Succeeding with Cardiac Transplants March 2005 Doctors at the University of Pennsylvania in collaboration with physicians at the University of Iowa have identified 91 genes that have different expression patterns in patients with heart transplant rejection(1). Expression profiling with these genes may lead to a non-invasive diagnostic screen for organ rejection in transplant patients. Presently invasive biopsies are the only way to definitively detect rejection. Since the first successful heart transplant in 1968, over 2000 heart transplants are performed each year in the US alone(2). Currently doctors check for organ rejection by biopsying heart tissue taken through a catheter inserted in the neck or groin of the patient. This procedure is costly and introduces the chance for infection or complications. Doctors are looking for a more practical and non-invasive method to detect heart transplant rejection. In the December 2004 issue of Circulation, Dr. Cappola and his colleagues developed a new procedure using blood samples instead of biopsies to determine the likelihood of transplant rejection. Cappola's team analyzed the blood samples with GeneChip® microarrays and compared the expression profiles from patients with confirmed heart transplant rejection vs. transplant recipients without rejections. The researchers discovered 91 genes expressed differently between the two groups. Of the 91 genes, 40 were found to be consistently altered by over 25% specifically during acute rejection. Moreover, the level of expression for these genes was found to return to normal after rejection treatment in follow-up blood specimens. The group used real-time PCR to verify two of the 40 genes comprosing the rejection expression profile. One such gene, CFLAR, an inhibitor of programmed cell death was found to be very promising as a rejection marker. CFLAR was downregulated over 75% during rejection and returned to control levels post-rejection. Overall the results showed a direct connection between indicator gene expression levels in the blood and heart transplant rejection. Cappola used the GeneChip® HG-U133A Array to screen for the expression levels of over 14,500 genes at one time. Previous methods were limited to focus on a few genes at a time. The group took an RNA sample obtained from blood samples to test the expression of thousands of human genes at once in each patient using microarrays. Variations in the possible indicator genes expression levels correlated with patients having confirmed organ rejection. "In contrast to previously employed methods, microarray technology offers the possibility of simultaneously screening thousands of potential candidate genes in an unbiased fashion," said Cappola. "These advantages allow for the identification of gene-expression profiles that may be much more sensitive and specific than any one candidate marker." If confirmed in larger studies, gene profiling using the candidate genes identified in this study and microarrays may offer an alternative to the current invasive biopsy diagnosis of heart transplant rejection. Developing a diagnostic tool will be an immense step forward for heart transplant patient care. With further experimentation of the genes upregulated during rejection, better anti-rejection therapies may be developed as a result of this study. All of this translates to safer and cheaper testing for the over 2000 heart transplant recipients each year and perhaps ultimately the 20,000 plus organ transplant recipients each year. 1) Horwitz, P.A. et al. Detection of Cardiac Allograft Rejection and Response to Immunosuppressive Therapy with Peripheral Blood Gene Expression. Circulation 2004 Dec 21;110(25):3815-21. (2004). 2) 2002 Annual Report of the U.S. Scientific Registry of Transplant Recipients and the Organ Procurement and Transplantation Network: Transplant Data 2002-2003.