Sperm chromatin heterogeneity as an infertility factor

The Disappearing Sperms: Analysis of Reports Published Between 1980 and 2015

Reports regarding the changes in sperm concentration in different counties of the world are inconsistent. Furthermore, the reports that sprung up from specific epidemiological and experimental examinations did not include data of prior studies or geographical variations. The current study, following a previous report of massive fall in semen volume over the past 33 years, attempts to delineate the trend of altering sperm concentrations and factors responsible for this by reviewing article published from 1980 to July 2015 with geographic differences. The current study identified an overall 57% diminution in mean sperm concentration over the past 35 years ( r = -.313, p = .0002), which, when analyzed for each geographical region, identified a significant decline in North America, Europe, Asia, and Africa. An increasing trend of sperm concentration was identified only in Australia. The association of male age with such a trend ( R² = .979) is reported. The authors also correlated male fertility with sperm concentration. Thus, this comprehensive, evidence-based literature review aims to concisely and systematically present the available data on sperm concentration from 1980 to 2015, as well as to statistically analyze the same and correlate male health with the declining pattern of sperm count in a single scientific review to serve the scientific research zone related to reproductive health. It points to the threat of male infertility in times ahead.

Organophosphorous pesticide exposure alters sperm chromatin structure in Mexican agricultural workers

Our objective was to evaluate alterations in sperm chromatin structure in men occupationally exposed to a mixture of organophosphorus pesticides (OP) because these alterations have been proposed to compromise male fertility and offspring development. Chromatin susceptibility to in situ acid-induced denaturation structure was assessed by the sperm chromatin structure assay (SCSA). Urinary levels of alkylphosphates (DAP) were used to assess exposure. Diethylthiophosphate (DETP) was the most frequent OP metabolite found in urine samples indicating that compounds derived from thiophosphoric acid were mainly used. Chromatin structure was altered in most samples. About 75% of semen samples were classified as having poor fertility potential (>30% of Percentage of DNA Fragmentation Index [DFI%]), whereas individuals without OP occupational exposure showed average DFI% values of 9.9%. Most parameters of conventional semen analysis were within normality except for the presence of immature cells (IGC) in which 82% of the samples were above reference values. There were significant direct associations between urinary DETP concentrations and mean DFI and SD-DFI but marginally (P = 0.079) with DFI%, after adjustment for potential confounders, including IGC. This suggests that OP exposure alters sperm chromatin condensation, which could be reflected in an increased number of cells with greater susceptibility to DNA denaturation. This study showed that human sperm chromatin is a sensitive target to OP exposure and may contribute to adverse reproductive outcomes. Further studies on the relevance of protein phosphorylation as a possible mechanism by which OP alter sperm chromatin are required.

In vitro fertilizing capacity and chromatin condensation of deep frozen boar semen packaged in 0.5 and 5 ml straws

The effect of the straw volume employed for semen freezing was studied in 14 ejaculates from seven boars, by evaluating the viability, IVF capacity and chromatin state of spermatozoa. Frozen-thawed semen from 0.5 and 5 ml straws was compared to fresh semen. The chromatin condensation degree was determined by flow cytometry, using propidium iodide as fluorochrome, and the chromatin stability was evaluated by inducing its decondensation with SDS and EDTA. The results obtained for IVF, motility and normal apical ridge (NAR) were: 91.64, 78.14 and 81.47% sperm penetration, 80.78, 68.38 and 70.83% monospermy, 10.86, 9.76 and 10.64% polyspermy, 87.14, 50.71 and 47.86% motility, 79.14, 56.14 and 53.36% NAR, for fresh semen, thawed semen in 0.5 and 5 ml straws, respectively. Frozen-thawed spermatozoa showed significantly increased (P < 0.05) chromatin compactness compared to fresh spermatozoa (55.42, 48.41 and 47.08 fluorescence units (MIFU), for fresh semen, thawed semen in 0.5 and 5 ml straws, respectively). Chromatin was significantly more unstable (P < 0.05) in spermatozoa frozen in 0.5 ml straws (174.7 MIFU) compared to those frozen in 5 ml straws (155.53 MIFU) or to those in fresh semen (149.74 MIFU).

Comparison between human sperm preservation medium and TEST-yolk buffer on protecting chromatin and morphology integrity of human spermatozoa in fertile and subfertile men after freeze-thawing procedure

The aim of this study was to identify the detrimental effect of the freeze-thaw process on chromatin integrity and morphology of human spermatozoa, and to determine whether human sperm preservation medium (HSPM) or TEST-yolk buffer (TYB) offers a better protection to spermatozoa from cryodamage after the freeze-thaw procedure. Thirty-five semen samples obtained from couples childless because of male factor infertility (subfertile men, group 1) and 25 semen samples from healthy, normal volunteers of proven fertility (group 2) were included in the study. Each semen sample was divided into 2 parts, the first part was mixed with HSPM and the other with TYB (1:1), and frozen with a controlled slow-stage freezer, before plunging into liquid nitrogen. Twelve smears from each semen sample were made before (n = 4) and after (n = 8) the freeze-thaw process. Chromatin structure was evaluated after staining using the acridine orange (AO) test, whereas morphology was analyzed according to strict criteria. The mean percentage of spermatozoa that exhibited normal morphology and intact chromatin structure was decreased after freeze-thaw in all samples treated with HSPM or TYB in comparison with the value observed in the native semen samples of both groups. However, TYB preserved chromatin and morphology significantly better than HSPM did (9.3% +/- 5.6% and 88.7% +/- 11.2% vs. 7.8% +/- 4.2% and 85.5% +/- 12.5%, respectively). Therefore, TYB could be recommended as a first choice cryoprotectant for semen preservation in order to avoid extra chromatin structure damage and morphology alterations of spermatozoa not only for patients pursuing assisted reproduction, but also for donor samples.

Poor quality of sperm as it affects repeated early pregnancy loss

A study was carried out to determine whether males contribute to repeated early pregnancy loss. Semen samples were analyzed from proven-fertile men (n = 51 group I) and from men whose partners presented with early pregnancy loss (>3 first trimester abortions, n = 32 group II). Routine analysis, sperm function tests, and ultrastructural studies of sperms were carried out. Female factor could be identified in 25 (78%) couples, and in 7 (22%) no cause either male or female could be identified and the semen analysis was normal. Percent morphologically normal did not differ significantly between the groups, but increased sperm head abnormalities were seen. The functional tests were all normal except for a significant decrease in the capacity of nuclear chromatin to decondense in vitro. The ultrastructural studies showed defects of chromatin condensation and irregular nuclei with vacuoles. This study points to the loss of chromatin integrity as a possible contributing factor from males to early pregnancy loss.

Use of acridine orange to evaluate chromatin integrity of human spermatozoa in different groups of infertile men

To study the sperm chromatin compactness various methods, such as acidic aniline blue or acridine orange staining, have been applied. Due to its metachromatic properties, acridine orange dye fluoresces green with double- and red with single-stranded DNA. Samples (n = 181) were evaluated and grouped as follows: group I, normal recently fertile; group II, male having female partner with repeated early pregnancy loss; group III, male with varicocele; and group IV in-vitro fertilization and intrauterine insemination failures. Routine semen analyses were carried out in all the cases. Amorphous particulate matter as observed under phase contrast microscope was graded on the scale of nil to +4. Fixed smears were stained with an aqueous solution of acridine orange and viewed under a fluorescence microscope. Two hundred cells were counted and the percentage of fluorescence calculated. Groups II, III and IV exhibited significantly low green fluorescence compared with the control group. The study also indicates that increased amorphous particulate matter (indicating infection) might be one of the contributing factors to lower acridine orange stainability. Thus acridine orange staining can be used to evaluate the integrity of the nucleus, disorders of which can cause unexplained infertility or lower fertilization potential that may go undetected by routine analysis.

Relationship between abnormal sperm chromatin packing and IVF results

This study was initiated to determine the relationship between the fertilizing potential of spermatozoa and abnormalities in the compact packing of their chromatin which occurs in the final stage of male germ cell differentiation. Chromatin packing involves disulphide bridge covalent cross-linking. The degree of packing was determined from the accessibility of DNA to a fluorescent dye, ethidium bromide, following detergent treatment of the spermatozoa. The amount of dye bound was determined by flow cytometry in the presence or absence of heparin, a polyanion which removes only non-disulphide bridge-linked proteins. The results of a number of different sperm samples were compared with their results following in-vitro fertilization, and a relationship between disordered sperm chromatin packing and rates of embryo cleavage was observed. This study suggests that abnormal chromatin packing in spermatozoa may contribute to male fertility.

Differences in the DNA-stainability of spermatozoa from fertile and suspected infertile men

The aim of this work was to determine whether it is possible to distinguish between fertile (control group, already fathers) and infertile men (suspected infertility), by comparing the fluorescence intensity of the sperm-DNA after incubation with appropriate dyes. First we examined two different DNA-specific dyes (DAPI and YOYO-1) using bull spermatozoa. Based on good results in immunohistochemical applications, YOYO-1 was chosen for further work. The fluorescence-intensity of 200 single, morphologically normal spermatozoa in each semen sample were measured in a cytophotometer, means + SD determined and histograms delineated. Of 20 samples from the control group, 17 had markedly higher fluorescence-intensity than did 7/15 of the suspected infertile men. It is concluded that the DNA of the latter seven samples was less accessible to the dye than was the DNA of the control group. There are cases of infertility known in which there is loss of one or more of the DNA-binding proteins, which in spermatozoa are mainly (85%) protamines. The relationship between the stainability of the sperm-DNA and the packaging with DNA-binding proteins is discussed. Two of the histograms showed abnormalities in the distribution of the fluorescence-intensities, one sample was extremely fragile and most of the sperm lysed during the staining-procedure. Five samples showed normal histograms in comparison with the control group.

Evidence for decreasing quality of semen during past 50 years

OBJECTIVE

To investigate whether semen quality has changed during the past 50 years.

DESIGN

Review of publications on semen quality in men without a history of infertility selected by means of Cumulated Index Medicus and Current List (1930-1965) and MEDLINE Silver Platter database (1966-August 1991).

SUBJECTS

14,947 men included in a total of 61 papers published between 1938 and 1991.

MAIN OUTCOME MEASURES

Mean sperm density and mean seminal volume.

RESULTS

Linear regression of data weighted by number of men in each study showed a significant decrease in mean sperm count from 113 x 10(6)/ml in 1940 to 66 x 10(6)/ml in 1990 (p < 0.0001) and in seminal volume from 3.40 ml to 2.75 ml (p = 0.027), indicating an even more pronounced decrease in sperm production than expressed by the decline in sperm density.

CONCLUSIONS

There has been a genuine decline in semen quality over the past 50 years. As male fertility is to some extent correlated with sperm count the results may reflect an overall reduction in male fertility. The biological significance of these changes is emphasised by a concomitant increase in the incidence of genitourinary abnormalities such as testicular cancer and possibly also cryptorchidism and hypospadias, suggesting a growing impact of factors with serious effects on male gonadal function.

Effect of different culture techniques used to induce capacitation on the chromatin stability of human sperm

To validate an in-vitro bioassay for assessing chromatin stability of human sperm, 38 semen samples from infertile men were studied using sodium dodecyl sulphate, an anionic detergent which disorganizes only the cytoplasmic membrane. Assay sensitivity was 50 sperm, whilst the within- and between-assay variation, and the between-observer variation were found to be within the accepted range for this type of bioassay. The influence of different in-vitro treatments currently used in some clinical assisted fertilization programmes was evaluated: a destabilizing effect occurred in Grade I (stable) and Grade III (swollen) sperm. In the former, all treatments reduced stable sperm; in the latter, a significant (P less than 0.001) increase in swollen sperm was shown with two methods that used Ham's F-10 as culture medium. Different chromatin patterns found in the treated sperm suggest the possibility that the recovered samples could be modified compared to their status at the time of isolation.

Techniques for selection of normal-chromatin sperm preparations

Various sperm preparation techniques, swim-up and Percoll gradient, and the newly developed Wang's tube system, were evaluated for their ability to recover normal-chromatin sperm. Twenty human semen samples, collected by masturbation, were studied simultaneously with the three methods. Analysis by Acridine orange fluorescence test was performed on all samples. Pretreated semen contains 58 +/- 22% green sperm (fertile/normal). Treatment with Wang's tube system resulted in 99 +/- 1.0% green sperm; Percoll gradient, 78 +/- 11%; and swim-up technique, 72 +/- 15%. It would appear that Wang's tube system yields a high-quality sperm preparation with enough concentration, very active forward progression, and greatly improved sperm morphology, while containing normal-chromatin, double-stranded DNA.