Periadventitial adipose tissue modulates the effect of PROLI/NO on neointimal hyperplasia.

BACKGROUND: Periadventitial delivery of nitric oxide (NO) inhibits neointimal hyperplasia; however, the effect of periadventitial adipose tissue on the efficacy of NO at inhibiting neointimal hyperplasia has not been studied. The aim of our study was to assess the effect of NO in the presence and absence of periadventitial adipose tissue. We hypothesized that removal of periadventitial adipose tissue will increase neointimal formation and that NO will be more effective at inhibiting neointimal hyperplasia.

METHODS: The effect of NO on 3T3 fibroblasts, adventitial fibroblast (AF), and vascular smooth muscle cell (VSMC) proliferation was assessed by (3)H-thymidine incorporation in adipocyte-conditioned or regular media. The rat carotid artery balloon injury model was performed on male Sprague-Dawley rats. Before balloon injury, periadventitial adipose tissue was removed (excised model) or remained intact (intact model). Treatment groups included injury or injury with periadventitial application of PROLI/NO. Adiponectin receptor (AR) levels were assessed via immunofluorescence.

RESULTS: Adipocyte-conditioned media had an antiproliferative effect on 3T3 and AF and a proproliferative effect on VSMC in vitro. Interestingly, NO was less effective at inhibiting 3T3 and AF proliferation and more effective at inhibiting VSMC proliferation in adipocyte-conditioned media. In vivo, the excised group showed increased neointimal hyperplasia 2 wk after surgery compared with the intact group. NO reduced neointimal hyperplasia to a greater extent in the excised group compared with the intact group. Although NO inhibited or had no impact on AR levels in the intact group, NO increased AR levels in media and adventitia of the excised group.

CONCLUSIONS: These data show that periadventitial adipose tissue plays a role in regulating the arterial injury response and the efficacy of NO treatment in the vasculature.