Experimental Study Of Angiogenesis Stimulated By Ultrasound-Mediated Microbubble Destruction For Myocardial Infartion In Rat

PARTⅠTHE EFFECT OF ULTRASOUND-MEDIATED MICROBUBBLE DESTRUCTION IN MYOCARDIUM IN RATSObjective: To explore the effects of ultrasound-mediated microbubble destruction in rat myocardium, and to select the best experiment condition.Methods : Different ultrasound power density(0.5 W/cm2,1.0 W /cm2,2.0 W/cm2,2.5 W/cm2 )at the same time(2min) and the same frequency(300kHz) were applied on rats'chest wall after intravenous injection of the microbubbles at dose of 1ml. The microstructure of the tissue were observed by electron microscope and light microscope.Results : There was no vascular engorgement and red blood cells exudation in 0.5 W/cm2 group; in 1.0 W/cm2 group , hyperraemia in blood vessels and little red blood cells exudation could be seen; in 2.0 W/cm2 group, significant hyperraemia in blood vessels and red blood cells exudation could be observed; in 2.5 W/cm2 group,the lesion of myocardium could be seen. Electron microscope showed that no ultrastructure change in group 0.5 W/cm2,1.0 W/cm2 and 2.0 W/cm2; but in 2.5 W/cm2group, muscle fiber deliquescence and fragmentation and organelle swelling could be seen.Conclusion : Different energy of ultrasound -mediated microbubble destruction had different effects in rat myocardium, and ultrasound with frequency of 300kHz , intensity of 0.5 W/cm2～2.0 W/cm2 is suitable for therapy.The intensity of 2.0 W/cm2 is the best condition for therapy.PARTⅡEXPERIMENT STUDY OF STIMULATION OF MYOCARDIAL ANGIOGENESIS BY ULTRASOUND-MEDIATED MICROBUBBLE DESTRUCTION IN RATSObjective: To investigate whether ultrasound-mediated microbubble destruction can stimulate secretion of vascular endothelial growth factor (VEGF) and angiogenesis in rat myocardium.Methods: A total of 36 normal Wistar rats were randomly devided into 3 group: in group A,the myocardium was exposed to ultrasound (300kHz,2.0 W/cm2)after intravenous injection of microbubble of 1.0 ml; in group B, ultrasound was simply used in the myocardium ; only was 1.0ml NS infused in the control group(group C). Each group was treated 3 times, and 3 days after the first experiment, three rats in each group were killed and myocardium were harvested for HE staining to observe the microstructure of the tissue. The left 27 rats were received immunohistochemical staining of VEGF and CD34 2 weeks later.Result : Significant hyperraemia in blood vessels, red blood cells exudation and inflammatory cell infiltration could be observed in group A, and muscle fiber deliquescence and fragmentation and organelle swelling could not be seen in group A;less in group B and little hyperraemia, red blood cells exudation and inflammatory cell infiltration in the control group. There was significant expression of VEGF and CD34 in group A; less in group B and little expression in the control group.Conclusion: Ultrasound-mediated microbubble destruction can facilitate the endogenous secretion of VEGF and accelerate the vascularization in the rat myocardium. PartⅢEXPERIMENTAL STUDY OF STIMULATION OF MYOCARDIAL ANGIOGENESIS BY ULTRASOUND-MEDIATED MICROBUBBLE DESTRUCTION IN RAT WITH MYOCARDIAL INFARCTIONObjective: To investigate the feasibility of ultrasound-mediated microbubble distruction for the treatment of rat's myocardium ischemia resulted from secretion of VEGF.Methods: fourty normal Wistar rats were randomly devided into 4 groups, each group was successed raised myocardial infarction model. In group A, the myocardium was exposed to ultrasound after intravenous injection of microbubble of 1.0 ml; in group B, ultrasound was simply used in the myocardium; in group C, microbubble was intravenous injection only; the energy of ultrasound , the time of exposure and the dose of microbubble were the same as partⅡ.In the control group(group D), normal saline was infused . each group was received 3 experiments. Immunohistochemical staining of CD45 ,VEGF and CD34 were performed , and the quantitation of was detected by ELISA 4 weeks later.Western blot was performed for expression of VEGF.Result: Immunohistochemical staining show that the expression of VEGF and CD34 and CD45 was higher than those in group B, C ,D,and the new vessels degeneration were significant observed in group A than those in B, C, D. ELISA detection showed that the quantity of VEGF was the highest in ultrasound-mediated microbubble destruction group. A protein strap about 21kD was shown in the first group by Western blot detection. A tenuous protein strap about 21kD was shown respectively in the other three groups.Conclusion: ultrasound-mediated microbubble distruction could promote new vessels growth and collateral circulation development in ischemic myocardium. It provide a new method for the treatment of myocardium ischemia disease.