Cremona O, Savoia P, Marchisio P C, Gabbiani G, Chaponnier C
Département de Pathologie, Centre Médical Universitaire, Genève, Switzerland.
J Histochem Cytochem. 1994 Sep;42(9):1221-8. doi: 10.1177/42.9.8064129.
The alpha 6 beta 4 integrin complex is generally thought to be expressed by epithelial cells, where it is localized in specific adhesion structures, the hemidesmosomes. Recent observations have suggested a new localization of the beta 4 integrin chain in small vessels, possibly in endothelial cells, i.e., in cells of mesenchymal origin. In the present study we show that (a) the alpha 6 and beta 4 integrin chains are not expressed by endothelial cells, since they are not localized in von Willebrand factor-producing cells; (b) instead, smooth muscle cells of small vessels are intensely positive to antibodies to both alpha 6 and beta 4 intergrin chains; and (c) in some restricted regions of these smooth muscle cells there is a clear colocalization between alpha-smooth muscle actin and alpha 6 and beta 4 integrin chains, suggesting that a new type of cytoskeletal linkage for the alpha 6 beta 4 integrin complex may occur in mesenchyme-derived cells. Our observations are supported by confocal laser microscopy (CLSM) images of specimens labeled by double immunofluorescence. This technical choice was made to take advantage of the higher resolution offered by CLSM in comparison with conventional immunofluorescence. A careful selection of barrier filters was necessary to separate accurately emission and excitation spectra of the fluorochromes used in this study, resulting in an efficient colocalization analysis.
α6β4整合素复合体通常被认为由上皮细胞表达，它定位于特定的黏附结构——半桥粒中。最近的观察结果表明β4整合素链在小血管中存在新的定位，可能在内皮细胞中，即间充质来源的细胞中。在本研究中，我们发现：（a）α6和β4整合素链不由内皮细胞表达，因为它们不在产生血管性血友病因子的细胞中定位；（b）相反，小血管的平滑肌细胞对α6和β4整合素链的抗体呈强阳性；（c）在这些平滑肌细胞的一些特定区域，α-平滑肌肌动蛋白与α6和β4整合素链之间存在明显的共定位，这表明α6β4整合素复合体可能在间充质来源的细胞中形成一种新型的细胞骨架连接。我们的观察结果得到了双重免疫荧光标记标本的共聚焦激光显微镜（CLSM）图像的支持。做出这种技术选择是为了利用CLSM相对于传统免疫荧光提供的更高分辨率。需要仔细选择屏障滤光片以准确分离本研究中使用的荧光染料的发射光谱和激发光谱，从而进行有效的共定位分析。
