Niki T, Pekny M, Hellemans K, Bleser P D, Berg K V, Vaeyens F, Quartier E, Schuit F, Geerts A
Laboratory for Cell Biology and Histology, Faculty of Medicine and Pharmacy, Free University of Brussels (VUB), Belgium.
Hepatology. 1999 Feb;29(2):520-7. doi: 10.1002/hep.510290232.
Hepatic stellate cells are considered to be liver-specific pericytes that play a key role in liver fibrosis. Because these cells express desmin and smooth muscle alpha-actin, they were assumed to be of myogenic origin. This hypothesis became doubtful when it was reported that stellate cells also express glial fibrillary acidic protein and neural cell adhesion molecule. In the present study, we show that activated stellate cells express nestin, a class VI intermediate filament protein originally identified as a marker for neural stem cells. Expression of nestin was first studied during spontaneous activation of stellate cells in culture. Immunohistochemistry showed that nestin-positive stellate cells already appeared at day 3, and nearly all the cells became positive for nestin at day 6 and 15. The immunoreaction was present in filaments except in dividing cells. The presence of messenger RNA transcript for nestin was shown by reverse transcription polymerase chain reaction and sequencing of amplified complementary DNA. We then compared the presence of nestin with that of other intermediate filament proteins and smooth muscle alpha-actin. Immunoblotting showed that the relative concentrations of nestin, desmin, and vimentin increased between day 2 and 6 in primary culture. After the initial increase vimentin leveled off, while nestin and desmin showed a tendency to decrease. This pattern was quite different from that of glial fibrillary acidic protein, which kept declining, and smooth muscle alpha-actin, which increased continuously up to day 13 in culture. We then studied the presence of nestin in normal and CCl4-injured rat liver. In normal liver, minimal immunoreaction for nestin was observed within the liver parenchyma. During induction of fibrosis by carbon tetrachloride, nestin-positive stellate cells appeared at 6 weeks, which was late in comparison with the induction of desmin and smooth muscle alpha-actin. We conclude that nestin is induced in stellate cells during transition from the quiescent to the activated phenotype; culture activation is a stronger stimulus than in vivo activation by injection of CCl4. Taken together with reports on expression of glial fibrillary acidic protein and neural cell adhesion molecule by stellate cells, new experimental studies on the embryonic origin of these cells are required.
肝星状细胞被认为是肝脏特异性的周细胞，在肝纤维化中起关键作用。由于这些细胞表达结蛋白和平滑肌α-肌动蛋白，它们被假定起源于肌源性。当有报道称星状细胞也表达胶质纤维酸性蛋白和神经细胞黏附分子时，这一假说受到质疑。在本研究中，我们发现活化的星状细胞表达巢蛋白，这是一种VI类中间丝蛋白，最初被鉴定为神经干细胞的标志物。首先在培养的星状细胞自发活化过程中研究巢蛋白的表达。免疫组织化学显示，巢蛋白阳性的星状细胞在第3天就已出现，在第6天和第15天几乎所有细胞都变为巢蛋白阳性。免疫反应存在于细丝中，但分裂细胞除外。通过逆转录聚合酶链反应和扩增互补DNA的测序显示了巢蛋白信使RNA转录本的存在。然后我们比较了巢蛋白与其他中间丝蛋白和平滑肌α-肌动蛋白的存在情况。免疫印迹显示，在原代培养中，巢蛋白、结蛋白和波形蛋白的相对浓度在第2天至第6天之间增加。在最初增加后，波形蛋白水平趋于平稳，而巢蛋白和结蛋白则有下降趋势。这种模式与持续下降的胶质纤维酸性蛋白以及在培养至第13天前持续增加的平滑肌α-肌动蛋白的模式截然不同。然后我们研究了正常和四氯化碳损伤大鼠肝脏中巢蛋白的存在情况。在正常肝脏中，肝实质内观察到对巢蛋白的最小免疫反应。在四氯化碳诱导纤维化过程中，巢蛋白阳性的星状细胞在6周时出现，与结蛋白和平滑肌α-肌动蛋白的诱导相比，这一出现时间较晚。我们得出结论，在星状细胞从静止表型转变为活化表型的过程中诱导了巢蛋白的表达；培养活化是比注射四氯化碳体内活化更强的刺激。结合关于星状细胞表达胶质纤维酸性蛋白和神经细胞黏附分子的报道，需要对这些细胞的胚胎起源进行新的实验研究。
