Cryopreservation: A chance for highly endangered mammals

February 28, 2013, Forschungsverbund Berlin e.V. (FVB)
Iberian lynx, most endangered wild cat worldwide. Credit: IZW

Oocytes of lions, tigers and other cat species survive the preservation in liquid nitrogen. Scientists of the Leibniz Institute for Zoo and Wildlife Research (IZW) in Berlin succeeded in carrying out cryopreservation of felid ovary cortex.

"We have successfully frozen and thawed oocytes in the ovary cortex of different cat species at minus 196 degrees Celsius. This freezing process and the storage of living cellular material in is called cryopreservation", said Caterina Wiedemann, doctoral candidate at the IZW.

The ovarian cortex is regarded as a reservoir of . It contains thousands of immature oocytes. Successful cryopreservation of ovarian tissue of wild cats is therefore a key element for the establishment of genome resource banks, an important tool for the preservation of . All felid species except for the are listed on the Red List for endangered species of the International Union for Conservation of Nature (IUCN).

Taking a freezing procedure developed in human medicine as their model, scientists at the Department of Reproduction Biology of the IZW developed a method for cryopreserving the ovarian cortex of different cat species. In the original procedure, ovarian tissue of women who suffer from cancer is removed to avoid its damage by chemotherapy or radiotherapy. After successful tumor treatment the tissue is re-transplanted so that the normal female cycle, including fertility, can be restored. In the meantime, the tissue is conserved in liquid nitrogen. The IZW adapted this method to preserve female from .

The particular challenge in the cryopreservation of ovarian cortex tissue comes from the fact that the cells are embedded in a very complex system. Ovarian cortex is composed of immature oocytes surrounded by small , different connective tissue and . In addition, the cellular properties of every species are unique, thus it not possible to develop a common freezing procedure applicable to all species. For the cat cells, the scientists of the IZW worked out a "slow" freezing protocol. The cortex was dissected into evenly chopped pieces, each 2 mm in diameter. The cellular material was frozen at a speed of 0.3 degrees per minute. Ethylene glycol and saccharose were used as cryoprotectant agents. To demonstrate their survival after thawing the ovaries, the cortex was cultured in a medium for up to 14 days before and after the freezing.

The IZW owns the genome resource bank "Arche", which contains, inter alia, a variety of sperm samples of various wildlife species. The newly developed cryopreservation method will substantially improve the future storage of feline germ cells.

"This is a large step towards preserving biodiversity. In particular to endangered the successful of female and male gametes is a ray of hope", commented the head of the department, Prof Dr Katarina Jewgenow (IZW).

In 2007 the IZW initiated the "Felid Gametes Rescue Project" in order to build up an European network for the extraction and storage of feline gametes, which are made available to breeding programmes of zoos. Within the framework of this project, different European zoos are sending ovaries and testes of big and small cats to the IZW in Berlin for research. The scientists involved are confident that these good results will encourage even more zoos to participate in the network.

Explore further: Cryopreservation techniques bring hopes for women cancer victims and endangered species

More information: Wiedemann C, Zahmel J, and Jewgenow K (2013): Short-term culture of ovarian cortex pieces to assess the cryopreservation outcome in wild felids for genome conservation. BMC VET RES 9, 37; doi: 10.1186/1746-6148-9-37

Related Stories

Saving the snow leopard with stem cells

January 23, 2012

( -- The survival of the endangered snow leopard is looking promising thanks to Monash University scientists who have, for the first time, produced embryonic stem-like cells from the tissue of an adult leopard.

Scientists establish cell cultures of endangered frog

November 3, 2011

San Diego Zoo Global Wildlife Conservancy scientists have taken a tremendous leap forward in banking viable amphibian cells. This was achieved through the first successful establishment of cell cultures from frozen biopsy ...

What does delaying childbearing cost?

March 14, 2012

Freezing eggs or ovarian tissue for the sole purpose of delaying childbearing for social reasons may prove too costly for society, according to a recent analysis by a University of Illinois at Chicago researcher.

Recommended for you

Spotlighting differences in closely-related species

October 22, 2018

There are millions of fungal species, and those few hundred found in the Aspergillus genus play important roles in areas ranging from industrial production to agricultural plant pathogens. Reported October 22, 2018, in Nature ...

Cellular trash cans reveal the roles of proteins in disease

October 22, 2018

If we really want to know how our body's cells work—or don't work, in the case of disease—we might need to look beyond their genes and even beyond the proteins they are made of. We may need to start going through the ...

Cells that change jobs to fight diabetes

October 22, 2018

Diabetes is characterized by persistent high blood sugar levels that occur when certain cells in the pancreas—the insulin-producing β cells—are destroyed or are no longer able to secrete insulin. Researchers at the University ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.