Localization of c-Myb and induction of apoptosis by antisense oligonucleotide c-myb after angioplasty of porcine coronary arteries

Previous studies have shown that inhibition of the proto-oncogene c-myb inh ibits neointimal formation in various animal models. However, the temporal and spatial expression of c-Myb in the vessel wall after injury is not know n, and the mechanism of action of antisense oligonucleotide (AS-ODN-c-myb) inhibition remains unclear. One potential effect of cell cycle dysregulatio n by inhibition of c-myb is an increase in the rates of apoptosis. In this study, c-Myb expression after percutaneous transluminal coronary angioplast y (PTCA) injury and induction of apoptosis after AS-ODN-c-myb treatment wer e determined. Immunohistochemistry and cellular phenotyping were used to lo calize c-Myb expression in porcine coronary arteries at various time interv als after PTCA. In vitro, the effects of AS-ODN-c-myb on the apoptosis of p orcine vascular smooth muscle cells (PVSMCs) and endothelial cells were det ermined by using a cell-death ELISA and time-lapse video microscopy. In viv o, local delivery of AS-ODN-c-myb was performed after PTCA of pig coronary arteries, and apoptosis was quantified at 6 hours. c-Myb is induced in pig coronary arteries after angioplasty, with maximal expression in inflammator y cells at 18 hours and in vascular smooth muscle cells at 3 to 7 days. In vitro, AS-ODN-c-myb enhanced PVSMCs (6.8 +/- 0.8% [P = < 0.001] versus 0.5% serum) but not endothelial cell apoptosis (1.4 +/- 0.5% [P = NS] versus 0. 5% serum). In vivo, 6 hours after porcine coronary angioplasty and delivery of AS-ODN-c-myb, the proportion of apoptotic cells within the media was 4. 2 +/- 0.8% (PTCA alone), 2.3 +/- 0.2% (PTCA+vehicle), and 9.0 +/- 1.1% (PTC A+AS-ODN-c-myb; P < 0.05 versus PTCA alone and P < 0.01 versus PTCA+saline) . c-Myb is expressed after PTCA of pig coronary arteries, and AS-ODN-c-myb induces apoptosis of PVSMCs in vitro and medial cells in vivo.