Fibrin II induces endothelial cell capillary tube formation.

Abstract

We studied the formation of capillary tubes by endothelial cells which were sandwiched between two fibrin gels under serum-free conditions. After formation of the overlying fibrin gel, the endothelial cell monolayer rearranged into an extensive net of capillary tubes. Tube formation was apparent at 5 h and was fully developed by 24 h. The capillary tubes were vacuolated, and both intracellular and intercellular lumina were present. Maximal tube formation was observed with fibrin II (which lacks both fibrinopeptide A and B), minimal tube formation with fibrin I (which lacks only fibrinopeptide A), and complete absence of tube formation with fibrin 325 (which lacks the NH2- terminal beta 15-42 sequence, in addition to fibrinopeptides A and B). The inability of fibrin 325 to stimulate capillary tube formation supports the idea that beta 15-42 plays an important role in this process, and its importance was confirmed by the finding that exogenous soluble beta 15-42 inhibited fibrin II-induced capillary tube formation. This effect was specific for fibrin, since beta 15-42 did not inhibit tube formation by endothelial cells sandwiched between collagen gels. The interaction of the apical surface of the endothelial cell with the overlying fibrin II gel, as opposed to the underlying fibrin gel upon which the cells were seeded, was necessary for capillary tube formation. These studies suggest that the beta 15-42 sequence of fibrin interacts with a component of the apical cell surface and that this interaction plays a fundamental role in the induction of endothelial capillary tube formation.

The VE‐cadherin binding domain of fibrinogen induces endothelial barrier permeability and enhances transendothelial migration of malignant breast epithelial cells

“…We have shown that lung, prostate and breast cancer epithelial cells synthesize and secrete Fg that enhances FGF-2-mediated cell proliferation, assembles into extracellular matrices and binds to cancer cell surfaces. 2,14,[32][33][34][35][36][37] In addition, others have demonstrated Fg production in adenocarcinoma cell lines of cervical 15 and intestinal 16 origin. Recent expression array profiling studies have confirmed that the Fg genes are expressed in breast 17 and lung carcinomas 18,19 isolated from patients.…”

“…The negative control peptide corresponding to fibrinopeptide A induced minimal %FITC-Dextran Flux compared with Fg or peptide b 15-42 (#p < 0.0001); however, the 13% relative fluorescence was significant (-p 5 0.001) compared with basal levels that were 1% of intact Fg-induced permeability. Peptides missing b 15-17 residues (b [18][19][20][21][22][23][24][25][26][27][28][29][30][31] or b [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42] ) or truncated at the C-terminus (b [15][16][17][18][19][20][21][22][23][24][25][26][27] (Fig. 2c).…”

“…Because b [15][16][17] residues are critical for the binding specificity of b to VE-cadherin, 17 synthetic peptides containing or missing residues of the b 15-42 primary structure were used in the permeability assay (Fig. 2c).…”

“…14,[26][27][28] Control experiments indicated that Fg added to breast cancer or endothelial cells was not processed further by protease degradation or crosslinking to higher ordered structures (data not shown). Synthetic peptides corresponding to the Fg b-chain primary structure were custom synthesized as previously described, 11 and include b , b [15][16][17][18][19][20][21][22][23][24][25][26][27] , b 18-31 and b [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42] (Table I). Fibrinopeptide A (Bachem) was used as a nonspecific peptide for permeability studies.…”

“…Breakdown of VE-cadherin-mediated endothelial barrier function leads to altered vascular permeability and remodeling, which are associated with a number of disease processes including ischemia-reperfusion injury, inflammation, angiogenesis, and cancer growth and metastasis. VE-cadherin also supports EC capillary tube formation in fibrin gels, 15 which requires exposure of the fibrin b 15-42 neo-aminoterminus 16 ; portions of the third and fourth extracellular domains of VE-cadherin constitute a fibrin b 15-42 receptor. 17,18 Using the fibrin-specific monoclonal antibody (MoAb) T2G1, we showed that binding of fibrin monomer to the surface of EC is b 15-42 -dependent, which leads to reduced accessibility of b 15-21 to T2G1.…”