High glucose conditions suppress the function of bone marrow-derived endothelial progenitor cells via inhibition of the eNOS-caveolin-1 complex

The present study aimed to reveal how high glucose affects rat bone marrow-derived endothelial progenitor cells in vitro. Total mononuclear cells of bone marrow were obtained, cultured in endothelial cell growth medium-2 and identified by fluorescence microscopy. Using immunofluorescence, endothelial progenitor cells were identified by expression of VEGFR-2 as well as CD133 and were further characterized as those adherent cells which were double positive by Dil-Ac-LDL uptake and FITC-UEA-1 lectin binding. The attached cells were collected and glucose was added to the culture medium at various final concentrations (11.1, 33.3 and 55.5 mmol/l). Proliferation, migration and in vitro angiogenic ability of endothelial progenitor cells were measured. The change in mRNA and protein levels of caveolin-1 and endothelial nitric oxide synthase (eNOS) were examined; in addition, nitric oxide (NO) levels in the cell medium were measured. Based on the results, with increasing glucose concentration in the medium, proliferation, migration and in vitro angiogenic capacity of the cells were reduced, whereas mRNA and protein levels of caveolin-1 gene increased gradually. The mRNA levels of the eNOS gene did not differ, but the protein expression was reduced and NO levels in the culture medium declined. In conclusion, high glucose conditions are detrimental to the function of bone marrow-derived endothelial progenitor cells in vitro, probably by damaging the eNOS-caveolin-1 complex, which results in the reduction of NO synthesis, eventually leading to the impaired function of endothelial progenitor cells.