Expression Profiling In Acute and Chronic Cardiac Allograft Rejection

急性同种异体心脏移植细胞排斥反应仍然是心脏移植后一年内发病率和死亡率的重要来源。之后，同种异体心脏移植血管病变（CAV），作为慢性血管排斥反应的结果，是发病率和死亡率的主要原因。在移植后的第一年，几乎三分之二的受者会经历至少一次排斥反应。移植后5年，近50%的幸存者将患有CAV。在移植后的第一年，近63%的患者至少经历一次心脏排斥反应，其中约三分之一的患者会多次发生心脏排斥反应。急性心脏排斥反应的临床症状相对无特异性（疲劳、呼吸困难、低烧）。大多数CAV患者在出现严重问题（如心肌梗死、心力衰竭、室性心律失常或心源性猝死）之前没有症状。目前尚无无创诊断急性或慢性心脏排斥反应的方法。无创方法，如心电图、超声心动图和核研究都已经研究过，但迄今为止，对任何一种情况都没有成功。已经研究了几种方法，包括心电图、超声心动图、核成像和磷光谱，但没有成功。目前诊断急性细胞排斥反应的金标准仍然是右心室心肌内膜活检。这是一种受发病率、随机抽样和解释误差影响的侵入性诊断方法。同样，诊断CAV的金标准是血管内超声心导管插入术，这是一种侵入性手术，也容易发病。

Acute cardiac allograft cellular rejection remains a significant source of morbidity and mortality within the first year after heart transplantation. Afterwards, cardiac allograft vasculopathy (CAV), as a result of chronic vascular rejection, is the major cause of morbidity and mortality. Within the first year post-transplantation, almost two-thirds of recipients will experience at least one rejection episode. At five years post-transplantation, nearly 50% of survivors will have CAV. In the first year after transplantation, nearly 63% of patients experience at least one episode of cardiac rejection and approximately one third of these patients will have multiple episodes. The clinical symptoms of acute cardiac rejection are relatively nonspecific (fatigue, dyspnea, low grade fever). Most CAV patients remain asymptomatic until they develop serious problems such as myocardial infarction, heart failure, ventricular dysrhythmias or sudden cardiac death. No noninvasive method exists for the diagnosis of acute or chronic cardiac rejection. Noninvasive methods such as electrocardiography, echocardiography, and nuclear studies all have been studied, but have been unsuccessful, thus far, for either condition. Several methodologies have been studied including electrocardiography, echocardiography, nuclear imaging, and phosphorus spectroscopy without success. The current gold standard for the diagnosis of acute cellular rejection remains right ventricular endomyocardial biopsy. This is an invasive method of diagnosis subject to morbidity and random sampling and interpretation error. Likewise, the gold standard for diagnosing CAV is cardiac catheterization with intravascular ultrasound, an invasive procedure also subject to morbidity. We are applying functional genomics to study acute cardiac allograft cellular rejection and CAV. Our group has developed and tested standard laboratory procedures for sample processing and if necessary amplification. We have established laboratory and bioinformatics infrastructure to support oligonucleotide microarray investigations. Two major local transplant programs (Johns Hopkins University and INOVA-Fairfax) have been or are currently collaborating. We have an IRB approved protocol and are currently actively enrolling patients (134 individuals enrolled to date). We hypothesize that large scale expression profiling of circulating peripheral blood mononuclear cells (PBMC, predominantly T lymphocytes) will identify genes that can serve as reliable biomarkers of acute and chronic cardiac cellular rejection. In the initial bench phase of the project, PBMCs are obtained from heart transplant recipients during periods of immunological tolerance of the allograft (no acute rejection) and immunologic intolerance of the allograft (acute rejection) and from heart transplant recipients with and without CAV to determine whether unique gene expression patterns are associated with each state. Other analytic tools that may be employed include proteomics, RT-PCR, Western blot, insitu-hybridization, immunohistochemistry, and histopathology. In the latter phase of the project we hope to translate these profiles into an acceptable bedside test for acute and chronic cardiac allograft cellular rejection. In addition to developing a biomarker approach to the diagnosis of rejection in cardiac transplant patients, expression profiling has the potential to identify immunoregulatory pathways that can serve as new targets for immunosuppressive therapy (rational drug development).