Hepatocyte Transplantation and Acute Hepatic Injury-- Therapeutic Potential and Mechanism of Liver Remodeling after Hepatocyte Transplantation

• Main Authors: Chun-Hsien Yu, 余俊賢
• Other Authors: Mei-Hwei Chang
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/81454392258619150227

博士 === 臺灣大學 === 臨床醫學研究所 === 98 === Efficient repopulation by transplanted hepatocytes in the severely injured liver is essential for their clinical application in the treatment of acute hepatic failure. We studied here (1) whether and how the transplanted hepatocytes are able to efficiently repopulate the toxin-induced acute injured liver, and (2) the impacts of hepatocyte transplantation on the response and fate of oval cells that are activated to proliferate in acute severe hepatic injury. To address the first issue, we used retrorsine-plus-D- galactosamine (R+D-gal) treatment or D-galactosamine alone (D-gal-alone) to induce acute hepatic injury, or retrorsine-alone in male Dipeptidyl peptidase IV-deficient F-344 rats. In these models, retrorsine was used to inhibit the proliferation of endogenous hepatocytes while D-galactosamine induced acute hepatocyte damage. Wild-type hepatocytes (1x107/ml) were transplanted intraportally 24 hours after D-galactosamine or saline injection. The kinetics of proliferation and repopulation of transplanted cells and the kinetics of cytokine response, hepatic stellate cell (HSC) activation, and matrix metalloproteinase (MMP2) expression were analyzed. We observed that early entry of transplanted hepatocytes into the hepatic plates and massive repopulation of the liver by transplanted hepatocytes occurred in acute hepatic injury induced by R+D-gal treatment but not by D-gal-alone or retrorsine-alone. The expressions of transforming growth factor-α and hepatocyte growth factor genes in the R+D-gal injured liver were significantly up-regulated and prolonged up to 4 weeks after hepatocyte transplantation. The expression kinetics were parallel with the efficient proliferation and repopulation of transplanted hepatocytes, which replaced 54.6+7.1% of damaged parenchyma by four weeks. HSC was activated rapidly, markedly, and prolongedly up-to 4 weeks after hepatocyte transplantation, when the expression of HGF gene and repopulation of transplanted hepatocytes were reduced afterward. Furthermore, the expression kinetics of MMP2 and its specific distribution in the host areas surrounding the expanding clusters of transplanted hepatocytes are consistent with those of activated HSC. To address the second issue, we used retrorsine-plus-D-galactosamine (R+D-gal) treatment to induce acute hepatic injury and to elicit extensive activation of oval cells in male Dipeptidyl-peptidase-IV-deficient F-344 rats. These rats were then randomized to receive wild-type hepatocyte transplantation or vehicle intraportally. The kinetics of oval cell response and their differentiation fate were analyzed using histochemical, immunohistochemical, and immunofluorescent stainings for DPPIV, OV6, CK19, laminin, γ-glutamyl-transpeptidase, and glucose-6-phosphotase. We observed that oval cells were activated early and differentiated into hepatocytes in R+D-gal-treated rats without hepatocyte transplantation. With hepatocyte transplantation, the oval cells were recruited later and continued to proliferate in parallel with the massive proliferation of transplanted hepatocytes. They formed ductules and differentiated into biliary cells. When hepatocytes were transplanted at the day when oval cells were at their peak response, the numerous activated oval cells ceased to differentiate into hepatocytes and remained in ductular form. The ductular oval cells were capable of differentiating into hepatocytes again when the donor hepatocytes were inhibited to proliferate. In conclusion, impaired hepatocyte regeneration after acute severe hepatic injury may initiate serial compensatory repair mechanisms which facilitate the extensive repopulation by transplanted hepatocytes that enter early the hepatic plates. In addition, hepatocyte transplantation changes the mechanism of liver reconstitution from oval cell-mediated to donor hepatocyte-mediated and affects the differentiation fate of host oval cells in acute severe hepatic injury. Hepatocyte transplantation has a great potential in the treatment of patients with acute hepatic failure.