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Published on: July 6, 2022
An attempt to reduce polyspermic penetration in lamb oocytes
T Slavík1, M Libik, E Wierzchos
1Institute of Animal Physiology and Genetics, Libechov, Czech Republic. slavik@iapg.cas.cz
Folia Biologica
|May 26, 2005
Summary
High polyspermy in immature lamb oocytes reduces embryo potential. Supplementing maturation media with BSA or oviductal fluid improved monospermy, but a two-step maturation protocol did not significantly reduce polyspermy, indicating developmental imperfections.
Area of Science:
- Reproductive Biology
- Developmental Biology
- In Vitro Fertilization
Background:
- Polyspermy, the fertilization of an oocyte by multiple sperm, is a significant issue in in vitro fertilization (IVF) of ovine oocytes, particularly from prepubertal donors.
- This high incidence of polyspermy leads to reduced embryo developmental potential, hindering efficient assisted reproductive technologies in sheep.
Purpose of the Study:
- To investigate methods for producing lamb oocytes more resistant to polyspermy.
- To evaluate the effects of different maturation media supplements and a two-step maturation protocol on reducing polyspermy in prepubertal lamb oocytes.
Main Methods:
- Oocytes from prepubertal lambs (7-12 weeks) and adult donors were matured in vitro with various supplements including Bovine Serum Albumin (BSA), Oviductal Fluid (OF), Llama Serum (LS), Sheep Serum (SS), and Fetal Calf Serum (FCS).
- Fertilization was performed in vitro, and monospermic penetration rates were assessed.
- A two-step maturation protocol involving a 24-hour arrest using a cyclin-dependent kinase (cdk) inhibitor (BL-I) was employed to improve cytoplasmic maturation before assessing fertilization outcomes.
Main Results:
- Maturation media supplemented with BSA (3 mg/ml) and OF (20%) resulted in significantly higher monospermic penetration rates (63.9% and 55.8%, respectively) in prepubertal oocytes compared to LS, SS, or FCS.
- Oocytes from adult donors showed higher monospermy rates (78.7%) than prepubertal oocytes under identical conditions.
- The two-step maturation protocol, including cdk inhibitor-induced arrest, did not significantly alter monospermic penetration rates in either prepubertal or adult oocytes compared to controls, suggesting the arrest did not resolve the underlying issue.
Conclusions:
- High polyspermy in prepubertal lamb oocytes is likely due to inherent developmental imperfections.
- While optimizing culture media composition can improve monospermy rates, it cannot fully eliminate polyspermy.
- Prolonging the culture interval or using specific maturation protocols does not appear to resolve the fundamental issue of polyspermy in immature oocytes.
