Adenovirus-encoded hammerhead ribozyme to Bcl-2 inhibits neointimal hyperplasia and induces vascular smooth muscle cell apoptosis

Objective: The balance between apoptosis and cell proliferation is vital fo r cellular homeostasis, yet little is known about the mechanisms that coord inate these two cell fates, particularly in the vessel wall. It is well est ablished that the members of Bcl-2-gene family are regulators of apoptosis, but their role in cellular proliferation is less clear. Methods: We analyz ed the effects of disrupting Bcl-2 expression in vascular smooth muscle cel ls (VSMCs) by adenoviral-mediated delivery of a hammerhead ribozyme against bcl-2 mRNA (Ad-Rbz-Bcl-2). Results: Forced ablation of Bcl-2 in balloon-in jured rat carotid arteries reduced cell number and inhibited neointimal hyp erplasia. In vitro, VSMCs transduced with the Ad-Rbz-Bcl-2, underwent apopt osis as indicated by a reduction in cell number and DNA fragmentation. Ad-R bz-Bcl-2-transduced cells also exhibited aberrations in both G1- and S-phas es of the cell cycle. However, forced perturbations in cell cycle activity by serum-stimulation or treatment with chemical inhibitors did not affect A d-Rbz-Bcl-2-induced cell death, indicating that these cell cycle changes ar e not essential for apoptosis. Conclusion: These data show that physiologic al levels of Bcl-2 are essential for VSMC viability and that ablation of Bc l-2 alters cell cycle activity through the execution of the apoptotic proce ss. (C) 2000 Elsevier Science B.V. All rights reserved.