Growth control in capillary endothelium.

The phenomenon of angiogenesis depends upon several biological processes including enzymatic degradation of matrix, chemotaxis, lumen formation, tissue remodeling, and matrix control of differentiation. These processes are expressed in a sequential order during the growth of a capillary and during its regression. Capillary endothelial cells and endothelial cells of embryonic and fetal origin have the capacity to express the information necessary to build a complete capillary network. However, the signals that initiate this expression usually come from other cell types, such as tumor cells, macrophages, lymphocytes or adipocytes. The rate of capillary growth can also be modulated by mast cells which normally reside in the neighborhood of mature cap-