We tested the hypothesis that hyperbaric oxygen (HBO) (100% oxygen/2.4 atmospheres) facilitated the effect of autologous endothelial progenitor cell (EPC) therapy on restoring the blood flow in rat critical-limb ischemia (CLI). Adult-male-SD rats (n = 8/each group) were categorized into group 1 [sham control (SC)], group 2 (CLI-treated with culture medium), group 3 [CLI-intermittent HBO (3 h/day for 5 consecutive days after CLI), group 4 (CLI-EPC/2.0 × 106 cells), and group 5 (CLI-HBO-EPC). By day 5 after CLI, flow cytometry showed that the circulating EPC (Sca-1/CD31+/C-kit/CD31+/CD34+) levels were highest in group 5 and lowest in group 2 (all P < 0.001). By day 14, laser Doppler demonstrated that the ratio of blood flow (i.e., CLI to normal hind-limb) was highest in group 1, lowest in group 2 and significantly higher in group 5 than in groups 3 and 4 (all P < 0.0001). The protein expressions of endothelial-cell biomarkers (CD31/vWF/eNOS), and numbers of endothelial-cell markers (CD31+/vWF+) and small vessels exhibited a similar pattern to blood-flow ratio among five groups, whereas the angiogenesis parameters in protein (CXCR4/SDF-1α/HIF-1α/VEGF) and cellular (HIF-1α/SDF-1α/CXCR4+) levels were progressively increased from groups 1 to 5 (all P < 0.0001). The protein expression of apoptotic (mitochondrial-Bax/cleaved-capspase-3/PARP), fibrotic (p-Smad3/TGF-ß) and mitochondrial-damaged (cytosolic-cytochrome C) exhibited an opposite pattern, whereas the protein expressions of anti-fibrotic (BMP-2/p-Smad1/5) and mitochondrial integrity (mitochondrial-cytochrome C) exhibited an identical pattern of ratio of blood flow among the five groups (all P < 0.0001). Combined HBO-EPC therapy is superior to either one alone in improving ischemia in rodent CLI.
Keywords: Critical limb ischemia; angiogenesis; apoptosis; endothelial progenitor cells; fibrosis; hyperbaric oxygen.