Estudio de los microRNAs como biomarcadores no invasivos de rechazo post-trasplante cardiaco

Abstract

INTRODUCTION: acute cellular rejection (ACR) is an important complication after heart transplantation (HTx). Endomyocardial biopsy is the reference method for the early detection of this ACR, but it has important limitations. These include being invasive, the probable sampling error, the high cost and the subjective interpretation of the pathologist, which cause great variability in the final results. Therefore, it would be very useful to find a non-invasive biomarker for detecting ACR in the transplant patient. Among the possible candidates are circulating microRNAs. The main objective of the central study of this thesis is to discover and validate microRNAs in serum samples for the early detection of ACR in the follow-up of HTx. METHODS: 121 HTx patients were included in this prospective, observational, single-center study. RCA based on EMB was classified according to the International Society of Heart and Lung Transplantation (ISHLT) in 2004, with 4 grades: “0R” without rejection, “1R” mild rejection, “2R” moderate rejection, “3R” rejection serious. Initially, in an initial search phase, an experiment was carried out with microRNA expression profiles in the serum of pre-RCA patients “0RS1”, during rejection “2RS2” and after rejection “0RS3”. The entire episode was called “0RS1 →2RS2 →0RS3”. A total of 179 microRNAs in each serum were analyzed by RT-qPCR (Reverse Transcriptase quantitative Polymerase Chain Reaction) and those microRNAs with a significant rise/fall pattern (or vice versa) during the episode “0RS1 →2RS2 →0RS3” were selected. The next validation phase will check the diagnostic efficacy to detect RCA of the selected microRNAs. For this, new serum samples will be sought to form two new groups of patients, a group without “NoR” rejection and another with ACR (BEM≥2R). RESULTS: in the initial search phase, microRNAs were analyzed in a total of 21 episodes of RCA “0RS1 →2RS2 →0RS3”, and their respective serum samples (n = 63). Among the 179 microRNAs analyzed, only miR-181a-5p met the criteria for significant up- and down-regulation and therefore, the only microRNA selected for the next phase. In validation, miR-181a-5p was analyzed in 45 samples with RCA and 45 samples without RCA, being found significantly overexpressed in the group with RCA. The miR-181a-5p candidate also achieved an area under the curve AUC = 0.804 (95% CI: 0.707-0.880), and a sensitivity and specificity of 78% and 76%, respectively, with a high negative predictive value (98%). CONCLUSION: miR-181a-5p has demonstrated very good qualities as a non-invasive biomarker of ACR in HTx. A high negative predictive value together with a reduced cost and simplicity of analysis would justify its use as an aid in the management and monitoring of the heart transplant patient.