Plasmin(ogen) dependency of capillarylike tubular structure formation in a fibrin matrix by hMVECs.

hMVECs were cultured on top of a 3-dimensional fibrin matrix in M199 with 10% human serum and 10% newborn calf serum (NBCS) and were not stimulated (A) or stimulated with the addition of 10 ng/mL bFGF and 10 ng/mL TNF-α (B). After 4 days of culture, nonphase photomicrographs were taken. Histologic analysis of cross-sections of structures in the underlying fibrin matrix (C,F). Arrows indicate endothelial cells present in the underlying fibrin matrix. Addition of aprotinin (100 U/mL) (D) or depletion of plasminogen from the matrix and the culture media alter the formation of structures (E-F). Scale bar represents 300 μm.