Regrowing human body parts: The dream comes within reach

Ken Muneoka
Ken Muneoka, a professor at Tulane University, has been identifying genes that regulate the growth of digits in mouse embryos.

For centuries, humans have dreamt of the day when we could grow new body parts to replace the ones we lost, just like salamanders that can sprout new limbs. Now researchers are actually finding ways to turn those dreams into reality.

Sometime in the next few decades, humans may be able to regrow a finger here, a toe there – and maybe even fresh patches of beating heart tissue.

Human hearts are among the most promising targets: "Fifteen years ago we would have said 50 years, but it could be as soon as 10 years from now," Ken Poss, a cell biologist at Duke University, told NBC News.

A decade ago, Poss and his colleagues demonstrated that zebrafish had the ability to repair a badly damaged heart, thanks to a particular protein that regulates the regenerative process.

That trick could work for humans as well as fish: Just this month, researchers from the Gladstone Institutes showed that they could turn human scar tissue into electrically conductive tissue in a lab dish by fiddling with just a few key genes.

"It's an intriguing idea, because you could turn bad cells into good cells," Poss explained. Among the hurdles that lie ahead: taking that technique out of the lab and applying it to living human hearts.

Fountain of regenerative youth
We humans already have demonstrated some ability to regenerate body parts: For example, very young children can fill out the tips of chopped off fingers and toes. We've got nothing on the salamander, which can regrow a whole arm below the joint – but in principle, "it's the whole shebang in terms of regenerative response," Ken Muneoka, a cell biologist at Tulane University, told NBC News. 

Young mice are able to regenerate toes, too. Since the mid-1980s, Muneoka has been studying mouse toes to understand how a similar regrowth mechanism can be reactivated or imitated in adult humans. In 2010, his lab showed it was possible to enhance the regenerative response in adult mice.

"Ultimately I think we're going to be able to regenerate a mouse digit and a mouse limb," he said. And then, "if we can regenerate a digit, we should be able to regenerate hearts and muscle," he said. 

Other researchers are focusing on flatworms, which have exceptional regenerative capabilities. Last month, researchers working with headless flatworms showed they could reprogram chopped slices of worm tail to grow whole heads again.

Not so fast…
Despite the recent progress, some researchers are cautious about predicting how studies of animal regeneration will be applied to humans.

"We can envision using the knowledge to promote organs or tissue to grow," Elly Tanaka, who studies regeneration in salamanders at the Max Planck Institute in Germany, told NBC News. But "it's dangerous to say, 'Yes, we expect to regenerate a limb,'" she added.

At the same time, Tanaka acknowledges that the field is reaching a turning point. Within the next two or three years, studies of salamander genetics should "break open a lot of possibilities," she said.

Muneoka said future progress could well depend on how much we’re willing to spend to make the dream of human regeneration come true.

"It's a commitment issue whether it's possible or not in humans," he said. "Someone has to fund this research."

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Nidhi Subbaraman writes about science and technology. You can follow her on FacebookTwitter and Google+.