Dual phenotypic expression of hepatocytes and bile ductular markers in developing and preneoplastic rat liver.
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.
Tee
L B
LB
Department of Zoology, University of Western Australia, Nedlands, Western Australia.
Kirilak
Y
Y
Huang
W H
WH
Smith
P G
PG
Morgan
R H
RH
Yeoh
G C
GC
D000818:Animals; D001652:Bile Ducts / Q000737:chemistry* / Q000166:cytology / Q000196:embryology; D015415:Biomarkers; D002454:Cell Differentiation; D002794:Choline / Q000008:administration & dosage; D005982:Glutathione Transferase / Q000032:analysis*; D007633:Keratins / Q000032:analysis*; D008099:Liver / Q000737:chemistry* / Q000166:cytology / Q000196:embryology; D008297:Male; D010641:Phenotype; D011230:Precancerous Conditions / Q000737:chemistry* / Q000473:pathology; D011770:Pyruvate Kinase / Q000032:analysis*; D051381:Rats; D017208:Rats, Wistar; D013234:Stem Cells / Q000737:chemistry* / Q000166:cytology
D015415:Biomarkers; D007633:Keratins; D005982:Glutathione Transferase; D011770:Pyruvate Kinase; D002794:Choline