Objective To establish chronic hindlimb ischemia model with suture-occluded method in rats， and then compare the effects of chronic hindlimb ischemia model with acute ischemia model. Methods Models of chronic hindlimb ischemia were established by using suture-occluded femoral artery method. The laser Doppler blood flow analysis and angiography were performed on day 7， 14， 28， 42， and 49 after operation， and then the rats were sacrificed after angiography， respectively， the quadriceps and gastrocnemius of contralateral and ipsilateral （surgical side） were gotten， which were tested by HE staining and α-actin immunohistochemistry staining， and then calculate arteriolar density. Results There were no lameness and limb necrosis after operation in chronic hindlimb ischemia models. Laser Doppler analysis found that chronic hindlimb ischemia models were still maintained in ischemia state on day 49 after operation compared with acute ischemic models. The resluts of HE staining showed no acute necrosis and muscle fibrosis in chronic hindlimb ischemia model group. Chronic hindlimb ischemia models after operation did not appear obvious lameness and limb necrosis. The arteriolar density of quadriceps femoris on day 7 after operation in chronic hindlimb ischemia models were less than that in acute hindlimb ischemia models （0.015 2 vs. 0.036 4）. Conclusions Compared with the commonly used acute ischemic models， the duration of arterial limb ischemia in chronic hindlimb ischemia rats， which were established by suture-occluded method， is longer and less likely to be affected by the compensatory mechanisms. So suture-occluded method can provide a new animal hindlimb ischemia model for further study of ischemia angiogenesis mechanism and treatment of severe lower extremity ischemia.
Objective To explore the mechanism of mesenchymal stem cells （MSCs） transplantation for chronic hindlimb ischemia in Lewis rats by using cell tracer technique. Methods MSCs were isolated and cultured by using density gradient centrifugation and adherence method respectively， then labeled by 5-bromo-2-deoxyuridine （BrdU）. Eight chronic hindlimb ischemia models of Lewis rats were prepared by using suture-occluded method and then divided randomly to MSCs transplantation group and control group， each group enrolled 4 rats， accepting MSCs transplantation and saline respectively. Then on 7 days and 14 days after transplantation， clinical observation， determination of blood flow， and angiography were performed on rats of the 2 groups. At the same time points after previous tests， rats of the 2 groups were sacrificed to get quadriceps tissues and gastrocnemius tissues to perform HE staining and BrdU immunohis-tochemistry. Results The 8 rats were all survived on 14 days after transplantation， with no tumor happened and necroses in the transplanted area. On 14 days after transplantation， the blood flow ratio of operated side to un-operated side in the hindlimb （1.773 vs. 1.279） of rats in MSCs transplantation group and control group increased， and the angiography results showed that there were no much increase in ratio of collateral vessels number （0.908 vs. 0.835）. There were no significant change in the quadriceps tissues and gastrocnemius tissues by HE staining. The BrdU positive kernels located in the inter-stitial substance cells and vascular endothelia cells， and divided differently in different parts of hindlimb at different time points， that the ratio of positive cells in gastrocnemius tissue was higher than those of quadriceps tissue on 7 days after transplantation， but lower on 14 days. Conclusions MSCs transplantation can increases the blood perfusion of hindlimb in the early stage of chronic hindlimb ischemia model， and the possible mechanism may be the paracrine effect of MSCs but not the number increase of collateral vessels.