Initial insights regarding the role of p53 in maintaining sperm DNA integrity following treatment of mice with ethylnitrosourea or cyclophosphamide

p53 Protein Evaluation on Spermatozoa DNA in Fertile and Infertile Males

Introduction and Objectives:

Protein p53 role in the spermatogenesis is demonstrated, it guarantees both the appropriate quality and quantity of mature spermatozoa. In this observational study we evaluate the eventual correlation between “corrected” p53 concentration on human spermatozoa DNA and male fertility potential.

Materials and Methods:

Our work is based on an observational study made of 169 male in a period between March 2012 and February 2017. The entire study group is composed by 208 male partners aged between 26-38 years with ejaculate volume from 0.6 to 5.8 mL and heterogeneous seminal valuation: 86/208 (41,3%) normospermic; 19/208 (9,1%) mild oligospermic; 51/208 (24,5%) moderate oligospermic to; 52/208 (25,1%) with severe oligospermic. The “control” group A includes 39 male partners considered “fertile”, because we did the p53 “corrected” test on their spermatozoa after 28 ± 3,5 days from the positives of their partners pregnancy test (betaHCG> 400 m U/m L). The group B, subdivided in B1, B2 and B3, includes 169 male partners for a observational period of 60 months. This partners don't report previous conceptions, they aren't smokers, don't make use neither of alcohol nor drugs and don't present pathologic varicocele studied with ecoColorDoppler. They are all married or stable cohabitants from a period of 27-39 months and report to have frequent sex without protection with their partners. Determination of p53 procedure: To separate the spermatozoa from seminal fluid we utilized the Differex™ kit System and the DNA IQ™ kit (Promega). For the p53 test we used the direct DuoSet IC kit and quantitative (R&D System). The p53 values were corrected in respect to the spermatozoa concentration expressed in ng/millions of spermatozoa.

Results:

Group A (39 male) presents “correct” p53 values that vary from 0.35 to 3.20 ng/millions of spermatozoa and group B presents values that vary from 0.68 to 14.53. From group B (48 male) in the observational period we have recorded 21 pregnancies with initial “correct” p53 values that vary from a minimum of 0.84 to a maximum of 3.29. In the subgroup B1 we obtained 8 pregnancies from male partners with a “correct” p53 concentration included between 0.84 to 1.34. In the subgroup B2 we obtained 13 pregnancies from male partners with a “correct” p53 concentration included between 1.66 and 3.29. In the subgroup B3 (121 male) there weren't neither pregnancies nor miscarriages and “correct” p53 values were included between 3.58 and 14.53.

Conclusion:

The results show that the member of the group A with values of 'corrected' p53 between 0.35 and 3.20 were considered “Fertile”, although in the observational period 3 miscarriages happened for 3 partners. 36 partners on 39 (92,3%) had a p53 concentration inferior to 1.65, this value were considered as the extreme to identify this group. The member of the group B1 had “corrected” p53 concentration that were included in the group. In the group B2 were observe 13 pregnancies, so its member were considered “potentially fertile” In the group B3 (121 male) weren't observe neither pregnancies nor miscarriages, so its member were considered “potentially infertile”. If further studies confirm these data, we will consider the p53 test ELISA inspected in “correct” p53 as a new and accurate marker of the potential of male fertility.

TP53 gene Arg72Pro polymorphism and male infertility risk: A meta-analysis

To evaluate the association between TP53 codon72 polymorphism and male infertility risk. We conducted a search on Medline, Embase, Web of Science and CNKI up to April 30, 2017. Odds ratio (OR) and 95% confidence interval (95% CI) were used to assess the strength of the association. Seven studies including 1,818 cases and 2,278 controls met the inclusion criteria. The pooled results indicated that no significant association was observed between TP53 codon72 polymorphism and male infertility risk (G versus C: OR = 1.11, 95%CI = 0.94-1.32; GG versus CC: OR = 1.26, 95%CI = 0.90-1.78; GG versus GC+CC: OR = 1.16, 95%CI = 0.90-1.49; GG+GC versus CC: OR = 1.15, 95%CI = 0.88-1.49). In the subgroup analysis by ethnicity, significant association was observed between TP53 codon72 polymorphism and male infertility risk in non-Chinese (G versus C: OR = 1.47, 95%CI = 1.14-1.89), but not in Chinese population (G versus C: OR = 1.03, 95%CI = 0.87-1.22). In conclusion, this study suggested that TP53 codon72 polymorphism might be associated with an increased susceptibility to male infertility in non-Chinese population, but not in Chinese population. Studies with larger sample sizes and representative population-based cases and well-matched controls are needed to validate our results.

An miR-200 Cluster on Chromosome 23 Regulates Sperm Motility in Zebrafish

Besides its well-documented roles in cell proliferation, apoptosis, and carcinogenesis, the function of the p53-microRNA axis has been recently revealed in the reproductive system. Recent studies indicated that miR-200 family members are dysregulated in nonobstructive azoospermia patients, whereas their functions remain poorly documented. The aim of this study was to investigate the function of the miR-200 family on zebrafish testis development and sperm activity. There was no substantial difference in testis morphology and histology between wild-type (WT) and knockout zebrafish with deletion of miR-200 cluster on chromosome 6 (chr6-miR-200-KO) or on chromosome 23 (chr23-miR-200-KO). Interestingly, compared with WT zebrafish, the chr6-miR-200-KO zebrafish had no difference on sperm motility, whereas chr23-miR-200-KO zebrafish showed significantly improved sperm motility. Consistently, ectopic expression of miR-429a, miR-200a, and miR-200b, which are located in the miR-200 cluster on chromosome 23, significantly reduced motility traits of sperm. Several sperm motility-related genes, such as amh, wt1a, and srd5a2b have been confirmed as direct targets of miR-200s on chr23. 17α-ethynylestradiol (EE2) exposure resulted in upregulated expression of p53 and miR-429a in testis and impairment of sperm motility. Strikingly, in p53 mutant zebrafish testis, the expression levels of miR-200s on chr23 were significantly reduced and accompanied by a stimulation of sperm motility. Moreover, the upregulation of miR-429a associated with EE2 treatment was abolished in testis with p53 mutation. And the impairment of sperm activity by EE2 treatment was also eliminated when p53 was mutated. Together, our results reveal that miR-200 cluster on chromosome 23 controls sperm motility in a p53-dependent manner.

The Magea gene cluster regulates male germ cell apoptosis without affecting the fertility in mice

While apoptosis is essential for male germ cell development, improper activation of apoptosis in the testis can affect spermatogenesis and cause reproduction defects. Members of the MAGE-A (melanoma antigen family A) gene family are frequently clustered in mammalian genomes and are exclusively expressed in the testes of normal animals but abnormally activated in a wide variety of cancers. We investigated the potential roles of these genes in spermatogenesis by generating a mouse model with a 210-kb genomic deletion encompassing six members of the Magea gene cluster (Magea1, Magea2, Magea3, Magea5, Magea6 and Magea8). Male mice carrying the deletion displayed smaller testes from 2 months old with a marked increase in apoptotic germ cells in the first wave of spermatogenesis. Furthermore, we found that Magea genes prevented stress-induced spermatogenic apoptosis after N-ethyl-N-nitrosourea (ENU) treatment during the adult stage. Mechanistically, deletion of the Magea gene cluster resulted in a dramatic increase in apoptotic germ cells, predominantly spermatocytes, with activation of p53 and induction of Bax in the testes. These observations demonstrate that the Magea genes are crucial in maintaining normal testicular size and protecting germ cells from excessive apoptosis under genotoxic stress.

Ghrelin Prevents Cisplatin-Induced Testicular Damage by Facilitating Repair of DNA Double Strand Breaks Through Activation of p53 in Mice

Cisplatin administration induces DNA damage resulting in germ cell apoptosis and subsequent testicular atrophy. Although 50 percent of male cancer patients receiving cisplatin-based chemotherapy develop long-term secondary infertility, medical treatment to prevent spermatogenic failure after chemotherapy is not available. Under normal conditions, testicular p53 promotes cell cycle arrest, which allows time for DNA repair and reshuffling during meiosis. However, its role in the setting of cisplatin-induced infertility has not been studied. Ghrelin administration ameliorates the spermatogenic failure that follows cisplatin administration in mice, but the mechanisms mediating these effects have not been well established. The aim of the current study was to characterize the mechanisms of ghrelin and p53 action in the testis after cisplatin-induced testicular damage. Here we show that cisplatin induces germ cell damage through inhibition of p53-dependent DNA repair mechanisms involving gamma-H2AX and ataxia telangiectasia mutated protein kinase. As a result, testicular weight and sperm count and motility were decreased with an associated increase in sperm DNA damage. Ghrelin administration prevented these sequelae by restoring the normal expression of gamma-H2AX, ataxia telangiectasia mutated, and p53, which in turn allows repair of DNA double stranded breaks. In conclusion, these findings indicate that ghrelin has the potential to prevent or diminish infertility caused by cisplatin and other chemotherapeutic agents by restoring p53-dependent DNA repair mechanisms.

Quantitative evaluation of p53 as a new indicator of DNA damage in human spermatozoa

BACKGROUND

Sperm DNA integrity is considered an important parameter to assess seminal fluid quality and can be used as a predictive test of potential fertility. Amongst the various tests to determine sperm DNA integrity, one is the Acridine Orange test. Recent studies have demonstrated the importance of p53 in maintaining sperm DNA integrity. The aim of this study was to assess if a p53 ELISA assay could be a new indicator of DNA damage in human spermatozoa.

MATERIALS AND METHODS

103 human semen samples were evaluated using both Acridine Orange test and p53 ELISA and results were compared.

RESULTS

A clear correlation between the values measured by two methods was obtained.

CONCLUSIONS

If this hypothesis will be confirmed by further studies, the p53 ELISA assay could become a new and more precise indicator of DNA damage in human spermatozoa.