Roles of Hepatoma-derived growth factor(HDGF) on the proliferation and differentiation of hepatic stem cells and liver development

肝癌衍生生长因子（Hepatoma-derived growth factor，HDGF）是一种肝素结合蛋白，已从HuH-7肝癌细胞的条件培养液中纯化得到。最近的研究表明，HDGF显着参与肝脏，心血管系统，肠道和肾脏的发育。在本研究中，我们研究了HDGF在肝前体细胞（包括卵圆细胞）增殖和分化以及在肝个体发育中的作用。肝卵圆细胞是一种双能肝祖细胞，可分化为肝实质细胞和胆管细胞。采用Western blot、北方印迹、原位杂交、免疫组化等方法检测乙酰氨基芴/部分肝切除后大鼠肝脏HDGF的表达。北方印迹和Western印迹显示HDGF的表达水平与肝脏中出现的卵圆细胞数量平行。原位杂交显示HDGF在卵圆细胞中表达，在核中表达更强。 关于我们 免疫组化染色显示，在大鼠卵圆细胞系Oct 15 -5中，HDGF在细胞核和细胞质中也有明显表达，但主要表达于细胞核。重组HDGF轻度刺激Oct 15 -5细胞增殖。PPAR-γ配体15 d-PG J2可抑制Oct 15 -5细胞的增殖，并显著抑制HDGF的表达。因此，这些数据表明，HDGF质粒对卵圆细胞的增殖具有重要作用。在正常肝脏中，生后肝细胞成熟过程中葡萄糖-6-磷酸酶（G-6-phosphatase，G-6-P）表达降低，色氨酸加氧酶（Tryptophan Oxygenase，TO）被诱导;而在HDGF转基因小鼠肝脏中，生后12周G-6-P的表达未受抑制，TO未被诱导。这些结果表明，HDGF的持续过表达可能抑制肝细胞的分化，提示HDGF在肝个体发育中对肝祖细胞的增殖和分化起重要作用。少

Hepatoma-derived growth factor(HDGF) is a heparin-binding protein, which has been purified the conditioned media of HuH-7 hepatoma cells. Recent studies suggest that HDGF is significantly involved in the development of the liver, cardiovascular system, gut and kidney. In the present study, we investigated the roles of HDGF in the cellular proliferation and differentiation of hepatic progenitor cells, including oval cells, and in the hepatic ontogeny. Hepatic oval cells are one of bipotential hepatic progenitor cells, which can differentiate to both parenchymal hepatocytes and bile duct cells. We analyzed the expression of HDGF in rat liver after acetoaminofluorene/partial hepatectomy treatment by Western blot, Northern blot, immunohistochemisry and in situ hybridization. The expression levels of HDGF by Northern blot and Western blot are parallel to the number of oval cells appeared in the liver. HDGF was expressed in oval cells by in situ hybridization, and more strongly in the nucleu … More s than the cytoplasm by immunohistochemistry. In rat oval cell line, Oct15-5,HDGF was also prominently expressed both in the nucleus and cytoplasm, but in dominantly in the nucleus. Recombinant HDGF mildly stimulated the proliferation of Oct15-5 cells. PPAR-γ ligand, 15d-prostaglandins(PG) J2 inhibited the proliferation of Oct15-5 cells, and significantly suppressed the expression of HDGF. Thus, these data suggest that HDGF plas an important roles on the proliferation of oval cells.We generated HDGF transgenic mouse using albumin promoter. In normal liver, the expression of glucose-6-phoshatase(G-6-Pase) decreases and tryptophan oxygenase(TO) is significantly induced through hepatocyte maturation after birth, however in the liver of HDGF transgenic mouse, the expression of G-6-Pase was not suppressed and TO was not induced at 12 weeks after birth. These findings suggest that the continuous over-expression of HDGF may suppress the differentiation of hepatocytes.Present findings suggest that HDGF should play important roles on the proliferation and differentiation of hepatic progenitor cells in liver ontogeny. Less