DNA integrity of canine spermatozoa during chill storage assessed by the sperm chromatin dispersion test using bright-field or fluorescence microscopy

Effect of Procyanidin on Canine Sperm Quality during Chilled Storage

Procyanidin (PC) is a polyphenolic compound with antioxidant activity. The purpose of this study was to determine the influence of PC on canine sperm quality after 72 h of storage at 4 °C. The collected ejaculates were separated into four equal aliquots and treated with various concentrations of PC (0, 10, 30, and 50 μg/mL) in Tris-citric-fructose-egg yolk (TCFE) extender and stored at 4 °C for 72 h. The findings revealed that 30 μg/mL PC was the optimum concentration for significantly improving sperm motility (p < 0.05). Sperm samples treated with 30 μg/mL PC had substantially greater plasma membrane integrity, acrosome integrity, and mitochondrial membrane potential than the control group (p < 0.05). Furthermore, T-AOC and the expression levels of superoxide dismutase 1 (SOD1), catalase (CAT), and glutathione peroxidase 1 (GPx1) genes were significantly higher in sperm treated with 30 μg/mL PC than those in control (p < 0.05). In summary, this study discovered that adding PC to the TCFE extender enhanced sperm quality and that 30 μg/mL PC was the optimal concentration for canine sperm when stored at 4 °C.

Evaluation of DNA fragmentation in dog sperm using the sperm chromatin dispersion test

The study's objective was to adapt the Sperm Chromatin Dispersion (SCD) protocol to evaluate sperm DNA fragmentation and implement a fragmentation control in dogs. Correlation between DNA status and routine sperm parameters was also analysed. To adapt the SCD, two different mercaptoethanol (ME) concentrations were assayed (2.5 and 5%) in fourteen ejaculates from seven dogs and semen incubation with 0.3 M NaOH for 15 min at room temperature was assayed as a control for sperm DNA fragmentation. Data were analysed using a Mann-Whitney test and either Pearson's or Spearman's correlation. The selected ME concentration to use in the SCD test was 5%, as it produced the largest DNA dispersion halo while preserving the core nucleus structure. Four DNA halo patterns were identified: large dispersion halos, medium halos, small halos and nuclei without halos. Semen incubated with NaOH showed 100% sperm without halos (damaged DNA). A significant positive correlation was observed between sperm with fragmented DNA and sperm with coiled tails. Thus, it was possible to adapt the SCD protocol to evaluate dog sperm DNA fragmentation in raw semen without using a commercial kit and establish incubation with NaOH as a DNA fragmentation control. Only coiled tails showed correlation with DNA fragmentation.

Flow-cytometric analysis of membrane integrity of stallion sperm in the face of agglutination: the "zombie sperm" dilemma

PURPOSE

To define the effect of sperm agglutination, associated with incubation under capacitating conditions, on accuracy of membrane assessment via flow cytometry and to develop methods to mitigate that effect.

METHODS

Sperm motility was measured by CASA. Sperm were stained with PI-PSA or a novel method, LD-PSA, using fixable live/dead stain and cell dissociation treatment, before flow-cytometric analysis. Using LD-PSA, acrosome reaction and plasma membrane status were determined in equine sperm treated with 10 μm A23187 for 10 min, followed by 0, 1, or 2 h incubation in capacitating conditions.

RESULTS

Using PI-PSA, measured membrane integrity (MI; live sperm) was dramatically lower than was total motility (TMOT), indicating spurious results ("zombie sperm"). Sperm aggregates were largely of motile sperm. Loss of motility after A23187 treatment was associated with disaggregation and increased MI. On disaggregation using LD-PSA, MI rose, and MI then corresponded with TMOT. In equine sperm incubated after A23187 treatment, as the percentage of live acrosome-reacted sperm increased, TMOT decreased to near 0.

CONCLUSION

Flow cytometry assesses only individualized sperm; thus, agglutination of viable sperm alters recorded membrane integrity. As viable sperm become immotile, they individualize; therefore, factors that decrease motility, such as A23187, result in increased measured MI. Disaggregation before assessment allows more accurate determination of sperm membrane status; in this case we documented a mismatch between motility and live acrosome-reacted equine sperm that may relate to the poor repeatability of A23187 treatment for equine IVF. These findings are of profound value to future studies on sperm capacitation.

Dog sperm DNA: Raw semen evaluation with Toluidine blue stain

The toluidine blue (TB) stain has been used in different species to evaluate the degree of chromatin condensation. The objectives of this study were as follows: simplify the TB stain to evaluate sperm in canine raw semen, verify the staining patterns for this species using this simplified technique and establish a protocol for using dithiothreitol (DTT) as a positive control for TB staining in dogs. Twenty-one ejaculates were collected from 7 adult male dogs; semen was extended, fixed with ethanol 96° and stained with TB using 2 staining times: 15 and 30 min. In addition, 3 incubation times with 1% DTT were assayed (2, 5 and 30 min). Three staining patterns were established: light blue colouring (TB negative, normal chromatin condensation), light violet (TB intermediate, some degree of chromatin decondensation) and dark blue-violet (TB positive, high degree of chromatin decondensation). No significant differences (p > 0.05) were observed between the staining times (15 and 30 min) for any of the TB patterns. All DTT incubation times (2, 5 and 30 min) showed 100% sperm positive to TB. To conclude, it was possible to simplify the TB stain and determine the different patterns in canine spermatozoa. Also, DTT can be used both as a positive control for the stain and to evaluate individual susceptibility to decondensation in vitro.

Identification of sperm morphometric subpopulations in cooled-stored canine sperm and its relation with sperm DNA integrity

The aims of this study were to (i) identify different morphometric subpopulations in cooled-stored canine sperm and their patterns of distribution during cool-storage for up to 240 hr and (ii) determine whether or not morphometric sperm subpopulations (sP) are related to sperm DNA integrity. For that purpose, morphometric parameters were analysed by computer-assisted sperm analysis (CASA) and sperm DNA fragmentation (sDFi) using the sperm Halomax test. Four morphometric sperm heads subpopulations were identified: sP1 (large and rounded), sP2 (large and elongated), sP3 (small and rounded) and sP4 (small and elongated). sP1 was the most predominant subpopulation for up to 72 hr and thereafter sP3 increased progressively. sDFi increased after 48 hr of cool-storage. Although sP3 showed a positive correlation with sDFi, and both increased over time, it could not be ensured that only the sperm with fragmented DNA are accumulated in sP3. In conclusion, sP3 and DNA fragmentation increased progressively during cool-storage, becoming possible indicators of sperm damage. However, it cannot be concluded that sP3 only contains sperm with fragmented DNA.