NEW TECHNIQUE DRAMATICALLY IMPROVES SURVIVAL RATES OF FROZEN EGGS

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Embargoed For Release:                                                  CONTACT: 
January 11, 2001                                                                  Eleanor Nicoll at 202/863-2439, enicoll@asrm-dc.org

                                                                                                  Sean Tipton at 202/863-2494 or stipton@asrm-dc.org             
 

 

 

HIGHLIGHTS IN FERTILITY AND STERILITY 
Vol. 77, No. 1, January 2002 

NEW TECHNIQUE DRAMATICALLY IMPROVES SURVIVAL RATES OF FROZEN EGGS *

 

Mother Nature may be impartial but that doesn't mean she's fair. For about half a century, men have been able to freeze their sperm quite successfully. Whether for donation, or to preserve future fertility in the face of disease and treatment, the option of putting a few vials into storage is fairly easy, available throughout the developed world, and not prohibitively expensive. The same is not true for women who may wish to freeze their eggs. Eggs don't survive freezing very well. 

Searching for a way to increase the chances of survival for frozen eggs, doctors and scientists at Massachusetts General Hospital and Harvard Medical School tried a new technique for freezing eggs. 

Freezing methods involve the use of various chemicals- cryoprotectants- in different concentrations depending on speed of the freezing. Different types of cells react differently to the procedure. It turns out that egg cells are particularly delicate, suffering rupture of the cell membrane and damage to internal structures when frozen. (Embryos, however, freeze very well.) While traditional cryopreservation methods use sugars outside the frozen cells, studies on types of cells other than eggs have shown that, to enhance protection, the sugars should also be present inside the cells.

Using IVF patients' donated eggs that had failed to fertilize or mature, Dr. Eroglu and his colleagues compared the results of three freezing protocols. The cryoprotectant they used was trehalose, a type of sugar found in high concentrations inside the cells of many anhydrobiotic organisms that, in the wild, survive extreme conditions of dehydration. One set of eggs was frozen, as a control, without trehalose, another had trehalose as a component of the extra-cellular medium, and the third set had a small amount of trehalose (comparable to the amount found within the cells of anhydrobiotic organisms) injected intracellularly and was also frozen in trehalose-containing medium.

Eggs preserved according to the three protocols were frozen, thawed and examined for survival by evaluating their appearance and membrane integrity. In the control group, only 13% of eggs survived freezing. In the group frozen in trehalose-containing medium, 22% survived. However, the group of eggs that were both injected with trehalose and frozen in medium containing the sugar exhibited a much greater survival rate: 63% at -15ºC. This clearly indicates that intracellular trehalose has a beneficial effect on freezing human eggs.

"The use of intracellular sugars for freezing eggs is very promising. We need to do more work to find a solution to this problem. Young women facing treatment for cancer or other diseases shouldn't at the same time have to face the end of their dreams to have a family," commented William Keye, Jr., MD, President of the ASRM.

ASRM, founded in 1944, has more than 8,500 members who are devoted to advancing knowledge and expertise in reproductive medicine and biology. ASRM-affiliate societies include the Society of Reproductive Surgeons, the Society for Reproductive Endocrinology and Infertility, the Society for Male Reproduction and Urology, and the Society for Assisted Reproductive Technology.

 

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(Eroglu, et al., "Beneficial effect of microinjected trehalose on the cryosurvival of human oocytes," Fertility & Sterility, Vol.77, No.1, January 2002) 

Editors Note: Fertility and Sterility is now available on-line.

 

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