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Plasma membrane and cytocortex alterations in frozen/thawed mouse embryos deprived of the zona pellucida
M Martí1, M Grossmann, J Santaló
1Departament de Biologia Cellular i Fisiologia, Universitat Autònoma de Barcelona, Spain.
Abstract:
We analyzed the morphological and ultrastructural abnormalities present in two-cell mouse embryos frozen/thawed without the zona pellucida (ZP). Transmission electron microscopy revealed that these embryos had plasma membrane abnormalities that were not observed in the embryos frozen/thawed with an intact ZP. The most frequent anomalies were a decreased number of microvilli with a nonhomogeneous distribution and showing an abnormal morphology and the presence of an increased number of vesicles in the periphery of the cell. The distribution of actin filaments, studied by fluorescence microscopy revealed alterations in both embryos, frozen/ thawed with ZP and embryos frozen/thawed without ZP: an increased staining in some regions of the peripheral actin band, discontinuities or gaps in the band, or the presence of a second actin band connected to the peripheral one.
Insights
Cryopreservation of mouse embryos without the zona pellucida (ZP) causes plasma membrane abnormalities. These include altered microvilli and actin filament distribution, impacting embryo viability.
Area of Science:
- Embryology
- Reproductive Biology
- Cell Biology
Background:
- Cryopreservation is crucial for assisted reproductive technologies.
- The zona pellucida (ZP) typically protects embryos during freezing and thawing.
- Understanding ZP-free cryopreservation effects on early embryos is vital.
Purpose of the Study:
- To investigate morphological and ultrastructural changes in two-cell mouse embryos after ZP-free cryopreservation.
- To identify specific plasma membrane and actin cytoskeleton alterations.
Main Methods:
- Transmission electron microscopy (TEM) for ultrastructural analysis.
- Fluorescence microscopy to study actin filament distribution.
- Comparison between embryos frozen with and without the ZP.
Main Results:
- ZP-free cryopreserved embryos exhibited plasma membrane abnormalities not seen in ZP-intact embryos.
- Key findings include reduced, irregularly distributed, and abnormally shaped microvilli.
- Increased peripheral vesicles and altered actin filament organization (peripheral band changes, discontinuities) were observed.
Conclusions:
- Cryopreservation without the zona pellucida induces significant plasma membrane and cytoskeletal damage in mouse embryos.
- These ultrastructural changes may affect embryo development and implantation potential.
- Further research is needed to optimize ZP-free cryopreservation protocols.