Ultrastructural studies of attachment site formation in aortic smooth muscle cells cultured on collagen-hydroxyethylmethacrylate hydrogels.

Hydroxyethylmethacrylate (HEMA) hydrogels have a peculiar crater-like topography which renders them ideal for studying cell-to-substrate contact formation. The hydrogel is quite suitable for such studies since it is transparent, which allows for light microscopic observations, it is not toxic, and it will support cell growth only when an additional protein component such as collagen is integrated into its surface. Cultured rabbit aortic smooth muscle cells (SMC) were grown on collagen-HEMA hydrogels, and the ultrastructure of developing cell attachment sites was studied. By 3 hr after cell seeding, both the rounded and the spreading SMC appeared anchored to the hydrogel via extracellular connective tissue-like material. The fully formed attachment site present at 5-8 days was characterized by large bundles of intracellular myofilaments inserting onto areas of increased electron density along the plasmalemmal membrane; large amounts of extracellular connective tissue-like material also appeared attached to the areas of increased electron density. Fully formed cell substratum attachment sites were not observed when either elastin-HEMA hydrogels or hydrogels polymerized in the absence of protein were employed.