Mesenchymal cells stimulate capillary morphogenesis via distinct proteolytic mechanisms |
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Authors: | Cyrus M Ghajar Ekaterina Kniazeva Sylvain V Costes Andrew J Putnam |
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Institution: | a Department of Biomedical Engineering, University of California, Irvine, Irvine, CA 92697, USA b Department of Cancer & DNA Damage Responses, Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA c Department of Chemical Engineering and Materials Science, University of California, Irvine, Irvine, CA 92697, USA d Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, 48109, USA |
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Abstract: | During angiogenesis, endothelial cells (ECs) degrade their surrounding extracellular matrix (ECM) to facilitate invasion. How interactions between ECs and other cells within their microenvironment facilitate this process is only partially understood. We have utilized a tractable 3D co-culture model to investigate the proteolytic mechanisms by which pre-committed or more highly committed mesenchymal cells stimulate capillary formation. On their own, ECs invade their surrounding matrix, but do not form capillaries. However, in the presence of either mesenchymal stem cells (MSCs) or fibroblasts, ECs form polarized, tubular structures that are intimately associated with mesenchymal cells. Further, ECs up-regulate gene expression of several extracellular proteases upon co-culture with either mesenchymal cell type. The administration of both broad spectrum and specific protease inhibitors demonstrated that MSC-stimulated capillary formation relied solely on membrane-type matrix metalloproteinases (MT-MMPs) while fibroblast-mediated sprouting proceeded independent of MMP inhibition unless the plasminogen activator/plasmin axis was inhibited in concert. While other studies have established a role for the ECM itself in dictating proteolysis and matrix degradation during capillary morphogenesis, the present study illustrates that heterotypic cellular interactions within the microenvironment can direct the proteolytic mechanisms required for capillary formation. |
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Keywords: | 3D three-dimensional αSMA α-smooth muscle actin EACA ?-aminocaproic acid EC endothelial cell ECM extracellular matrix GFP green fluorescent protein IF immunofluorescent MMP matrix metalloproteinase MSC mesenchymal stem cell MT-MMP membrane-type matrix metalloproteinase PA plasminogen activator TIMP tissue inhibitor of metalloproteinases uPA urokinase-type plasminogen activator uPAR urokinase plasminogen activator receptor tPA tissue plasminogen activator |
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