Tuesday, 27 February, 2001, 00:14 GMT
Human ovaries 'grown in mice'
The mice were implanted with human tissue
Frozen human ovary tissue - a potential
fertility lifeline for hundreds of UK women - has
been successfully thawed and revived in mice.
And in more potentially good news for women
threatened with infertility, a new technique
appears to have greatly increased the number
of frozen human eggs which can be
subsequently fertilised.
However, the restoration of working ovarian
tissue - even allowing natural conception to
take place, is described as the "holy grail" in
this field.
Women who undergo ovarian removal or
chemotherapy for cancer often lose their
fertility as a result, and can suffer early
menopause.
While men whose
fertility is threatened
can elect to have
semen frozen for later
use, at the moment,
the preservation - and
reactivation - of eggs,
and tissue from the
ovary, is far more
problematic.
A team of scientists from Melbourne, Australia,
has now demonstrated that frozen human
ovarian tissue, once thawed, can grow in a
"normal" fashion.
The tissue was implanted into mice, and
immature follicles within the tissue, which are
supposed eventually release the eggs for
fertilisation, began to develop in a similar way
to conventional ovarian tissue.
Dr Debra Gook, who led the team at the city's
Royal Women's Hospital, said: "Our study is the
first to confirm normal growth and development
of human follicles.
"The high rate of functional preservation of
follicles following cryopreservation also
suggests that cryopreservation of ovarian
tissues has real potential for clinical
application."
Another piece of
Australian research
also found that mouse
ovarian follicles could
be frozen and thawed,
then similarly
developed under
laboratory conditions.
Pioneering doctors
have implanted
previously-frozen
ovarian tissue into an
American woman,
Margaret Lloyd-Hart, but the procedure was
not a success.
The follicles within the ovarian tissue did not
develop fully.
Dr Simon Fishel, of the Care IVF clinic in
Nottingham, described the ovarian advance as
"very exciting", although he stressed it was
unlikely to be a reliable treatment inside five
years.
He said: "It's certainly an extension of what
has been done before - this is certainly going
to happen - it's just a question of when and
how."
Egg success
Only 30 babies have been born worldwide using
frozen eggs - the success rate is extremely
low.
However, a team from the University of
Bologna say they have found a way of
improving the egg's chances during the
freezing process.
Water left in the egg causes damage to its
fragile contents during freezing.
Sucrose in the freezing solution is used to
draw water out through the cell membrane.
The Bologna team
doubled or even tripled
the concentration of
sucrose, and found
great improvements in
the proportion of eggs
which survived the
freezing process.
Doubling the
concentration improved
the egg survival rate
from 34% to 60%.
Tripling it boosted egg
survival to 82%.
Furthermore, 57% could be fertilised using
fertility techniques, and 90% of those fertilised
showed all the characteristics of "healthy"
embryos.
Dr Rafaella Fabbri, who led the research, said:
"It is very important that we improve the
possibilities for women to become pregnant
after having their eggs frozen."
Dr Fishel commented that while frozen egg
fertility treatments seemed to have the
greatest current potential in the short term,
there were still safety concerns about possible
genetic damage within the egg during the
dehydrating and freezing process.
news.bbc.co.uk |
