Evaluation of sperm deoxyribonucleic acid (DNA) damage and effects on embryo development using a mouse cryptorchidism model

Rapid evolution and molecular convergence in cryptorchidism-related genes associated with inherently undescended testes in mammals

BACKGROUND

The mammalian testis is an important male exocrine gland and spermatozoa-producing organ that usually lies in extra-abdominal scrotums to provide a cooler environment for spermatogenesis and sperm storage. Testicles sometimes fail to descend, leading to cryptorchidism. However, certain groups of mammals possess inherently ascrotal testes (i.e. testes that do not descend completely or at all) that have the same physiological functions as completely descended scrotal testes. Although several anatomical and hormonal factors involved in testicular descent have been studied, there is still a paucity of comprehensive research on the genetic mechanisms underlying the evolution of testicular descent in mammals and how mammals with ascrotal testes maintain their reproductive health.

RESULTS

We performed integrative phenotypic and comparative genomic analyses of 380 cryptorchidism-related genes and found that the mammalian ascrotal testes trait is derived from an ancestral scrotal state. Rapidly evolving genes in ascrotal mammals were enriched in the Hedgehog pathway-which regulates Leydig cell differentiation and testosterone secretion-and muscle development. Moreover, some cryptorchidism-related genes in ascrotal mammals had undergone positive selection and contained specific mutations and indels. Genes harboring convergent/parallel amino acid substitutions between ascrotal mammals were enriched in GTPase functions.

CONCLUSIONS

Our results suggest that the scrotal testis is an ancestral state in mammals, and the ascrotal phenotype was derived multiple times in independent lineages. In addition, the adaptive evolution of genes involved in testicular descent and the development of the gubernaculum contributed to the evolution of ascrotal testes. Accurate DNA replication, the proper segregation of genetic material, and appropriate autophagy are the potential mechanisms for maintaining physiological normality during spermatogenesis in ascrotal mammals. Furthermore, the molecular convergence of GTPases is probably a mechanism in the ascrotal testes of different mammals. This study provides novel insights into the evolution of the testis and scrotum in mammals and contributes to a better understanding of the pathogenesis of cryptorchidism in humans.

An Update on Oxidative Damage to Spermatozoa and Oocytes

On the one hand, reactive oxygen species (ROS) are mandatory mediators for essential cellular functions including the function of germ cells (oocytes and spermatozoa) and thereby the fertilization process. However, the exposure of these cells to excessive levels of oxidative stress by too high levels of ROS or too low levels of antioxidative protection will render these cells dysfunctional thereby failing the fertilization process and causing couples to be infertile. Numerous causes are responsible for the delicate bodily redox system being out of balance and causing disease and infertility. Many of these causes are modifiable such as lifestyle factors like obesity, poor nutrition, heat stress, smoking, or alcohol abuse. Possible correctable measures include foremost lifestyle changes, but also supplementation with antioxidants to scavenge excessive ROS. However, this should only be done after careful examination of the patient and establishment of the individual bodily antioxidant needs. In addition, other corrective measures include sperm separation for assisted reproductive techniques. However, these techniques have to be carried out very carefully as they, if applied wrongly, bear risks of generating ROS damaging the germ cells and preventing fertilization.

GLP-1 Receptor Agonist Exenatide Attenuates the Detrimental Effects of Obesity on Inflammatory Profile in Testis and Sperm Quality in Mice

PROBLEM

Male obesity has been linked to subfecundity. This study is to investigate the effects of GLP-1 receptor (GLP-1R) agonist exenatide on sperm quality in high-fat diet (HFD)-induced obese mice.

METHOD OF STUDY

After 12 weeks of chow diet (CD) or HFD challenge, mice on HFD were allocated to either saline or exenatide (24 nmol/kg/day) interventions for 8 weeks. Sperm quality and the inflammatory profile of testis were compared among three groups.

RESULTS

Obesity reduced the quality of sperm and changed the inflammatory profile characterized by increased mRNA expression levels of TNF-α, MCP-1, and F4/80 in testis. Exenatide intervention reduced the expression of pro-inflammatory cytokines and improved the quality of sperm.

CONCLUSION

HFD-induced obesity leads to the impairment of sperm quality and increased inflammation of testis in mice, and the abnormal physiology can be attenuated by exenatide treatment. Exenatide treatment may bring additional profits to obese and diabetes men by improving sperm function.