Mouse Epididymal Epithelial Cells

NEU1 is Transported from Epididymal Epithelium to Spermatozoa to Promote Maturation

Male infertility is one of the most prevalent reproductive disorders. Decreased sperm motility and fertilization capacity are the major causes of infertility in males. Sialylation is an important process during sperm maturation; however, the role of Neuraminidase-1 (NEU1) in this process is yet to be determined. In this study, Yi et al. explored NEU1's source, function, and role in sperm motility and fertilization capacity, thus providing a theoretical basis for the study of male infertility.

They studied NEU1 in the epididymis, which is key for sperm maturation. scRNA-seq showed rising NEU1 expression in epididymal epithelial cells during sperm maturation (Fig. 1A). Confocal microscopy placed NEU1 in these cells' cytoplasm and plasma membrane (Fig. 2A). They cultured primary epididymal epithelial cells from mice, with the fastest growth in the caput region (Fig. 1B). Cell purity was confirmed by E-cadherin staining (Fig. 1C), and enzyme activity was highest in the caput (Fig. 1D). Mouse epididymal fluid had high sialidase activity and NEU1 expression (Fig. 1E), hinting that epididymal epithelial cells secrete active NEU1 for sperm. To further determine NEU1's function, the authors cocultured mouse testicular sperm with epididymal fluid to increase sperm NEU1 content (Fig. 2B). Then, the authors transfected three siRNAs into primary mouse epididymal epithelial cells to knock down NEU1 and chose 100 nM siRNA3 for 72 hours transfection as the low-NEU1 model. The coculture of low-NEU1 epididymal epithelial cells with mouse sperm reduced sperm NEU1 content (Fig. 2C) and inhibited sperm motility (Fig. 2D), increased sialylation (Fig. 2E), and decreased capacitation markers (Fig. 2F). Thus, reduced NEU1 secreted from the epididymal epithelium inhibits sperm maturation.