Expression of platelet-derived growth factor receptor in rat heart allografts

Growth factors may play a role in the tissue remodeling of long-surviving allografts. The aim of these experiments was to investigate the pattern of expression of platelet-derived growth factor and epidermal growth factor receptors in relation to the immunohistopathology of rat cardiac allografts. Heart grafts were transplanted between LEW and F344 and LEW.1A and LEW.1AR2 strains and removed for analysis at graft asystole or at predetermined time intervals. The grafts were studied with direct and indirect immunofluorescence and immunoperoxidase staining techniques and monoclonal antibodies against T lymphocytes, monocytes/macrophages, and endothelium. Expression of growth factor receptor was studied with the use of a monoclonal antibody against the platelet-derived growth factor-beta receptor and autoradiography with platelet-derived growth factor-BB or epidermal growth factor labeled with iodine 125. Increased expression of platelet-derived growth factor-beta receptors was observed in the media of graft arteries and in a number of myocardial cells in association with infiltration of the graft with T cells and monocytes/macrophages. Autoradiography with epidermal growth factor labeled with 125I failed to show changes in the binding pattern in relation to rejection. Upregulation of platelet-derived growth factor receptors may suggest involvement of platelet-derived growth factor in the tissue remodeling that occurs in conjunction with chronic rejection.