ABSTRACT
BACKGROUND:To date, it is stil unclear whether the intramuscular injection of heterogeneous umbilical cord mesenchymal stem cel s (UC-MSC) can cause cardiac ectopic pathological angiogenesis as wel as increase col agen synthesis to promote myocardial fibrosis. OBJECTIVE:To explore the effects of intramuscular injection of human UC-MSCs on myocardial micrangium and col agen expression in normal Wistar rats. METHODS:After 2 weeks of feeding, 60 male SPF Wistar rats were randomly assigned to receive intramuscular injection of PBS (normal group), DMEM (culture medium group), human UC-MSCs supernatant (supernatant group), 0.25×105, 1.0×105, 4.0×105 human UC-MSCs (low-, moderate-and high-dose groups), respectively (n=10 per group). Al the rats were subjected to second injection (same dose) at 4 weeks after first intramuscular injection. Then, the rats were kil ed under anesthesia at 4 weeks after second injection, to take heart tissues from the left ventricle for pathological observation, immunohistochemical examination and Masson staining. RESULTS AND CONCLUSION:No alteration of the response, activity, victualage, faeces, weight growth, and fur was found, and there was no death in rats during the experiment. Al the rats had no symptoms of molt, inflammation, skin ulcer, scleroma. Strong positive expression of CD34 for the micrangium in the myocardial tissue was observed, and positive expression of the col agen in the myocardial tissue observed by Masson staining. There were no significant differences in the microvessel density and col agen expression in the myocardium among the groups (F=0.110 and 0.585, P>0.05). To conclude, hUC-MSCs or its supernatant via intramuscular injection has no effect on the micrangium and col agen expression in normal rats.