Ultrasound-Targeted Microbubble Destruction-Mediated Bax Silencing Inhibits Acute Rejection Following Heart Transplantation

Abstract Background: Ultrasound‑targeted microbubble destruction (UTMD) has been developed as a promising approach for organ‑ and tissue‑specific gene or drug delivery. The aim of the present study was to explore the role of UTMD‑mediated Bax gene silencing in acute rejection(AR) response after heart transplantation(HT).Methods: Bax-short hairpin RNA (shRNA) bound with polyethyleneimine (PEI) and microbubbles(MBs) were synthesized and effective ultrasound-targeted delivery of Bax-shRNA/PEI into rat cardiomyocyte H9c2 confirmed in vitro. Based on these observations, three transplant rat models were tested： ①Allograft (ALLO); ② ALLO+cyclosporine(CsA); and ③ALLO+UTMD+Bax-shRNA/PEI. The protein expression of Bax gene was detected through Western blot analysis. The pathological examination and survival time of cardiac allografts were also evaluated.Results: Bax protein expression was significantly inhibited in ALLO+UTMD+Bax-shRNA/PEI group compared to the other two groups(p<0.01). At 6 days post HT, the ALLO+UTMD+Bax-shRNA/PEI group had Grade II rejection or less inflammatory infiltration and myocyte damage using International Society For Heart and Lung Transplantation grading, compared to Grade IIIB or IV in ALLO group and Grade II or III in ALLO+CsA group.The survival time of allografts in ALLO+UTMD+Bax-shRNA/PEI group was(16.21±5.01)days, which was obviously longer than that in ALLO (p < 0.05) and ALLO+CsA(p < 0.01) group.Conclusions: UTMD mediated Bax gene inhibition with shRNA/PEI can prevent acute cellular rejection and improve survival time of the grafted heart in the early post-transplant period. These findings may provide a new strategy for gene therapy in patients after HT.