Membrane-type matrix metalloproteinases in human dermal microvascular endothelial cells: Expression and morphogenetic correlation

Membrane-type matrix metalloproteinases (MT-MMP) activate the zymogen form of MMP-2/Gelatinase A on cell surfaces and are expressed in invasive tumors . We sought to identify and characterize MT-MMP in a nonmalignant cell type that undergoes a physiologic and reversible invasive phenotype during angi ogenesis. Human dermal microvascular endothelial cells (HDMEC) were isolate d from neonatal tissue and purified by anti-CD31 (PECAM) affinity beads. MT -MMP-1 and -3 transcripts were amplified by reverse transcriptase-polymeras e chain reaction and northern blots showed a single 4.5 kB mRNA for MT-MMP- 1 that was modulated by angiogenic factors and phorbol ester. Immunoblottin g of reduced cellular extracts with different MT-MMP-1 antibodies showed th e presence of the 63-65 kDa and 57-60 kDa forms, as well as additional form s at lower molecular weights. HDMEC membranes extracted with Triton X114 we re incubated with gelatin-sepharose purified MMP-2 and MMP-9 to show activa tion of proenzymes. Pre-incubation of HDMEC with anti-MT-MMP-1 antibodies d ecreased proMMP-2 conversion activity only. The movement of HDMEC and the f ormation of tubule-like structures in three-dimensional collagen gels was m arkedly delayed by preincubation with the same anti-MT-MMP-1 antibodies. Th ese results demonstrate the presence of MT-MMP in cutaneous microvascular c ells in vitro. Modulation of these cell surface proteinases by angiogenic f actors, demonstration of multiple processed forms, and specific attenuation of HDMEC morphogenetic patterns in three-dimensional collagen gels implica te their potential roles in the formation of new blood vessels in the skin.