In vitro maturation of mammalian spermatozoa.

During epididymal transit, mammalian spermatozoa undergo maturation and acquire full fertilizing capacity. The contribution of factors from the epididymal epithelium appears to be essential for this process. Although complete in vitro maturation of epididymal spermatozoa has not been achieved, stages of maturation can be induced under various conditions. The most successful results have been obtained by incubating epididymal spermatozoa with primary cultures of epididymal epithelium. These co-incubation methods promote sperm motility and the capacity of spermatozoa to bind to and fertilize oocytes, and extend the viability of spermatozoa in vitro. Specific androgen-dependent secretory proteins from epididymal principal cells that may be involved in this maturation process have been identified using pulse-labelling techniques.