Sitagliptin therapy enhances the number of circulating angiogenic cells and angiogenesis-evaluations in vitro and in the rat critical limb ischemia model

Background aims: We tested the hypothesis that sitagliptin is capable of increasing blood flow in the rat critical limb ischemia (CLI) model by enhancement of angiogenesis. Methods: Adipose tissue from adult-male Fischer 344 rats (n= 6) were cultured in endothelial progenitor cell culture medium for 14 d with (25 μmol/L) or without sitagliptin. CLI was induced by ligation of the left femoral artery. Rats (n= 32) were equally separated into four groups: untreated controls (group 1), sitagliptin (4 mg/kg per day; group 2), CLI (group 3) and CLI with sitagliptin (group 4). Results: In vitro, 7 and 14 d after cell culture, endothelial progenitor cell biomarkers assessed by flow cytometry (Sca-1/CD31+, CXCR4+, c- kit+ and CD34+ cells) and Western blot (vascular endothelial growth factor, CXCR4 and stromal-derived factor [SDF]-1α) were remarkably higher in group 4 than in the other groups (all P< 0.01). In vivo, 2 and 14 d after the CLI procedure, circulating angiogenic cell (Sca-1/CD31+, Sca-1+ and CD31+) numbers were significantly higher in group 4 than in the other groups (all P< 0.001). Additionally, the messenger RNA and protein expression of angiogenic biomarkers (CXCR4, SDF-1α and vascular endothelial growth factor), immunofluorescent staining of angiogenic cells (CXCR4+, SDF-1α+, CD31+, von Willebrand factor+ cells) and immunohistochemical staining of small vessel numbers in the ischemic area were significantly higher in group 4 than in the other groups (all P< 0.01). Furthermore, laser Doppler showed that the ratio of ischemic/normal blood flow was remarkably higher group 4 than in group 3 by days 14 and 28 after the CLI procedure (all P< 0.01). Conclusions: Sitagliptin therapy enhances circulating angiogenic cell numbers, angiogenesis and blood flow in the CLI area.