embryos from many strains tend to freeze and recover well. Gametes from hybrid mice also can be cryopreserved, but those from most inbred strains and genetically modified strains cannot. Bovine sperm has been routinely cryopreserved for a long time. In other species, the success is much more variable. Aquatic organisms cannot be successfully preserved by either embryo or gamete cryopreservation. Some models have been lost because no practical preservation methods were available at the time when an individual laboratory could no longer support a particular model. Some wild-derived models are lost because of inadequate funding to bring them into the laboratory or develop them for use as models.
The cost of cryopreservation is an impediment for most researchers because research grants typically do not provide funding for cryopreservation and because current methods, such as freezing embryos in mice, are relatively expensive. Providing funds for development of more cost-effective methods, such as freezing gametes, would alleviate this preservation cost. For example, the cost of cryopreserving a mouse strain might vary from a few thousand to 10,000 dollars, depending on the method and ease of freezing. Once the initial investment in cryopreserving a stock is made, the maintenance cost drops to a few dollars per year, compared with $3,000–4,000 per year to maintain a minimal breeding colony. The cost of recovery may be a few hundred to $3,000, but one recovery is less than the annual cost of keeping a stock in the breeding colony.
Improvement, perfection, and reduction of the cost of embryo, ovum, ovary and sperm freezing are needed. Demand for some models might lessen from time to time, but often increases later. If these models' gametes could be frozen easily and stored during down periods, there could be reductions not only in per diem charges but also in the space required. Animal research space for genetically engineered mice now being produced is becoming scarce. Maximal use of that space could be accomplished if strains and stocks being held in animal rooms were cryopreserved.
Today, more than ever, animals of the highest quality are needed to support the sophisticated animal models required to meet today's research challenges. Additional high-quality animal holding and maintenance space is required throughout the research community. A major problem that became apparent from all of our sources is that animal space has been depleted at many institutions. Major forces causing the depletion are the explosion in the number of genetically altered mice; the increasing animal care regulations; the increased demand for space to respond to them; the increased technology, such as barrier caging, required for housing laboratory animals; and the decrease in funding available from NCRR for construction and renovation of animal care facilities.
Biomedical science is moving into the next phase of understanding the function at the whole-organism level of genes identified at the molecular level. During the