Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Durable critters providing insight for human egg preservation

20.12.2006
A tiny, six-legged critter that suspends all biological activity when the going gets tough may hold answers to a better way to cryopreserve human eggs, researchers say.

Tardigrades, also called water bears, can survive Himalayan heights or ocean depths as long as they have moisture.

When they don’t, they produce a sugar, trehalose, slowly dehydrate and essentially cease functioning until the rain comes, says Dr. Ali Eroglu, reproductive biologist and cryobiologist at the Medical College of Georgia.

Tardigrades are not alone in their amazing ability to outlast adverse conditions. A type of brine shrimp, often called a sea monkey, comes back to life with water. The Baker’s yeast Dr. Eroglu uses when he bakes bread with his children does as well. Similarly arctic wood frogs use the sugar, glucose, to tolerate frigid temperatures until the summer thaw.

... more about:
»Eroglu »Trehalose »coat »cryoprotectants »jelly »penetrate

While humans don’t naturally produce trehalose, researchers think they can use it to safely preserve human eggs – and those of endangered species – giving better options to young women facing cancer therapies that may leave them infertile and others who simply want to delay reproduction.

"Our hypothesis is when we introduce sugars into cells and into oocytes, we can protect them against freezing-associated stresses," says Dr. Eroglu, who received a $1.2 million grant from the National Institute of Child Health and Human Development to continue pursuing his hypothesis. "We also hypothesized if we used trehalose, we also could use conventional cryoprotectants, which can be toxic, in lower concentrations to minimize their toxicity while maximizing overall protection."

Pilot data show it works like a charm, at least in mouse eggs. Researchers injected eggs with trehalose, cooled them to liquid nitrogen temperature, thawed them and exposed them to sperm. They got healthy babies at a similar rate to unfrozen controls.

"We were very excited," says Dr. Eroglu, whose work has prompted desperate calls from young cancer patients wanting to preserve their eggs. "We got very good development rates, then we transferred the embryos to foster mothers and got pups that were completely healthy." In fact, those pups had healthy pups. His limited testing in human eggs indicates they also can be preserved and thawed safely using this approach, however further research is needed to pursue clinical applications.

The NIH grant enables him to use monkey eggs, which are similar to human eggs, to find the optimal mix of sugar, conventional cryprotectants and freezing to maximize egg preservation. Collaborators at Emory University are providing the eggs and at the Georgia Institute of Technology are developing a mathematical model to predict cooling rates while avoiding destructive intracellular ice formation. Dr. Eroglu also is working with the MCG Section of Reproductive Endocrinology, Infertility and Genetics In vitro Fertilization Program to obtain discarded eggs that failed to fertilize.

Dr. Eroglu looks for a better way because current approaches are fraught with problems. Scientists have been freezing human eggs for about two decades but not very successfully. "Embryo cryopreservation is relatively successful, but to freeze oocytes, we have to overcome many hurdles," he says. A major problem is the protective, exterior jelly coat of an egg doesn’t freeze well. The jelly coat protects the egg from mechanical stress and serves as a receptor for sperm. Sperm must pass through the coat then penetrate the interior plasma membrane. As soon as a single sperm penetrates, it triggers intracellular signaling that transforms the coat into a hard, impermeable structure and with good reason: if multiple sperm penetrate, chromosomal abnormalities result. Interestingly, traditional freezing, even with cryopreservatives, can cause these problems and more. The jelly coat hardens, making it impossible for sperm to get through the traditional way. "You don’t have this issue with an embryo because fertilization already has occurred," Dr. Eroglu says.

Intracytoplasmic sperm injection came into use in 1997 to help overcome the hardened jelly coat but other problems persist. Chemical stress, freezing or warming can disrupt the egg’s mechanism for dividing chromosomes – babies get half their chromosomes from mom and half from dad – so they don’t line up as they should. In addition to hardening the jelly coat, cold stress can change intracellular signaling resulting from sperm penetration. Lipids or fats in the egg can fuse and the membrane can become leaky.

The bottom line is only about 1-5 percent of eggs develop to term after standard cryopreservation techniques, which include a combination of slow freezing in conjunction with low levels of cryoprotectants such as dimethyl sulfoxide, or rapid freezing with more cryoprotectants.

Dr. Eroglu says the sugars, which help protect the natural structure of proteins, enable use of warmer temperatures and fewer cryoprotectants. He uses the tried and true intracytoplasmic sperm injection approach to deliver sugar – instead of sperm - to eggs before cooling. One of his ultimate goals is to design sugars that can easily penetrate the egg’s membrane, but at least for now, tardigrade sugars seems to work just fine in mice.

One of his many hopes is that freezing embryos won’t always be necessary, whether it’s a human or an endangered species. Rather, eggs and sperm – which have been frozen successfully for decades – can be kept apart until fertilization is desirable. This could preclude the controversy of destroying unused embryos and perhaps the debate over embryonic stem cells, he says.

Eggs, which can reprogram cell function by turning genes off and on, can produce cells that can become essentially anything, Dr. Eroglu says. If he can better understand how they do this, regular body cells might be reprogrammed in a test tube to embryonic-like stem cells for therapeutic use.

Toni Baker | EurekAlert!
Further information:
http://www.mcg.edu

Further reports about: Eroglu Trehalose coat cryoprotectants jelly penetrate

More articles from Life Sciences:

nachricht Symbiotic bacteria: from hitchhiker to beetle bodyguard
28.04.2017 | Johannes Gutenberg-Universität Mainz

nachricht Nose2Brain – Better Therapy for Multiple Sclerosis
28.04.2017 | Fraunhofer-Institut für Grenzflächen- und Bioverfahrenstechnik IGB

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Fighting drug resistant tuberculosis – InfectoGnostics meets MYCO-NET² partners in Peru

28.04.2017 | Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

 
Latest News

Wireless power can drive tiny electronic devices in the GI tract

28.04.2017 | Medical Engineering

Ice cave in Transylvania yields window into region's past

28.04.2017 | Earth Sciences

Nose2Brain – Better Therapy for Multiple Sclerosis

28.04.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>