A team of scientists led by University of Missouri-Columbia professor of reproductive biotechnology Randy Prather just changed that with a breakthrough process. The new technique allows cloned transgenic pig embryos to be cryopreserved and potentially shipped to scientists worldwide.

"We will be able to make genetically modified pig embryos as models for many types of human diseases, preserve them for future use or distribute them worldwide," Prather said. "This has never been done before."

Until now, successfully cryopreserving pig embryos, lab-created or otherwise, was difficult. Prather and his team found that the key was removing the lipids, or fat droplets within the cells, after centrifugation, the process of using centrifugal force to separate the lipids. The cloned embryos were then allowed to advance to the blastocyst stage where they could survive freezing and thawing. The embryos could then be stored until needed and thawed for implantation into a surrogate.

"In our research, 163 cyropreserved in vitro produced somatic cell nuclear transfer swine embryos were transferred to two surrogates and produced 10 piglets," Prather said. "It takes a number of embryos to obtain a few offspring. Also, the embryos must be transferred to a surrogate in the correct stage of her cycle or the embryos will be wasted. This is part of why it so important to be able to cryopreserve large numbers of cloned embryos."

The new technique will allow MU�s National Swine Resource and Research Center to distribute the cloned embryos worldwide to scientists who need certain genetically altered pigs for research. In many cases, piglets cannot be successfully shipped because of the potential for disease transmission.

"This means we can work better as a core facility," Prather said. "Researchers will now just need pigs and a surgery suite. The resulting babies will have the genetic modifications that the researchers need and have passive immunity to the local diseases."

The research is in press with the journal Biology of Reproduction, published by the Society for the Study of Reproduction. The research was funded by the National Center for Research Resources.

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