Interaction of vascular smooth muscle cells with collagen-impregnated embolization coils studied with a novel quantitative in vitro model.

BACKGROUND AND PURPOSE Modifications of aneurysm occlusion devices and other biologically active molecules may reduce the risk of recanalization by promoting vascular cell migration, adhesion, and proliferation. Our purpose was to apply in vitro methods in the qualitative and quantitative analysis of vascular smooth muscle cell (VSMC) interactions with collagen-impregnated microcoils. METHODS The adhesion of rat aortic VSMCs to collagen fiber bundles (CFBs), nitinol coils, and collagen-impregnated nitinol coils (CINCs) was examined by using an assay consisting of monopulse exposure to increasing concentrations of rat aortic VSMCs. Exposed devices were washed and examined by using confocal fluorescence microscopy. Adhesion coefficients, which quantitatively express the cell-binding quality of a surface, were determined by using a mathematical model for cell-device interactions. RESULTS VSMCs, attached to devices, spread out and extended cytoplasmic projections over the contact surface. Cell distribution was random on CFBs and within interloop troughs on nitinol coils. On collagen-impregnated coils, VSMCs were selectively concentrated on the collagen between coil loops. The average adhesion coefficient was 25.0 for CFBs, 8.5 for CINCs (250-microm pitch), and 6.5 for nitinol coils. Adhesion coefficient differences for the three devices were significant (P =.044). CONCLUSION The monopulse exposure assay is a simple and reproducible in vitro test that provides qualitative information about the morphology and topography of cell-device contacts and permits quantitative measurement of the intrinsic cell-binding quality of the test device. VSMCs exposed to collagen-impregnated microcoils selectively attach to collagen. Collagen enhances the rate of VSMC adhesion to embolic devices, and the degree of enhancement correlates with the surface area constituted by collagen.