Inhibition of matrix metalloproteinase-9 attenuates acute small-for-size liver graft injury in rats

Ischemia/reperfusion (I/R) and portal hypertension have been implicated in small-for-size liver graft dysfunction. Matrix metalloproteinases-2 and -9 (MMP-2/9) are critically proposed to involve in hepatic I/R injury and activated by hemodynamic force. We hypothesized that MMP-2/9 overexpression played a crucial role in acute graft injury following small-for-size liver transplantation (LT). Rats were randomly assigned into four groups: 75% partial hepatectomy (PH); 100% LT; 25% LT and 25% LT treated with CTT peptide (MMP-2/9 inhibitor). ELISA, real-time PCR, gelatin zymography and immunohistochemistry were used to determine the expression pattern of MMP-2/9 in liver tissue. MMP-9 expression was significantly increased 6 h after reperfusion and reached a peak 12 h in the 25% LT group, whereas MMP-2 was expressed in all groups invariably. Compared with the 25% LT group, rats from CTT-treated group exhibited markedly decreased alanine aminotransferase and total bilirubin values, downregulated proinflammatory cytokines, attenuated malondialdehyde (MDA) and myeloperoxidase (MPO) activities, and improved liver histology. Likewise, MMP-9 inhibition significantly reduced number of TUNEL-positive cells and caspase-3 activity, along with decreased protein levels of Fas and Fas-L. Specifically, rat survival was also improved in the CTT-treated group. These results support critical function of MMP-9 involved in acute small-for-size livergraft injury.