MMP 9-instructed Assembly Of BFGF Nanofibers In Ischemic Myocardium To Promote Heart Repair

Objective The only effective treatment for myocardial infarction(MI)is the timely restoration of coronary blood flow in the infarcted area,but further reperfusion exacerbates myocardial injury and leads to distal coronary no-reflow,which affects patient prognosis.Angiogenesis could be an important therapeutic strategy for re-establishing the blood supply to save the ischemic myocardium after myocardial infarction.Basic fibroblast growth factor(b FGF),as an effective drug promoting vascular remodeling,has been widely used in the treatment of ischemic diseases.However,direct intravenous injection of b FGF is not a viable option because of its short half-life in vivo.We investigated whether self-assembled nanofibers in ischemic myocardium mediated by Matrix metallopeptidase 9(MMP-9)can be loaded with b FGF intravenously and its retention time can be prolonged to promote the repair of ischemic myocardial injury.Methods Based on the micelle-forming property of amphiphilic peptides,the micellar factor polypeptide Lys-Lys-Pro-Leu-Gly-Leu-Ala-Gly-Phe(K2)was designed and synthesized to form nanofibers in vitro,and b FGF was loaded to form b FGF@K2micelle.In vitro validation b FGF@K2 micelle transitions from micellar state to b FGF@-nanofiber transition validation mediated by MMP-9.The MMP-9 mediated transition of b FGF@K2 micelle from micelle state to b FGF@-nanofiber was verified in vitro.Rat myocardial ischemia-reperfusion model was established and rhodaminelabeled b FGF@K2 micelle was injected into the tail vein.The retention rate of b FGF@K2 micelle was verified by immunofluorescence,transmission electron microscopy and Western blot.Twenty-five male SD rats were randomly divided into:Sham operation group(Sham group),myocardial ischemia-reperfusion group(Saline group),tail vein injection of single Micelle group(K2 micelle group),tail vein injection of b FGF group(b FGF group),tail vein injection of b FGF-micelle group(b FGF@K2micelle group).TUNEL staining was used to assess the level of myocardial cell apoptosis in each group at early phase.After 28 days of MI/R,echocardiography was used to detect the left ventricular function,immunofluorescence staining was used to detect the expression levels of α-SMA and CD31 in ischemic myocardium,and MASSON staining was used to assess the infarct area and the degree of myocardial fibrosis in rats.Results In vitro results revealed that the b FGF@K2 micelle could be cleaved by matrix metallopeptidase 9(MMP-9)and self-assembled to form b FGF@Nanofiber by amphipathic effect.In vivo experiments have shown that b FGF@K2 micelle could be self-assembled into b FGF@Nanofiber in ischemic myocardial through Aggregation-induced retention(AIR)effect and high expression of MMP-9 after intravenous injection.The retention efficiency of b FGF in the ischemic myocardium of rats was prolonged.In a myocardial ischemia-reperfusion model,the b FGF@K2 micelle group reduced apoptosis in the ischemic myocardium at an early stage compared with the Saline group,and promoted revascularization after 28 days of ischemia-reperfusion,significantly improving cardiac function and reducing ventricular remodeling in MI/R rats.Conclusion The self-assembly of drug-loaded nanofibers in ischemic myocardium mediated by MMP-9 protease through intravenous injection can effectively improve the retention time of drugs in ischemic myocardium,reduce myocardial ischemia-reperfusion injury and myocardial fibrosis,and improve cardiac function.This provides a new idea for the design of intravenous drugs for the treatment of ischemic myocardium in vivo.