| Background:Myocardial infarction is a common clinical ischemic heart disease in which atherosclerosis of coronary arteries leads to vascular occlusion,and acute myocardial ischemia in the distal coronary blood supply region for more than 1 hour results in acute myocardial infarction.In the basic research of myocardial infarction,mesenchymal stem cells（MSC）and their exosomes have attracted much attention and have achieved excellent results in the treatment of myocardial infarction.Exosomes have recently been identified as the major paracrine functional unit of stem cells.Exosome is a miniature vesicle with a double-layered membrane structure,40-150 nm in diameter,which exists stably outside the cell and carries a variety of biologically active substances such as proteins,lipids,RNA,etc.It is involved in cell communication,immune response,cell migration,angiogenesis and tumor cell growth.It protects the heart by exerting the effects of anti-inflammation,anti-apoptosis,inhibition of oxidative stress,protection of vascular endothelial function,promotion of therapeutic vascular renewal,diastole,improvement of circulation,and resistance to myocardial ischemia and ischemia-reperfusion injury.It has been shown that treatment of mice heart MSC with suxiao jiuxin pills can increase their exosome secretion and the exosome can promote cardiomyocyte proliferation,suggesting that exosome has an important role in the treatment of myocardial infarction with suxiao jiuxin pills.Based on this,this study proposes that exosomes from MSCs pretreated with suxiao jiuxin pills regulate inflammatory response and promote vascular neogenesis through TLR4/TRAF6/NFκB signaling pathway,which in turn ameliorates cardiac injury after myocardial infarction.Methods:SD rats were given with suxiao jiuxin pills 64.8 mg/kg/day or equivalent saline by gavage for 7 days,and whole blood was extracted from the rat’s abdominal aorta 2 h after day 7 administration,and the isolated rat serum was used to treat human umbilical cord blood mesenchymal stem cells（HUMSCs）,and the supernatant was collected after 24 h.Exosomes were collected by ultracentrifugation.Exosomes were identified by Western Blot,electron microscopy,and particle size analysis.A rat model of acute myocardial infarction was prepared by left anterior descending branch ligation,and two types of exosomes were injected into the tail vein three days before modeling:drug-containing serum from rats and exosomes secreted from HUMSCs pretreated with non-drug-containing serum,and the effects of exosomes on cardiac function,infarct size,collagen deposition,inflammatory infiltration and vascularity after acute infarction were observed using echocardiography,immunofluorescence,real-time fluorescence quantitative PCR,protein immunoblotting,and other methods.The effect of exosomes on cardiac function,infarct size,collagen deposition,inflammatory infiltration and vascular regeneration after acute infarction and whether the effect of exosomes secretion from HUMSCs pretreated with suxiao jiuxin pill-containing serum was stronger in rats.By reviewing the relevant literature and combining the results of miRNA high-throughput sequencing,we screened the miR-146a-3p differentially expressed in the two exosomes and interfered with the miR-146a-3p in the exosomes for functional validation.Results:Exosomes with diameters in the range of 40-150 nm,with lipid bilayer membrane structures,and expressing exosomal surface protein markers were successfully isolated using ultracentrifugation.The tail vein injection of drug-free serum-treated HUMSC exosomes(NC-MSCexo)improved cardiac function,reduced infarct size,decreased collagen deposition,inhibited inflammatory infiltration and promoted vascular renewal in rats after acute myocardial infarction,and the effect of drug-containing serum pretreated HUMSC exosomes(SXJX-MSCexo)was more significant.Decreased miR-146a-3p levels in exosomes exacerbated cardiac injury after acute myocardial infarction and greatly diminished the post-infarction effects of SXJX-MSCexoin suppressing inflammatory response and promoting vascular neovascularization,confirming that SXJX-MSCexomay suppress inflammatory response as well as promote vascular neovascularization by transporting miR-146a-3p.Conclusion:SXJX-MSCexoexerts an inhibitory effect on the inflammatory response and promotes vascular neovascularization through transporting miR-146a-3p. |
