Impact of time between repeated sperm freezing cycles on sperm quality

The effects of repeated freezing and thawing on bovine sperm morphometry and function

Refreezing the remaining genetic resources after in vitro fertilization (IVF) can conserve genetic materials. However, the precise damage inflicted by repeated freezing and thawing on bovine sperm and its underlying mechanism remain largely unexplored. Thus, this study investigates the impact of repeated freeze-thaw cycles on sperm. Our findings indicate that such cycles significantly reduce sperm viability and motility. Furthermore, the integrity of the sperm plasma membrane and acrosome is compromised during this process, exacerbating the advanced apoptosis triggered by oxidative stress. Additionally, transmission electron microscopy exposed severe damage to the plasma membranes of both the sperm head and tail. Notably, the "9 + 2" structure of the tail was disrupted, along with a significant decrease in the level of the axonemal protein DNAH10, leading to reduced sperm motility. IVF outcomes revealed that repeated freeze-thaw cycles considerably impair sperm fertilization capability, ultimately reducing the blastocyst rate. In summary, our research demonstrates that repeated freeze-thaw cycles lead to a decline in sperm viability and motility, attributed to oxidative stress-induced apoptosis and DNAH10-related dynamic deficiency. As a result, the utility of semen is compromised after repeated freezing.

Sperm parameters in Israeli transgender women before and after cryopreservation

BACKGROUND

The application of fertility preservation, initially intended for oncological patients prior to gonadotoxic treatment, has extended in recent years to transgender and gender-non-conforming individuals undergoing therapy for gender compatibility.

OBJECTIVES

To examine semen quality and survival in transgender women pursuing semen cryopreservation in the presence or absence of gender-affirming hormonal medication.

MATERIALS AND METHODS

In this retrospective cohort study, we reviewed data of 74 consecutive transgender women presenting for semen cryopreservation at a single center between 2000 and 2019. Semen parameters before and after cryopreservation were compared to a control group composed of 100 consecutive sperm bank donor candidates. A subgroup analysis of subjects who had used gender-affirming hormonal treatment was also performed.

RESULTS

Compared to the control group, transgender women had lower total sperm count (144.0 vs. 54.5 million, respectively, p < 0.001), lower sperm motility percentage (65.0% vs. 51.0%, respectively, p < 0.001), and lower total motile sperm count (94.0 vs. 27.0 million, respectively, p < 0.001). Values were further decreased in transgender women who had received hormonal treatment before sperm cryopreservation. Post-thawing motility rate remained lower in the transgender group compared to the control group (20.0% vs. 45.0%, respectively, p < 0.001), and the total motile count remained lower as well (2.7 vs. 9.0 million, respectively, p < 0.001). Following sperm cryopreservation, the post-thaw decreases in total motile sperm count were higher in the transgender group compared with the control group (91.5% vs. 90.0%). Further subdivision in the transgender group showed that the decrease in total motile sperm count was lower for transgender women who did not use gender-affirming hormonal treatment compared to those who did (-89.7% vs. -92.6%, respectively, p < 0.01).

DISCUSSION AND CONCLUSION

Sperm parameters in transgender women are poor compared to candidates for sperm donation representing the general population. Specimens collected after discontinuation of gender-affirming hormone treatments were further impaired. Moreover, post-thawing sperm total motile count, motility, and overall sperm survival were reduced in transgender women.