The epididymis is a long convoluted organ of the male reproductive tract. Its
functionality has been overlooked for many years, but it is currently accepted that it has
a preponderant role in spermatozoa post-testicular maturation. The epididymis presents
a high secretory activity. Several proteins can be released in bulk through apical blebs
or can be associated with epididymosomes, which fuse with sperm plasma membrane
becoming integral proteins. The interaction of epididymal proteins with spermatozoa is
a very important factor in the regulation of spermatozoa maturation along their passage
through the different epididymal regions. A mature sperm cell recovered from the
epididymal caudal region should present the ability to move (activated motility) and to
fertilize the oocyte. The atmosphere created within the epididymal lumen is very
dynamic, since the epididymal fluid composition is relatively different between the
tubule compartments. The blood-epididymal barrier (BEB) created by junctions
between principal cells of the epididymal epithelium is not only responsible for the
control of epididymal luminal fluid composition, but also acts as a defense mechanism
to protect spermatozoa from the immune system, harmful xenobiotics and oxidative
stress. While the caput and corpus of epididymis are mainly involved in sperm
maturation, the caudal region is the site of mature sperm storage in a quiescent and
protected state. In this chapter, we discuss the biochemical events occurring during the
transit of spermatozoa through the epididymis. We will focus on the involvement and
structural organization of epididymal epithelial cells and secretory proteins on
spermatozoa modifications during their maturational process.
Keywords: Androgens, Apical blebs, Blood-epididymal barrier, Coating proteins,
Epididymal epithelial cells, Epididymal secreted proteins, Epididymis,
Epididymosomes, Fertilizing ability, Integral membrane proteins, Luminal micro-environment, Motility acquisition, Sperm protection, Sperm maturation, Sperm storage.
