Chemical activation of mammalian oocytes and its application in camelid reproductive biotechnologies: A review
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Dionet Keny Bellido-Quispe1, Irving Mitchell Laines Arcce2, César Augusto Pinzón-Osorio3
1Laboratório de Genômica Estrutural, Universidade Federal de Pelotas (UFPel), Pelotas, RS, Brazil.
Abstract:
Mammalian oocyte activation is a critical process occurring post-gamete fusion, marked by a sequence of cellular events initiated by an upsurge in intracellular Ca2+. This surge in calcium orchestrates the activation/deactivation of specific kinases, leading to the subsequent inactivation of MPF and MAPK activities, alongside PKC activation. Despite various attempts to induce artificial activation using distinct chemical compounds as Ca2+ inducers and/or Ca2+-independent agents, the outcomes have proven suboptimal. Notably, incomplete suppression of MPF and MAPK activities persists, necessitating a combination of different agents for enhanced efficiency. Moreover, the inherent specificity of activation methods for each species precludes straightforward extrapolation between them. Consequently, optimization of protocols for each species and for each technique, such as PA, ICSI, and SCNT, is required. Despite recent strides in camelid biotechnologies, the field has seen little advancement in chemical activation methods. Only a limited number of chemical agents have been explored, and the effects of many remain unknown. In ICSI, despite obtaining blastocysts with different chemical compounds that induce Ca2+ and calcium-independent increases, viable offspring have not been obtained. However, SCNT has exhibited varying outcomes, successfully yielding viable offspring with a reduced number of chemical activators. This article comprehensively reviews the current understanding of the physiological activation of oocytes and the molecular mechanisms underlying chemical activation in mammals. The aim is to transfer and apply this knowledge to camelid reproductive biotechnologies, with emphasis on chemical activation in PA, ICSI, and SCNT.
Insights
Mammalian oocyte activation requires precise calcium signaling. Current chemical methods for artificial activation, especially in camelids, are suboptimal and require species-specific optimization for assisted reproductive technologies.
Area of Science:
- Reproductive Biology
- Cellular Signaling
- Biotechnology
Background:
- Mammalian oocyte activation is a complex process initiated by intracellular calcium increase post-fertilization.
- This calcium surge regulates key kinases, including MPF, MAPK, and PKC, crucial for developmental progression.
- Existing artificial activation methods often yield suboptimal results, with incomplete suppression of critical kinase activities.
Purpose of the Study:
- To review the physiological and molecular mechanisms of mammalian oocyte activation.
- To evaluate the efficacy of current chemical activation strategies in assisted reproductive technologies (ART).
- To explore the application of this knowledge to advance camelid reproductive biotechnologies, focusing on chemical activation in Parthenogenesis Activation (PA), Intracytoplasmic Sperm Injection (ICSI), and SCNT.
Main Methods:
- Comprehensive literature review of mammalian oocyte activation.
- Analysis of chemical agents used for artificial oocyte activation (Ca2+-dependent and independent).
- Evaluation of success rates in PA, ICSI, and SCNT across different species, with a focus on camelids.
Main Results:
- Current chemical activation protocols are often species-specific and yield suboptimal outcomes, necessitating combined agents.
- In camelid ICSI, blastocyst development has been achieved, but viable offspring remain elusive.
- SCNT in camelids has shown more promise, with viable offspring produced using fewer chemical activators.
Conclusions:
- Optimization of chemical activation protocols is crucial for each species and ART technique (PA, ICSI, SCNT).
- Further research into novel chemical activators and their mechanisms is needed for camelid reproductive advancements.
- Bridging the knowledge gap between general mammalian oocyte activation and camelid-specific applications is essential for improving ART success rates.
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