This study was undertaken to determine whether and how
advanced glycation end products (AGE), senescent macroproteins accumulated in various tissues under hyperglycemic states, cause angiogenesis, the principal vascular derangement in
diabetic microangiopathy. We first prepared AGE-
bovine serum albumin (BSA) and anti-AGE antiserum using AGE-
RNase A. Then
AGE-BSA was administered to human skin microvascular endothelial cells in culture, and their growth was examined. The
AGE-BSA, but not nonglycated BSA, was found to induce a statistically significant increase in the number of viable endothelial cells as well as their synthesis of
DNA. The increase in
DNA synthesis by
AGE-BSA was abolished by anti-AGE
antibodies.
AGE-BSA also stimulated the tube formation of endothelial cells on
Matrigel. We obtained the following evidence that it is
vascular endothelial growth factor (
VEGF) that mainly mediates the angiogenic activities of AGE. (1) Quantitative reverse transcription-polymerase chain reaction analysis of
poly(A)+ RNA from microvascular endothelial cells revealed that
AGE-BSA up-regulated the levels of mRNAs for the secretory forms of
VEGF in time- and dose-dependent manners, while endothelial cell expression of the genes encoding the two
VEGF receptors,
kinase insert domain-containing receptor and
fms-like tyrosine kinase 1, remained unchanged by the AGE treatment. Immunoprecipitation analysis revealed that
AGE-BSA did increase de novo synthesis of
VEGF. (2)
Monoclonal antibody against human
VEGF completely neutralized both the AGE-induced
DNA synthesis and tube formation of the endothelial cells. The results suggest that AGE can elicit angiogenesis through the induction of autocrine vascular
VEGF, thereby playing an active part in the development and progression of
diabetic microangiopathies.