Objective To investigate the effects of soluble components derived from bone marrow mesenchymal stem cells (BMSCs) on the expression of vascular endothelial growth factor (VEGF) and liver regeneration caused by 70％ portal branch ligation (PBL) in rats.Methods Isolated and cultured BMSCs were lysed by sonication.PBL was performed in male SD rats followed by splenic injection of BMSCs or PBS as control.Animals were analyzed for liver regeneration index,hepatocytes proliferation,hepatic function,histopathological changes,and hepatic genes expression.Expression of VEGF was assessed by Western blot and immunohistochemistry.Results The liver regeneration index increased in the BMSCs group especially 2 and 5 days after PBL compared with the control group (P＜0.05) and reached (51.71±1.62)％ and (76.82±0.81)％ respectively.A 2-fold increase was showed in the PCNA labeling index of hepatocytes in rats treated with BMSCs compared with the control group (P＜0.05).Histopathological findings showed that vacuolar change and sinusoidal congestion were lower in the BMSCs group.Alanine transaminase (ALT) and Aspartate transferase (AST) showed no significant difference between the two groups (P＞0.05).On post operation day 2,hepatic interleukin-6 (IL6),tumor necrosis factor α (TNFα),hepatocyte growth factor (HGF),vascular endothelial growth factor A (VEGFA),and vascular endothelial growth factor 2 (VEGFR2) mRNAs tended to increase in the BMSCs group (P＜0.05) while transforming growth factor β1 (TGFβ1) mRNA decreased (P＜0.05).Western blot showed that the expression level of VEGF in the two groups were equal 2 and 5 days after surgery (P＞0.05).On day 2 post operation,positive VEGF immunoreactivity was present in both pericentral and periportal hepatocytes in the BMSCs group,while only in periportal hepatocytes in the control group.Conclusion These results demonstrate that BMSCs accelerated liver regeneration caused by PBL,which may result from hepatoprotection,enhanced hepatocyte proliferation,and VEGF-mediated angiogenesis early after the operation,potentially creating a new avenue for the study of hepatic regeneration.

Remarkable progress has been achieved in the transplantation of mesenchymal stem cells (MSCs)for the treatment of liver injury and hepatic failure.However,there are obstacles such as low engraftment capacity,tumorigenesis,and a fibrogenic potential that all hamper the use of MSCs in clinical trials.Therefore,it is worthwhile to talk about the alternatives that will increase the safety and efficacy of MSCs therapy.To date,applications of MSCs-derived hepatocytes,genetically modified MSCs,or MSC-conditioned medium for promoting liver regeneration have shown encouraging results.This review summarizes the current applications of MSCs in the study of hepatic regeneration.