The Role of Epididymis and “Bio-Active Cargo” Exosome in Sperm Cells Maturation

Male infertility may result from impaired posttesticular sperm maturation, a process in which the epididymis provides a specialized luminal microenvironment essential for sperm development and functional competence. This narrative literature review examined the anatomical and physiological roles of the epididymis and the potential contributions of epididymosome-associated bioactive cargo to sperm maturation. Relevant literature published between 2015 and 2025 was identified through PubMed, ScienceDirect, and other scientific sources and synthesized according to epididymal structure, epithelial cell functions, extracellular vesicle biology, and the transfer of proteins and small regulatory RNAs. The reviewed evidence indicated that epididymosomes, a heterogeneous population of extracellular vesicles released into the epididymal lumen, participate in intercellular communication and may transfer bioactive molecules to spermatozoa during epididymal transit. These molecular interactions have been associated with sperm plasma membrane remodeling, acquisition of motility, protection against oxidative stress, and other posttesticular modifications essential for sperm functional maturation. Experimental studies further suggested that epididymosome-mediated cargo transfer contributes to molecular communication between the epididymal epithelium and developing spermatozoa. However, much of the mechanistic evidence was derived from animal models and in vitro experiments, limiting its direct applicability to human reproductive physiology. Furthermore, the clinical relevance of specific epididymosomal cargo molecules in human infertility remains insufficiently established. Overall, this review highlighted the potential of epididymosomes as sources of reproductive biomarkers and targets for future investigations rather than validated diagnostic or therapeutic tools. Further research should clarify cargo-specific mechanisms in humans and distinguish molecular changes acquired during epididymal maturation from those associated with subsequent sperm capacitation in the female reproductive tract.