AUGUSTA, Ga. Cryoprotectants needed to preserve eggs for reproduction need to be given in stages, albeit rapid ones, say scientists who have developed a mathematical model that predicts optimal time for loading and unloading these drugs.
Their studies in Rhesus monkey eggs, which are very similar to human eggs, show that a two-step process of easing into and out of the drugs needed to help protect eggs at subzero temperatures dramatically reduces the amount eggs contract and expand in the process.
These dramatic size shifts can literally rip an egg apart or, at the very least, reduce the chances it can be fertilized, says Dr. Ali Eroglu, reproductive biologist and cryobiologist in the Medical College of Georgia Schools of Medicine and Graduate Studies.
Scientists first looked at how fast the three most commonly used cryoprotectants dimethylsulfoxide, ethylene glycol and propylene glycol permeate monkey eggs. Faster permeability is better with these drugs which must be given at room temperature when their toxicity levels are high. With permeability rates in hand, MCG scientists used a mathematical model, developed in collaboration with Villanova University in Pennsylvania, to successfully predict optimal loading and removal times.
They found propylene glycol works best in monkeys. The drug penetrated the egg membrane faster and got out faster, Dr. Eroglu and his colleagues report in the April issue of Molecular Reproduction & Development.
All of the drugs worked best when used incrementally: putting some in the medium around the egg and a few minutes later adding a little more when it was time for cryopreservation and, conversely, transferring them to increasingly lower concentrations of the drugs when it was time for thawing.
While still less than 10 percent, success rates for egg preservation to help protect an endangered species or enable a cancer patient to retain fertility have improved in re
|Contact: Toni Baker|
Medical College of Georgia