Epithelial Basal Cells Are Distinct from Dendritic Cells and Macrophages in the Mouse Epididymis1

Abstract

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.

Macrophages and dendritic cells in the post-testicular environment

“…Due to their proximity and morphological similarities, BCs have occasionally been confused with Mϕ (Seiler, et al, 2000, Seiler, et al, 1999, Seiler, et al, 1998, Yeung, et al, 1994). Although a role of BCs in immune regulation cannot be excluded, others and we have shown that BCs and Mϕ constitute two clearly distinct cells types (Serre and Robaire, 1999, Shum, et al, 2014). In addition to halo cells and Mϕ, dendritic cells have been identified in the murine epididymis based on the expression of markers such as CD11c, CD103 and MHC class II (Da Silva, et al, 2011).…”

“…While flow cytometry is the most convenient way to simultaneously analyze multiple cellular markers, it requires the disruption of tissues and the preparation of single-cell suspensions. This procedure can be misleading in the epididymis, particularly for the CX3CR1 + CD11c + cells that are embedded in the initial segment epithelium (Da Silva, et al, 2011, Shum, et al, 2014, Smith, et al, 2014). These highly ramified cells are found mostly in the IS, where they establish extremely intricate interactions with surrounding epithelial cells and occasionally communicate with the luminal milieu.…”

The cellular localization and redistribution of multiple aquaporin paralogs in the spermatic duct epithelium of a maturing marine teleost

“…The seabream Aqp1aa ortholog also shows a conserved localization in the apical microvilli of the spermatic duct epithelium at the resting stage, whereas at spermiation this channel is no longer expressed by the epithelial cells and it appears only in the apical membrane of endothelial cells of blood vessels within the connective tissue, as previously reported in the rat (Badran & Hermo, 2002;Oliveira et al 2005). However, the tandemly duplicated Aqp1ab paralog is exclusively expressed in dispersed interstitial lamina cells, that could represent lymphocytes or macrophages embedded within the connective tissue (Da Silva et al 2011;Shum et al 2014), which suggests the neofunctionalization of this channel in the seabream spermatic duct as observed in spermatozoa (Boj et al 2015c). Interestingly, seabream Aqp3a is also expressed in other groups of interstitial cells not expressing Aqp1ab that are located close to the epithelium of the spermtic duct, but their identities are not yet known.…”

“…; Shum et al. ), which suggests the neofunctionalization of this channel in the seabream spermatic duct as observed in spermatozoa (Boj et al. ).…”

The epididymis and its role on sperm quality and male fertility

“…This compartmentalized gene expression results in segment-specific protein secretions into the luminal fluid, creating sperm microenvironments where specific modifications in spermatozoa happen. The composition of the intra luminal milieu is defined by the pseudostratified epithelium composed of six cell types possessing distinct physiological functions: narrow and apical cells found in the proximal region of the epididymis and principal cells, clear cells, machophages, dentritic cells, basal cells and halo cells found throughout the organ (Breton et al, 2016;Da Silva and Barton, 2016;Kempinas and Klinefelter, 2014;Shum et al, 2014). Each cell type contributes to the establishment and regulation of a unique luminal environment for the concentration, maturation, storage, and viability of spermatozoa.…”