Inhibition of intimal hyperplasia after vein grafting by in vivo transfer of human senescent cell-derived inhibitor-1 gene

The senescent cell-derived inhibitor (sdi)-1 (p21) protein has been identified as a downstream mediator of the tumor suppressor p53 in the cell cycle regulation. In this study, we focused on the function of sdi-1 gene in inhibiting vascular smooth cell (VSMC) proliferation after vein grafting in a rabbit model. To test the hypothesis, we transfected human sdi-1 gene by an intra-operative approach. Accompanied by markedly increased sdi-1 protein, the significant increase in PCNA-stained VSMCs in vein grafts was inhibited by transfection of sdi-1 gene. Moreover, at 2 weeks after transfection, transfer of sdi-1 gene resulted in a significant inhibition in neointimal formation, compared with control vector. Of importance, immunohistological studies determining the expression pattern of myosin heavy isoforms, adult type specific SM2 and embryonic specific SMemb/NMHC-B, demonstrated expression of the adult phenotype of VSMCs in the neointima of sdi-1 gene-1 transfected Vein grafts at 2 weeks after the operation, while the neointima was predominantly composed of embryonic phenotype of VSMCs in the control grafts. Overall, these results demonstrate that a single intraluminal incubation of human sdi-1 gene can result in a significant inhibition of neointimal formation after vein grafting, associated with phenotypic change of VSMCs from neonatal to adult type in a rabbit model. Inhibition of hyperplasia in a graft model by transfection of sdi-1 gene may be due to the change in VSMC phenotype from neonatal to adult, in addition to the inhibition of VSMC growth.