A Combination Of Ultrasound-targeted Microbubble Destruction With Transplantation Of Bone Marrow Mesenchymal Stem Cells Promotes The Recovery Of Acute Liver Injury

Objective: Ultrasound-targeted microbubble destruction(UTMD)is an innovative drug and gene delivery method with high specificity and efficiency.It has been shown that UTMD could enhance the targeted migration rate of stem cells,which and then could improve heart function and repair ischemic myocardium.In this study,we intended to investigate the feasibility and efficacy of UTMD in the homing of bone marrow mesenchymal stem cells(BMSCs)to the injured liver,then evaluated the therapeutic effect of BMSCs on injuried liver.Furthermore,we attempted to analyze the potential mechanism by which UTMD promoted the homing of transplanted stem cells.Methods: BMSCs were isolated from the femurs and tibias of Sprague-Dawley(SD)rats.The isolated BMSCs were stably transfected with a lentivirus expressing enhanced green fluorescent protein(EGFP)that can be visualized in vivo after transplantation.SD rats were injected intraperitoneal with 1.5g/kg D-galactosamine(D-Gal)in a single dose to establish acute liver injury model.After 24 h,serological markers and hepatic histological structure were used to confirm that the model was successfully established.Both tumor necrosis factor α(TNF-α)and stromal cell-derived factor 1(SDF-1)were used to verify the appropriate ultrasound parameters.The sixty ALI rats were divided into the following four groups: Control,BMSCs,UTMD and UTMD + BMSCs.48 hours after the experimental treatment,3 rats in each group were randomly selected to detect the quantity of BMSCs in the liver.In addition,the protein and mRNA expression levels of SDF-1,monocyte chemotactic protein 1(MCP-1),intercellular cell adhesion molecule(ICAM-1),vascular cell adhesion molecule 1(VCAM-1)and hepatocyte growth factor(HGF)in the exposed livers were analyzed.Biochemical parameters of rats were measured at 48 h,72h,1w and 2w after treatment: alanine transaminase(ALT),aspartate transaminase(AST)and alkaline phosphatase(ALP).At the same time,changes of hepatic lobules structure were evaluated 2w after treatment,hepatocyte apoptosis and proliferation were detected in each group.Results: The isolated rat BMSCs demonstrated a good proliferation potential that was both osteogenic,adipogenic and chondrogenic differentiation and expressed cluster of differentiation(CD)29 and CD90,but not CD45 or CD11b/c.The protein levels of SDF-1 and TNF-α of liver increased with the increase of ultrasound intensity(p<0.01).After BMSCs and/or UTMD treatment,the number of GFP-labeled BMSCs in the UTMD + BMSCs group was significantly higher than that of the BMSCs group.In addition,the expression levels of SDF-1,MCP-1,ICAM-1,VCAM-1 and HGF were higher(p<0.01)in UTMD+BMSCs group.The serum levels of biomarkers and the apoptotic rate of hepatocytes were significantly lower in the UTMD + BMSCs group(all p<0.05).The hepatic pathology was significantly alleviated in the UTMD + BMSCs group.Conclusion:UTMD could enhance hepatic homing of BMSCs in ALI rats by up-regulating the expression of certain molecules and cytokines,resulting in improving impaired liver function,inhibiting apoptosis,and promoting hepatocyte proliferation.UTMD treatment appeared to be an effective and noninvasive approach to achieve better efficacy of BMSC-based therapy for repairing injured liver.