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Regenerating Body Parts? USF Biologist Discovers How It’s Done


A Procotyla fluviatilis flatworm with its regenerative powers restored begins to grow a second head. Photo courtesy of James Sikes.

Cut off a salamander’s tail, and within a few weeks, it’ll have a new one. A starfish can grow a whole new body from a severed leg. Even humans can regenerate fingertips—but only until the age of two. 

Why do we lose this ability while other creatures keep it for life? 

Unmatched regeneration 

That is the question that drove University of San Francisco Assistant Professor of Biology James Sikes to study flatworms, which are unmatched at regeneration. One worm, cut into 275 pieces, will grow into 275 new worms within a week. Sikes wanted to know flatworms’ secret. 

After three years of research, he found the answer, which was recently published in the leading scientific journal, Nature. His surprising findings were also covered by the Los Angeles Times, WBUR Radio in Boston, Scientific American, and The Scientist.

To uncover the secret to flatworm regeneration, Sikes and his team took a counterintuitive approach. They focused on the other end of the spectrum, studying a type of flatworm that lost most of its regenerative ability to evolution, the Procotyla fluviatilis. They sequenced its DNA and compared it to that of regenerative flatworms. The gambit paid off. The team was able to isolate the gene responsible for regeneration, called Wnt. 

'It was amazing' 

What would happen, Sikes wondered, if they modified the Wnt gene in the Procotyla fluviatilis? The answer: restore its ability to regenerate, which had been lost millions of years ago. It was the first time the ability to regenerate had been recovered in any creature.

“It was amazing. I couldn’t believe it. I looked at these animals and saw them regenerating heads,” said Sikes. “The fact that it could be reversed with a single gene is mind blowing— one little switch.”

While it’s unlikely that people will ever regrow heads, the findings could have major medical implications for complex organisms, including humans, who, like the Procotyla fluviatilis, once had and then lost the capacity to regenerate.

Treat brain damage, paralysis ...

“The idea that there is an underlying ability to regenerate, that maybe you’re still holding onto it, and that maybe you can turn that ability back on gives a boost to research on regenerative medicine,” Sikes said. 

In fact, research is already being done on adult stem cells to regenerate tissues that could one day treat brain damage, heart attack patients, and the paralyzed. 

“Can we do it today? No. Tomorrow? Probably not,” Sikes said. “But we probably have more underlying abilities in our bodies than we realize.”

Written by Monica Villavicencio »email usfnews@usfca.edu | Twitter @usfcanews