Gelatinases, consisting of gelatinase A (MMP-2; 72 KDa) and gelatinase B (MMP-9; 92KDa), are a subgroup of matrix metalloproteinases (MMPs) with key roles in a wide variety of physiological and pathological conditions. Both gelatinases are prominently activated in damaged livers, and MMP-9 deficient mice are protected against hepatic ischemia reperfusion injury (IRI). In this study, we generated global gelatinase A/B deficient mice to further study gelatinase roles in hepatic IRI. Methods: MMP-9/MMP-2 dKO, MMP-2KO, MMP-9KO and C57/BL6 wild-type (WT) mice were subject to 90min partial liver ischemia followed by 6h reperfusion. Additionally, WT and single KO mice were either treated with anti-MMP-2 neutralizing monoclonal antibodies (MMP-2 mAb; 3mg/kg, i.v.) or isotype matched IgG before surgery. Results: Double deletion of MMP-2 and MMP-9 or mAb-mediated depletion of MMP-2 in MMP-9KO mice resulted in an exacerbation of histological liver damage and increased AST (p<0.05) and ALT (p<0.05) levels post-IRI, when compared to single MMP-9KO control mice. The levels of liver histological damage and serum transaminases of MMP-9/MMP-2 dKO mice and anti-MMP-2 mAb treated MMP-9KO mice post-hepatic IRI were comparable to those observed in WT control mice; however, they were significantly lower when compared to single MMP-2KO mice or WT mice injected with MMP-2 mAb. Administration of MMP-2 mAb to MMP-2KO mice had no effect on AST/ALT levels or hepatocellular necrosis. Compared to both MMP-2KO mice and WT mice injected with MMP-2 mAb, MMP-2/MMP-9 dKO mice showed reduced inflammatory CD11b⁺ (p<0.05) and Ly-6G⁺ (p<0.05) leukocyte infiltration and pro-inflammatory cytokine (TNF-α, IFN-γ and IL-6) expression (p<0.05). The latter suggests that the loss of MMP-2 activity exacerbates hepatic IRI in part through a MMP-9 dependent mechanism. On the other hand, compared to MMP-9KO livers, MMP-2/MMP-9 dKO livers showed markedly reduced sinusoidal PECAM-1 expression and tomato lectin staining post-IRI, suggesting a protective MMP-9-independent role for MMP-2 in the sinusoidal endothelium. In conclusion: Our results demonstrate that global loss of gelatinase activity does not protect against hepatic IRI. Moreover, they confirm that loss of MMP-2 enhances MMP-9-mediated leukocyte infiltration, and it promotes MMP-9-independent sinusoidal endothelial damage post-IRI.

CITATION INFORMATION: Duarte S., Matian P., Ma S., Busuttil R., Coito A. Double Deficiency of Gelatinase-A and Gelatinase-B Does Not Protect against Hepatic Ischemia Reperfusion Injury Am J Transplant. 2017;17 (suppl 3).

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