Association between body mass index and sperm quality and sperm DNA integrity. A large population study.

This study aimed to analyse whether the functional quality of spermatozoa is associated with body mass index (BMI). Semen samples were obtained from 1824 men undergoing fertility evaluation/treatment. Semen analysis was performed using World Health Organization (WHO) criteria, and morphology was evaluated with the motile sperm organelle morphology examination (MSOME). The percentages of sperm DNA fragmentation (using TdT (terminal deoxynucleotidyl transferase)-mediated dUTP nick-end labelling (TUNEL) assays), sperm chromatin packaging/underprotamination (using chromomycin A3/CMA3 ), mitochondrial damage (using MitoTracker Green) and apoptosis (using annexin V) were also assessed. At least 200 spermatozoa were examined in each evaluation. The following BMI values were used as cut-off points: ≤24.9 kg/m2 , 25-29.9 kg/m2 (overweight) and ≥30 kg/m2 (obese). High BMI negatively affects sperm concentration, vitality, motility and morphology (p < .05). Conversely, high BMI does not seem to be associated with impaired sperm DNA integrity, as assessed by DNA fragmentation, sperm protamination and sperm apoptosis (p > .05). However, increased BMI is associated with increased mitochondrial damage in spermatozoa (p < .05). In conclusion, given the adverse consequences of obesity and the possible effect of male BMI on assisted reproduction technology (ART) outcomes, the benefits of weight reduction should be discussed when counselling couples interested in fertility treatment.

Large nuclear vacuoles are indicative of abnormal chromatin packaging in human spermatozoa.

The aim of this investigation was to determine the presence of abnormal sperm chromatin packaging in spermatozoa with large nuclear vacuoles (LNV) selected via high magnification by analysing the pattern of chromomycin A3 (CMA3) staining. A prospective observational study was designed to analyse semen samples obtained from 66 men undergoing infertility diagnosis and treatment. The numbers of cells with normal (dull yellow staining of the sperm head/CMA3-negative) and abnormal (bright yellow fluorescence of the sperm head/CMA3-positive) chromatin packaging were determined on slides with normal and LNV spermatozoa. The presence of bright yellow fluorescence (CMA3-positive) was significantly higher (p < 0.0001) in spermatozoa with LNV than in normal spermatozoa (719/1351; 53.2% vs. 337/835; 40.3%, respectively), reflecting a higher percentage of abnormal chromatin packaging in spermatozoa with large LNV. Our data support the hypothesis that the presence of LNV reflects the presence of abnormal chromatin packaging, which may facilitate sperm DNA damage. As sperm nuclear vacuoles are evaluated more precisely at high magnifications using motile sperm organelle morphology examination (MSOME), the present results support the use of high-magnification sperm selection for intracytoplasmic sperm injection (ICSI).

Relationship between DNA damage and sperm head birefringence.

Birefringence or double refraction is the decomposition of a ray of light into two rays when it passes through an anisotropic material such as quartz. Sperm cells have been demonstrated to be optically anisotropic. The objective of this study was to evaluate the relationship between the pattern of human sperm head birefringence (SHBF) and DNA damage. A total of 26 patients with normal semen were included. DNA damage (fragmentation and denaturation) was evaluated in the sperm head in the context of birefringence, both total (SHBF-T) and partial (SHBF-P), by terminal deoxyribonucleotidyl transferase (TdT)-mediated dUDP nick-end labelling assay and acridine orange fluorescence, respectively. Positive DNA fragmentation in spermatozoa with SHBF-T (205/1053; 19.5%) was significantly higher (P<0.0001) than in spermatozoa that presented SHBF-P (60/820; 7.3%). However, the percentage of denatured DNA in spermatozoa with SHBF-T (824/1256; 65.6%) was not significantly different from the ones with SHBF-P (666/1009; 66.0%). In conclusion, the data support a positive relationship between spermatozoa with total SHBF in their head and increased DNA fragmentation.

Significance of extruded nuclear chromatin (regional nuclear shape malformation) in human spermatozoa: implications for ICSI.

The aim of this study was to determine the extent of DNA fragmentation and the presence of denatured single-strand or normal double-strand DNA in spermatozoa with extruded nuclear chromatin (ENC) selected by high magnification. Fresh semen samples from 55 patients were prepared by discontinuous isolate concentration gradient. Spermatozoa with normal nucleus (NN) and ENC were selected at 8400× magnification and placed on different slides. DNA fragmentation was determined by TUNEL assay. Denatured and double-stranded DNA was identified by the acridine orange fluorescence method. DNA fragmentation was not significantly different (p = 0.86) between spermatozoa with ENC (19.6%) and those with NN (20%). However, the percentage of spermatozoa with detectable denatured-stranded DNA in the ENC spermatozoon group (59.1%) was significantly higher (p < 0.0001) than in the NN group (44.9%). The high level of denatured DNA in spermatozoa with ENC suggests premature decondensation and disaggregation of sperm chromatin fibres. The results show an association between ENC and DNA damage in spermatozoa, and support the routine morphological selection and injection of motile spermatozoa at high-magnification intracytoplasmic sperm injection.