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Cryopreservation of human sperms and
embryos have been in existence for longalmost
since 18th century! And is yet another
milestone in ART. Now it is the turn of oocytes
to be successfully frozen and retrieved and also
retain their genetic integrity to be able to
undergo fertilization and further division and
culminate in a healthy offspring. Why do this?
The primary advantages of this technique
would be preservation of fertility in women
with reproductive disorders such as premature
ovarian failure,endometriosis and pelvic
inflammatory disease or for that matter those
who wish to resume childbearing functions
following intensive chemo/radiotherapy for
neoplasms.
It is also an advantage for single working
women without partners or those who wish to
delay childbearing owing to career options.
There would be no need for a synchronized
cycle in a donor programme and last but not the
least it would circumvent all those legal,
ethical, moral and religious issues shrouding
embryo freezing. In comparison to embryo or
sperm freezing, oocytes have been eluding
very good results owing to certain gamete
related variables that influence their overall
survival rates. What are these? For instance
there could be possible damages to the
following structures like meiotic spindle,
cytoskeleton, cortical granules and the zona.
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The stage at which freezing is done also
influences results however conflicting data
have been published with few studies
supporting prophase I and others in favor of
metaphase II oocytes. The advantages for the
former being absence of a spindle formation,
lack of a defined zona pellucida and also being
metabolically quiescent-hence theoretically not
prone for “ cold shock”.
The only problem is the need for in vitro
maturation of these thawed oocytes prior to
achieving fertilization. Any differences in
protocols of freezing and thawing such as
seeding temperatures and use of sucrose as a
cryoprotectant did not seem to influence the
survival and fertilization rates. The entry of
vitrification as a novel method of rapid freezing
has also been endorsed with favorable results.
However a learning curve for all these
techniques is still at large with only few centers
around the world producing results on a
consistent basis. Closer home, we are
comparing the outcomes between slow freezing
and vitrification and yet to offer it on a regular
basis to our clients for oocyte freezing.
While we perfect our techniques, our Kudos to
the wonderful “ART” of sperm and embryo
freezing without which we would be “frozen”
in progress.
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