Da. Gook et al., Effect of cooling rate and dehydration regimen on the histological appearance of human ovarian cortex following cryopreservation in 1,2-propanediol, HUM REPR, 14(8), 1999, pp. 2061-2068
Thin slices of human ovarian cortex were evaluated following cryopreservati
on in 1,2-propanediol (PROH)/sucrose under various conditions, Following ra
pid thawing, 1 mu m sections were assessed by light microscopy and oocyte a
bnormalities were further examined by electron microscopy. Follicles (n = 5
03) were predominantly primordial (91%), with no follicles larger than the
proliferating primary stage. Proportions of intact pre-granulosa cells and
oocytes (expressed as percentages of the total numbers observed) were signi
ficantly reduced following cooling at three different rates with the highes
t levels of intactness (55 and 85% respectively) being achieved with slow c
ooling. The frequency of oocyte abnormalities [loss of organelles (mitochon
dria), organelle-free areas, and/or cytoplasmic vacuolation] was significan
tly increased at all cooling rates with slow cooling resulting in the highe
st proportion (56%) of normal oocytes, With slow cooling, increasing dehydr
ation time increased the proportions of intact pre-granulosa cells and oocy
tes (maximum 74 and 91% respectively after 90 min dehydration). Under these
conditions, the highest proportion of follicles with all pre-granulosa cel
ls intact (44%) was observed, as was the highest proportion of 'normal' ooc
ytes (85%), In this study, single step dehydration in PROH/sucrose for 90 m
in and slow cooling/rapid thawing results in the highest proportion of inta
ct human primordial and primary follicles.