Qualitative and morphometric analysis of the ultrastructure of human oocytes cryopreserved by two alternative slow cooling protocols.
OBJECTIVE
To ascertain possible cell damage from cryopreservation, the ultrastructure of human oocytes cryopreserved by slow cooling was assessed.


METHODS
Cryopreservation was performed through two protocols with one-step or two-step propanediol. Fresh control oocytes were examined for comparison. Samples were processed for transmission electron microscopy analysis.


RESULTS
By light microscopy, both fresh and frozen-thawed oocytes appeared regularly rounded, with intact zona pellucida, and homogeneous cytoplasm. By electron microscopy observation, organelles were abundant and uniformly dispersed. Mitochondria-smooth endoplasmic reticulum associations appeared regular. However, both the amount and density of cortical granules appeared abnormally reduced in frozen-thawed samples. Slight to moderate vacuolization was also found in the ooplasm of oocytes of both frozen groups.


CONCLUSIONS
Slow cooling ensures a good overall preservation of human oocytes. However, cytoplasmic vacuolization and cortical granule loss appears associated with cryopreservation, irrespective of the protocol used.
Coticchio
Giovanni
G
Tecnobios Procreazione, Centre for Reproductive Health, Bologna, Italy. coticchio@hotmail.it
Borini
Andrea
A
Distratis
Vincenzo
V
Maione
Marta
M
Scaravelli
Giulia
G
Bianchi
Veronica
V
Macchiarelli
Guido
G
Nottola
Stefania A
SA
D000328:Adult; D015925:Cryopreservation; D003451:Cryoprotective Agents / Q000494:pharmacology*; D003594:Cytoplasmic Granules / Q000648:ultrastructure; D018871:Endoplasmic Reticulum, Smooth / Q000648:ultrastructure; D005260:Female; D005615:Freezing; D006801:Humans; D046529:Microscopy, Electron, Transmission; D008928:Mitochondria / Q000648:ultrastructure; D009865:Oocytes; D009926:Organ Preservation; D011409:Propylene Glycols / Q000494:pharmacology*
D003451:Cryoprotective Agents; D011409:Propylene Glycols