Ulrik Kvist

Sperm DNA: organization, protection and vulnerability: from basic science to clinical applications—a position report

This article reports the results of the most recent in a series of EHSRE workshops designed to synthesize the current state of the field in Andrology and provide recommendations for future work (for details see Appendix). Its focus is on methods for detecting sperm DNA damage and potential application of new knowledge about sperm chromatin organization, vulnerability and repair to improve the diagnosis and treatment of clinical infertility associated with that damage. Equally important is the use and reliability of these tests to identify the extent to which environmental contaminants or pharmaceutical agents may contribute to the incidence of sperm DNA damage and male fertility problems. A working group (for workshop details, see Appendix) under the auspices of ESHRE met in May 2009 to assess the current knowledgebase and suggest future basic and clinical research directions. This document presents a synthesis of the working groups understanding of the recent literature and collective discussions on the current state of knowledge of sperm chromatin structure and function during fertilization. It highlights the biological, assay and clinical uncertainties that require further research and ends with a series of 5 key recommendations.

Seminal Plasma Proteins: What Role Do They Play?

Citation Rodríguez‐Martínez H, Kvist U, Ernerudh J, Sanz L, Calvete JJ. Seminal Plasma Proteins: What Role Do They Play? Am J Reprod Immunol 2011; 66 (Suppl. 1): 11–22

Human sperm chromatin stabilization: a proposed model including zinc bridges

The primary focus of this review is to challenge the current concepts on sperm chromatin stability. The observations (i) that zinc depletion at ejaculation allows a rapid and total sperm chromatin decondensation without the addition of exogenous disulfide cleaving agents and (ii) that the human sperm chromatin contains one zinc for every protamine for every turn of the DNA helix suggest an alternative model for sperm chromatin structure may be plausible. An alternative model is therefore proposed, that the human spermatozoon could at ejaculation have a rapidly reversible zinc dependent chromatin stability: Zn(2+) stabilizes the structure and prevents the formation of excess disulfide bridges by a single mechanism, the formation of zinc bridges with protamine thiols of cysteine and potentially imidazole groups of histidine. Extraction of zinc enables two biologically totally different outcomes: immediate decondensation if chromatin fibers are concomitantly induced to repel (e.g. by phosphorylation in the ooplasm); otherwise freed thiols become committed into disulfide bridges creating a superstabilized chromatin. Spermatozoa in the zinc rich prostatic fluid (normally the first expelled ejaculate fraction) represent the physiological situation. Extraction of chromatin zinc can be accomplished by the seminal vesicular fluid. Collection of the ejaculate in one single container causes abnormal contact between spermatozoa and seminal vesicular fluid affecting the sperm chromatin stability. There are men in infertile couples with low content of sperm chromatin zinc due to loss of zinc during ejaculation and liquefaction. Tests for sperm DNA integrity may give false negative results due to decreased access for the assay to the DNA in superstabilized chromatin.

Human fertility does not decline: evidence from Sweden

OBJECTIVE To assess changes in human fertility over time. DESIGN Time-trend analyses and age-period-cohort modeling. SETTING Sweden, 1983-1993. PATIENT(S) All primiparous women aged > or =20 years during the study period. There were 401,653 women who were identified through the nationwide Medical Birth Register. INTERVENTION(S) None. MAIN OUTCOME MEASURE(S) Risk of subfertility, defined as > or =1 year of involuntary childlessness. RESULT(S) Subfertility problems decreased dramatically over successive maternal birth cohorts. Further, the risk of subfertility increased with age and decreased with increasing formal education. CONCLUSION(S) A decrease in male fertility cannot be ruled out on the basis of these results, but if present, it is minor and totally outweighed by other favorable developments. As the main explanation for our findings, we propose a decrease in the prevalence of secondary subfertility as a result of the eradication of gonorrhea.

Sequence of ejaculation affects the spermatozoon as a carrier and its message

It is a widespread misunderstanding that the human ejaculation produces a homogeneous fluid with constant environment for the spermatozoa. On the contrary, spermatozoa are mainly expelled together with the zinc-rich prostatic fluid in the first ejaculation fractions. In nature, these spermatozoa most likely enter the cervical mucus before any significant contact with the later, sperm hostile fractions takes place. Spermatozoa collected in the laboratory for diagnosis, treatment or research purposes face challenges in the form of light, high oxygen concentration, low carbon dioxide concentration, increased pH, extreme variations in osmolarity, and changed bioavailability of zinc and calcium in the man-made laboratory product called seminal plasma. Possible future implications of these unphysiological conditions are discussed in relation to assisted reproduction and sperm research.

Zinc in Sperm Chromatin and Chromatin Stability in Fertile Men and Men in Barren Unions

The stability and the content of zinc of the chromatin were studied in spermatozoa from ten men with unexplained infertility, and in spermatozoa from five fertile donors. A positive relation was found between zinc in sperm nuclei (X-ray microanalysis) and the resistance of the chromatin to decondense in sodium dodecylsulfate (SDS). The infertile men had lower degree of sperm chromatin stability and lower sperm zinc content than the fertile donors. A subgroup of the infertile men, which all had minor clinical signs of prostatic inflammatory reaction, had the lowest content of zinc in the chromatin and the lowest degree of chromatin stability. A low content of nuclear zinc would impair the structural stability of the chromatin and thereby increase the vulnerability of the male genome. This mechanism may be one explanation for the reduced fertility of the men with minor inflammation of the prostate.

THE INTRINSIC MECHANISM OF CHROMATIN DECONDENSATION AND ITS ACTIVATION IN HUMAN SPERMATOZOA

In vitro decondensation of human sperm chromatin induced by the activation of an intrinsic mechanism was studied by light microscopy, scanning and transmission electron microscopy. Morphological evidence was provided to support the concept that this mechanism is essential for the chromatin decondensation occurring in vivo. Prostatic zinc is hypothesized to preserve this potential decondensation ability from oxidative destruction, by reversibly binding to free thiol‐groups. The unique occurrence of disulphide‐stabilized structures in eutherian spermatozoa may serve to protect the spermatozoon from structural degradation by its own proteolytic activity during the relatively slow passage through the eutherian egg investments.

Testicular atrophy and loss of nerve growth factor-immunoreactive germ cell line in rats exposed to n-hexane and a protective effect of simultaneous exposure to toluene or xylene

Testicular and germ cell line morphology in rats were studied 2 weeks, 10 months and 14 months after cessation of a 61-day inhalation exposure to 1000 ppm n-hexane. Androgen biosynthetic capacity of testis, testosterone blood concentration, vas deferens morphology and noradrenaline (NA) concentration, epididymal sperm morphology, and fertility were also studied. Severe testicular atrophy involving the seminiferous tubules with loss of the nerve growth factor (NGF) immunoreactive germ cell line was found. Total loss of the germ cell line was found in a fraction of animals up to 14 months post-exposure, indicating permanent testicular damage. No impairment of androgen synthesis or androgen dependent accessory organs was observed. Simultaneous administration of 1000 ppm n-hexane and 1000 ppm toluene, or 1000 ppm n-hexane and 1000 ppm xylene, did not cause germ cell line alterations or testicular atrophy. Toluene and xylene were thus found to protect from n-hexane induced testicular atrophy.

Sexual Function in Men Treated for Testicular Cancer

INTRODUCTION Testicular germ cell cancer (TGCC) patients may be at risk of developing sexual dysfunction after treatment. AIM The aim of this study was to assess the prevalence of sexual dysfunctions in TGCC patients 3 to 5 years after treatment, and relate findings to biochemical hypogonadism, treatment intensity, and the expected prevalence in the Swedish male population. METHODS A questionnaire study on 129 consecutive TGCC patients 3 to 5 years post-treatment was performed. Comparators were an age-matched nationally representative group of men (N = 916) included in a study on sexual life in Sweden. MAIN OUTCOME MEASURES Sexual functions (including erectile dysfunctional distress), time since last intercourse, sexual satisfaction, and experience of sexological treatment seeking were assessed using the same questions used in the epidemiological study on sexual life in Sweden. The findings in TGCC patients were correlated to biochemical signs of hypogonadism and type of oncological treatment: Surveillance, adjuvant chemotherapy, adjuvant radiotherapy, or standard doses of chemotherapy. RESULTS A higher proportion of TGCC patients than comparators were likely to report low sexual desire (odds ratio [OR] 6.7 [95% confidence interval {CI} 2.1-21]) as well as erectile dysfunction (OR 3.8 [95% CI 1.4-10]). No significant differences were observed regarding erectile dysfunctional distress, change of desire over time, interest in sex, premature or delayed ejaculation, time since last intercourse, need for or receiving sexual advice, or sexual satisfaction. Hypogonadism did not predict erectile dysfunction (OR 1.1 [95% CI 0.26-4.5]) or low sexual desire (OR 1.2 [95% CI 0.11-14]). Treatment modality had no obvious impact on sexual function. CONCLUSION Men treated for testicular cancer had higher risk of having low sexual desire and erectile dysfunction 3 to 5 years after completion of therapy than comparators. These sexual dysfunctions were not significantly associated with treatment intensity or hypogonadism.

Male infertility after mesh hernia repair: A prospective study

BACKGROUND Several animal studies have raised concern about the risk for obstructive azoospermia owing to vasal fibrosis caused by the use of alloplastic mesh prosthesis in inguinal hernia repair. The aim of this study was to determine the prevalence of male infertility after bilateral mesh repair. METHODS In a prospective study, a questionnaire inquiring about involuntary childlessness, investigation for infertility and number of children was sent by mail to a group of 376 men aged 18-55 years, who had undergone bilateral mesh repair, identified in the Swedish Hernia Register (SHR). Questionnaires were also sent to 2 control groups, 1 consisting of 186 men from the SHR who had undergone bilateral repair without mesh, and 1 consisting of 383 men identified in the general population. The control group from the SHR was matched 2:1 for age and years elapsed since operation. The control group from the general population was matched 1:1 for age and marital status. RESULTS The overall response rate was 525 of 945 (56%). Method of approach (anterior or posterior), type of mesh, and testicular status at the time of the repair had no significant impact on the answers to the questions. Nor did subgroup analysis of the men ≤40 years old reveal any significant differences. CONCLUSION The results of this prospective study in men do not support the hypothesis that bilateral inguinal hernia repair with alloplastic mesh prosthesis causes male infertility at a significantly greater rate than those operated without mesh.