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(Circulation Research. 2003;93:1059.)
© 2003 American Heart Association, Inc.

Molecular Medicine

Akt Controls Vascular Smooth Muscle Cell Proliferation In Vitro and In Vivo by Delaying G1/S Exit

Eugenio Stabile, Yi Fu Zhou, Motoyasu Saji, Marco Castagna, Matie Shou, Timothy D. Kinnaird, Richard Baffour, Matthew D. Ringel, Stephen E. Epstein, Shmuel Fuchs

From the Cardiovascular Research Institute (E.S., Y.F.Z., M.C., M. Shou, T.D.K., R.B., S.E.E., S.F.) and the Laboratory of Molecular Endocrinology (M. Saji, M.D.R.), MedStar Research Institute, Washington Hospital Center, Washington, DC.

Correspondence to Eugenio Stabile, MD, Cardiovascular Research Institute, Washington Hospital Center, 110 Irving St NW, 4B-1, Washington, DC 20010. E-mail geko50{at}katamail.com

Constitutive activation of serine/threonine kinase Akt causes uncontrolled cell-cycle progression in different cell types and in malignancy. To investigate how Akt activation modulates cell-cycle progression in vascular smooth muscle cells (SMCs) in vitro and in the intact animal, we inhibited Akt-dependent signaling by adenovirus-mediated transfection of a dominant-negative Akt mutant (AA-Akt). We observed reduced proliferation rate (P<0.01), DNA synthesis (P<0.01), and a significant arrest in G1/S exit (P<0.01) both in vitro in response to serum stimulation and in vivo after vascular injury. In vivo transfection of the balloon-injured vessel with AA-Akt reduced SMC proliferation, resulting in decreased neointima compared with control virus (P<0.01). These effects were at least in part modulated, both in vitro and in vivo, by increased p21^Cip1 expression, as demonstrated by lack of effect of AA-Akt on cell proliferation in p21^-/- mouse SMCs. In conclusion, this study demonstrates that Akt-dependent signaling enhances cell-cycle progression of nontransformed SMCs in vitro and in response to vascular injury in the intact animal. These results suggest a role for Akt signaling in modulating the response of normal tissues to stress and the response of the arterial wall to acute and possibly repetitive injuries that ultimately contribute to restenosis and atherosclerosis.

Key Words: Akt • p21 • restenosis • cell cycle • smooth muscle cell

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