Human aortic endothelial cell migration onto stent surfaces under static and flow conditions

PURPOSE: The objective of the present study is to establish an in vitro model designed to quantitatively define human aortic endothelial cell (HAEC) migration onto stainless steel stent material under both static and flow conditions of high and low wall shear stress. MATERIALS AND METHODS: To simulate implantation of a stent onto the intact arterial wall, HAECs were seeded and grown to confluence on thick, firm collagen gels. Flat 1 x 1-cm square, stainless steel pieces were implanted on this endothelialized surface and migration of HAECs onto the steel surface was monitored, measured, and compared under static and high (15 dynes/cm²) and low (2 dynes/cm²) wall shear stress flow conditions designed to model wall shear stress levels encountered at different sites within the human arterial system. RESULTS: Under no flow, endothelial cell migration occurred uniformly from the periphery, attaining complete confluence over the square surface within 14 days. The initial migratory rate was approximately 10 μm/h ± 0.5 on days 1- 3 and increased to a rate near 15 μm/h ± 0.5 between days 10 and 14. High shear stress significantly (P < .001) increased HAEC migration rate to 25 μm/h ± 0.8 in the direction of flow, resulting in an increase in total area endothelial coverage from 59% under no flow to 87% under high shear stress flow conditions when compared at 7 days. CONCLUSIONS: These results indicate the rate and extent of endothelial migration onto a prosthetic material surface are influenced by the level and direction of flow-related wall shear stress. Furthermore, these results demonstrate an in vitro model that provides a method to quantitatively evaluate and possibly predict the relative ability of different prosthetic materials to endothelialize under variable in vivo flow conditions.