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Fertility Preservation Through Oocyte Vitrification: Clinical and Laboratory Perspectives
Published on: September 16, 2021
Oocyte Vitrification Reduces its Capability to Repair Sperm DNA Fragmentation and Impairs Embryonic Development
Niloofar Khajedehi1,2, Rouhollah Fathi3, Vahid Akbarinejad4
1Department of Genetics, Reproductive Biomedicine Research Center, Royan Institute for Reproductive Biomedicine, ACECR, Tehran, Iran.
Abstract:
Oocytes play a crucial role in repairing sperm DNA damage, which can affect the next generation; however, certain factors can impair this ability. This study examined whether oocyte vitrification, a widely used method for fertility preservation, negatively affects repair ability. Male DBA/2 mice (n = 28) were injected with 101.60 µmol/100 g body weight of tert-Butyl hydroperoxide (tBHP) for 14 days to induce sperm DNA damage. Histological changes, sperm functions, and DNA fragmentation were assessed using the TUNEL assay. Cumulus-oocyte-complexes (COCs) of superovulated female DBA/2 mice (n = 28) were vitrified using the Cryotop method. Fresh and vitrified oocytes were then fertilized by tBHP-treated and untreated sperms, and subsequent embryonic development was monitored. Additionally, the expression of Mre11a, Rad51, Brca1, and Xrcc4 was assessed in resulting zygotes and blastocysts using real-time PCR. The sperm tBHP treatment reduced differentiated spermatogenic cells in the testicular tissue, sperm concentration, and motility, while increasing DNA fragmentation (P < 0.05). The fertilization rate was decreased in the tBHP-treated sperm-vitrified oocyte group (P < 0.05), and the two-cell rate diminished in tBHP-treated sperm-fresh and vitrified oocyte groups (P < 0.05). The four-cell to blastocyst rate decreased in the untreated sperm-vitrified oocyte and the tBHP-treated sperm-fresh and vitrified oocyte groups (P < 0.05), and the tBHP-treated sperm-vitrified oocyte groups had the lowest blastocyst rate. In zygotes, Brca1 was upregulated in the tBHP-treated sperm-vitrified oocyte group (P < 0.05). Also, in blastocysts, Rad51, Brca1, and Xrcc4 were significantly upregulated in the untreated sperm-vitrified oocytes group (P < 0.05). Damages to the oocyte due to vitrification can disrupt the repair of sperm DNA fragmentation and consequently impair the embryo development.
Insights
Oocyte vitrification may impair the ability to repair sperm DNA damage, negatively impacting embryo development. This fertility preservation technique can disrupt crucial DNA repair mechanisms, affecting reproductive outcomes.
Area of Science:
- Reproductive biology
- Developmental biology
- Genetics
Background:
- Oocytes are vital for repairing sperm DNA damage, ensuring genomic integrity for the next generation.
- Factors that impair oocyte DNA repair can have significant consequences for fertility and offspring health.
- Oocyte vitrification is a common fertility preservation method, but its impact on oocyte repair capacity is not fully understood.
Purpose of the Study:
- To investigate whether oocyte vitrification affects the oocyte's ability to repair sperm DNA damage.
- To assess the impact of vitrified oocytes and damaged sperm on subsequent embryonic development.
- To examine the expression of key DNA repair genes in response to sperm damage and oocyte vitrification.
Main Methods:
- Sperm DNA damage was induced in male DBA/2 mice using tert-Butyl hydroperoxide (tBHP).
- Cumulus-oocyte-complexes (COCs) from female DBA/2 mice were vitrified using the Cryotop method.
- Fresh and vitrified oocytes were fertilized with tBHP-treated and untreated sperm, and embryonic development was monitored.
- Expression of DNA repair genes (Mre11a, Rad51, Brca1, Xrcc4) was analyzed in zygotes and blastocysts via real-time PCR.
Main Results:
- tBHP treatment significantly increased sperm DNA fragmentation and reduced sperm quality.
- Fertilization and early embryonic development rates were reduced, particularly in the group using tBHP-treated sperm and vitrified oocytes.
- Vitrification of oocytes, especially when combined with damaged sperm, led to the lowest blastocyst rates.
- Expression of DNA repair genes (Brca1, Rad51, Xrcc4) was altered in zygotes and blastocysts, suggesting a disrupted repair response.
Conclusions:
- Oocyte vitrification can compromise the oocyte's capacity to repair sperm DNA fragmentation.
- Impaired DNA repair due to vitrification negatively affects embryonic development, especially when sperm DNA integrity is compromised.
- These findings highlight potential risks associated with using vitrified oocytes for fertility preservation when sperm quality is suboptimal.
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