What if I told you that the secret to saving some of the world's most endangered species lies in a couple of nondescript freezers at San Diego Zoo's Frozen Zoo?
As an American Junior Academy of Sciences lifetime fellow, this February I was given a special back room tour of the conservation center housing this unique zoo. In these freezers are samples of tissue from rare and endangered animals frozen in liquid nitrogen ever since 1972. Essentially a vital world bank of biodiversity, animals long extinct live on in the form of skin cells at the Frozen Zoo. One day, the hope is that these cells can be reprogrammed into sperm and egg cells, which can then be used for breeding.
Creating life from death? Sound like science fiction? Actually, this is closer to reality than you may think. Scientists at Scripps Research Institute, also in San Diego, have recently successfully altered skin cells of the endangered silver-maned drill monkey into induced pluripotent stem (iPS) cells.
I first had the opportunity to work with iPS cells last summer as an intern at the City of Hope National Medical Center. The concept is nothing short of miraculous: take any body cell, insert a mere four reprogramming genes, and the cell will revert back to a pluripotent state. A pluripotent cell, like an embryonic stem cell, has the ability to differentiate into any cell of the human body.
The implications of this are huge: it embodies the benefits of embryonic stem cells without the moral dilemma and carries the hope of creating patient-specific stem cells for therapy.
Research at the Scripps Institute has added a new benefit of these amazing cells: saving endangered animals. By applying this same concept to tissue from the Frozen Zoo, scientists Friedrich Ben-Nun and Jeanne Loring succeeded in creating iPS cells. So far, the iPS cells obtained from the silver-maned drill monkeys achieved a breakthrough by differentiating into brain cells.
Already scientists are seeing great promise in this technology. If brain cells are possible, then why not sperm and egg cells? Soon, all the tissue stored in the Frozen Zoo can be turned into living, breathing animals. Through this method, genetic diversity can be added to struggling populations, increasing the chances of healthy reproduction, and animals that are notoriously hard to breed in captivity still have hope for a boost in population size.
There are, however, some current limitations. Although the technique has worked with the drill monkeys, so far it has not worked with white rhinos. It is hypothesized that since the reprogramming genes used currently to induce pluripotency are human, they can produce an effect in the more closely related primate monkey species but is not efficacious with the rhino species. But the atmosphere right now is largely hopeful as work continues on determining how to best use this technology to aid some of the world's most endangered animals.
Photo: Bonnie Lei