Background: Increased expression of smooth muscle and nonmuscle myosin heavy chains has been previously reported in animal models of cardiac allograft rejection. However, altered expression of beta-myosin heavy chain in human cardiac rejection has not been determined.
Methods: Two-dimensional (2D)-gel electrophoresis of endomyocardial biopsies taken from patients with (Grade 3A, n = 6) and without (Grade 0, n = 6) acute rejection were analyzed. Increased expression of two protein spots (MW approximately 12 kDa) were identified in the presence of acute rejection and were further characterized by mass spectrometry analysis. In patients who had acute rejection, protein expression was subsequently analyzed by immunoblotting on biopsies preceding, during, and following treatment of rejection.
Results: Mass spectrometric analysis of the protein spots detected 6 and 22 tryptic peptides, respectively. Protein sequence database search analysis identified the first protein as beta-myosin heavy chain and the second spot consisted of proteins of unidentified nature that may represent novel proteins. Immunoblotting analysis showed 1.4 x fold increase (p < 0.01) of protein expression of beta-myosin heavy chain expression in the presence of acute rejection.
Conclusions: To our knowledge, this is the first 2D-gel study to describe increased expression of beta-myosin heavy chain and other proteins of unidentified nature in association with human cardiac allograft rejection.