DOWN-REGULATION OF CYCLIN G1 EXPRESSION BY RETROVIRUS-MEDIATED ANTISENSE GENE-TRANSFER INHIBITS VASCULAR SMOOTH-MUSCLE CELL-PROLIFERATION AND NEOINTIMA FORMATION

Background The contemporary treatment of coronary athero-occlusive dis ease by percutaneous transluminal coronary angioplasty is hampered by maladaptive wound healing, resulting in significant failure rates. Mor bid sequelae include smooth muscle cell (SMC) hyperplasia and restenos is due to vascular neointima formation. Methods and Results In this st udy, we examined the inhibitory effects of a concentrated retroviral v ector bearing an antisense cyclin G1 gene on aortic SMC proliferation in vitro and on neointima formation in vivo in a rat carotid injury mo del of restenosis. Retroviral vectors bearing an antisense cyclin GI c onstruct inhibited the proliferation of transduced aortic SMCs in 2- t o 6-day cultures, concomitant with downregulation of cyclin G1 protein expression and decreased [H-3]thymidine incorporation into DNA. Morph ological examination showed evidence of cytolysis, giant syncytia form ation, and apoptotic changes evidenced by overt cell shrinkage, nuclea r fragmentation, and specific immunostaining of nascent 3'-OH DNA ends generated by endonuclease-mediated DNA fragmentation. Pronounced ''by stander effects'' including neighboring cells were noted in aortic SMC s transduced with the antisense cyclin G1 vector, as determined by qua ntitative assays and fluorescent labeling of nontransduced cells. In a n in vitro tissue injury model, the proliferation and migration of ant isense cyclin G1 vector-transduced aortic SMCs were inhibited. Moreove r, in vivo delivery of high-titer antisense cyclin G1 vector supernata nt to the balloon-injured rat carotid artery in vivo resulted in a sig nificant reduction in neointima formation. Conclusions These findings represent the first demonstration of the inhibitory effects of an anti sense cyclin G1 retroviral vector on nonneoplastic cell proliferation. Taken together, these data affirm the potential utility of antisense cyclin G1 constructs in the development of novel gene therapy approach es to vascular restenosis.