Biochemistry Behind the Journey of Spermatozoa Through the Female Reproductive Tract
Pp. 257-290 (34)
Sperm released in the lumen of seminiferous tubules are functionally
immature. These cells acquire maturation during their passage through the epididymis.
The epididymis exhibits an extraordinary structure showing different segments with
distinct luminal composition, which act as a whole for the gradual differentiation of
sperm. This organ is permanently targeted by neuronal and hormonal factors, in
particular by androgens. The study of the biochemical mechanisms that mediate sperm
maturation has been a matter of intense debate. The current advances on the knowledge
of sperm physiology was possible due to studies conducted in laboratory and domestic
species, whereas in humans these processes remain to be fully explored. This is a
subject with high relevance in the field of reproductive biology since defects in these
events may end-up in infertility. Maturation of sperm begins in the epididymis, but
does not end in this organ, since after ejaculation sperms are still unable to fertilize the
oocyte. After being deposited in the reproductive female tract, sperm undergo a number
of structural and biochemical changes to become “capacitated”. Non-capacitated sperm
cannot interact with eggs In vivo as their failure to hyperactivate motility precludes
ascent to the site of fertilization. Sperm and egg must interact so that gamete fusion and
the introduction of paternal information into the egg occurs, and the program of
development must be activated. Male gametes are the “vehicle” by which the genetic
information is passed from fathers to the offspring. In this context, there is increasing
evidence that parental lifestyle and the environment influence phenotypes of the next
generation. Sperm epigenome has huge implications for the success of male fertility,
fertilization, pregnancy and in the transmission of undesirable information to the next
generations. In this chapter we will discuss these topics from a biochemical point of
view by exploring the mechanisms that govern the most relevant processes.
Acrosome reaction, Capacitation, Epididymis, Fertilization,
Glycosylation, Male Reproductive tract, Phosphorylation, Post-translational
modifications, Sperm-egg interactions, Sperm Epigenome, Sperm proteins.
Health Sciences Research Centre, University of Beira Interior, Rua Marquês d’Ávila e Bolama, 6201-001, Covilhã, Portugal.