Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Israeli scientists successfully transplant frozen-thawed ovaries in sheep

15.09.2005


New freezing technique raises future hopes for human applications



Israeli scientists report today (Thursday 15 September) in Human Reproduction[1] that they have successfully transplanted whole frozen and thawed ovaries in sheep, retrieved oocytes from these ovaries and triggered them in the laboratory into early embryonic development.

Follow-up tests showed that the ovaries in the two sheep from which oocytes were recovered were still functioning normally three years later.


Lead author Dr Amir Arav, senior scientist at the Institute of Animal Science, Agriculture Research Organisation, Bet Dagan, said that these results demonstrate for the first time that it is possible in a large animal species, to remove, freeze, thaw and replace ovaries, obtain oocytes and maintain normal ovarian long-term function. This holds out hope that this approach could become a feasible treatment for women facing premature ovarian failure, and furthermore, that the advances they have demonstrated from new freezing techniques may have potential for other human organ transplants, which are currently done using only fresh grafts.

Co-author Yehudit Nathan, program manager at Core Dynamics, the biotech company that funded and provided the scientific and technological expertise for the project, said the next goal was to attempt to transplant ovaries in women at risk of losing their fertility.

"There is a lot of research still to be done, but we hope that it will not take more than a few years for this to become a practicable option for women, such as young cancer patients, who would otherwise be left infertile after their treatment," she said.

Whole ovary autologous transplants have already been attempted twice in women – in 1987 and 2004 – in both cases into the upper arm, but in neither case was the ovary frozen and thawed first[2].

Another much-researched option is freezing and transplanting thawed ovarian tissue. Two babies have been born using this technique[3]. However, adhesions and the loss of blood to the ovarian follicles that occurs during the interval before new blood vessels are being formed, remain major obstacles.

The first aim of the Israeli team was to test in vitro whether whole ovaries from sheep, together with the blood vessels, could survive the freeze-thaw process using a technique they have developed that allows precise control over the propagation of ice crystals during the freezing process, thus reducing the damage caused to cells by conventional methods[4]. Sheep were chosen because their ovaries are similar to those of humans. The technique worked – the frozen-thawed ovaries produced comparable numbers of follicles as the fresh control ovaries.

The next objective was to see if they could remove, freeze and thaw the right ovary from eight sheep, including the vascular pedicles (the attachment that contains the main blood vessels), and replace the ovary up to a fortnight later, either at the original site or by grafting it on to the pedicle of the (removed) left ovary. Of the five sheep where normal blood flow resumed immediately, indicating that the transplant had succeeded, one had severe adhesions and it was not possible to attempt oocyte collection, but two yielded one oocyte each and repeat aspiration four months later produced four more oocytes from one of these sheep.

All six ooctyes were activated parthenogenically using chemicals that mimic the normal fertilisation process, and developed into 8-cell embryos.

"We used parthenogenic activation as we had only a low number of oocytes and because IVF success in sheep depends on the quality of the ram’s sperm. This way, we knew that the development of the embryo depended solely on the quality of the ooctye," said Dr Arav.

Two years after transplantation the researchers carried out magnetic resonance imaging (MRI) on one sheep with a transplanted ovary and one untreated control sheep. It showed that the transplanted ovary contained small oocyte follicles, and although a little smaller than the ovary in the control sheep it was within the normal range. The blood vessels were also intact.

"Adhesions on the transplant might interfere with natural conception so pregnancy may require IVF techniques, but we have been able to demonstrate long-term intact organ cryopreservation with restored function following thawing and transplantation, in a large animal for around 36 months post- transplantation," said Dr Arav. "This approach could revolutionise the field of cryopreservation for diverse human applications, such as organ transplants, as well as helping women who face the loss of their fertility."

The research may also have far-reaching applications for animals. The team recently froze the ovary of the Gazelle gazelle acaiae, an endangered sub-specie of the Gazelle gazelle, so that it can be transplanted in the future into an immune-suppressed surrogate.

Margaret Willson | alfa
Further information:
http://www.mwcommunications.org.uk

More articles from Life Sciences:

nachricht Molecular microscopy illuminates molecular motor motion
26.07.2017 | Penn State

nachricht New virus discovered in migratory bird in Rio Grande do Sul, Brazil
26.07.2017 | Fundação de Amparo à Pesquisa do Estado de São Paulo

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Carbon Nanotubes Turn Electrical Current into Light-emitting Quasi-particles

Strong light-matter coupling in these semiconducting tubes may hold the key to electrically pumped lasers

Light-matter quasi-particles can be generated electrically in semiconducting carbon nanotubes. Material scientists and physicists from Heidelberg University...

Im Focus: Flexible proximity sensor creates smart surfaces

Fraunhofer IPA has developed a proximity sensor made from silicone and carbon nanotubes (CNT) which detects objects and determines their position. The materials and printing process used mean that the sensor is extremely flexible, economical and can be used for large surfaces. Industry and research partners can use and further develop this innovation straight away.

At first glance, the proximity sensor appears to be nothing special: a thin, elastic layer of silicone onto which black square surfaces are printed, but these...

Im Focus: 3-D scanning with water

3-D shape acquisition using water displacement as the shape sensor for the reconstruction of complex objects

A global team of computer scientists and engineers have developed an innovative technique that more completely reconstructs challenging 3D objects. An ancient...

Im Focus: Manipulating Electron Spins Without Loss of Information

Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.

For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...

Im Focus: The proton precisely weighted

What is the mass of a proton? Scientists from Germany and Japan successfully did an important step towards the most exact knowledge of this fundamental constant. By means of precision measurements on a single proton, they could improve the precision by a factor of three and also correct the existing value.

To determine the mass of a single proton still more accurate – a group of physicists led by Klaus Blaum and Sven Sturm of the Max Planck Institute for Nuclear...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

Closing the Sustainability Circle: Protection of Food with Biobased Materials

21.07.2017 | Event News

»We are bringing Additive Manufacturing to SMEs«

19.07.2017 | Event News

 
Latest News

CCNY physicists master unexplored electron property

26.07.2017 | Physics and Astronomy

Molecular microscopy illuminates molecular motor motion

26.07.2017 | Life Sciences

Large-Mouthed Fish Was Top Predator After Mass Extinction

26.07.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>