Although the ability of the liver to regenerate to a predetermined size after resection made adult-to-adult living donor liver transplantation (LDLT) possible, there is little information regarding the growth regulatory mechanism for a small-for-size graft. Forty-one cases of LDLT were divided into two groups by graft volume to standard liver volume ratio (GV/SLV); small graft group (Group S, GV/SLV < 40%, n = 16) and non-small graft group (Group NS, GV/SLV > 40%, n = 25). The regeneration rate (GV at 1 week/harvested GV) and serum levels of hepatocyte growth factor (HGF), transforming growth factor-α (TGF-α) and transforming growth factor-β1 (TGF-β1) were compared between two groups. The regeneration rates in Group S were significantly higher than that of Group NS (217 ± 12% and 178 ± 10%, respectively, P<0.01). The serum HGF levels of Group S were significantly higher than those of Group NS on POD 1. The TGF-β1 levels of Group S were significantly higher than those of Group NS on POD 3 and 5. The TGF-α levels were not different at any time points studied. These results indicate that a small-for-size graft retains the capacity to regenerate faster by modulation of expression pattern of HGF and TGF-β1 immediately after LDLT. After the acceleration of the regenerative response by HGF, subsequent elevation of TGF-β1 synergistically controls graft size, regulating uncontrolled proliferation of hepatocytes.
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