Adrenomedullin gene delivery inhibits neointima formation in rat artery after balloon angioplasty.

Adrenomedullin (AM) is a potent vasodilator expressed in tissues relevant to cardiovascular function. AM peptide has been shown to inhibit the proliferation and migration of vascular smooth muscle cells in vitro. However, the effect of AM on blood vessels after vascular injury in vivo has not been elucidated. In order to explore the potential roles of AM in vascular biology, we evaluated the effect of AM by local gene delivery on neointima formation in balloon-injured rat artery. Adenovirus carrying the human AM cDNA under the control of cytomegalovirus promoter/enhancer (Ad.CMV-hAM) was generated by homologous recombination. After delivery of Ad.CMV-hAM into rat left carotid artery, we identified the expression of human AM mRNA in the left carotid artery, but not in the right carotid artery, heart or kidney by reverse transcription-polymerase chain reaction (RT-PCR) followed by Southern blot analysis. Following local AM gene delivery, we observed a 51% reduction in intima/media ratio at the injured site as compared with that of control rats injected with the luciferase gene (n=7, P<0.01). AM gene transfer resulted in regeneration of endothelium as compared to the control. AM gene delivery significantly increased cGMP levels in balloon-injured arteries. These results indicate that AM contributes to reduction of neointima formation by promotion of re-endothelialization and inhibition of vascular smooth muscle cell proliferation via cGMP-dependent signaling pathway.