Effects of Tenascin-C on Normal and Diabetic Retinal Endothelial Cells in Culture

Tenascin-C (TN-C) is expressed in embryogenesis, tissue remodeling, and healing. It is up-regulated in retinas of patients affected by diabetic retinopathy (DR). Because TN-C may promote neovascularization, its potential angiogenic effects were examined in vitro in normal and diabetic retinal endothelial cells (RECs). Bovine and human RECs were cultured on plastic or reconstituted basement membrane (BM) matrix. Production of TN-C, capillary-like tube formation, secondary sprouting, and cell migration, survival, and proliferation were measured with or without angiogenic growth factors (GFs). Antibodies and inhibitors were used to determine the involvement of specific TN-C receptors and signaling pathways. TN-C significantly delayed collapse of REC capillary-like tubes on BM matrix. It decreased tube involution associated with serum deprivation, high glucose, and exposure to TGF-beta. TN-C's enhancement of tube stability was mediated by alphavbeta3 integrin. TN-C increased REC viability in 0.5% serum and stimulated REC proliferation in 10% serum. It promoted REC secondary sprouting on BM matrix, which involved signaling through mitogen-activated kinase kinase (MEK) and p38 mitogen-activated protein kinase. TN-C also enhanced tube branching after treatment with VEGF and stimulated REC migration twofold. Angiogenic GF increased TN-C production by RECs in an additive manner, which may explain higher levels of TN-C deposition in DR cells. TN-C was overexpressed in diabetic and DR REC cultures. TN-C enhanced the sprouting, migratory, and survival effects of angiogenic GFs, and had distinct proliferative, migratory, and protective capacities. The data suggest that TN-C may act as a proangiogenic mediator in DR and other pathologic conditions involving neovascularization.