Developmental potential of murine germinal vesicle stage cumulus-oocyte complexes following exposure to dimethylsulphoxide or cryopreservation: loss of membrane integrity of cumulus cells after thawing.
BACKGROUND
Cumulus cells of the cumulus-oocyte complex (COC) are important in oocyte maturation. Thus, in preserving immature oocytes it is prudent to also preserve their associated cumulus cells. The survival and function of oocytes and their associated cumulus cells was assessed following cryopreservation or exposure to cryoprotectant without freezing.


METHODS
Immature COCs were collected from mice primed with pregnant mare's serum. COCs were either slow-cooled or exposed to 1.5 mol/l dimethylsulphoxide without freezing. Treated and fresh COCs were stained for membrane integrity or, after in-vitro maturation and IVF, were assessed for developmental capability. Development of cumulus-denuded fresh oocytes, as well as denuded and frozen-thawed oocytes co-cultured with fresh cumulus cells, was assessed.


RESULTS
Slow-cooled oocytes had significantly reduced coverage by intact cumulus cells compared with fresh COCs. Cumulus cell association and developmental capability were not substantially affected by exposure to cryoprotectant without freezing. Denuded fresh oocytes and cryopreserved COCs had decreased developmental potential that was not overcome by co-culture with fresh cumulus cells.


CONCLUSIONS
Loss of association between oocyte and cumulus cells was induced by cryopreservation, but not by treatment with cryoprotectant alone. The data indicate that direct physical contact between cumulus cells and the oocyte, throughout maturation, improves subsequent embryo development.
Ruppert-Lingham
C J
CJ
Department of Obstetrics and Gynaecology, University of Wales College of Medicine, Heath Park, Cardiff CF14 4XN, UK. Ruppert_LinghamCJ@cardiff.ac.uk
Paynter
S J
SJ
Godfrey
J
J
Fuller
B J
BJ
Shaw
R W
RW
D000818:Animals; D002450:Cell Communication; D002462:Cell Membrane / Q000502:physiology; D002478:Cells, Cultured; D016922:Cellular Senescence; D018920:Coculture Techniques; D015925:Cryopreservation; D003451:Cryoprotective Agents / Q000494:pharmacology*; D004121:Dimethyl Sulfoxide / Q000494:pharmacology*; D005260:Female; D051379:Mice; D009865:Oocytes / Q000187:drug effects* / Q000502:physiology*; D006080:Ovarian Follicle / Q000166:cytology* / Q000187:drug effects* / Q000502:physiology; D013194:Staining and Labeling; D013997:Time Factors
D003451:Cryoprotective Agents; D004121:Dimethyl Sulfoxide