Selective α v β 3 integrin blockade potently limits neointimal hyperplasia and lumen stenosis following deep coronary arterial stent injury: Evidence for the functional importance of integrin α v β 3 and osteopontin expression during neointima formation

Lumen loss from vascular restenosis remains a leading cause of chronic revascularization failure. Objective: We hypothesized that cell-matrix adhesion, migration, and differentiation events that underlie restenosis are mediated by αvβ3 integrin-ligand interactions. Methods: Using immunohistochemistry and in situ hybridization, we examined the spatial and temporal vessel wall expression of αvβ3 and osteopontin following deep coronary arterial injury. Cell migration and adhesion assays were performed to demonstrate the affinity and specificity of XJ735 for various vessel wall integrins. The effects of XJ 735 (a selective cyclic Arg-Gly-Asp (ROD) peptidomimetic ∅vβ3 antagonist) on neointimal hyperplasia and lumen stenosis were tested in a porcine coronary injury model. Normolipemic swine underwent oversized stent injury followed by XJ 735 administration (9 animals, 28 lesions; 1 mg/kg bolus + 7 days 4 mg/kg/d infusion + 21 days 2 mg/kg i.v. bolus 12 hourly) or placebo (10 animals, 30 arterial lesions). Results: Maximal αvβ3 immunoreactivity was observed between 7-14 days following injury in the neointima, media, and adventitia. Maximal osteopontin mRNA signal in the neointima, media, and adventitia was observed at 14, 7 and 28 days respectively. IC₅₀ for XJ 735 αvβ3-mediated inhibition of human and porcine endothelial cell adhesion, and vascular smooth muscle cell migration, ranged from 0.6 to 4.4 μM. In contrast, IC₅₀ for porcine or human αIIb/β3, α4β1, αvβ5, and α5β1 inhibition exceeded 100 μM. Steady state XJ 735 plasma levels exceeded 5 μM. Despite slightly higher injury scores in XJ 735 treated animals, significant reductions in mean neointima area (43% reduction; p = 0.0009), and mean percent lumen stenosis (~ 2.9 fold reduction; p = 0.04) were observed in XJ 735 treated animals. XJ 735 treatment did not significantly alter the relative size of the arterial injury and reference sites (geometric remodeling). Comparison of neontima area vs. injury score regression lines revealed significant reductions in slope (p = 0.0001) and intercept (p = 0.0001) for XJ 735. Conclusions: Selective αvβ3 blockade is an effective anti-restenosis strategy that potently limits neointimal growth and lumen stenosis following deep arterial injury. The co-ordinate spatial and temporal upregulation of αvβ3 expression following vessel wall injury, and the high affinity and specificity of XJ 735 for αvβ3, confirms the importance of this integrin in adhesive and migratory cell-matrix events underlying coronary restenosis.