Late onset antibody-mediated rejection and endothelial localization of vascular endothelial growth factor are associated with development of cardiac allograft vasculopathy

Background. Improvements in cardiac transplant practice and immunosuppressive treatment have done much to curb the incidence of acute cellular rejection (ACR); however, antibody-mediated rejection (AMR) and cardiac allograft vasculopathy (CAV) remain prevalent. Recent studies have shown that allograft rejection is governed by both allogeneic and nonallogeneic factors such as inflammation. Initial studies have suggested that vascular endothelial growth factor (VEGF), a leukocyte mitogen produced by activated endothelial cells and leukocytes, may play a specific role in not only leukocyte trafficking, but also in the augmentation of ACR and development of CAV. Methods. We investigated the localization of VEGF protein using immunohistochemistry in a cohort of 76 heart transplant patients during periods of ACR and AMR and assessed the development of CAV. Results. We showed a significant correlation between lymphocytic localization of VEGF protein and severe ACR (P<0.001). Antibody-mediated rejection positive biopsies taken at 12 months posttransplantation showed significantly greater endothelial localization of VEGF than time-matched AMR negative biopsies (P=0.006). Diffuse endothelial expression of VEGF was also associated with a 2.5-fold increase in the risk of developing CAV (P=0.001). Conclusions. These results show that localization of VEGF protein to the vascular endothelium during AMR is significantly increased in patients who develop CAV. This study also highlights the potential pathogenic role of the endothelial cell in late onset AMR and the development of CAV.