[Identification of a cardiac allograft rejection marker using microarray gene expression analysis in lymphocytes from heart transplant patients].

The diagnosis of graft rejection is one of the fundamental aspects of caring for patients with heart transplantation. Endomyocardial biopsy (EMB) has important limitations, as it is an invasive procedure, with variable interpretation and limited sensitivity.1-3 Thus, it would be of interest to have a noninvasive diagnostic method that facilitates follow-up of patients with heart transplantation. The gene expression patterns of peripheral blood lymphocytes may represent a highly sensitive, highly specific tool that would identify patients who present rejection and avoid the inconvenience of EMB. We present the preliminary results of a study performed to determine a set of candidate genes for use in a noninvasive molecular expression test with peripheral blood to detect cardiac graft rejection. The experiments to analyze gene expression were conducted with 6 peripheral blood samples taken from heart transplant recipients on the day of EMB. Rejection was diagnosed according to the International Society of Heart and Lung Transplantation (ISHLT) classification.4 Three of the samples corresponded to patients with rejection (ISHLT Grade ≥2 ISHLT rejection) and three to patients without rejection (ISHLT Grade 0 rejection). The blood samples were collected in tubes containing a solution for RNA stabilization (PAXgene Blood RNA Tubes, Qiagen) and stored at –80oC until the time of analysis. Genetic tests were performed with Affymetrix microarrays (GeneChip Human Genome U133 Bonus 2.0 Array). Differences in the expression of 262 genes were found when using the GeneSpring comparison algorithm. Two-dimensional hierarchical cluster allows verification of the presence of differential expression patterns consisting of samples with rejection compared to the control samples. Of these 262 genes, Table lists the candidate genes. Five metabolic pathways with at least 2 genes of modified expression level were found. These metabolic pathways were: LETTERS TO THE EDITOR