Fluorescent enzyme-based biosensor for sensitive analysis of DNA damage in cryopreserved sperm

The freeze-thaw process can induce irreversible structural and functional changes in human sperm, particularly sperm DNA damage. Selecting a more accurate and sensitive detection method for evaluating sperm DNA integrity is crucial. To accurately assess sperm DNA integrity following the freeze-thaw process and significantly improve the clinical and scientific utilization of cryopreserved sperm. In this study, we utilized a novel fluorescent biosensor, assisted by terminal deoxynucleotidyl transferase (TdT) and Endonuclease IV, to detect DNA breakpoints during sperm cryopreservation. We evaluated the biosensor's performance by comparing it with the conventional DNA fragmentation index (DFI) measured using sperm chromatin structure analysis (SCSA). The cryopreserved group exhibited a significantly higher sperm DFI compared to the fresh group. No significant difference was observed between the antioxidant group and the cryopreserved group. However, the new method revealed a significant reduction in the number of DNA breakpoints in the antioxidant group compared to the cryopreserved group. The novel biosensor demonstrated superior accuracy and effectiveness in assessing sperm DNA integrity during cryopreservation compared to the conventional SCSA method. We believe that the biosensor holds significant potential for widespread use in the field of reproductive medicine.

Long-term effect of cytotoxic treatments on sperm DNA fragmentation in patients affected by testicular germ cell tumor

INTRODUCTION

Testicular germ cell tumor is the most frequent neoplasia in men of reproductive age, with a 5-year survival rate of 95%. Antineoplastic treatments induce sperm DNA fragmentation, especially within the first year post-therapy. Data in the literature are heterogeneous concerning longer follow-up periods, and the large majority is limited to 2 years.

OBJECTIVE

To define the timing for the recovery of sperm DNA damage and the proportion of patients with severe DNA damage at 2 and 3 years from the end of therapy.

MATERIALS AND METHODS

Sperm DNA fragmentation was evaluated in 115 testicular germ cell tumor patients using terminal deoxynucleotidyl transferase dUTP nick end labeling assay coupled with flow cytometry before (T0 ) and 2 (T2 ) and 3 (T3 ) years post-treatment. Patients were divided based on the type of treatment: carboplatin, bleomycin-etoposide-cisplatin, and radiotherapy. For 24 patients, paired sperm DNA fragmentation data were available at all time-points (T0 -T2 -T3 ). Seventy-nine cancer-free, fertile normozoospermic men served as controls. Severe DNA damage was defined as the 95th percentile in controls (sperm DNA fragmentation = 50%).

RESULTS

Comparing patients versus controls, we observed: (i) no differences at T0 and T3 and (ii) significantly higher sperm DNA fragmentation levels (p < 0.05) at T2 in all treatment groups. Comparing pre- and post-therapy in the 115 patients, the median sperm DNA fragmentation values were higher in all groups at T2 , reaching significance (p < 0.05) only in the carboplatin group. While the median sperm DNA fragmentation values were also higher in the strictly paired cohort at T2 , about 50% of patients returned to baseline. The proportion of severe DNA damage in the entire cohort was 23.4% and 4.8% of patients at T2 and T3 , respectively.

DISCUSSION

Currently, testicular germ cell tumor patients are advised to wait 2 years post-therapy before seeking natural pregnancy. Our results suggest that this period may not be sufficient for all patients.

CONCLUSION

The analysis of sperm DNA fragmentation may represent a useful biomarker for pre-conception counseling following cancer treatment.

Human sperm parameter improvement associated with Ceratonia siliqua extract as a cryopreservation supplement after vitrification

OBJECTIVE

Given the destructive effects of oxidative stress on sperm structure, this study was conducted to investigate the antioxidant effects of different concentrations of Ceratonia siliqua plant extract on human sperm parameters after the freezing-thawing process.

METHODS

A total of 20 normozoospermic samples were frozen. Each sample was divided into two control groups (fresh and cryopreservation) and three cryopreservation experimental groups (containing C. siliqua extract at concentrations of 20, 30, and 40 μg/mL in the freezing extender). Motility, intracellular levels of reactive oxygen species (ROS), plasma membrane integrity (PMI), mitochondrial membrane potential (MMP), viability, and acrosome reaction parameters were evaluated.

RESULTS

Statistical analysis showed that the highest motility, viability, and PMI were associated with the 20 μg/mL concentration of C. siliqua extract. At all concentrations, intracellular ROS levels were significantly lower and the levels of MMP and the acrosome reaction were significantly higher than in the cryopreservation control group (p≤0.05).

CONCLUSION

C. siliqua extract supplements at concentrations of 20, 30, and 40 μg/mL improved sperm motility, viability, PMI, MMP, intracellular ROS, and the acrosome reaction.

Testicular and Haematological Cancer Induce Very High Levels of Sperm Oxidative Stress

Cancer impairs spermatogenesis, whereas results on sperm DNA integrity are controversial and no data are available about sperm oxidative stress. In cancer patients, we detected sperm DNA fragmentation (sDF) and both viable (ROS production in viable sperm fraction/viable spermatozoa) and total (ROS production in viable sperm fraction/total spermatozoa) oxidative stress. We found that cancer (22.50 (17.00-26.75)%, n = 85) increased sDF with respect to the control groups in both normozoospermic subfertile patients (NSP) (12.75 (8.63-14.88)%, n = 52, p < 0.001) and in healthy donors (HD) (8.50 (7.00-14.00)%, n = 19, p < 0.001). The induction of viable oxidative stress (n = 96) with cancer was even higher: 36.60 (24.05-58.65)% versus 11.10 (8.63-14.90)% in NSP (p < 0.001) and 9.60 (8.00-14.03)% in HD (p < 0.001). Similar, albeit lower, differences were found for total oxidative stress. SDF sharply correlated to viable oxidative stress when we considered all subjects (cancer patients and controls) (r = 0.591, p < 0.001, n = 134), but no correlation was found when only cancer patients were studied (r = 0.200; p > 0.05, n = 63). In conclusion, cancer significantly increases sDF and sperm oxidative stress levels. Additional mechanisms to oxidative attack might be responsible for increased sDF in cancer patients. Because sperm oxidative stress might affect the outcomes of sperm cryopreservation, of cancer treatments and of sperm epigenoma, the detection of oxidative stress could be of help in managing the reproductive issues of cancer patients.

Cryopreservation of Human Spermatozoa: Functional, Molecular and Clinical Aspects

Cryopreservation is an expanding strategy to allow not only fertility preservation for individuals who need such procedures because of gonadotoxic treatments, active duty in dangerous occupations or social reasons and gamete donation for couples where conception is denied, but also for animal breeding and preservation of endangered animal species. Despite the improvement in semen cryopreservation techniques and the worldwide expansion of semen banks, damage to spermatozoa and the consequent impairment of its functions still remain unsolved problems, conditioning the choice of the technique in assisted reproduction procedures. Although many studies have attempted to find solutions to limit sperm damage following cryopreservation and identify possible markers of damage susceptibility, active research in this field is still required in order to optimize the process. Here, we review the available evidence regarding structural, molecular and functional damage occurring in cryopreserved human spermatozoa and the possible strategies to prevent it and optimize the procedures. Finally, we review the results on assisted reproduction technique (ARTs) outcomes following the use of cryopreserved spermatozoa.

The outcome of IVF/ICSI cycles in male cancer patients: retrospective analysis of procedures from 2004 to 2018

Introduction

Fertility preservation is an important aspect of quality of life in oncological patients, and in men is achieved by semen cryopreservation prior to treatment. Results of in vitro fertilization (IVF) procedures in healthy infertile couples are comparable, regardless of whether fresh or cryopreserved semen is used, but are scarce in male oncological patients.

Patients and methods

We performed a retrospective analysis of IVF/intracytoplasmic sperm injection (IVF/ICSI) procedures in infertile couples where men had been treated for cancer in the past. We additionally compared the results of IVF/ICSI procedures with respect to the type of semen used (fresh, cryopreserved).

Results

We compared the success rates of 214 IVF/ICSI cycles performed in the years 2004–2018. Pregnancy (30.0% vs. 21.4%; p = 0.12) and live-birth rates (22.3% vs. 17.9%; p = 0.43) per oocyte aspiration were similar between the groups in fresh cycles; however embryo utilization (48.9% vs. 40.0%; p = 0.006) and embryo cryopreservation rates (17.3% vs. 12.7%; p = 0.048) were significantly higher in the cryopreserved semen group. The cumulative pregnancy rate (60.6% vs. 37.7%; p = 0.012) was significantly higher, and the live-birth rate (45.1% vs. 34.0%; p = 0.21) non-significantly higher, in the cryopreserved semen group.

Conclusions

The success of IVF/ICSI procedures in couples where the male partner was treated for cancer in the past are the same in terms of pregnancies and live-births in fresh cycles regardless of the type of semen used. However, embryo utilization and embryo cryopreservation rates are significantly higher when cryopreserved semen is used, leading to a significantly higher cumulative number of couples who achieved at least one pregnancy.

Adverse effects of in vitro manipulation of spermatozoa

Development of in vitro reproduction techniques has not only offered some infertile couples the possibility to have a child, it also revolutionized animal reproduction. Although in vitro reproduction techniques for humans or domestic and non-domestic animals have been designed to mimic in vivo conditions, modifications due to environmental effects or in vitro manipulation of gametes and embryos are unavoidable. For male gametes, in vitro manipulations include techniques to select spermatozoa, cryopreservation and other incubation procedures, during which spermatozoa may be exposed to oxidative stress and other insults that may damage their functions and DNA. The aim of this review is to provide an overview of key studies reporting sperm damage during in vitro manipulation, with particular focus on effects on DNA integrity, a fundamental factor for fertilization and transmission of paternal genetic information to offspring.

Inclusion of ovine enriched serum with vitamin E and polyunsaturated fatty acids in the freezing medium: a new strategy to improve human frozen-thawed sperm parameters

The objective was to evaluate the effect of inclusion of 2.5% and 5% ovine serum, enriched with vitamin E (Vit E) and fish oil (FO), in human sperm freezing medium. Serum samples were prepared from sixteen rams (n = 4) feeding on a without supplemented diet, and diets supplemented with Vit E, FO and Vit E + FO. Semen samples, from 60 normozoospermic men, were frozen in: (I) a commercial freezing medium (SpermFreeze™; control medium), (II) the commercial freezing medium containing foetal bovine serum, (III) the commercial freezing medium + nonenriched serum (serum group), (IV) the commercial freezing medium + Vit E enriched serum (Vit E group), (V) the commercial freezing medium + FO enriched serum (FO group) and (VI) the commercial freezing medium + Vit E + FO enriched serum (Vit E + FO group). Sperm total and progressive motility, morphology, viability and plasma membrane integrity were significantly higher (p ≤ .05) in Vit E and Vit E + FO groups compared with the control group. Mitochondrial membrane potential did not differ between treatments (p > .05). It was concluded that ovine serum enriched with vitamin E and vitamin E + FO improved the quality of human spermatozoa but enriched serum containing FO could not improve the sperm cryo-injuries.

Knockout serum replacement is an efficient serum substitute for cryopreservation of human spermatozoa

The freeze-thaw procedure causes irreversible structural and functional changes in human spermatozoa. In order to decrease the detrimental effects of cryopreservation and improve the quality of post-thawed spermatozoa, the constituents of the freezing solution attracted considerable attention. In this study, for the first time, we evaluated the efficacy of knockout serum replacement (KSR) as a substitute for human serum albumin (HSA) for cryopreservation of human spermatozoa. Twenty semen samples were collected from normozoospermic men and divided them into five equal groups. One of the aliquots was diluted with glycerol-based medium as a control group (CON). The other four aliquots were diluted with the sucrose solution containing 5% HSA (H5), 10% HSA (H10), 5% KSR (K5), and 10% KSR (K10). The diluted samples were frozen and preserved in liquid nitrogen. Post thawed sperm parameters including motion characteristics, viability, membrane integrity, mitochondrial activity, acrosome integrity and DNA intactness in all of the sucrose-based groups were comparable with glycerol-based medium. The replacement of HSA by 10% KSR in the freezing medium resulted in significantly higher post-thawed viability, acrosome integrity and DNA intactness compared with other sucrose-based groups. In conclusion, the addition of 10% KSR to the sucrose-based freezing solution improves the quality of post-thawed human spermatozoa and may have potential to develop chemically defined freezing medium.

Sperm DNA Damage in Cancer Patients

Fertility is a growing healthcare issue for a rising number of cancer survivors. In men, cancer itself and its treatment can negatively affect spermatogenesis by targeting the dividing spermatogonia and their cellular environment, ultimately leading to a reduction of testicular germ cells and sperm count. Experimental data and prospective longitudinal studies have shown that sperm production can recover after cancer treatment. But despite this, yet unpredictable, recovery in sperm production, cancer survivors are more at risk to produce sperm with aneuploidy, DNA damage, abnormal chromatin structure, and epigenetic defects even 2 years post-treatment. Sperm DNA alteration is of clinical concern, as these patients may father children or seek assisted reproduction technologies (ART) using gametes with damaged genome that could result in adverse progeny outcomes. Interestingly, large cohort studies revealed lower birth rate but no significant impact on the health of the children born from male cancer survivors (naturally or using ART). Nevertheless, a better understanding of how cocktail of chemotherapy and new anticancer agents affect spermatogenesis and sperm quality is needed to reduce side effects. Moreover, developing new fertility preservation strategies is essential as sperm cryopreservation before treatment is currently the only option but does not apply for prepubertal/young postpubertal patients.

Process and Pitfalls of Sperm Cryopreservation

Sperm cryopreservation has been utilized routinely for over 40 years to preserve fertility in men undergoing cancer therapy and allow conception for infertile couples. This article provides a concise and up-to-date review of the literature and covers the latest advances in sperm cryopreservation and its array of clinical indications. Over recent years, the scope of clinical indications used for sperm cryopreservation has expanded widely. Consequently, more patient groups are eligible for sperm freezing, requiring specialist resources and higher running costs. Although sperm cryopreservation prior to cancer therapy is readily available in many countries, referral rates by oncology specialists and levels of patient engagement with cryopreservation services are both reported as low. Furthermore, sperm banking continues to raise ethical issues such whether sperm donation should be anonymous and whether sperm can be utilized posthumously by the surviving partner without consent from the patient. This review focuses on the technological advances and ethical controversies in sperm cryopreservation, and how better understanding of these issues could lead to improved access to fertility preserving treatment for patients.