Published in:
01-12-2016 | Gamete Biology
Freeze/thaw stress induces organelle remodeling and membrane recycling in cryopreserved human mature oocytes
Authors:
Stefania Annarita Nottola, Elena Albani, Giovanni Coticchio, Maria Grazia Palmerini, Caterina Lorenzo, Giulia Scaravelli, Andrea Borini, Paolo Emanuele Levi-Setti, Guido Macchiarelli
Published in:
Journal of Assisted Reproduction and Genetics
|
Issue 12/2016
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Abstract
Purpose
Our aim was to evaluate the ultrastructure of human metaphase II oocytes subjected to slow freezing and fixed after thawing at different intervals during post-thaw rehydration.
Methods
Samples were studied by light and transmission electron microscopy.
Results
We found that vacuolization was present in all cryopreserved oocytes, reaching a maximum in the intermediate stage of rehydration. Mitochondria-smooth endoplasmic reticulum (M-SER) aggregates decreased following thawing, particularly in the first and intermediate stages of rehydration, whereas mitochondria-vesicle (MV) complexes augmented in the same stages. At the end of rehydration, vacuoles and MV complexes both diminished and M-SER aggregates increased again. Cortical granules (CGs) were scarce in all cryopreserved oocytes, gradually diminishing as rehydration progressed.
Conclusions
This study also shows that such a membrane remodeling is mainly represented by a dynamic process of transition between M-SER aggregates and MV complexes, both able of transforming into each other. Vacuoles and CG membranes may take part in the membrane recycling mechanism.