I think you’ll agree that for a 45 year old man, Hugh Jackman isn’t doing so bad. His most famous persona, that of the super ‘hero’ Wolverine, possesses an incredible capacity for healing, and you’d be forgiven for wondering whether Mr Jackman himself has some trick up his sleeve in this respect too. The truth, however, is that young people have a better capacity for healing than older folk (sorry Hugh), and this is one of the key factors in ageing itself. Now, a group of scientists seem to have stumbled upon an explanation for this: an embryonic protein with the potential to regenerate adult tissues in living organisms.
There are some cellular processes that are active only during the development of the embryo and are never seen again in later life. In some amphibians and insects these traits are retained after birth, but mammals are not so fortunate: they demonstrate a dramatic reduction in their ability to regenerate tissue after birth. At least, most of them do.
Scientists from the Harvard Medical School, USA, were studying a group of mice that had supposedly been genetically engineered to develop tumours. However, instead the animals grew bigger and hairier. Stranger still, when the tips of their toes and ears were clipped off as a part of a routine tagging procedure, they often grew back.
“We were just so shocked that such a small change […] could have profound effects on a complex regenerating tissue,” says Hao Zhu, a cell biologist at the University of Texas Southwestern Medical Center in Dallas and a co-author of the study.
The underlying cause of this seemingly miraculous healing appears to revolve around a single protein. The mice were found to be carrying the protein Lin28a usually only produced in the development of the embryo. Lin28a has been studied previously for its role within cancer, and it is known to bind to Let7 – an RNA molecule which encourages cells to mature and lose their regenerative abilities. It also affects cellular metabolism by boosting the level of certain enzymes involved in the production of energy in cells.
‘Resetting’ cells using embryonic genes is not a new technique, and has been used in the past to create pluripotent stem cells that are themselves embryonic-like in state. The new discovery here is that anti-ageing changes can be achieved not simply in cell cultures, but also in the developed tissues of a living organism.
However, this discovery is far from a ‘fountain of youth’ treatment. Not every tissue infused with Lin28a gained healing powers; heart tissue, for instance, did not experience a change in regenerative ability. This raises questions over whether those tissues resist the treatment or whether other proteins are responsible for regulating ageing here. Perhaps unsurprisingly given the story of its discovery, Lin28a has also been linked to the development of tumours, and this has become the focus of a number of recent research studies. Such a link would pour cold water on the potential therapeutic uses of the discovery, but scientists are hopeful that they may yet be able to create a drug to treat conditions involving tissue degeneration, such as alopecia (hair loss). Growing back arms and legs? That’s a bit further off.