Dabeva M D, Laconi E, Oren R, Petkov P M, Hurston E, Shafritz D A
Marion Bessin Liver Research Center, and Department of Medicine, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
Cancer Res. 1998 Dec 15;58(24):5825-34.
Recently, we described a new model for hepatocyte transplantation with nearly total replacement of the liver by exogenous hepatocytes (E. Laconi et al., Am. J. Pathol., 153: 319-329, 1998). The model is based on the mitoinhibitory effect of the pyrrolizidine alkaloid retrorsine on hepatocytes in the resident liver while transplanted hepatocytes proliferate. In this study, we exploit this novel approach to address the important and controversial issue of whether hepatocytes, when proliferating extensively, undergo dedifferentiation and give rise to foci of undifferentiated hepatocytes. Genetically marked hepatocytes (isolated from normal Dipeptidyl peptidase IV+ Fischer 344 rats) were delivered intraportally (2 x 10(6) cells) into the liver of retrorsine-treated Dipeptidyl peptidase IV- mutant Fischer 344 rats in conjunction with partial hepatectomy. Transplanted hepatocytes were detected histochemically or immunohistochemically, and cell proliferation was studied by in situ hybridization for histone-3 mRNA. Expression of alpha-fetoprotein (AFP) mRNA, a marker of hepatocyte dedifferentiation, was also revealed by in situ hybridization. One day after partial hepatectomy and hepatocyte transplantation, endogenous hepatocytes and oval cells expanding in the liver expressed histone-3 mRNA (cells had entered S phase); 2 days later, transplanted hepatocytes and nonparenchymal cells also expressed histone-3 mRNA. Although the majority of endogenous hepatocytes did not divide and became arrested as quiescent megalocytes, the exogenous hepatocytes, as well as newly formed small hepatocytes, most probably derived from liver progenitor cells, underwent extensive proliferation. After 7-14 days, the nonparenchymal cells stopped proliferating, but transplanted hepatocytes and small endogenous hepatocytes continued to proliferate for 1 month, forming foci of dividing parenchymal cells. Although many of the hepatocytes in clusters were in S phase (histone-3 mRNA positive), none expressed AFP mRNA. In contrast, high expression of AFP mRNA was observed in proliferating oval and transitional cells, forming duct-like structures of cytokeratin-19-positive cells. From these studies, we conclude that hepatocyte proliferation in the adult liver is not associated with dedifferentiation.
最近，我们描述了一种肝细胞移植的新模型，通过外源性肝细胞几乎完全替代肝脏（E. 拉科尼等人，《美国病理学杂志》，153: 319 - 329, 1998）。该模型基于吡咯里西啶生物碱倒千里光碱对宿主体内肝细胞的有丝分裂抑制作用，而移植的肝细胞则会增殖。在本研究中，我们利用这种新方法来解决一个重要且有争议的问题，即肝细胞在大量增殖时是否会发生去分化并产生未分化肝细胞灶。将基因标记的肝细胞（从正常二肽基肽酶IV + 的费希尔344大鼠中分离）经门静脉注射（2×10⁶个细胞）到经倒千里光碱处理的二肽基肽酶IV - 突变型费希尔344大鼠肝脏中，并同时进行部分肝切除术。通过组织化学或免疫组织化学检测移植的肝细胞，并通过组蛋白 - 3 mRNA的原位杂交研究细胞增殖。α - 甲胎蛋白（AFP）mRNA的表达，作为肝细胞去分化的标志物，也通过原位杂交得以揭示。部分肝切除和肝细胞移植一天后，肝脏中增殖的内源性肝细胞和卵圆细胞表达组蛋白 - 3 mRNA（细胞已进入S期）；两天后，移植的肝细胞和非实质细胞也表达组蛋白 - 3 mRNA。尽管大多数内源性肝细胞不分裂并停滞为静止的巨细胞，但外源性肝细胞以及很可能源自肝祖细胞的新形成的小肝细胞却进行了广泛增殖。7 - 14天后，非实质细胞停止增殖，但移植的肝细胞和小的内源性肝细胞继续增殖1个月，形成分裂实质细胞灶。尽管聚集体中的许多肝细胞处于S期（组蛋白 - 3 mRNA阳性），但没有一个表达AFP mRNA。相反，在增殖的卵圆细胞和过渡细胞中观察到AFP mRNA的高表达，这些细胞形成了细胞角蛋白 - 19阳性细胞的导管样结构。从这些研究中，我们得出结论：成年肝脏中的肝细胞增殖与去分化无关。
