There are some amazing genes and cellular processes active during embryonic development that are never seen again later in life. Though some insects and amphibians are able to carry those traits into adulthood, mammals have a dramatic decrease in the ability to regenerate tissue after birth. A new study has shown that one embryonic protein can be used to help regenerate adult tissue in a living organism, not just in a dish.

The protein Lin28a typically only contributes to processes during embryogenesis, affecting things like metabolism and the pluripotency of stem cells. A study published Nov. 7 in Cell has shown that these proteins can actually be used in adult tissue and help in the regeneration of cartilage, hair follicles, bone, and mesenchyme, a type of undifferentiated connective tissue. It works by binding microRNA in the cell’s nucleus to inhibit let7. Let7 encourages cells to mature and lose the regenerative abilities.

Mice that had been genetically altered to produce Lin28a throughout life had outstanding regenerative power. Though regular mice typically stop producing new hair at around 10 weeks, those with a continued presence of Lin28a kept growing fur throughout their lives. Lin28a also boosted regeneration of limbs. During development, Lin28a is commonly found in the limb buds, but is hardly expressed in those regions after birth. For the mice over expressing Lin28a, some digits that were amputated early in life grew back nearly completely. This ability was diminished as the mouse approached adulthood. Because cardiac tissue also wasn’t regenerated by the presence of Lin28a, there could be other unknown proteins that regulate body aging.

Lin28a was also shown to promote prompt healing of damaged ears, increase metabolism, and contribute to cell proliferation and migration, which are necessary for tissue repair. Unfortunately, some of these attributes can also lead to tumorigenesis, which has been the focus of a great deal of recent cancer research.

This discovery is a long way off from having clinical significance as a miracle “fountain of youth” treatment. Because Lin28a binds to RNA, not the surface of the cell, current drug delivery systems would be very ineffective. Also, because the protein affects so many different tissues in the body, it would be incredibly difficult to target only the desired area. In the future, however, this could be used as a treatment for diseases like alopecia and for tissues that have been injured or are degenerating.