Sperm maturation in vitro: co-culture of spermatozoa and epididymal epithelium

Sperm maturation involves an intimate interaction between spermatozoa and t he epididymal epithelium. Aspects of this relationship can be examined by c o-incubating epididymal spermatozoa with epididymal epithelium in vitro. Pl aques of epididymal epithelium from a variety of species (for example roden ts, dogs, humans) can be maintained in culture medium supplemented with gro wth factors and androgens. When co-incubated with these epithelial cultures , immature epididymal spermatozoa undergo maturation changes that lead to t he acquisition of progressive motility, zona binding and, in some instances , fertilizing capacity in vitro. The use of such co-culture techniques for the understanding of sperm maturation in vitro and in vivo is reviewed with reference to recent experiments.