Amplification of Plasma MicroRNAs for Non-invasive Early Detection of Acute Rejection after Heart Transplantation With Ultrasound-Targeted Microbubble Destruction

Objective: Acute rejection (AR) screening has always been the focus of patient management in the first several years after heart transplantation (HT). As potential biomarkers for the non-invasive diagnosis of AR, microRNAs (miRNAs) are limited by their low abundance and complex origin. Ultrasound-targeted microbubble destruction (UTMD) technique could temporarily alter vascular permeability through cavitation. We hypothesized that increasing the permeability of myocardial vessels might enhance the abundance of circulating AR-related miR-NAs, thus enabling the non-invasive monitoring of AR.Methods: The Evans blue assay was applied to determine efficient UTMD parameters. Blood biochemistry and echocardiographic indicators were used to ensure the safety of the UTMD. AR of the HT model was constructed using Brown-Norway and Lewis rats. Grafted hearts were sonicated with UTMD on postoperative day (POD) 3. The polymerase chain reaction was used to identify upregulated miRNA biomarkers in graft tissues and their rela-tive amounts in the blood. Results: Amounts of six kinds of plasma miRNA, including miR-142-3p, miR-181a-5p, miR-326-3p, miR-182, miR-155-5p and miR-223-3p, were 10.89 +/- 1.36, 13.54 +/- 2.15, 9.84 +/- 0.70, 8.55 +/- 2.00, 12.50 +/- 3.96 and 11.02 +/- 3.47 times higher in the UTMD group than those in the control group on POD 3. Plasma miRNA abun-dance in the allograft group without UTMD did not differ from that in the isograft group on POD 3. After FK506 treatment, no miRNAs increased in the plasma after UTMD.Conclusion: UTMD can promote the transfer of AR-related miRNAs from grafted heart tissue to the blood, allowing non-invasive early detection of AR.