Matrix Metalloproteinases in Chronic Liver Disease and Liver Transplantation

Matrix metalloproteinases (MMPs) are the main degrading enzymes of extracellular matrix proteins and basement membranes, and they play an important role in the processes of tissue remodeling and repair in many physiological and pathological processes. A subgroup of the MMP family, the gelatinases MMP-2 and MMP-9, is thought to be particularly involved in the degradation of matrix in the liver. MMP-2 can be expressed by many cell types in the liver, however, the hepatic stellate cell is suggested to be the main cellular source. The principal source of MMP-9 in the liver is the Kupffer cell, but MMP-9 can also be released from inflammatory cells, e.g. neutrophils. The potential contribution to and role of (circulating) MMP-2 and MMP-9 in liver fibrosis, hepatocellular carcinoma (HCC), ischemia/reperfusion (I/R) injury and acute rejection after orthotopic liver transplantation (OLT) is described.