrawal Injury

Aim To investigate the influence of all-trans retinoic acid (ATRA) on the process of luminal narrowing, the expression of some cell cycle modulatory factors in rats artery after aortic balloon withdrawal injury. Methods 54 SD rats were randomly divided into 3 groups. In control group (n=6) rats were killed at the 28th day after procedure. In operation group (n=24) and ATRA group (n=24) rats had balloon induced endothelium denudation at thoracic aorta and were killed at the 2nd, 7th, 14th, 28th day after artery injury. All rats were predosed with ATRA (30 mg/kg.d) or corn oil by gavage 4 days before injury and continued to each indicated time. After the thoracic aorta were harvested, we used immunohistochemistry staining to measure the protein expression of cyclin dependent kinase inhibitor P27 and proliferation cell nuclear antigen. Meanwhile vessel morphological measurement was taken. Results ①In normal rat arteries P27 was detected. After balloon injury, P27 expression in media decreased, reached the lowest level at the 2nd day and then upregulated while vascular smooth muscle cell (VSMC) reached peak proliferation at the 2nd day and then decreased quickly. In neointima, VSMC proliferated extremely at the 7th day, P27 could be detected at the 14th and 28th day when the proliferation of VSMC decreased. ②In ATRA-treated group P27 downregulation was inhibited in media, and P27 was already present in the neointima at the 7th day and strongly expressed at the 14 th and 28 th day while the proliferation of VSMC was significantly decreased (P0.01). As a result ATRA group had a smaller noeintima /media area ratio, larger internal or external elastic lamina area and luminal area (P0.01). ③The expression of P27 and the cell proliferation were in remarkable negative correlation (P0.001). Conclusion The decreased expression of P27 may have an important role in the process of luminal narrowing after aortic balloon withdrawal injury.