Iatrogenic genetic damage of spermatozoa

The efficacy of novel centrifugation-free sperm selection (Io-Lix) on sperm parameters and ICSI reproductive outcomes

RESEARCH QUESTION

What is the effect of a novel non-centrifugation method (Io-Lix) of sperm selection on sperm parameters and intracytoplasmic sperm injection (ICSI) reproductive outcomes?

DESIGN

This pilot study elevated the capacity of the Io-Lix sperm selection protocol to improve sperm parameters (concentration, motility and sperm DNA fragmentation) of the neat ejaculate. Once established, the reproductive outcomes of Io-Lix selected spermatozoa were used for autologous and donor oocyte ICSI programmes and their efficacy compared with those using conventional swim-up.

RESULTS

Io-Lix sperm selection resulted in lower sperm concentration yield (P < 0.001) and sperm DNA fragmentation (P < 0.001) but higher sperm motility (P < 0.001) when compared with spermatozoa in the neat ejaculate. When compared with swim-up sperm selection the Io-Lix protocol resulted in a 14.7% (P = 0.028) increase in pregnancy rate and 16.3% (P = 0.047) reduction in miscarriages in the autologous ICSI programme. A similar comparison of sperm selection procedures employed for a donor oocyte ICSI programme showed no difference in terms of their respective reproductive outcomes.

CONCLUSIONS

The Io-Lix sperm selection protocol resulted in improved pregnancy rate and reduction in miscarriage when applied to autologous ICSI, which was attributed to a reduction in the proportion of spermatozoa with DNA damage post-selection. A similar finding was not apparent in the donor oocyte programme, which may be associated with the capacity of the donor oocyte to repair sperm DNA post-syngamy.

Effect of Tris-extender supplemented with a combination of turmeric and ethylene glycol on buffalo bull semen freezability and in vivo fertility

The objective of this study was to evaluate the effect of Tris-extender supplemented with a combination of turmeric and ethylene glycol on buffalo bull semen preservability and in vivo fertility. Five tubes (each contain 5 ml Tris-citric acid-fructose yolk, TCFY). The first tube contains turmeric extract and ethylene glycol and kept as a control. The other four tubes contain 1.5% ethylene glycol plus turmeric extract as follows: 100 μl/5 ml, 200 μl/5 ml, 300 μl/5 ml, and 400 μl/5 ml v/v). Pooled bull semen was added to the Tris extender and to Tris turmeric ethylene glycol. Extended semen was subjected to semen freezing protocol. Semen assessment was carried out. In Tris turmeric ethylene glycol post-cooling, sperm motility and alive sperms were significantly higher in the first concentration of Tris turmeric ethylene glycol (TTE₁), sperm abnormalities were significantly lower in TTE₁ and TTE₂, and sperm membrane integrity (HOST) was significantly higher in TTE₁ and acrosome percent was significantly higher in TTE₁, TTE₂, and TTE₄ if compared to the control. Post-thawing, sperm motility was significantly higher in TTE₁ as compared to the control and other concentrations of TE. All concentrations of TE were significantly higher in sperm membrane integrity (HOST) as relative to the control. Alive sperms were kept in TTE₁ as the control. Acrosome percent was kept in most concentrations as the control. It is concluded that, in cooled and post-thawed semen, the first concentration (TTE₁) gave the best sperm quality and conception rate.

Equivalent seminal characteristics in human and stallion at first and second ejaculated fractions

Sperm quality was assessed in normozoospermic human (n = 10) and Spanish breed stallion (n = 10) after sperm fractionation during ejaculation. The first ejaculated fraction was separated from the second. A third sample was reconstituted using equivalent proportion of both fractions (RAW). Fraction 1, Fraction 2 and RAW semen were incubated for 30 min at 37°C to homogenise the impact of iatrogenic damage between both species. Sperm concentration, motility and sperm DNA damage were assessed in each fraction and RAW semen. The results showed two important facts: (i) spermatozoa confined at Fraction 1 exhibit superior parameters than those included at Fraction 2 in both species, and (ii) there is a certain level of concordance between species in the proportion of benefit observed when Fraction 1 is compared to RAW semen. Altogether, these results call into question whether the standard practice of whole ejaculate collection can be considered the best strategy when using male gametes for artificial insemination. In fact, the reconstituted RAW semen exhibits poorer semen characteristics than those found in Fraction 1.

Causes and consequences of oxidative stress in spermatozoa

Spermatozoa are highly vulnerable to oxidative attack because they lack significant antioxidant protection due to the limited volume and restricted distribution of cytoplasmic space in which to house an appropriate armoury of defensive enzymes. In particular, sperm membrane lipids are susceptible to oxidative stress because they abound in significant amounts of polyunsaturated fatty acids. Susceptibility to oxidative attack is further exacerbated by the fact that these cells actively generate reactive oxygen species (ROS) in order to drive the increase in tyrosine phosphorylation associated with sperm capacitation. However, this positive role for ROS is reversed when spermatozoa are stressed. Under these conditions, they default to an intrinsic apoptotic pathway characterised by mitochondrial ROS generation, loss of mitochondrial membrane potential, caspase activation, phosphatidylserine exposure and oxidative DNA damage. In responding to oxidative stress, spermatozoa only possess the first enzyme in the base excision repair pathway, 8-oxoguanine DNA glycosylase. This enzyme catalyses the formation of abasic sites, thereby destabilising the DNA backbone and generating strand breaks. Because oxidative damage to sperm DNA is associated with both miscarriage and developmental abnormalities in the offspring, strategies for the amelioration of such stress, including the development of effective antioxidant formulations, are becoming increasingly urgent.