Paradoxical impairment of angiogenesis, endothelial function and circulating number of endothelial progenitor cells in DPP4-deficient rat after critical limb ischemia

INTRODUCTION: We hypothesized that dipeptidyl peptidase-IV (DPP4) may impair angiogenesis, endothelial function, and the circulating number of endothelial progenitor cells (EPC) in a model of critical limb ischemia (CLI) through ligating the left femoral artery using DPP4-deficient rats. METHODS: Adult male DPP4-deficient (DPP4(D)) rats (n = 18) were equally divided into CLI only (DPP4(D)-CLI) and CLI treated by granulocyte colony-stimulating factor (GCSF) (DPP4(D)-CLI-GCSF). For comparison, age-matched wild-type (WT) Fischer 344 rats (n = 18) were randomized into two groups receiving identical treatment compared to their DPP4-deficient counterparts and labeled as WT-CLI (n = 9) and WT-CLI-GCSF (n = 9), respectively. RESULTS: The circulating number of EPCs (CD31+, CD34+, CD133, C-kit+) was significantly lower in DPP4-deficient than in WT rats on post-CLI days 1 and 4 (all P < 0.01). The ratio of ischemia/normal blood flow was remarkably lower in DPP4(D)-CLI-GCSF rats than in WT-CLI-GCSF animals on post-CLI Day 14 (all P < 0.01). Protein expressions of pro-angiogenic factors (endothelial nitric oxide synthase (eNOS), CXCR4, SDF-1α, vascular endothelial growth factor (VEGF)) were remarkably higher in WT-CLI than in DPP4(D)-CLI rats, and higher in WT-CLI-GCSF than in DPP4(D)-CLI-GCSF animals (all P < 0.01). Moreover, the numbers of small vessel in the ischemic area were substantially higher in WT-CLI-GCSF than in DPP4(D)-CLI-GCSF rats (P < 0.001). Furthermore, vasorelaxation and nitric oxide production of the normal femoral artery were significantly reduced in DPP4-deficient than in WT Fischer rats (all P < 0.01). CONCLUSIONS: Contrary to our hypothesis, DPP4-deficient rats were inferior to age-matched WT Fischer rats in terms of angiogenesis, endothelial function, circulating EPC number and response to GCSF, suggesting a positive role of DPP4 in maintaining vascular function and tissue perfusion in this experimental setting.