ILAR Journal Online, Volume 41(4) 2000: Cryobiology of Embryos, Germ Cells, and Ovaries

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ILAR Journal V41(4) 2000
Cryobiology of Embryos, Germ Cells, and Ovaries

Summary
J. K. Critser and Robert J. Russell

J. K. Critser, Ph.D., is Director of the Cryobiology Institute and Professor in the Departments of Pediatrics and Immunology and Microbiology, Indiana University Medical School, Indianapolis, Indiana. Robert J. Russell, D.V.M., is Director of Laboratory Animal Medicine at Harlan Sprague Dawley, Inc., Indianapolis, Indiana.

Cryopreservation of mouse embryos has been used successfully for more than 25 yr. However, the general area of the cryobiology of mouse and rat reproductive cells and tissues is still in its infancy, and there is still much to learn to make cryopreservation techniques and procedures more effective with reduced costs. Research to evaluate new techniques is currently under way, and more exciting advances are expected during the next several years. In the meantime, the need for the cryopreservation of rat and mouse strains, stocks, and lines continues to increase due to the worldwide explosion of genetically engineered mice and rats. This explosion in animal requirements has placed a significant impact on the currently available animal holding and research facilities. Many investigators require the immediate preservation of some of their current animal lines to protect against loss, prevent genetic change, and reduce maintenance costs until these animals are needed again for future research programs. Improved use and availability of cryopreservation techniques will help meet this challenge.

Although, relative to banking embryos, the cryopreservation of sperm and ovaries/oocytes results in increased time to reconstitute the line/strain due to the heterozygosity of the rederived animals, these procedures increase the likelihood of successful strain preservation for little additional cost. Less freezer space is also required for the storage of sperm and ovaries compared with embryos.

The preceding articles provide a summary of techniques that are practical today to assist investigators and institutions in meeting the challenge described above. As noted by contributors to this issue of ILAR Journal, good success has been achieved to date with the cryopreservation of mouse embryos, moderate success has been achieved with rat embryos and mouse ovarian tissue, relatively little but improving success continues with mouse spermatozoa and oocytes, and no success has resulted with rat spermatozoa. Additional work is ongoing in all of these areas to further improve capabilities; however, continued research and development in this area will require a greater awareness and appreciation for the importance of this area and associated increases in funding for both the basic science and technology aspects of the field.