Co-Culture of Endothelial Cells and Smooth Muscle Cells in a Flow Environment: An Improved Culture Model of the Vascular Wall?

Numerous studies have demonstrated that the neighboring smooth muscle cells (SMC) influence the morphology, cytoskeleton and growth of co-cultured endothelial cells (EC). Also, flow-induced laminar shear stress has been shown to induce cell elongation, F-actin reorganization and growth inhibition in cultured EC. We investigated the effect of neighboring SMC and collagen matrix on the response of EC to shear stress. The co-culture system was made by growing porcine aortic SMC in a gel of collagen type I and then seeding porcine aortic EC (P AEC) on the top surface. Then the coculture was exposed to steady, laminar shear stress of 10 and 30 dynes/cm2 in a parallel-plate flow chamber. EC had a different morphology when cultured on top of collagen gels as compared to cells grown on plastic. When grown in static co-culture with SMC, EC were already elongated and showed a random wavy pattern of orientation. When exposed to 30 dynes/cm2, the EC aligned with the direction of flow after 24 to 48 hours. We suggest that the elongation and orientation of the EC, when cultured on a collagen matrix under static conditions, may be due to contact guidance on the collagen fibers previously rearranged by the SMC during gel retraction. Shear stress, however, was sufficient to induce cell orientation along the direction of flow.