The making of abnormal spermatozoa: Cellular and molecular mechanisms underlying pathological spermiogenesis

CHEMES, H.E.; RAWE, V.Y.

The spermatozoon: 40 years of research

Lugar: Siena; Año: 2007;

Fertilization in mammals is the result of a series of well defined events such as sperm capacitation and the acrosome reaction, sperm-zona binding, fusion of gamete membranes and oocyte penetration and activation (Yanagimachi, 1994). This intricate process has occurred across millennia in the secluded environment of the female reproductive tract and the mode of selection of the fertilizing spermatozoon has evaded the inquiring eye of many generations of scientists. Since the introduction of in vitro fertilization by sperm microinjection into the oocyte (ICSI), reproductive biologists have been in a position to choose what they considered was the best suited spermatozoon for microinjection. However, this selection has proven to be very difficult and, at the same time, it became evident that abnormal spermatozoa could successfully fertilize oocytes. In these extreme conditions, post-fertilization events, early embryonic development and implantation are significantly compromised, which indicates that the contribution of spermatozoa extends beyond sperm penetration (Chemes and Rawe 2003). Microscopic identification of normal spermatozoa is a well standardized procedure (Kruger et al 1986; WHO, 1999), but insight into the mechanisms that lead to aberrant sperm differentiation  and into the subcellular nature of sperm abnormalities has only recently began to unfold. The spermatozoon is the result of a complex development in which spermatid organelles give rise to various structural components with characteristic functions. Similar to other differentiated cells the spermatozoon has a specific pathology that is most clearly idfentified by the use of ultrastructural evaluation coupled with immunocytochemistry and molecular techniques. This multidisciplinary approach allows a precise characterization of sperm abnormalities including their structural, molecular and functional aspects. This paper summarizes our studies on the physiopathology of spermiogenesis in two abnormal sperm phenotypes of infertile men, the Dysplasia of the Fibrous Sheath and acephalic spermatozoa/abnormal head-tail attachment.