Effects of insulin on proliferation, sene-scence and NO secretion of endothelial progenitor cells

AIM: To investigate the effects of insulin on endothelial progenitor cell (EPC) proliferation, senescence and nitric oxide (NO) secretion. METHODS: Mononuclear cells were collected from rat bone marrow by density gradient centrifugation, cultured with Medium 199, and were identified to be EPC on day 7 by flk-1 and AC133 double staining. EPC were harvested and incubated with vehicle or insulin (0.1, 1, 10 nmol/L). After 24 h of incubation, NO secretion of EPC was assessed by Griess reaction. After 7 d of incubation, proliferative capacity was mea-sured by MTT assay, and senescent level was measured through senescence associated β-galactosidase (SA-β-Gal) staining. RESULTS: Compared with control group, 0.1 and 1 nmol/L insulin group showed higher EPC proliferative capacity (absorbance: 0.262±0.015, 0.290±0.021 vs control 0.232±0.021, P0.01), lower EPC senescence [(17.1±1.6)%, (11.7±1.8)% vs control (27.9±13.5)%, P0.05] after 7 d of incubation, and higher NO production [μmol/L, (42.4±1.4), (54.4±5.8) vs control (35.7±1.3), P0.05] after 24 h incubation, while 10 nmol/L insulin group showed no or only minor difference as compared with control group. CONCLUSION: Low-level insulin can stimulate EPC proliferation, inhibit its senescence, and enhance its NO secretion capacity.