Effect of p53 Gene Therapy Combined with CTLAff4Ig Selective Immunosuppression on Prolonged Neointima Formation Reduction in a Rat Model

Abstract

In a previous study, we have demonstrated a significant reduction of neointimal formation following adenovirus-mediated gene transfer of p53 to the injured rat carotid artery. The purpose of this study was to determine if the effect of p53 gene in reducing neointimal formation would still be present up to 8 weeks after arterial injury and whether it could be enhanced by adding immunosuppression. Cytotoxic T lymphocyte–associated antigen-4 Ig (CTLAff4Ig), a novel immunosuppressive agent, is a recombinant soluble protein that blocks T cell–dependent immune response. Animals were divided into eight groups (n= 6 in each). In vivo gene transfer was used in isolated segments of balloon-injured rat carotid arteries. Genetically modified adenovirus encoding for wild-type p53 protein was applied at 8 × 10¹⁰ pfu/mL. Control rats received adenovirus null at the same concentration. A daily dose of 300 μg of CTLAff4Ig was given intraperitoneally, either once, twice, or three times. Expression of p53 was determined by Western blot analysis. Neointimal formation was assessed at 4 or 8 weeks by harvesting carotid arteries and determining the intima/media (I/M) ratio cross-sectional area measurements. p53 expression was confirmed by Western blot analysis. We concluded that adenovirus-mediated p53 gene transfer significantly decreases the formation of neointima up to 8 weeks following rat carotid injury. However, there is loss of effectiveness on neointimal formation inhibition as time elapses. When CTLAff4Ig is added, there is significant improvement in results, with sustained neointimal formation inhibition at 8 weeks after the procedure.