I039 Role of PRG-1, a neuronal phospholipid phosphatase, in the function of vascular smooth muscle cells

Proliferation and migration of vascular smooth muscle cells (VSMCs) leading to neointima formation are a hallmark of development and progression of some cardiovascular diseases. LPA (lysophosphatidic acid) which has been shown to induces a dedifferenciation of VSCM, resulting in cell proliferation and migration in vitro, and vascular remodelling in vivo. The aim of our project is to understand the role of PRG-1 (Plasticity Related Gene-1), or LPPR4 (Lipid Phosphate Phosphatase Related protein 4), in the regulation of VSMCs proliferation and migration induced by LPA. This enzyme acts as en ecto-enzyme dephosphorylating LPA, thereby inhibiting its activity, and was found in previous studies to be down-regulated in the media of aging and hypertensive rats. We showed that PRG-1 is expressed in the rat and human aortic media and rat VSMCs by PCR, immunofluorescence and western blot. This expression was highly decreased in cultured VSMCs as compared with what was observed in the aortic media, and restored by cells starvation, suggesting that PRG-1 expression is dependent on the differentiated phenotype of these cells. We studied the response to LPA of VSMCs infected with an adenovirus containing the human sequence of PRG1 (PRG1-VSMCs) or with an adenovirus expressing LacZ (LacZ-VSMCs). In vitro, LPA-induced migration of PRG1-VSMCs (measured by scrapewound assays) and LPA-induced proliferation (measured by BrdU incorporation) were inhibited (by 60 % and 40 % respectively) as compared with LacZ-VSMCs. In vivo, experiments of left carotid injury by ballooning followed by gene transfer with adenovirus injection, showed a 70 % reduction of neointima formation when carotids were infected with PRG-1 adenovirus as compared with infection with LacZ adenovirus. Current investigations indicate that PRG-1 seems to block Erk1/2 signalling pathway activated by LPA. Our results demonstrate that PRG-1 is expressed in the VSMCs of the media ; and this expression is modulated in conditions of vascular remodelling and primary culture. PRG-1 overexpression inhibits VSMCs migration and proliferation in vitro and neotintima formation in vivo. Taken together, these findings suggest that, in the media, PRG-1 plays a protective role in pathophysiological conditions