Sperm DNA fragmentation and oxidation are independent of malondialdheyde

Abstract

Background: There is clinical evidence to show that sperm DNA damage could be a marker of sperm quality and extensive data exist on the relationship between DNA damage and male fertility status. Detecting such damage in sperm could provide new elements besides semen parameters in diagnosing male infertility. We aimed to assess sperm DNA fragmentation and oxidation and to study the association between these two markers, routine semen parameters and malondialdehyde formation.

Methods: Semen samples from 55 men attending the Histology-Embryology Laboratory of Sfax Faculty of Medicine, Tunisia, for semen investigations were analysed for sperm DNA fragmentation and oxidation using flow cytometry. The Sperm was also assessed spectrophotometrically for malondialdehyde formation.

Results: Within the studied group, 21 patients were nonasthenozoospermic (sperm motility ≥ 50%) and 34 patients were considered asthenozoospermic (sperm motility < 50%). A positive correlation was found between sperm DNA fragmentation and oxidation (p = 0.01; r = 0.33). We also found a negative correlation between sperm DNA fragmentation and some sperm parameters: total motility (p = 0.001; r = -0.43), rapid progressive motility (type a motility) (p = 0.04; r = -0.27), slow progressive motility (type b motility) (p = 0.03; r = -0.28), and vitality (p < 0.001; r = -0.65). Sperm DNA fragmentation was positively correlated with coiled tail (p = 0.01; r = 0.34). The two parameters that were found to be correlated with oxidative DNA damage were leucocytes concentrations (p = 0.01; r = 0.38) and broken neck (p = 0.02; r = 0.29). Sperm MDA levels were negatively correlated with sperm concentration (p < 0.001; r = -0.57), total motility (p = 0.01; r = -0.35) and type a motility (p = 0.03; r = -0.32); but not correlated with DNA fragmentation and DNA oxidation.

Conclusions: Our results support the evidence that oxidative stress plays a key role in inducing DNA damage; but nuclear alterations and malondialdehyde don't seem to be synchronous.

Figure 1

TdT (terminal deoxynucleotidyltransferase)-mediated dUTP nick-end labeling (TUNEL) assay of spermatozoa. Histograms show: (A) negative control with 1.35% TUNEL positive cells. (B) Positive control (spermatozoa treated with DNaseI) with 90.2% TUNEL positive cells. (C) Semen sample of one patient with 21.4% TUNEL positive cells. M: window adjusted to detect the percentage of TUNEL positive cells.

Figure 2

Flow cytometric 8-oxoguanine detection histograms. (A) Negative control with 1.95% FITC labelled cells. (B) Positive control with 96.3% FITC labelled cells. (C) Semen sample of one patient with 13.7% FITC labelled cells. M: window adjusted to detect the percentage of DNA oxidation in sperm cells.

Figure 3

Correlation between sperm DNA fragmentation and sperm DNA oxidation (n = 55).