MORPHOLOGY OF CAPILLARY-LIKE STRUCTURES IN A 3-DIMENSIONAL AORTA COLLAGEN GEL CULTURE

The morphology of capillary-like tubes was investigated by electron mi croscopy (TEM and SEM) using an in vitro model of capillarogenesis (ao rta/collagen type I gel). This model allowed morphological comparisons with in vivo capillaries and an evaluation of the functional maturity of the endothelium to be made. The lumina developing in vitro were de marcated by endothelial cells of varying thickness (0.1-2 mu m). Peric ytes were resting on the outside. The endothelial cells were character ized by contacts of varying length with tight and gap junctions and oc casional indentations. The inner surface exhibited areas both with pro nounced and without any endocytotic activity. In addition to a large G olgi apparatus, a varying number of cell organelles occurred depending on the thickness of the endothelium Bundles consisting of microfilame nts were often located underneath the outer cell membrane and in the v icinity of contact areas. A lamina densa was in the process of formati on. The capillaries grown in vitro closely resembled those in vivo and showed a high degree of differentiation. Hence, this in vitro model a llows the study of a number of functions of endothelial cells.