Cytoplasmic lipid droplets and mitochondrial distribution in equine oocytes: Implications on oocyte maturation, fertilization and developmental competence after ICSI.
Abstract: Lipid droplets (LDs) and mitochondria in the ooplasm are essential for energy production required for maturation, fertilization and embryo development. This study investigates the correlations between cytoplasmic LDs polar aggregation and: (1) nuclear maturation (Experiment 1); (2) mitochondrial (mt) distribution pattern and localization (Experiment 2); (3) fertilization and embryonic development after intracytoplasmic sperm injection (ICSI; Experiment 3) in equine oocytes recovered from slaughtered mares and matured in vitro. Morphologically normal oocytes were selected after culture and categorized as having polar (P) aggregation or uniform (U) distribution of LDs. In Experiment 1, the maturation rate was significantly higher in P compared with U oocytes (69%, 40/58 vs. 32%, 13/41; P<0.001). In Experiment 2, it was observed that P and U oocytes showed heterogeneous mt distribution at comparable rates (68%, 25/37 vs. 50%, 2/4 for P and U respectively; NS). Moreover, only in 8/25 (32%) of P oocytes, LDs overlapped with mt aggregates in the area containing meiotic spindle. In Experiment 3, normal fertilization (51%, 19/37 vs. 60%, 6/10, for P and U) and cleavage rates (83%, 20/24 vs. 67%, 4/6, for P and U) did not differ between groups, also in oocytes with LDs located nearby the polar body. Overall, P aggregation of LDs was related to cumulus expansion at collection. In conclusion, in equine matured oocytes, P aggregation of LDs is related with cumulus expansion and nuclear maturation. However, it is not related with heterogeneous mt distribution and cannot be considered a predictive indicator for normal fertilization and embryo development.
Publication Date: 2009-01-23 PubMed ID: 19167745DOI: 10.1016/j.theriogenology.2008.12.002Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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This research article is a study into how the distribution and aggregation patterns of lipid droplets (LDs) and mitochondria in horse egg cells (oocytes) can impact their maturation, fertilization, and embryonic development, particularly following a procedure known as intracytoplasmic sperm injection (ICSI).
Objective of the Research
- The aim of this study was to examine the relationship between the polar aggregation of lipid droplets (substances used for energy storage) in the cytoplasm and three aspects:
- Firstly, the process of nuclear maturation in the egg cells (oocytes) of horses.
- Secondly, the pattern and location of mitochondria (which produce energy in cells).
- Thirdly, the fertilization and embryonic development after intracytoplasmic sperm injection (ICSI), a treatment for infertility.
Methodology
- Oocytes were harvested from slaughtered mares and matured in a laboratory setting. They selected those that were shaped normally and divided them according to whether they had a polar (concentrated in one area) or uniform (spread evenly) distribution of lipid droplets.
- They then performed three experiments focused on nuclear maturation, mitochondrial distribution, and the outcome of ICSI.
Findings
- Experiment 1: They found that the rate of maturation was higher in oocytes with polar aggregation of lipid droplets (69%) compared to those with a uniform distribution (32%).
- Experiment 2: Oocytes with both polar and uniform lipid droplet distribution showed an inconsistent mitochondrial distribution at similar rates. Interestingly, in only 32% of oocytes with polar aggregation, lipid droplets overlapped with mitochondrial aggregations in the area containing the meiotic spindle (which helps in cell division).
- Experiment 3: The rates of normal fertilization and cell division (cleavage) did not differ significantly between oocytes with polar and uniform lipid droplet distribution, even when lipid droplets were located close to the polar body (part of the egg cell that contains half the genetic material).
- Finally, they observed that the polar aggregation of lipid droplets was associated with the expansion of surrounding cells called the cumulus at the time of collection.
Conclusion
- Overall, while the polar aggregation of lipid droplets relates to the expansion of cumulus cells and nuclear maturation of horse egg cells, it does not seem to be linked with irregular mitochondrial distribution.
- This aggregation as such, cannot be used to predict successful fertilization or embryonic development after ICSI.
Cite This Article
APA
Ambruosi B, Lacalandra GM, Iorga AI, De Santis T, Mugnier S, Matarrese R, Goudet G, Dell'aquila ME.
(2009).
Cytoplasmic lipid droplets and mitochondrial distribution in equine oocytes: Implications on oocyte maturation, fertilization and developmental competence after ICSI.
Theriogenology, 71(7), 1093-1104.
https://doi.org/10.1016/j.theriogenology.2008.12.002 Publication
Researcher Affiliations
- Department of Animal Production, University of Bari, Strada Provinciale per Casamassima km 3. 70010 Valenzano, Bari, Italy. barbara.ambruosi@hotmail.it
MeSH Terms
- Animals
- Cytoplasm / chemistry
- Cytoplasm / metabolism
- Embryonic Development / physiology
- Fertilization / physiology
- Horses / embryology
- Lipids / analysis
- Mitochondria / physiology
- Oocytes / cytology
- Oocytes / physiology
- Sperm Injections, Intracytoplasmic / veterinary
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