Career women who want to postpone their pregnancies until later in life may soon be able to prolong their period of fertility. How? By having one of their ovaries frozen so it can be re-implanted when they want.

A Notre-Dame Hospital team led by Dr Huifang Chen, a researcher in the Department of Surgery at Université de Montréal, has just carried out successful frozen ovary grafts in animals. The results were published in Nature in January. The Montréal team worked closely with Roger G. Gosden of McGill University and Samuel Kim of University of Washington.

In their experimental surgery laboratory, the researchers removed the right ovaries from seven female rats, which they kept for one night in liquid nitrogen at -196ºC. The ovaries were then transplanted into seven genetically identical rats. Four rats succeeded in secreting hormones and producing ova. One rat became pregnant after mating. These results suggest similar possibilities for humans. In addition to delaying menopause, the new technology would allow young women who have to undergo chemotherapy treatments to avoid problems of sterility associated with their treatments.

But ovary grafts are not the main application of interest to Dr Chen. This technique could alleviate the shortage of organs that has plagued all western countries for several years. In Quebec alone, 936 patients were waiting for organs at the end of 2001. Next to a lack of donors, the short period of time organs can be preserved outside the human body is the main cause of the shortage. Currently, the organs are preserved in a physiological solution at 4ºC. A heart and lungs can be kept for barely four hours. The liver and pancreas, which are more resistant, can keep for 20 hours. The kidney can survive up to 30 hours. With cryogenic techniques, Dr Chen hopes to be able to preserve organs indefinitely. "The ideal would be to establish an organ bank," notes Dr Chen. "Hearts, lungs, kidneys, livers and pancreases would be stored there until a compatible donor appears." There are already tissue banks for serious burn victims. But preserving entire organs is much more difficult. "The more complex the organ and the more cavities it contains, the more delicate the procedure," explains Minh Diem Vu, a doctoral student working with Dr Chen. "The freezing and thawing phases are especially hazardous. The formation of ice crystals must be avoided at all cost, since the crystals can cause damage."

Dr Chen's team is now doing experiments with a much more complex organ than the ovary: the kidney. If their tests on rodents are conclusive, they will extend testing to larger animals such as monkeys or pigs. Human tests will come later.

Researcher: Huifang Chen
Telephone: (514) 890-8000, ext. 27081
Funding: Centre de recherche du CHUM