Kidney Transplant Recipients with Acute Antibody-Mediated Rejection Show Altered Levels of Matrix Metalloproteinases and Their Inhibitors: Evaluation of Circulating MMP and TIMP Profiles.

Antibody-mediated rejection (ABMR) remains a major cause of renal graft dysfunction and loss. The histological hallmark of antibody-mediated rejection is progressive tissue damage, in which extracellular matrix turnover plays an important role. This turnover is mainly regulated by matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs). Recent studies suggest that MMP/TIMP imbalance may favor the progression of renal damage, inflammation, and fibrosis, but the utility of these molecules as a biomarker of antibody-mediated turnover has not been fully explored. We measured plasma MMP and TIMP levels by ELISA in 15 patients with antibody-mediated renal transplant rejection and 12 patients without rejection. There was a significant increase in MMP-1, MMP-2, and MMP-3 concentrations in the plasma of patients with rejection, directly correlating with the severity of different renal lesions. In contrast, TIMP-3 levels were elevated in patients without rejection, showing a negative correlation with the severity of histopathological lesions. The concentrations of these molecules demonstrated good diagnostic capacity for patients with rejection. Our results show that MMP-1, MMP-2, MMP-3, and TIMP-3 could be potential biomarkers of rejection.