Effect of cold ischemia/reperfusion injury and/or shear stress with portal hypertension on the expression of matrix metalloproteinase-9

Background Matrix metalloproteinase (MMP)-9 plays an important role in liver regeneration after liver surgery. MMP-9 behavior is complicated in cold ischemia/warm reperfusion injury (CIWRI) and/or shear stress with portal hypertension. Small-for-size grafts (SFSGs) are also an issue. Materials and Methods We used a rat model to examine MMP-9 expression 6 h after  laparotomy, a temporal clamp (Pringle maneuver), orthotopic liver transplantation (OLT) with a whole-liver graft (100% OLT), partial hepatectomy without the Pringle maneuver (60% hepatectomy) and split orthotopic liver transplantation (SOLT) with a SFSG (40% SOLT) were investigated. Four liver samples were collected in each group. Results The normalized ratio of MMP-9 was not significantly different with a temporal clamp (P = 0.1963), 100% OLT (P = 0.1781) and 60% hepatectomy (P = 0.2367), but it was significantly higher with 40% SOLT compared to that with laparotomy (P = 0.0159). Conclusion Forty percent SOLT is accompanied by not only CIWRI but also shear stress. This fatal damage results in increased MMP-9 expression. Keywords extended hepatectomy, Pringle maneuver, remnant liver, split liver transplantation, small-for-size graft