Miki Rika, Tatsumi Norifumi, Matsumoto Ken, Yokouchi Yuji
Division of Pattern Formation, Department of Organogenesis, Institute of Molecular Embryology and Genetics, Kumamoto University, 2-2-1 Honjo, Kumamoto, 860-0811, Japan.
Am J Physiol Gastrointest Liver Physiol. 2008 Feb;294(2):G529-39. doi: 10.1152/ajpgi.00412.2007. Epub 2007 Dec 20.
Hepatoblasts have the potential to differentiate into both hepatocytes and biliary epithelial cells through a differentiation program that has not been fully elucidated. With the aim to better define the mechanism of differentiation of hepatoblasts, we isolated hepatoblasts and established new culture systems. We isolated hepatoblasts from E12.5 fetal mouse liver by using E-cadherin. The E-cadherin+ cells expressed alpha-fetoprotein (AFP) and albumin (Alb) but not cytokeratin 19 (CK19). Transplantation of the E-cadherin+ cells into mice that had been subjected to liver injury or biliary epithelial injury led to differentiation of the cells into hepatocytes or biliary epithelial cells, respectively. In a low-cell-density culture system in the absence of additional growth factors, E-cadherin+ cells formed colonies of various sizes, largely comprising Alb-positive cells. Supplementation of the culture medium with hepatocyte growth factor and epidermal growth factor promoted proliferation of the cells. Thus the low-cell-density culture system should be useful to identify inductive factors that regulate the proliferation and differentiation of hepatoblasts. In a high-cell-density system in the presence of oncostatin M+dexamethasone, E14.5, but not E12.5, E-cadherin+ cells differentiated into mature hepatocytes, suggesting that unidentified factors are involved in hepatic maturation. Culture of E-cadherin+ cells derived from E12.5 or E14.5 liver under high-cell-density conditions should allow elucidation of the mechanism of hepatic differentiation in greater detail. These new culture systems should be of use to identify growth factors that induce hepatoblasts to proliferate or differentiate into hepatocytes and biliary epithelial cells.
肝母细胞有潜力通过一个尚未完全阐明的分化程序分化为肝细胞和胆管上皮细胞。为了更好地确定肝母细胞的分化机制，我们分离了肝母细胞并建立了新的培养系统。我们利用E-钙黏蛋白从E12.5胎鼠肝脏中分离出肝母细胞。E-钙黏蛋白阳性细胞表达甲胎蛋白（AFP）和白蛋白（Alb），但不表达细胞角蛋白19（CK19）。将E-钙黏蛋白阳性细胞移植到遭受肝损伤或胆管上皮损伤的小鼠体内，分别导致这些细胞分化为肝细胞或胆管上皮细胞。在没有额外生长因子的低细胞密度培养系统中，E-钙黏蛋白阳性细胞形成了大小各异的集落，主要由Alb阳性细胞组成。向培养基中添加肝细胞生长因子和表皮生长因子可促进细胞增殖。因此，低细胞密度培养系统应有助于鉴定调节肝母细胞增殖和分化的诱导因子。在存在制瘤素M+地塞米松的高细胞密度系统中，E14.5而非E12.5的E-钙黏蛋白阳性细胞分化为成熟肝细胞，这表明有未明因子参与肝脏成熟过程。在高细胞密度条件下培养源自E12.5或E14.5肝脏的E-钙黏蛋白阳性细胞，应能更详细地阐明肝脏分化机制。这些新的培养系统应有助于鉴定诱导肝母细胞增殖或分化为肝细胞和胆管上皮细胞的生长因子。
