Song J Y, Van Noorden C J, Frederiks W M
Academic Medical Centre, University of Amsterdam, Department of Cell Biology and Histology, The Netherlands.
Hepatology. 1998 Mar;27(3):765-71. doi: 10.1002/hep.510270318.
The involvement of hepatocytes in proliferation of bile ductule-like structures during cholestasis remains controversial. The present study was an attempt to address the issue of whether hepatocytes transform into ductular epithelial cells in response to cholestasis and, if so, which mechanisms are involved. Cholestasis was induced by common bile duct-ligation (CBDL) in rat liver for 2, 7, and 14 days. Immunofluorescence microscopy of cytokeratin 19 (CK19) was performed to assess the proliferation of bile ductules. Hepatocellular filamentous actin (F-actin) was studied using fluorescence microscopy of 7-nitrobenzene-2-oxa-1,3-diazole phallacidin and electron microscopy. Double labeling of F-actin and laminin was performed to reveal the relationship between rearrangement of F-actin and deposition of the extracellular matrix protein. The results showed that the localization of F-actin in hepatocytes underwent considerable changes after CBDL, from an even distribution at the entire plasma membrane in control liver to a more concentrated localization at one domain of the plasma membrane. This was followed by formation of rosette-like structures in pericentral and midzonal areas of the parenchyma. CK19 was expressed, as in the control liver, in the epithelial cells of proliferated bile ductules in enlarged portal tracts but not in rosette-like structures of CBDL livers. Furthermore, CBDL induced increasing amounts of laminin in the basal lamina of bile ducts and in connective tissue of portal tracts. In parenchyma, the newly deposited laminin was in close association with the rosette-like structures. It is concluded that the rearrangement of hepatocellular F-actin after CBDL precedes the formation of rosette-like structures. It is speculated that the altered F-actin contracts at one side of hepatocytes leading to tubular structures. Laminin may play an important role in this transformation process.
在胆汁淤积期间，肝细胞是否参与胆小管样结构的增殖仍存在争议。本研究旨在探讨肝细胞是否会因胆汁淤积而转化为胆管上皮细胞，若如此，涉及哪些机制。通过大鼠肝脏胆总管结扎（CBDL）诱导胆汁淤积2、7和14天。进行细胞角蛋白19（CK19）免疫荧光显微镜检查以评估胆小管的增殖。使用7-硝基苯-2-恶唑-1,3-二氮杂菲鬼笔环肽荧光显微镜和电子显微镜研究肝细胞丝状肌动蛋白（F-肌动蛋白）。对F-肌动蛋白和层粘连蛋白进行双重标记，以揭示F-肌动蛋白重排与细胞外基质蛋白沉积之间的关系。结果显示，CBDL后肝细胞中F-肌动蛋白的定位发生了显著变化，从对照肝脏中整个质膜的均匀分布变为质膜一个区域的更集中定位。随后在实质的中央周围和中区形成玫瑰花结样结构。与对照肝脏一样，CK19在扩大门管中增殖胆小管的上皮细胞中表达，但在CBDL肝脏的玫瑰花结样结构中不表达。此外，CBDL诱导胆管基膜和门管结缔组织中层粘连蛋白含量增加。在实质中，新沉积的层粘连蛋白与玫瑰花结样结构紧密相关。结论是，CBDL后肝细胞F-肌动蛋白的重排在玫瑰花结样结构形成之前。推测改变的F-肌动蛋白在肝细胞的一侧收缩导致管状结构形成。层粘连蛋白可能在这一转化过程中起重要作用。
