New insights into epididymal biology and function

Abstract

Background: The epididymis performs an important role in the maturation of spermatozoa including their acquisition of progressive motility and fertilizing ability. However, the molecular mechanisms that govern these maturational events are still poorly defined. This review focuses on recent progress in our understanding of epididymal function including its development, role of the luminal microenvironment in sperm maturation, regulation and novel mechanisms the epididymis utilizes to carry out some of its functions.

Methods: A systematic search of Pubmed was carried out using the search term 'epididymis'. Articles that were published in the English language until the end of August 2008 and that focused on the specific topics described above were included. Additional papers cited in the primary reference were also included.

Results: While the majority of these findings were the result of studies in animal models, recent studies in the human epididymis are also presented including gene profiling studies to examine regionalized expression in normal epididymides as well as in those from vasectomized patients.

Conclusions: Significant progress has been made in our understanding of epididymal function providing new insights that ultimately could improve human health. The data also indicate that the human epididymis plays an important role in sperm maturation but has unique properties compared with animal models.

Figure 1

Mouse and human epididymides. Mouse: 1, initial segment, proximal caput; 2, midcaput; 3, distal caput; 4, corpus; 5, cauda. Adapted (regional divisions by the author) from Trevor Cooper, University of Muenster (Yeung and Cooper, 2002), with permission of author and publisher, Springer. Human: ED, efferent ducts; 1, anterior caput; 2, posterior caput; 3, anterior corpus; 4, midcorpus; 5, posterior corpus; 6, anterior cauda; 7, posterior cauda; DD, ductus deferens. Reprinted by permission of the author (Dacheux et al., 2006), UMR INRA-CNRS and publisher, Elsevier Limited. Scale bar, 1 cm.

Figure 2

Schematic diagram of the cellular organization in a representative cross-section of the rat epididymis. Modified and reprinted with permission of the author (Robaire et al., 2003), McGill University and publisher, The Van Doren Co, Charlottesville, VA.

Figure 3

Schematic diagram of apocrine secretion in principal cells of the epididymis. Inset, electron micrograph of epididymosomes. AB, apical bleb; EP, epididymosome; ILC, intraluminal compartment; MV, microvilli. Reprinted with permission of the author, University of Laval and the publisher Blackwell publishing (Sullivan et al., 2007).