Antisense strategies to inhibit restenosis

Restenosis after percutaneous transluminal coronary angioplasty (PTCA) and coronary stenting remains a major clinical problem. Vascular smooth muscle cell (SMC) proliferation and migration from the arterial wall media into the intima are believed to play a critical role in the pathogenesis of restenosis. Several studies have demonstrated that phosphorothioate (PS) oligodeoxynucleotides targeted against genes involved in SMC proliferation inhibit in vitro SMC proliferation and migration. Moreover, PS oligodeoxynucleotides targeted against the genes c-myb, c-myc, cdc2 kinase, cdk2 kinase, and proliferating cell nuclear antigen (PCNA) when delivered adventitially or intraluminally inhibit in vivo neointimal formation after balloon injury in both the rat carotid and porcine coronary artery models. The inhibitory effects of these PS oligodeoxynucleotides may be the result of their suppression of migration of medial SMC rather than suppression of medial or intimal cell proliferation. Other studies have demonstrated the presence of the potent guanosine or G-quartet aptameric inhibitory effect of the PS oligodeoxynucleotides. Experiments with cytidine homopolymers such as S-dC28, which lack guanosines, reveal the presence of potent non-G-quartet, non-sequence-specific inhibitory effects on in vitro SMC proliferation, migration, and adhesion as well as in vivo neointimal formation after rat carotid artery balloon injury. This is owing to the avid binding of these PS oligodeoxynucleotides to the SMC mitogens and chemoattractants platelet-derived growth factor (PDGF) and basic fibroblast growth factor (bFGF). The extent to which hybridization-dependent antisense, G-quartet aptameric, or non-G-quartet, non-sequence-specific inhibitory effects occurs is the result of PS oligodeoxynucleotide sequence, length, and concentration. The 18-mer guanosine-rich PS oligodeoxynucleotide ZK10 is a more potent in vitro SMC proliferation inhibitor than S-dC28, although both compounds manifest comparable in vivo inhibitory effects on neointimal formation in the rat carotid artery model of balloon injury. PS oligodeoxynucleotides also possess non-sequence-specific immunomodulatory effects, including the induction of interferon-gamma and the unmethylated CpG motif, which exhibits numerous immunomodulatory effects. Novel strategies to inhibit restenosis include the development of E2F transcription decoys that inhibit several cell cycle regulatory genes and diminish neointimal lesion formation. In addition, antisense oligonucleotides targeted against the anti-apoptotic gene bcl-xL, which when transfected into the vessel wall inhibits bcl-xl expression, induce a five-fold increase in apoptotic SMC intimal cells, and effect a marked attenuation of in vivo lesion dimensions, thereby suggesting frank vascular lesion regression.