Shum Winnie W, Smith Tegan B, Cortez-Retamozo Virna, Grigoryeva Lubov S, Roy Jeremy W, Hill Eric, Pittet Mikael J, Breton Sylvie, Da Silva Nicolas
Division of Nephrology/Program in Membrane Biology, Massachusetts General Hospital (MGH) and Harvard Medical School, Boston, Massachusetts.
Biol Reprod. 2014 May 1;90(5):90. doi: 10.1095/biolreprod.113.116681. Print 2014 May.
The epithelium that lines the epididymal duct establishes the optimal milieu in which spermatozoa mature, acquire motility, and are stored. This finely tuned environment also protects antigenic sperm against pathogens and autoimmunity, which are potential causes of transient or permanent infertility. The epididymal epithelium is pseudostratified and contains basal cells (BCs) that are located beneath other epithelial cells. Previous studies showed that in the mouse epididymis, BCs possess macrophage-like characteristics. However, we previously identified a dense population of cells belonging to the mononuclear phagocyte (MP) system (comprised of macrophages and dendritic cells) in the basal compartment of the mouse epididymis and showed that a subset of MPs express the macrophage marker F4/80. In the present study, we evaluate the distribution of BCs and MPs in the epididymis of transgenic CD11c-EYFP mice, in which EYFP is expressed exclusively in MPs, using antibodies against the BC marker keratin 5 (KRT5) and the macrophage marker F4/80. Immunofluorescence labeling for laminin, a basement membrane marker, showed that BCs and most MPs are located in the basal region of the epithelium. Confocal microscopy showed that in the initial segment, both BCs and MPs project intraepithelial extensions and establish a very intricate network. Flow cytometry experiments demonstrated that epididymal MPs and BCs are phenotypically distinct. BCs do not express F4/80, and MPs do not express KRT5. Therefore, despite their proximity and some morphological similarities with peritubular macrophages and dendritic cells, BCs do not belong to the MP system.
附睾管内衬的上皮细胞营造了精子成熟、获得运动能力并得以储存的最佳环境。这种精细调节的环境还能保护具有抗原性的精子免受病原体侵害以及自身免疫反应影响，而后两者是导致暂时性或永久性不育的潜在原因。附睾上皮为假复层结构，含有位于其他上皮细胞下方的基底细胞（BCs）。先前的研究表明，在小鼠附睾中，基底细胞具有类似巨噬细胞的特征。然而，我们之前在小鼠附睾的基底区发现了大量属于单核吞噬细胞（MP）系统（由巨噬细胞和树突状细胞组成）的细胞，并表明其中一部分单核吞噬细胞表达巨噬细胞标志物F4/80。在本研究中，我们使用针对基底细胞标志物角蛋白5（KRT5）和巨噬细胞标志物F4/80的抗体，评估了转基因CD11c-EYFP小鼠附睾中基底细胞和单核吞噬细胞的分布情况，在这种小鼠中，EYFP仅在单核吞噬细胞中表达。对基底膜标志物层粘连蛋白的免疫荧光标记显示，基底细胞和大多数单核吞噬细胞位于上皮的基底区域。共聚焦显微镜检查表明，在起始段，基底细胞和单核吞噬细胞均伸出上皮内延伸部分并形成非常复杂的网络。流式细胞术实验表明，附睾中的单核吞噬细胞和基底细胞在表型上是不同的。基底细胞不表达F4/80，单核吞噬细胞不表达KRT5。因此，尽管基底细胞与管周巨噬细胞和树突状细胞相邻且在形态上有一些相似之处，但它们并不属于单核吞噬细胞系统。
