Functional Roles for PECAM-1 (CD31) and VE-Cadherin (CD144. in Tube Assembly and Lumen Formation in Three-Dimensional Collagen Gels

Abstract

Various in vitro models have been described that emulate one or more of the processes involved in angiogenesis in vivo. In the present study endothelial cells were cultured in three-dimensional type I collagen lattices in the presence of a mixture of basic fibroblast growth factor, vascular endothelial cell growth factor, and phorbol myristate acetate. Under these conditions, the endothelial cells rapidly assemble into an interconnected network of tube-like structures with a high frequency of intercellular canals or lumens. The formation of the networks and lumens was completely blocked by cycloheximide and by actinomycin D. Monoclonal antibodies directed against CD31 or vascular endothelial cadherin (VE-cadherin) inhibited the formation of endothelial tubes. A subtle difference in the morphology of cells treated with anti-CD31 versus anti-VE-cadherin was noted; namely, cells incubated in the presence of CD31 antibodies were rounded or formed attenuated tube-like structures, both of which were characterized by a single, large intra- or intercellular vacuole. In contrast, tube formation by cells incubated in the presence of VE-cadherin antibodies was also impaired and, most notably, demonstrated a reduction in either vacuole formation or vacuole fusion, depending upon the monoclonal antibody used. We suggest that the two endothelial-junction-associated proteins, CD31 and VE-cadherin, play different roles in the process of tube formation. CD31 appears to be required for cell elongation, migration, and/or invasion in the gels as well as for cell-cell association to form the network structures. VE-cadherin also appears to be required for cell-cell association, but additionally appears to play some role in the process of vacuolization or vacuole fusion leading to intercellular lumen formation.

Pathogenic angiogenesis in IBD and experimental colitis: new ideas and therapeutic avenues

“…During vascular remodeling ␣ v ␤ 3 -integrin is associated with angiogenesis by stimulating endothelial cell proliferation and stabilizing endothelial-matrix interactions partially through its interaction with PECAM-1 (25,93). PECAM-1 is also implicated in endothelial cell migration, specifically being shown to be required for elongation of endothelial cells and invasion into 3D collagen gels (74,166). Importantly, PECAM-1 expression is not upregulated during inflammation; however, new vasculature constitutively expresses PECAM-1, making it an ideal marker for measuring changes in vascular density during IBD and experimental colitis (31,162).…”

Angiogenesis: The VE-Cadherin Switch

“…VE-cadherin seems also implicated in lumen formation ( ) and in cell proliferation through Rho-mediated tension in the Yang et al 1999 actin cytoskeleton ( ). VE-cadherin modulation of VEGF R2 signaling might be modified in angiogenic cells Nelson and Chen 2003 compared to resting cells, as VEGF R2 activation (phosphorylation) by VEGF is stronger in sparse than in confluent cells (Rahimi and ).…”

The effect of RhoA on human umbilical vein endothelial cell migration and angiogenesis in vitro

“…In vitro angiogenesis assays were performed in 3-dimensional fibrin matrixes as described previously (2 mg/ml collagen type I, 3 vol; 10X EBSS, 1 vol; 0.1 N NaOH, 1 vol; DMEM, 3 vol; and FCS, 2 vol) (14,15). The cells carrying PEGFP-C1 or PEGFP-C1-RhoA (1x10 4 cells/well) were suspended in the recommended medium, added to each well of Matrigel-coated 6-well plates, and the gels were incubated at 37˚C in 5% CO 2 at 100% humidity.…”