Tee L B, Kirilak Y, Huang W H, Smith P G, Morgan R H, Yeoh G C
Department of Zoology, University of Western Australia, Nedlands, Western Australia.
Carcinogenesis. 1996 Feb;17(2):251-9. doi: 10.1093/carcin/17.2.251.
This study supports the existence of a pluripotent liver stem cell population which has the potential to differentiate into hepatocytes and bile ductular cells. We compared the expression of hepatocyte-specific and bile ductular-specific markers in fetal and preneoplastic rat liver. L-pyruvate kinase (L-PK) and alpha glutathione S-transferase (GST) were used as adult hepatocyte-specific markers, while cytokeratin 19 (CK19) was used as a bile ductular-specific marker. pi GST and M2-pyruvate kinase (M2-PK), which are fetal hepatocyte-specific and expressed at high levels in the oval and duct-like cells, were also used. We characterized fetal liver derived from 13-21 days of gestation (E13-E21). pi GST was detected in the E18 hepatoblasts, which form the intrahepatic bile ducts, while CK19 was detected at E19. Some of these cells express alpha GST and L-PK from E19 to E21. Oval, duct-like and bile ductular cells in rats treated with a choline-deficient diet containing 0.07% ethionine (CDE diet) for up to 8 weeks were characterized by double immunocytochemistry. L-PK and alpha GST are absent from bile ductular cells in the normal adult liver and up to 3 weeks of CDE treatment. After 4-5 weeks on CDE treatment, the majority of bile ductular cells express L-PK, while at 6 weeks some co-express L-PK and alpha GST. There are two populations of oval cells, a major population expressing only the fetal hepatocyte markers, while a minor population expresses the fetal hepatocyte, adult hepatocyte and bile ductular markers. There are at least three different duct-like cell populations which co-express different markers and have characteristics of fetal hepatocytes at sequential stages of differentiation. One population co-expresses pi GST and M2-PK and is similar to fetal hepatocytes derived from E13-E14 fetuses. The second expresses the two fetal markers and L-PK, and this reflects characteristics of E15 hepatocytes. The third expresses pi GST, M2-PK, L-PK and alpha GST which is characteristic of E16-E19 hepatocytes. Upon withdrawal of the CDE diet, autoradiography using tritiated thymidine shows that oval and duct-like cells differentiate into hepatocytes. This study demonstrates that oval and duct-like cells express both hepatocytic and bile ductular markers, and have the capacity to differentiate into hepatocytes, characteristics similar to hepatoblasts in the developing rat liver.
本研究支持多能性肝干细胞群的存在，该细胞群具有分化为肝细胞和胆小管细胞的潜力。我们比较了胎儿和癌前大鼠肝脏中肝细胞特异性标志物和胆小管特异性标志物的表达情况。L-丙酮酸激酶（L-PK）和α-谷胱甘肽S-转移酶（GST）被用作成年肝细胞特异性标志物，而细胞角蛋白19（CK19）被用作胆小管特异性标志物。也使用了胎儿肝细胞特异性且在卵圆细胞和导管样细胞中高水平表达的π GST和M2-丙酮酸激酶（M2-PK）。我们对妊娠13 - 21天（E13 - E21）的胎儿肝脏进行了特征分析。在形成肝内胆管的E18肝母细胞中检测到π GST，而在E19检测到CK19。其中一些细胞从E19到E21表达α GST和L-PK。对用含0.07%乙硫氨酸的胆碱缺乏饮食（CDE饮食）处理长达8周的大鼠的卵圆细胞、导管样细胞和胆小管细胞进行了双重免疫细胞化学特征分析。在正常成年肝脏以及CDE处理长达3周的情况下，胆小管细胞中不存在L-PK和α GST。在CDE处理4 - 5周后，大多数胆小管细胞表达L-PK，而在6周时一些细胞同时表达L-PK和α GST。存在两种卵圆细胞群，主要群体仅表达胎儿肝细胞标志物，而次要群体表达胎儿肝细胞、成年肝细胞和胆小管标志物。至少有三种不同的导管样细胞群，它们共表达不同的标志物，并在分化的连续阶段具有胎儿肝细胞的特征。一个群体共表达π GST和M2-PK，类似于源自E13 - E14胎儿的胎儿肝细胞。第二个群体表达两种胎儿标志物和L-PK，这反映了E15肝细胞的特征。第三个群体表达π GST、M2-PK、L-PK和α GST，这是E16 - E19肝细胞的特征。在撤去CDE饮食后，使用氚标记胸腺嘧啶的放射自显影显示卵圆细胞和导管样细胞分化为肝细胞。本研究表明，卵圆细胞和导管样细胞表达肝细胞和胆小管标志物，并具有分化为肝细胞的能力，其特征与发育中的大鼠肝脏中的肝母细胞相似。
