Cumulative Episodes of Rejection Altered Myocardial Sarcoplasmic Reticulum Ca2+-ATPase and Ryanodine Receptor-2 mRNA Expression in Heart Transplant Recipients

The aim of the present study was to investigate the relationship between rejections and gene expression of Ca(2+)-handling proteins in heart transplant recipients. Thirty-seven heart transplant recipients underwent routine endomyocardial biopsy. Levels of sarcoplasmic reticulum Ca(2+)-ATPase (SERCA2) and ryanodine receptor-2 mRNAs in endomyocardial tissue were quantified by a real-time quantitative reverse transcription polymerase chain reaction (RT-PCR) method. Rejections were diagnosed according to the conventional International Society for Heart and Lung Transplantation criteria. Patients were classified as follows; group AR(+) (n = 9) with rejection grade of 2 or higher versus group AR(-) (n = 28) with rejection grade of 0, 1a or 1b at the time of biopsy, and group Rec-AR(+) (n = 6) with a history of more than 4 episodes of treatment required rejection versus group Rec-AR(-) (n = 31) without history of recurrent rejection. The mRNA levels of the SERCA2/GAPDH ratio and ryanodine receptor-2/GAPDH ratio were not different between group AR(+) and group AR(-); however, they were reduced in group Rec-AR(+) more than in group Rec-AR(-) (0.83 +/- 0.07 versus 0.90 +/- 0.07, P = 0.034, 0.74 +/- 0.06 versus 0.84 +/- 0.10, P = 0.027, respectively). A single episode of on-going rejection would not affect myocardial Ca(2+)-handling proteins; however, cumulative rejection episodes might alter the gene expression of myocardial Ca(2+)-handling proteins in heart transplant recipients.