Laminin-binding Integrins Regulate Angiogenesis by Distinct and Overlapping Mechanisms in Organotypic Cell Culture Models

Endothelial cells engage extracellular matrix and basement membrane components through integrin-mediated adhesion to promote angiogenesis. Our previous studies demonstrated that endothelial expression of laminin-411 and laminin-511 as well as 6 integrins is required for endothelial sprouting and tube formation in organotypic angiogenesis assays. These studies demonstrated that 6 integrins promote migration and regulate the expression of ANGPT2 and CXCR4 and that 6-dependent regulation of CXCR4 contributes to endothelial morphogenesis in our assays. However, these studies did not identify specific roles for the 6{beta}1, 6{beta}4, or 3{beta}1 laminin-binding integrins. Here, we employ RNAi technology to parse the contributions of these integrins. We demonstrate that 6{beta}4 promotes migration, sprouting, and tube formation, and also positively regulates the expression of ANGPT2, but does not promote CXCR4 expression, suggesting that 6{beta}1 functions in this regulation. Additionally, we show that 3{beta}1 regulates endothelial sprouting and tube formation, but is not required for migration in our assays or for the expression of ANGPT2 or CXCR4. Integrin 3{beta}1 promotes the expression of NRP1 and ID1 RNAs, both of which are known to promote angiogenesis. Taken together, our results indicate that laminin-binding integrins play distinct roles during endothelial morphogenesis and do not compensate for one another in organotypic culture. Summary StatementThe laminin-binding integrins 3{beta}1, 6{beta}1, and 6{beta}4 contribute to endothelial sprouting and tube formation in organotypic angiogenesis assays.