Japanese scientists have recently reported a major breakthrough in cloning, opening new possibilities for bringing extinct species back to life. Teruhiko Wakayama and his colleagues from the Center for Developmental Biology at the Riken Center in Japan have successfully grown healthy clones from mice frozen 16 years ago in -20C conditions.

The experts explained that after collecting the needed material (all cells used were ruptured after thawing), and by using brain nuclei as donors, they managed to produce healthy cloned mice. They also suggested that their nuclear transfer technique could be used to “resurrect” animals that have been frozen for long periods of time without cryopreservation.

The discovery is of significant importance, considering that up until recently, scientists did not believe it would ever be possible to clone material frozen for extended periods of time, out of fears that ice crystals would damage the cellular material used for cloning.

The scientists also reported that although brain material proved the most efficient in this particular case, other organs or tissues, such as frozen leukocytes, could also be used as donor nuclei.

“At present, the lack of suitable species for recipient oocytes and for surrogate mothers is one of the major problems that needs to be solved for the method to be applied in extinct or endangered animals,” the researchers wrote in the study published in Proceedings of the National Academy of Sciences.

The scientists were confident that the breakthrough would help resurrect species such as the wooly mammoth, whose cloning was believed to be impossible due to the lack of availability of live cells or less degraded genomic material.