TIMP-1 deficiency leads to lethal partial hepatic ischemia and reperfusion injury

Hepatic ischemia and reperfusion injury (IRI) remains an important challenge in clinical orthotopic liver transplantation (OLT). Tissue inhibitor of metalloproteinase-1 (TIMP-1) is the major endogenous regulator of matrix metalloproteinase-9 (MMP-9). In this study we investigated the functional significance of TIMP-1 expression in a well-established mouse model of partial liver IRI. Compared to wildtype mice, TIMP-1^-/- mice showed further impaired liver function and histological preservation after IRI. Notably, TIMP-1 deficiency led to lethal liver IRI, as over 60% of the TIMP-1^-/- mice died postreperfusion, whereas all TIMP-1^+/+ mice recovered and survived surgery. Lack of TIMP-1 expression was accompanied by markedly high levels of MMP-9 activity, which facilitates leukocyte transmigration across vascular barriers in hepatic IRI. Indeed, TIMP-1^-/- livers were characterized by massive leukocyte infiltration and by up-regulation of proinflammatory mediators, including tumor necrosis factor alpha, interferon-gamma, and inducible nitric oxide synthase post-IRI. The inability of TIMP-1^-/- mice to express TIMP-1 increased the levels of active caspase-3 and depressed the expression of Bcl-2 and the phosphorylation of Akt, emphasizing an important role for TIMP-1 expression on hepatocyte survival. Using independent parameters of regeneration, 5-bromodeoxyuridine incorporation, proliferating cell nuclear antigen expression, and histone H3 phosphorylation, we provide evidence that hepatocyte progression into S phase and mitosis was impaired in TIMP-1-deficient livers after IRI. Inhibition of the cell cycle progression by TIMP-1 deficiency was linked to depressed levels of cyclins-D1 and -E and to a disrupted c-Met signaling pathway, as evidenced by reduced phosphorylated c-Met expression and elevated c-Met ectodomain shedding postliver IRI. Conclusion: These results support a critical protective function for TIMP-1 expression on promoting survival and proliferation of liver cells and on regulating leukocyte recruitment and activation in liver IRI.