Putative creatine kinase M-isoform in human sperm is identifiedas the 70-kilodalton heat shock protein HspA2

Biochemical markers of sperm function: male fertility and sperm selection for ICSI

The expression of a 70 kDa chaperone protein, HspA2 (formerly called CK-M), has been identified in mature human spermatozoa. The central role of HspA2 has been established, as the expression level of this protein is related to sperm cellular maturity, DNA integrity, chromatin maturity, chromosomal aneuploidy frequency and sperm function, including fertilizing potential. The spermiogenetic events of cytoplasmic extrusion and remodelling of the plasma membrane, which facilitate the formation of zona pellucida binding site(s) in human spermatozoa, are related. Finally, the presence of the hyaluronic acid (HA) receptor on the plasma membrane of mature sperm coupled with the HA-coated slide sperm-binding assay, facilitates the testing of infertile men and the selection of single mature spermatozoa for ICSI. Because mature spermatozoa have no residual cytoplasm, the HA-bound sperm fraction is also enriched in spermatozoa that are normal by the Kruger strict morphology method.

Abnormal spermatozoa in the ejaculate: abortive apoptosis and faulty nuclear remodelling during spermatogenesis

The mechanisms responsible for producing abnormal spermatozoa in the ejaculate are relatively unknown. Numerous studies have now shown the presence of nuclear DNA strand breaks in human ejaculated spermatozoa and the abnormal persistence of apoptotic marker proteins. The reason why human spermatozoa, in particular from men with abnormal semen parameters, possess these abnormalities is still not clear. Two processes that have been linked to the presence of nuclear DNA strand breaks in spermatozoa are anomalies in apoptosis during spermatogenesis or problems in the replacement of histones with protamines during spermiogenesis. Understanding the mechanisms responsible for producing abnormal spermatozoa in the human will improve knowledge about certain causes of male infertility.

Leukocytospermia is associated with increased reactive oxygen species production by human spermatozoa

To investigate the role of increased seminal leukocytes in enhancing reactive oxygen species (ROS) production by human spermatozoa.A prospective study. Male infertility clinic.Forty-eight infertile men. Standard semen analysis. Assessment of sperm nuclear DNA damage by sperm chromatin structure assay. Incubation of spermatozoa from nonleukocytospermic samples with blood neutrophils. Spontaneous and phorbol 12-myristate 13-acetate (PMA)-induced ROS production in pure-sperm suspensions (after removal of leukocytes) as measured by a chemiluminescence assay. Levels of spontaneous and PMA-induced ROS production in pure-sperm suspensions from the infertile men with a diagnosis of leukocytospermia (n = 16) were significantly higher compared with the case of infertile men without leukocytospermia (n = 32) and with the case of a control group of healthy volunteers (n = 13). A similar pattern of increased ROS was observed when spermatozoa were incubated with blood neutrophils. Leukocytospermia was associated with a significant decrease in sperm motility and increase in DNA damage. Increased seminal leukocytes may play a role in stimulating ROS production by human spermatozoa. Such stimulation may be mediated via direct cell-cell contact or by soluble products released by leukocytes. Poor sperm quality in leukocytospermic samples may be due to leukocyte-mediated oxidative stress.

Defining the cellular and molecular mechanisms of toxicant action in the testis

A symposium was held at the 41st annual meeting of the Society of Toxicology with presentations that emphasized novel molecular and cellular pathways that modulate the response to testicular toxicants. The first two presentations described cellular alterations after exposure to the Sertoli cell toxicant, mono-(2-ethylhexyl) phthalate (MEHP). The expression of flamingo1, a G protei coupled receptor family member that may couple cell-cell adhesion to G protein-dependent signaling in Sertoli cells, was rapidly altered after MEHP exposure. Sertoli cell associated flamingo1 immunostaining was redistributed early (within 2 h) after MEHP exposure and disappeared by 12 h, suggesting that flamingo1 is a proximal phthalate target. MEHP was also described to alter the expression and activity of the newly identified death receptors DR4, 5 and 6 in the testis. The differential cellular changes in the levels of DR4, 5 and 6 after phthalate exposure suggested that they may act as surrogates or in concert with the widely described Fas-signaling pathway in the initiation of germ cell apoptosis after MEHP exposure. The next two presentations focused on revealing mechanisms that may explain the persistent post-exposure testicular atrophy that is observed in rodents after a variety of chemical or physical insults (radiation, chemotherapeutics, toxicants) and possible strategies to re-initiate spermatogenesis in the atrophic testis. Hormonal manipulations that lower testosterone and serum FSH levels allow for re-initiation of spermatogonial development. Recent investigation of additional models of persistent atrophy such as mutant mice, the aged Brown Norway rat, EDS-induced Leydig cell deficient rat, and primates, have broadened insight into the mechanisms responsible for persistent atrophy. The last presentation described the use of cDNA arrays in the investigation of cellular elements and mechanisms responsible for disruption of spermatogenesis by the drinking water disinfectant bromochloroacetic acid (BCA). A custom mouse testis cDNA array interrogating 950 genes was used for analysis of testis mRNA. BCA altered the expression of 53 of the 950 genes, including two encoding sperm proteins known to be significant for male fertility, and other genes involved in spermatogenesis, stress response, and cell communication/adhesion. These observations strengthen the hypothesis that BCA disrupts spermatogenesis by altering the process of spermiogenesis.

Sperm maturity and treatment choice of in vitro fertilization (IVF) or intracytoplasmic sperm injection: diminished sperm HspA2 chaperone levels predict IVF failure

OBJECTIVE

To reexamine whether low sperm HspA2 ratios (formerly sperm CK-M ratio) are predictive for failure to cause pregnancies by in vitro fertilization (IVF) and to explore whether there are other male or female factors that may be predictive for IVF pregnancy outcome.

DESIGN

Retrospective, cohort study.

SETTING

University-based IVF program.

PATIENT(S)

In 119 IVF cycles, three patient groups were studied: 25 men had a <10% sperm HspA2 ratio and a lack of pregnancies (HS <10% group), 50 men had a >10% sperm HspA2 ratio and no pregnancies (HS >10%NP group), and another 44 couples had a >10% sperm HspA2 ratio but did achieve pregnancies (HS >10%P group).

INTERVENTION(S)

Sperm HspA2 ratio determinations within 1 year of the IVF cycles and analysis of male and female IVF cycle parameters.

MAIN OUTCOME MEASURE(S)

Sperm HspA2 ratio determinations within 1 year of the IVF cycles and analysis of male and female IVF cycle parameters.

RESULT(S)

In the three groups, male and female ages, number and maturation level of oocytes, and morphology of embryos were similar. In the HS < 10% group, mean sperm concentration and motility were close to normal, the fertilization and cleavage rates were lower, and cycles without any oocyte fertilization were higher. These parameters were similar in the two HS > 10% groups. The receiver operating characteristic curve in men with sperm HspA2 ratios of <17% (diminished and borderline sperm maturity) provided a cutoff value of 10.84% HspA2 ratio with a 100% positive predictive value for failure to achieve pregnancy, whether the men were oligospermic or normospermic.

CONCLUSION(S)

HspA2 ratios of <10% in the diminished sperm maturity range predict the failure to cause pregnancies by IVF. Thus, IVF should be bypassed in favor of ICSI. The occurrence of pregnancy with ICSI depends on the maturity of sperm selected, and it may not be as likely as in other indications for ICSI.

Nature of DNA damage in ejaculated human spermatozoa and the possible involvement of apoptosis

Numerous studies have shown the presence of DNA strand breaks in human ejaculated spermatozoa. The nature of this nuclear anomaly and its relationship to patient etiology is however poorly understood. The aim of this study was to investigate the relationship between nuclear DNA damage, assessed using the TUNEL assay and a number of key apoptotic markers, including Fas, Bcl-x, and p53, in ejaculated human spermatozoa from men with normal and abnormal semen parameters. We also determined the nature of the DNA damage by examining the percentage of ejaculated spermatozoa exhibiting DNA damage using the comet assay and by challenging sperm chromatin to attack by micrococcal nuclease S7 and DNase I. We show that TUNEL positivity and apoptotic markers do not always exist in unison; however, semen samples that had a low sperm concentration and poor morphology were more likely to show high levels of TUNEL positivity and Fas and p53 expression. In addition, the DNA damage in ejaculated human sperm is represented by both single- and double-stranded DNA breaks, and access to the DNA is restricted by the compacted nature of ejaculated spermatozoa. This DNA protection is poorer in men with abnormal semen parameters. We propose that the presence of DNA damage is not directly linked to an apoptotic process occurring in spermatozoa and arises due to problems in the nuclear remodeling process. Subsequently, the presence of apoptotic proteins in ejaculated spermatozoa may be linked to defects in cytoplasmic remodeling during the later stages of spermatogenesis.

Creatine kinase as an indicator of sperm quality and maturity in men with oligospermia

OBJECTIVES

To determine the differences among the creatine kinase (CK) levels in the spermatozoa of subfertile men with mild, moderate, or severe oligospermia and to examine the differences in CK activity between infertile patients with various clinical diagnoses and a group of normal healthy donors (control). CK is a marker of sperm maturity that correlates with the sperm fertilizing capacity. Elevated levels are associated with an increased rate of functional abnormalities and increased cytoplasmic retention.

METHODS

We compared the CK levels in 51 oligospermic men who could not initiate a pregnancy. Patients were categorized according to their degree of oligospermia as defined by the total sperm count: mild (greater than 10 to 40 x 10(6); n = 30), moderate (5 to 10 x 10(6); n = 11), and severe (less than 5 x 10(6); n = 10). These patients were further classified according to their diagnosis (ie, varicocele, n = 24; unexplained infertility, n = 17; vasectomy reversal, n = 9; and unknown diagnosis, n = 1). A separate group consisting of 25 healthy donors was included as a control group. A computer-assisted semen analyzer assessed the sperm characteristics, and the CK levels were measured using a CK test kit after the enzyme was extracted with Triton-X.

RESULTS

The CK levels were significantly higher in the sperm of the severely oligospermic group (8.8 +/- 6.5 IU/10(8) sperm) than in the moderate (0.50 +/- 0.19 IU/10(8) sperm) and mild (0.49 +/- 0.15 IU/10(8) sperm) groups (P <0.0001). The mean CK level in the severely oligospermic group was 18-fold higher than that in the moderate (P = 0.03) and mild (P <0.001) groups. The CK levels were significantly higher in all three infertile groups compared with the donor group (0.06 +/- 0.01 IU/10(8) sperm). Patients with varicocele had the highest CK level (3.42 +/- 2.56 IU/10(8) sperm) compared with patients in the vasectomy reversal group (1.73 +/- 0.98 IU/10(8) sperm) and the idiopathic infertility group (0.26 +/- 0.08 IU/10(8) sperm).

CONCLUSIONS

Elevated CK levels are associated with severe oligospermia, irrespective of the clinical diagnosis. CK may be a sensitive indicator of sperm quality and maturity in the follow-up of patients treated for male factor infertility.

The search is on: finding accurate molecular markers of male fertility

Diagnosis of the fertility potential of a semen sample is essential for consistently high reproductive efficiency. The use of subfertile or infertile semen can have devastating consequences for those selling or using the semen. Therefore it is crucial to develop and use accurate diagnostic tests to determine the fertility of males and of individual semen samples. These diagnostic tests must be economically practical and provide consistent results. The goal of this review is to explore areas of fertility diagnostic research, including what we have termed functional and molecular tests, and consider the accuracy of each test. In this article, literature from several species is cited, and it is noteworthy that each diagnostic test may not be valuable in all species. Multiple functional and molecular tests will likely be needed to effectively characterize male fertility in each species.