Evaluation of sperm
David K. Gardner, Ariel Weissman, Colin M. Howles, Zeev Shoham in Textbook of Assisted Reproductive Techniques, 2017
The acrosome is an intracellular organelle, similar to a lysosome, which forms a cap-like structure over the apical portion of the sperm nucleus (36). The acrosome contains multiple hydrolytic enzymes, including hyaluronidase, neuraminidase, proacrosin, phospholipase, and acid phosphatase, which, when released, are thought to facilitate sperm passage through the cumulus mass, and possibly the zona pellucida as well (Figure 4.4). In fact, only acrosome-reacted sperm is capable of penetrating the zona pellucida, binding to the oolemma, and fusing with the oocyte (37). Once sperm undergoes capacitation, it is capable of an acrosome reaction. This reaction is apparently triggered by fusion of the sperm plasma membrane with the outer acrosomal membrane at multiple sites, leading to diffusion of the acrosomal enzymes into the extracellular space. This leads to the dissolution of the plasma membrane and acrosome, leaving the inner acrosomal membrane exposed over the head of the sperm (Figure 4.5). Although electron microscopy has produced many elegant pictures of acrosome-intact and acrosome-reacted sperm, it is not always possible to know whether sperm that fail to exhibit an acrosome have truly acrosome reacted, or could possibly be dead. In addition, electron microscopy is not a technique that is available to all andrologists.
Regulation of Reproduction by Dopamine
Nira Ben-Jonathan in Dopamine, 2020
ZP3, a glycoprotein in the zona pellucida (ZP), serves as a sperm recognition site. Species-selective sperm “receptors” account, in part, for the failure of fertilization between germ cells from unrelated species. The acrosome reaction is triggered by contact of the sperm with the egg, enabling sperm penetration into the ZP and its fusion with the oocyte’s membrane [80]. The acrosome reaction involves calcium-dependent release of hyaluronidase and exposure of masked membrane domains in the sperm’s head. In one study, heat-solubilized human ZP was used to study the induction of the acrosome reaction in capacitated human spermatozoa [81]. Pimozide, a D2R antagonist, prevented the activation of voltage-operated calcium channels (VOCCs), which mediate acrosomal exocytosis in response to contact with the ZP. In contrast, L-type VOCCs inhibitors such as nifedipine and verapamil failed to inhibit the ZP-mediated acrosome reaction.
The Importance of Sperm Surface Markers in Reproductive Success: Sperm Hyaluronan Binding
Nicolás Garrido, Rocio Rivera in A Practical Guide to Sperm Analysis, 2017
The events of spermiogenesis result in a structurally unique cell. Human sperm consists of a head and tail. The dense nucleus is covered by a vesicle called the acrosome.12 It is bound to the nucleus by the perinuclear theca, which intervenes between the nuclear envelope and the inner acrosomal membrane.13 The acrosomal cap that covers the anterior two-thirds of the nucleus contains enzymes such as hyaluronidase, neuraminidase, acid phosphatase, and a trypsin-like protease called acrosin. These acrosomal enzymes are crucial during the penetration of the zona pellucida of the oocyte.14 The acrosomal enzymes are released when sperm touches the oocyte, which is the first step of the acrosome reaction. Sperm penetration and fertilization are facilitated by these complex processes and also prevent the polyspermy.
Prediction of male infertility by the World Health Organization laboratory manual for assessment of semen analysis: A systematic review
Published in Arab Journal of Urology, 2018
Amir S. Patel, Joon Yau Leong, Ranjith Ramasamy
Another absolute predictor for male infertility is the detection of globozoospermia on semen analysis. It is a rare but severe form of teratozoospermia, characterised by the presence of round-headed spermatozoa lacking an acrosome [42]. The acrosome contains the digestive enzyme, acrosin, which is essential for binding and penetration of the zona pellucida of the ovum. It also facilitates cervical mucus penetration and intrauterine sperm migration. It also participates in chromatin decondensation in the oocyte [43]. Considering these factors, we can understand how globozoospermic cells have difficulties adhering and fusing with the oocyte membrane, ultimately causing infertility. A microscopic image of globozoospermic spermatozoa can be seen in Fig. 2 [44].
Role of reactive oxygen species in male infertility: An updated review of literature
Published in Arab Journal of Urology, 2018
Hillary Wagner, Julie W. Cheng, Edmund Y. Ko
For optimal sperm function and for fertilisation to occur, there must be a balance of ROS and antioxidants (Fig. 3 ). ROS induces cyclic adenosine monophosphate (cAMP) in spermatozoa that inhibits tyrosine phosphatase leading to tyrosine phosphorylation [25]. In particular, H2O2 stimulates capacitation via tyrosine phosphorylation triggering a cell signalling cascade [26]. Capacitation not only requires ROS, but it can be inhibited by catalase (CAT) [26]. It has been described that high levels of ROS promote the acrosome reaction, whereas the presence of CAT or superoxide dismutase (SOD) inhibits the acrosome reaction [27]. The mechanism of inducing the acrosome reaction appears to be ROS-modulated tyrosine phosphorylation [26]. Motility can also be affected by ROS. Hyperactivation is increased when spermatozoa are exposed to ROS [28]. ROS-mediated tyrosine phosphorylation in the flagellum causes hyperactivation [13,25]. Tyrosine phosphorylation also augments sperm membrane binding to the zona pellucida ZP-3 protein, promoting sperm–oocyte fusion [29].
Genetic variations as molecular diagnostic factors for idiopathic male infertility: current knowledge and future perspectives
Published in Expert Review of Molecular Diagnostics, 2021
Mohammad Karimian, Leila Parvaresh, Mohaddeseh Behjati
Many genes are involved during the various stages of spermiogenesis, including acrosome formation, chromatin remodeling, flagellum formation, and energy supply signaling [156]. Genetic variation in some of these genes may influence male infertility risk. One of the most important genes is protamine, which is described in the section ‘Sperm genome packaging proteins.’ Disruption of some mouse genes, including Hrb (HIV-1 Rev binding protein), Gopc (Golgi-associated PDZ and coiled-coil motif containing protein), Csnk2a2 (casein kinase 2, α prime polypeptide), and Pick1 (protein interacting with C kinase 1), leads to a phenotype similar to globozoospermia in humans, which indicates their potential role in development of this disease [157]. Liu et al., in their study, examined the above candidate genes in three patients with globozoospermic type I and discovered a homozygous mutation (G198A) in exon 13 of the PICK1 gene in a Chinese family. One family member affected by this homozygous mutation showed a complete absence of acrosome. Their study was the first project to identify an autosomal recessive genetic mutation in PICK1 that was responsible for development of globozoospermia in humans [158].