Tiggelman A M, Boers W, Moorman A F, de Boer P A, Van der Loos C M, Rotmans J P, Chamuleau R A
J. van Gool Laboratory for Experimental Internal Medicine, University of Amsterdam, The Netherlands.
Hepatology. 1996 May;23(5):1260-7. doi: 10.1002/hep.510230547.
alpha 2-Macroglobulin (alpha 2M) in the rat is a strong-reacting acute-phase protein with potent protease-inhibiting and cytokine-binding properties. Production of alpha 2M is ascribed mainly to liver parenchymal cells. In the present study, we investigated, by means of immunohistochemistry and in situ hybridization, whether fibrosis in the rat liver induced by Schistosoma mansoni eggs leads to local production of alpha 2M. alpha 2M protein and messenger RNA (mRNA) in the unaffected liver tissue, as well as serum values of alpha 2M, were comparable in control rats and egg-injected rats, at 1, 3, and 8 weeks after injection of the eggs. alpha 2M was homogeneously distributed across the liver lobule. In contrast, at the sites of the granulomas, a strong increase in alpha 2M was observed. alpha 2M mRNA was expressed by granuloma cells, but not by the surrounding liver parenchymal cells. Within the granulomas, alpha 2M protein was present in numerous spindle-shaped cells and was diffusely distributed in the extra-cellular matrix. Using double-staining techniques, a subpopulation of the alpha 2M-positive cells in the granulomas appeared to be desmin-positive, suggesting a myofibroblast origin. In addition, parenchymal cells directly surrounding the granulomas contained alpha 2M protein in approximately 50% of the granulomas 1 week after injection of the eggs. In situ hybridization on consecutive sections revealed that these parenchymal cells showed only background activity of alpha 2M mRNA, suggesting uptake of alpha 2M-protein by these parenchymal cells and previous activation of alpha 2M by proteases within the granuloma. The significance of the present study is that alpha 2M is produced locally at sites of inflammation and liver fibrosis, without measurable increase of serum levels of alpha 2M. Unexpectedly, alpha 2M present at the sites of the granulomas is not produced by the liver parenchymal cells, but rather by granuloma cells.
大鼠体内的α2-巨球蛋白（α2M）是一种反应强烈的急性期蛋白，具有强大的蛋白酶抑制和细胞因子结合特性。α2M的产生主要归因于肝实质细胞。在本研究中，我们通过免疫组织化学和原位杂交技术，研究曼氏血吸虫卵诱导的大鼠肝纤维化是否会导致α2M的局部产生。在注射虫卵后1周、3周和8周，对照大鼠和注射虫卵的大鼠未受影响的肝组织中的α2M蛋白和信使核糖核酸（mRNA）以及α2M的血清值相当。α2M在肝小叶中均匀分布。相反，在肉芽肿部位，观察到α2M有显著增加。α2M mRNA由肉芽肿细胞表达，但周围的肝实质细胞不表达。在肉芽肿内，α2M蛋白存在于许多梭形细胞中，并弥漫分布于细胞外基质中。使用双重染色技术，肉芽肿中α2M阳性细胞的一个亚群似乎结蛋白阳性，提示其起源于肌成纤维细胞。此外，在注射虫卵1周后，约50%的肉芽肿周围的实质细胞含有α2M蛋白。连续切片的原位杂交显示，这些实质细胞仅显示α2M mRNA的背景活性，提示这些实质细胞摄取了α2M蛋白，且肉芽肿内的蛋白酶先前已激活了α2M。本研究的意义在于，α2M在炎症和肝纤维化部位局部产生，而血清中α2M水平无明显升高。出乎意料的是，肉芽肿部位的α2M并非由肝实质细胞产生，而是由肉芽肿细胞产生。
