ADVANCED GLYCATION END PRODUCTS-DRIVEN ANGIOGENESIS IN-VITRO

This study was undertaken to determine whether and how advanced glycat ion end products (AGE), senescent macroproteins accumulated in various tissues under hyperglycemic states, cause angiogenesis, the principal vascular derangement in diabetic microangiopathy. We first prepared A GE-bovine serum albumin (BSA) and anti-AGE antiserum using AGE-RNase A . Then AGE-BSA was administered to human skin microvascular endothelia l cells in culture, and their growth was examined. The AGE-BSA, but no t nonglycated BSA, was found to induce a statistically significant inc rease in the number of viable endothelial cells as well as their synth esis of DNA. The increase in DNA synthesis by AGE-BSA was abolished by anti-AGE antibodies. AGE-BSA also stimulated the tube formation of en dothelial cells on Matrigel. We obtained the following evidence that i t is vascular endothelial growth factor (VEGF) that mainly mediates th e angiogenic activities of AGE. (1) Quantitative reverse transcription -polymerase chain reaction analysis of poly(A)(+) RNA from microvascul ar endothelial cells revealed that AGE-BSA up-regulated the levels of mRNAs for the secretory forms of VEGF in time- and dose-dependent mann ers, while endothelial cell expression of the genes encoding the two V EGF receptors, kinase insert domain-containing receptor and fms-like t yrosine kinase 1, remained unchanged by the AGE treatment. Immunopreci pitation analysis revealed that AGE-BSA did increase de novo synthesis of VEGF. (2) Monoclonal antibody against human VEGF completely neutra lized both the AGE-induced DNA synthesis and tube formation of the end othelial cells. The results suggest that AGE can elicit angiogenesis t hrough the induction of autocrine vascular VEGF, thereby playing an ac tive part in the development and progression of diabetic microangiopat hies.