| Objective Sympathetic nerve sprouting is thought to contribute to suddencardiac death (SCD) in myocardial infarction(MI).However,the mechanisms remainunknown, and the studies of how to ameliorate nerve reconstruction to decreaseepisodes of SCD are still deficiency.Ephrin-b2,guidance cue molecules for nervegrowth, play important roles in embryonic nerves system development and maturenerve injury,through the mechanisms of contact-dependent repulsion and growthcone collapse. Given the property of its regulating nerve growth,this study attemptedto inhibit nerve reconstruction directly to ameliorate arrhythmia after MI so that wecan test the feasibility of the new therapeutics and investigate itsmechanisms.Because lack of effective carriers that controlled release proteins totarget area would limit the sound effects,this study has taken advantage of selfassembling peptide (SAP) carrying ephrin-b2/Fc recombinat protein to investigatewhether or not ephrin-b2can ameliorate the myocardial arrhythmia after MI and itsrelative mechanism..Method1.In vivo, Sprague-Dawley rats were prepared to acute myocardialinfarction models by ligation of the left anterior descending branch.The survival ratswere divdided into2groups and separately intramyocardially injected ofrecombinant Ephrin-b2/Fc proteins(E group，n=25) and sapeptide-Ephrin-b2/Fcprotein complex(ES group，n=25). At set time(1h,3h,24h,7d,14d)，the samples ofthe myocardial tissue and sera were collected and respectively used forimmunofluorescence and westernblot to determine the remaining or losing of theprotein.2.After coronary artery ligation, rats were randomized to receive intramyocardial injection of PBS alone(MI Group,n=20)，ephrin-b2/Fc recombinantprotein(ENF group,n=20)，self-assembling peptide(SAP group,n=19), sapeptide-Ephrin-b2/Fc protein complex(EFN+SAP group,n=19) at the infarct border zone.Two weeks after transpkantation, the changes of limb lead II surface ECG weremonitored, the Heart rate variability(HRV) and the number of premature ventricularcontractions（PVCs） were calculated；Monophasic action potential duration at90%repolarization (MAPD90) was measured.Ventricular effective refractory period(VERP),ventricular arrhythmias (VAs) inducibility and ventricular fibrillationthreshold(VFT) were assessed by in vivo programmed electricalstimulation(PES).3.Sympathetic fibers were identified by the method of anti-THimmunofluorescence and the density of nerves was expressed as the area of positivesignal/the area of feid of view.Result1.As shown in Immunofluorescence, except that it did not reachstatistical significance in timepoint of1h, the retention duration of the chimericprotein in ES group significantly longer than that in E group at the same time（3h/24h/7d P <0.001,14d p<0.5）.And westernbolt also demonstrated that at timepoint of1h and3h, the amount of protein releasing into blood in ES group was significantlyless than that in E group（P <0.001）and it was almost undetectable after7d and14d.2.Compared with the MI group,EFN injection exhibited the trend to suppressVAs, except significant difference of MAPD90(P <0.05),other differences did notreach statistical significance. EFNs injection combined with SAP led to significantlydifferences compared with MI group.（P of PVCs and MAPD90<0.01，of VAsinducibility quotient and VFT <0.05）. All electrophysiological parameters were notaffected by the injection of SAP.HRV and VERP show no difference between groups.3.Nerves density in the SAP group was higher than other groups,EFN+SAP groupshow significant decreased density than MI group(P<0.05).Conclusion Ephrin-b2/Fc recombinant protein can modestly amelioratearrhythmia after MI.The mechanism may be through suppressing sympathieticsprouting.Combined with SAP, the ameliorating effect of EFN was enhanced significantly,which may be due to controlled-releasing effect of SAP in myocardialtisse of MI. SAP do not affect the electrophysiological parameters after MI,albeit itcan increase the density of nerve fibers in portion of myocardial tissue. |
PDF Full Text Request