1. What is the major problem being addressed by this study?
In cardiac transplantation, there are no reliable, blood-based markers to accurately detect heart transplant rejection or coronary disease. After transplant, patients are subjected to repetitive invasive procedures (~10-17) to screen for rejection. These procedures are associated with patient discomfort, significant healthcare cost, and carry a risk of complications. Also, the tissue obtained at the time of the biopsy is often interpreted incorrectly. Coronary disease of the transplanted heart is often silent clinically until it is too advanced to be treated effectively; this accounts for 30% of the mortality after transplant. The angiogram is not sensitive enough to detect disease until it is too advanced. A non-invasive marker of earlier coronary disease is urgently needed.

2. What specific questions are you asking and how will you attempt to answer them?
We propose developing a blood-based microRNA panel to replace two common invasive procedures employed after heart transplant to detect rejection and coronary disease: the endomyocardial biopsy and coronary angiogram. We will use next-generation sequencing technologies to identify specific microRNAs that can be detected in the blood and accurately diagnose rejection and coronary disease. We will accomplish this by evaluating blood-based microRNAs in 500 heart transplant patients from an existing study. Using statistical tools, we will identify key microRNAs that can be used in a blood-based panel to screen patients after heart transplant for rejection and coronary disease. This panel of microRNAs could replace the biopsy and angiogram to manage patients after heart transplant.

3. Overall, what is the potential impact of this work to the mission of the AHA?
Our work will lead to the development of a diagnostic test that can screen the blood of patients after heart transplant for rejection and coronary disease. This will significantly reduce patient morbidity and healthcare costs, as it will eliminate the need for an invasive endomyocardial biopsy or heart catheterization. Additionally, because microRNAs are not only markers of disease but can mediate disease as well, this proposal will identify microRNAs that might cause heart transplant rejection and coronary disease. These microRNAs can then be targeted in the future to develop new drugs to prevent or treat rejection and coronary disease. Additionally, these microRNAs may be implicated in rejection of other transplanted organs (e.g. kidneys, lung).

Aim 1: Using NGS, determine the miR transcriptome of cardiac transplant recipients and distinguish miR biomarkers of cardiac allograft rejection.
Hypothesis: Specific plasma miRs will be differentially expressed in patients with allograft rejection.

Aim 2: Contrast the ability of two genomic biomarkers to accurately diagnose TCMR and AMR.
Hypothesis: A set of miRs has superior ability to diagnose allograft rejection and can distinguish the subtypes of rejection when compared to dd-cfDNA.

Aim 3: Identify miRs implicated in the pathophysiological underpinnings of CAV.
Hypothesis: Specific miRs are involved in the development of CAV and can serve as non-invasive biomarkers of CAV. Following completion of these aims, we expect to have a panel of miRs that will be the basis for functional analyses and clinical validation studies. Our long-term goal is to develop a miR-based in vitro diagnostic multivariate index assay (IVDMIA) that replaces the endomyocardial biopsy and coronary angiogram as a diagnostic tool to accurately detect allograft rejection and CAV.