Immediate increase of portal pressure, reflecting sinusoidal shear stress, accelerated liver regeneration through increased production of IL-6 and HGF in small-for-size graft

The mechanisms whereby grafts in the recipients can be primed for regeneration following living donor liver transplantation (LDLT) are poorly understood. In the liver transplantation from a living donor, we sometimes have the only option of using proportionally small graft for a patient due to the living donor's condition. Out of LDLT cases, we included cases which had end-stage liver cirrhosis and subsequent transplantation without acute rejection, infection and vascular complications. At the end, we were left with 8 cases from each group, total of 16 cases. Then they were divided into 2 groups, group L and group S. Group L had a graft-recipient ratio (G/R ratio) of 1.0 or higher while group S had G/R ratio of less than 1.0. There are three components in this study to measure. Firstly, we compared the serum levels of IL-6, soluble IL-6 receptor (sIL-6R) and hepatocyte growth factor (HGF), which play a role in the regulation of liver regeneration, preoperatively and postoperatively by ELISA. The concentrations of total bilirubin (T-Bil), C-reactive protein (CRP), prothrombin time (PT), albumin (Alb) and platelet count (PLT) were also measured. Finally, we carried out haemodynamic analysis by measuring the portal and arterial peak velocity (Vp max/Va max). The differences in age range, pre-operative T-Bil, PT and MELD score between the two groups were not statistically significant. Before the operation, no statistical differences in the levels of IL-6, sIL-6R and HGF were found between the two groups, however, at post-operative days, IL-6 and HGF levels in group S significantly increased while sIL-6R level was almost the same in both groups. Delayed production of CRP and increased Vp max were observed in group S. Two week after LDLT, the regeneration rate in group S was significantly higher than that in group L. In conclusion, the increase in post-operative IL-6 and HGF levels in group S suggested that production of IL-6 and HGF was required to promote the rapid liver regeneration and less IL-6 and HGF was used up due to proportionally smaller volume of available liver tissue. It is temptating to speculate that immediate increase of portal pressure, reflecting sinusoidal shear stress, accelerated liver regeneration through increased production of IL-6 and HGF.