Telomere Length in Pig Sperm Is Related to In Vitro Embryo Development Outcomes

Telomere Dynamics in Livestock

Telomeres are repeated sequences of nucleotides at the end of chromosomes. They deteriorate across mitotic divisions of a cell. In Homo sapiens this process of lifetime reduction has been shown to correspond with aspects of organismal aging and exposure to stress or other insults. The early impetus to characterize telomere dynamics in livestock related to the concern that aged donor DNA would result in earlier cell senescence and overall aging in cloned animals. Telomere length investigations in dairy cows included breed effects, estimates of additive genetic control (heritability 0.12 to 0.46), and effects of external stressors on telomere degradation across animal life. Evaluation of telomeres with respect to aging has also been conducted in pigs and horses, and there are fewer reports of telomere biology in beef cattle, sheep, and goats. There were minimal associations of telomere length with animal productivity measures. Most, but not all, work in livestock has documented an inverse relationship between peripheral blood cell telomere length and age; that is, a longer telomere length was associated with younger age. Because livestock longevity affects productivity and profitability, the role of tissue-specific telomere attrition in aging may present alternative improvement strategies for genetic improvement while also providing translational biomedical knowledge.

Male Germ Cell Telomeres and Chemical Pollutants

In recent decades, male infertility has been correlated with the shortening of sperm telomeres. Telomeres regulate the reproductive lifespan by mediating the synapsis and homologous recombination of chromosomes during gametogenesis. They are composed of thousands of hexanucleotide DNA repeats (TTAGGG) that are coupled to specialized shelterin complex proteins and non-coding RNAs. Telomerase activity in male germ cells ensures that the telomere length is maintained at maximum levels during spermatogenesis, despite telomere shortening due to DNA replication or other genotoxic factors such as environmental pollutants. An emerging body of evidence has associated an exposure to pollutants with male infertility. Although telomeric DNA may be one of the important targets of environmental pollutants, only a few authors have considered it as a conventional parameter for sperm function. The aim of this review is to provide comprehensive and up-to-date data on the research carried out so far on the structure/function of telomeres in spermatogenesis and the influence of environmental pollutants on their functionality. The link between pollutant-induced oxidative stress and telomere length in germ cells is discussed.

Sperm Quality and Fertility of Livestock Animals

Recent research has focused on the understanding of the causes of subfertility observed in livestock species, evidencing that different factors could underlie this condition [...].

The Impact of Lifestyle on Sperm Function, Telomere Length, and IVF Outcomes

Many risk factors can potentially influence sperm quality. Telomeres confer stability on the chromosome and their dysfunction has been implicated in conditions such as cancer, aging, and lifestyle. The impact of lifestyle on sperm cell telomeres is unclear. The objectives of this study were to evaluate the impact of lifestyle behaviors on telomere length in sperm and to follow the correlation with pregnancy outcomes in patients undergoing in vitro fertilization (IVF). In this prospective observational study, sperm was analyzed for telomere length (TL). Men were asked to report lifestyle behaviors including occupation (physical or sedentary), smoking duration and amount, physical activity, dietary habits, and where they keep their cellular phone (bag, pants, or shirt pocket). Correlations among semen analysis, TL, men's habits, and embryo quality and pregnancy outcomes were evaluated. Among 34 patients recruited, 12 had longer TL and 13 shorter TL. Sperm motility was negatively correlated with TL (Pearson correlation = -.588, p = .002). Smoking adversely affected native sperm motility (53% motility in nonsmokers vs. 37% in smokers; p = .006). However, there was no significant impact on TL. The group with longer telomeres demonstrated significant association with healthy diet (10/12 vs. 6/13; p = .05) and a trend toward more sports activity, weekly (16/84 vs. 7/91; p = .04) compared with the shorter telomeres group. This study suggests that lifestyle, healthy diet, and sports activity are associated with long telomeres in sperm. Sperm quality is also influenced by patients' habits. The study strongly recommends maintaining a healthy lifestyle to preserve general health and fertility.

Sperm telomere length as a novel biomarker of male infertility and embryonic development: A systematic review and meta-analysis

BACKGROUND

Telomeres have an essential role in maintaining the integrity and stability of the human chromosomal genome and preserving essential DNA biological functions. Several articles have been published on the association of STL with male semen parameters and clinical pregnancy. The results, however, are either inconclusive or inconsistent. Therefore, this meta-analysis aimed to systematically assess the accuracy and clinical value of sperm telomere length (STL) as a new marker for diagnosing male infertility and predicting the quality of embryonic development.

METHODS

We performed a comprehensive systematic search for relevant publications in PubMed, the Cochrane Library, Web of Science, Embase, Scopus, and Ovid, from database build to August 2022. All experimental studies exploring the association of STL with male semen quality, male infertility, or embryonic development were included.

RESULTS

Overall, Twelve prospective observational cohort studies (1700 patients) were eligible for inclusion in the meta-analysis. The meta-analysis showed a positive linear correlation between STL and semen parameters. The optimal cut-off value for STL diagnosing male infertility was 1.0, with a sensitivity and specificity of 80%. Regarding STL and embryonic development, the clinical pregnancy rate was associated with longer STL, and there was no significant difference between the two groups regarding fertilization rate.

CONCLUSION

Our study showed that STL has good diagnostic and predictive value for male fertility and clinical pregnancy and could be used as a new biomarker for diagnosing male infertility and predicting embryonic development.

SYSTEMATIC REVIEW REGISTRATION

https://www.crd.york.ac.uk/PROSPERO/, identifier CRD42022303333.