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 Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY

nachricht NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Future electronic components to be printed like newspapers

A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.

The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

A smart safe rechargeable zinc ion battery based on sol-gel transition electrolytes

20.07.2018 | Power and Electrical Engineering

Reversing cause and effect is no trouble for quantum computers

20.07.2018 | Information Technology

Princeton-UPenn research team finds physics treasure hidden in a wallpaper pattern

20.07.2018 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>