P311	Osteopontin is involved in estradiol effect on endothelium healing.
1L.Lam shang Leen, 2B.Garmy-Susini, 1S.Jalvy, 1Ph.Alzieu, 1D.Daret, 2C.Filipe, 2L.Brouchet, 2P.Gourdy, 3N.Werner, 3G.Nickenig, 1C.Degranges, 2J-F.Arnal, 1A-P.Gadeau
1INSERM U441, Université Bordeaux2, Pessac, FR; 2INSERM U589, Toulouse, FR; 3Klinik und Poliklinik, Innere Medizin III, Universität des Saarlandes, Homburg, DE.

The quality of endothelium is a main determinant for limiting the development of initial events of the atherosclerosis process. Thus, molecules involved in the protection of endothelium is supposed to prevent atherosclerosis. 17B-estradiol (E2) is known to accelerate reendothelialisation and prevent the formation of fatty streaks. The aim of the present study was to explore the mechanisms of E2 effects and more precisely to determine the role of osteopontin (OPN), which is chemotactic and mediates adhesion and survival of endothelial cells. E2 effect was explored in parallel in two mouse models of carotid artery deendothelialisation. Endothelium injury was performed either by electric injury or by endovascular approach using a calibrated swab of 300 µm diameter. In OPN-/- mice, the velocity of spontaneous reendothelialization induced by endovascular injury was normal in comparison to that of wild type, but the accelerative effect of E2 was abolished. Five days after injury, endothelial regeneration (% of remaining deendothelialized area on total carotid area) was respectively 46±6% and 21±4% in control and E2-treated wild type mice and 40±5% and 37±4% in control and E2-treated OPN-/- mice. Very similar results were obtained using electric injury. Thus, we evaluate whether OPN is involved in a local or a systemic effect induced by E2. We first show that in vitro adhesion of endothelial cells from OPN-/- mice is significantly impaired. Indeed, the adhesion on collagen matrix of EC from OPN-/- measured 24 hours after plating, is decreased of about 30% in comparison with wild type. However on OPN or fibronectin no difference was observed. Then we check whether OPN was involved in E2-mediated endothelial cell progenitor mobilisation. For this purpose the number of EPC was measured in the blood and bone marrow of wild type or OPN-/- mice treated or not by E2. This experiment showed that the number of EPC is identical in the two mice and that E2 stimulated equivalently EPC in OPN-/- and wild type mice In conclusion, this study demonstrates for the first time that OPN plays a key role in the effects of E2 on reendothelialisation.

Copyright © 2005 S. Karger AG, Basel. Any further use of this abstract requires written permission from the publisher.