The Experimental Research For Enhancing Homing Of Bone Marrow Mesenchymal Stem Cells By Ultrasound-Mediated Microbubbles In Ischemic Stroke

Objective: To investigate enhancing homing effect of using ultrasound-mediated microbubbles to intervene bone marrow mesenchymal stem cells(BMSCs)intravenous transplantation in the treatment of ischemic stroke.And investigate the mechanisms.Methods:Bone marrow mesenchymal stem cells of rats were cultured in vitro.1 Healthy male mice were randomly divided into four groups: phosphate buffer saline control group(PBS group),mesenchymal stem cells group(MSCs group),ultrasound+MSCs group(US group)and ultrasound+MSCs+microbubble group(MB group).A middle cerebral artery occlusion(MCAO)model was induced by plug wire preparation.72 hours after MCAO,2ml PBS was injected via tail vein in PBS group.3×106 BMSCs cells which were diluted into 2 ml by PBS were injected via tail vein slowly in MSCs group.In US group,3×106 BMSCs which were diluted into 2 ml by PBS were injected via tail vein slowly,than the ultrasonic equipment(1 MHz,2 W/cm2)against skull was started for 120 seconds.In MB group,the same process as US group was done,but before turning on the ultrasonic equipment,0.1ml/kg microbubbles were injected via tail vein.Rats neurological severity scores(NSS),rate of stem cell homing(fluorescence staining method),water content(Dry/Wet method),brain infarct volume(TTC staining method)were detected at corresponding time points after MCAO.2 BMSCs and vascular endothelial cells(VECs)of rats were cultured in vitro,and then randomly divided into three groups: control group with no intervention;ultrasound group was exposed to ultrasound at 1 MHz,1 W/cm2 for 90 s,and ultrasound-mediated microbubble group was treated with 5 ?L ultrasound microbubbles(about 2×1011/L)than exposure to ultrasound as ultrasound group.Cell culture supernatant was collected.Stromal cell derived factor 1(SDF-1)and vascular endothelial growth factor(VEGF)secreted by VECs expression level was detected by ELISA method.CXC chemokine receptor 4(CXCR4)m RNA expression level in MSCs was detected by reverse transcription-polymerase chain reaction(RT-PCR).Results:1(1)48h after BMSCs were transplanted to MCAO model rats from vein,the MSCs homing rate in the brain in MB group was higher than BMSc group and US group(P < 0.05).(2)28d after MCAO,damage degree of nerve was lighter in MB group than the other groups(P < 0.05).(3)7d after transplantation,the Water content of MB group of rats was lower than the other groups(P < 0.05).(4)7d after transplantation,cerebral infarction volume of MB group was smaller than the other groups(P < 0.05).2 Compared with the control group and ultrasound group,expressions of VEGF and SDF-1 by VECs significantly increased in ultrasound-mediated microbubble group(P < 0.05).Compared with the control group,expressions of CXCR4 m RNA by BMSCs significantly increased in ultrasound group and ultrasound-mediated microbubble group(P < 0.01).Conclusions: Ultrasound-mediated microbubbles can enhance homing effect of vein transplanted BMSCs and increase effect of stem cells transplantation treating ischemic stroke.The mechanism is associated with promoting VEGF and SDF-1 secretion by VECs,and meanwhile promoting CXCR4 gene expression in BMSCs.