Three-Dimensional Analysis of Interstitial Cells in the Smooth Muscle Layer of Murine Vas Deferens Using Confocal Laser Scanning Microscopy and FIB/SEM

Insights on Platelet-Derived Growth Factor Receptor α-Positive Interstitial Cells in the Male Reproductive Tract

Male infertility is a significant factor in approximately half of all infertility cases and is marked by a decreased sperm count and motility. A decreased sperm count is caused by not only a decreased production of sperm but also decreased numbers successfully passing through the male reproductive tract. Smooth muscle movement may play an important role in sperm transport in the male reproductive tract; thus, understanding the mechanism of this movement is necessary to elucidate the cause of sperm transport disorder. Recent studies have highlighted the presence of platelet-derived growth factor receptor α (PDGFRα)-positive interstitial cells (PICs) in various smooth muscle organs. Although research is ongoing, PICs in the male reproductive tract may be involved in the regulation of smooth muscle movement, as they are in other smooth muscle organs. This review summarizes the findings to date on PICs in male reproductive organs. Further exploration of the structural, functional, and molecular characteristics of PICs could provide valuable insights into the pathogenesis of male infertility and potentially lead to new therapeutic approaches.

Sheet-like interstitial cells connect epithelial and smooth muscle cells in the mouse prostate

Epithelial-stromal relationship in the prostate gland is crucial for maintaining homeostasis, including functional differentiation, proliferation, and quiescence. Pathological stromal changes are believed to cause benign prostatic hyperplasia (BPH). The prostate stromal tissue is known to have several subtypes of interstitial cells that connect the epithelium and smooth muscle. However, the characteristics of their morphology and connection patterns are not fully understood. Therefore, we aimed to investigated the three-dimensional morphology and intercellular interactions of interstitial cells in the prostate ventral lobe of mature wild-type mice using immunohistochemistry and focused ion beam-scanning electron microscopy tomography (FIB-SEM tomography). The prostate interstitial cells exhibited immunohistochemical subtypes, including PDGFRα single-positive, CD34 single-positive, and CD34 and PDGFRα double-positive. PDGFRα single-positive cells were observed as elongated cells just below the epithelium, CD34 single-positive cells were observed as polygonal cells in the area away from the epithelium, and double-positive cells were observed as elongated cells situated slightly deeper than PDGFRα single-positive cells. Furthermore, connexin43-immunoreactive puncta were observed on interstitial cells just beneath the epithelium, suggestive of possible electrical connections among the PDGFRα single-positive interstitial cells. Three-dimensional structural analysis using FIB-SEM tomography revealed sheet-like multilayered interstitial cells that appear to separate the glandular terminal from the deeper interstitial tissue, which includes smooth muscle and capillaries. Further, epithelial cells might be indirectly connected to the smooth muscle and nerve fibers via these sheet-like multilayered interstitial cellular networks. These findings suggest that the cellular network that separates the glandular terminals from the deep interstitial tissue functionally bridges the epithelium and smooth muscle, possibly playing a pivotal role in prostate tissue homeostasis through the epithelial-smooth muscle or epithelial-stromal relationships.

Three-dimensional analysis of interstitial cells in the lamina propria of the murine vas deferens by confocal laser scanning microscopy and FIB/SEM

The present study aimed to explore the three-dimensional (3D) ultrastructure of interstitial cells (ICs) within the lamina propria of the murine vas deferens and the spatial relationships between epithelial cells and surrounding cells. Focused ion beam scanning electron microscopy and confocal laser scanning microscopy were performed. ICs within the lamina propria had a flat, sheet-like structure of cytoplasm with multiple cellular processes. In addition, two types of 3D structures that comprised cell processes of flat, sheet-like ICs were observed: one was an accordion fold-like structure and the other was a rod-shaped structure. ICs were located parallel to the epithelium and were connected to each other via gap junctions or adherens junctions. Moreover, multiple sphere-shaped extracellular vesicle-like structures were frequently observed around the ICs. The ICs formed a complex 3D network comprising sheet-like cytoplasm and multiple cell processes with different 3D structures. From this morphological study, we noted that ICs within the lamina propria of murine vas deferens may be involved in signal transmission between the epithelium and smooth muscle cells by physical interaction and by exchanging extracellular vesicles.