Protective effect of melatonin-supported adipose-derived mesenchymal stem cells against small bowel ischemia-reperfusion injury in rat

We tested the hypothesis that combined melatonin and autologous adipose-derived mesenchymal stem cells (ADMSC) was superior to either alone against small bowel ischemia-reperfusion (SBIR) injury induced by superior mesenteric artery clamping for 30min followed by reperfusion for 72hr. Male adult Sprague Dawley rats (n=50) were equally categorized into sham-operated controls SC, SBIR, SBIR-ADMSC (1.0x10(6) intravenous and 1.0x10(6) intrajejunal injection), SBIR-melatonin (intraperitoneal 20mg/kg at 30min after SI ischemia and 50mg/kg at 6 and 18hr after SI reperfusion), and SBIR-ADMSC-melatonin groups. The results demonstrated that the circulating levels of TNF-, MPO, LyG6+ cells, CD68+ cells, WBC count, and gut permeability were highest in SBIR and lowest in SC, significantly higher in SBIR-ADMSC group and further increased in SBIR-melatonin group than in the combined therapy group (all P<0.001). The ischemic mucosal damage score, the protein expressions of inflammation (TNF-, NF-B, MMP-9, MPO, and iNOS), oxidative stress (NOX-1, NOX-2, and oxidized protein), apoptosis (APAF-1, mitochondrial Bax, cleaved caspase-3 and PARP), mitochondrial damage (cytosolic cytochrome C) and DNA damage (-H2AX) markers, as well as cellular expressions of proliferation (PCNA), apoptosis (caspase-3, TUNEL assay), and DNA damage (-H2AX) showed an identical pattern, whereas mitochondrial cytochrome C exhibited an opposite pattern compared to that of inflammation among all groups (all P<0.001). Besides, antioxidant expressions at protein (NQO-1, GR, and GPx) and cellular (HO-1) levels progressively increased from SC to the combined treatment group (all P<0.001). In conclusion, combined melatonin-ADMSC treatment offered additive beneficial effect against SBIR injury.