Ovary-Freezing Animal Study Holds Human Hope
Putting donated organs on ice before transplantation works, study of rats finds
WEDNESDAY, Jan. 23, 2002 (HealthDayNews) -- A new study describing the successful freezing, thawing and transplanting of rat ovaries could offer hope to women facing potential sterility after cancer treatments, and perhaps open the door to a new era of freezing other donor organs for later use.
In tomorrow's issue of Nature, scientists in Montreal report they transplanted the right ovary, Fallopian tube and upper portion of the uterus from one rat to another after storing the organs in liquid nitrogen.
They are the first team to successfully implant whole ovaries and Fallopian tubes following freezing, says another expert in organ cryopreservation.
The experiments used eight untreated ovaries and seven ovaries treated with chemical cryoprotectants during the freezing process. These chemicals change the state of fluids inside the organ cells, making it less likely that potentially harmful ice crystals form during freezing. The cryoprotectants used were fructose and dimethylsulphoxide.
To further prevent damage during the freezing process, the organs were cooled slowly, then stored overnight in liquid nitrogen. After thawing them out the next day, the microsurgeries to implant the ovaries each lasted about two hours.
The researchers used vaginal smears to look for signs of ovarian function in the animals, and several females were paired with males after a few weeks. Ten weeks after the procedure, the animals were euthanized and examined in detail. Of the animals that received a frozen ovary, 57 percent showed signs of recent ovulation, and one had become pregnant since the procedure.
"I suspect that the ovaries are rather easier organs to cryopreserve than, say, the kidneys," says senior investigator Roger G. Gosden, an adjunct professor of obstetrics and gynecology at McGill University.
The technique was by no means perfect, and there are still many technical hurdles to overcome, he adds.
"There are problems due to ice crystal formation, and maybe salt accumulation in the cells," he says. "There's probably still a lot of room for innovation in this field."
However, he adds, "you can imagine the benefits that this could provide for the transplant business Organs for a human could just wait in the bank until there's a suitable match, and organs wouldn't be wasted."
"This is exciting, outstanding work. This article demonstrates that through these procedures, smaller-sized organs can be cryopreserved successfully," says Dayong Gao, an associate professor at the University of Kentucky's Center for Biomedical Engineering who has been studying cryopreservation for 15 years.
He says that cryopreserved, transplanted ovaries could both restore fertility after cancer therapy and treat menopause.
However, Gao also notes ice crystal formation remains a problem.
"Not only could ice crystals inside the cell kill the cell, but in an organ, ice crystals between the cells can also destroy the cell-to-cell communication," he says. "Even though individual cells could survive, the communication between the cells will be disconnected, and the whole organ will be destroyed."
He also warns that crystal formation in blood vessels serving the organ can fracture the vessels, damaging blood flow to the organ.
Gao and Gosden both anticipate it may prove more difficult to uniformly freeze and thaw larger organs. The next step will be to try the same procedure in a larger animal.