Department of Medicine, University of California, San Diego, School of Medicine, La Jolla, CA, USA.
Hepatology. 2010 Mar;51(3):1027-36. doi: 10.1002/hep.23368.
The origin of fibrogenic cells in liver fibrosis remains controversial. We assessed the emerging concept that hepatocytes contribute to production of extracellular matrix (ECM) in liver fibrosis through epithelial-mesenchymal transition (EMT). We bred triple transgenic mice expressing ROSA26 stop beta-galactosidase (beta-gal), albumin Cre, and collagen alpha1(I) green fluorescent protein (GFP), in which hepatocyte-derived cells are permanently labeled by beta-gal and type I collagen-expressing cells are labeled by GFP. We induced liver fibrosis by repetitive carbon tetrachloride (CCl(4)) injections. Liver sections and isolated cells were evaluated for GFP and beta-gal as well as expression of alpha-smooth muscle actin (alpha-SMA) and fibroblast-specific protein 1 (FSP-1). Upon stimulation with transforming growth factor beta-1, cultured hepatocytes isolated from untreated liver expressed both GFP and beta-gal with a fibroblast-like morphological change but lacked expression of other mesenchymal markers. Cells from CCl(4)-treated livers never showed double-positivity for GFP and beta-gal. All beta-gal-positive cells exhibited abundant cytoplasm, a typical morphology of hepatocytes, and expressed none of the mesenchymal markers including alpha-SMA, FSP-1, desmin, and vimentin. In liver sections of CCl(4)-treated mice, GFP-positive areas were coincident with fibrotic septa and never overlapped X-gal-positive areas.
Type I collagen-producing cells do not originate from hepatocytes. Hepatocytes in vivo neither acquire mesenchymal marker expression nor exhibit a morphological change clearly distinguishable from normal hepatocytes. Our results strongly challenge the concept that hepatocytes in vivo acquire a mesenchymal phenotype through EMT to produce the ECM in liver fibrosis.
肝纤维化中纤维生成细胞的起源仍存在争议。我们评估了一个新出现的概念，即通过上皮-间充质转化（EMT），肝细胞有助于肝纤维化中细胞外基质（ECM）的产生。我们繁殖了三重转基因小鼠，其表达 ROSA26 停止β-半乳糖苷酶（β-gal），白蛋白 Cre 和胶原α1（I）绿色荧光蛋白（GFP），其中肝细胞衍生的细胞通过β-gal 永久标记，并且表达 I 型胶原的细胞通过 GFP 标记。我们通过重复四氯化碳（CCl（4））注射诱导肝纤维化。评估肝组织切片和分离细胞的 GFP 和β-gal 以及α-平滑肌肌动蛋白（α-SMA）和纤维母细胞特异性蛋白 1（FSP-1）的表达。在转化生长因子β-1的刺激下，从小鼠未处理的肝脏中分离出的培养肝细胞均表达 GFP 和β-gal，具有成纤维细胞样形态变化，但缺乏其他间充质标记物的表达。从未处理的肝脏中分离出的 CCl（4）处理过的肝脏的细胞从未显示 GFP 和β-gal 的双重阳性。所有β-gal 阳性细胞均具有丰富的细胞质，这是肝细胞的典型形态，并且不表达任何间充质标记物，包括α-SMA、FSP-1、结蛋白和波形蛋白。在 CCl（4）处理的小鼠肝组织切片中，GFP 阳性区域与纤维性隔室一致，并且从未与 X-gal 阳性区域重叠。
产生 I 型胶原的细胞并非来自肝细胞。体内的肝细胞既不获得间充质标记物的表达，也不表现出与正常肝细胞明显不同的形态变化。我们的结果强烈挑战了体内肝细胞通过 EMT 获得间充质表型以在肝纤维化中产生 ECM 的概念。
