Scientists have discovered that humans have an innate or “salamander-like” ability to regenerate cartilage, which could lead to treatments for diseases such as osteoarthritis — and possibly provide a starting point for human limb regeneration.
Published on Oct. 9 in Science Advances, researchers from Duke University in North Carolina and Sweden’s Lund University began by analyzing the age of various proteins in human cartilage, through a process that would examine its amount of amino acid conversions — the more conversions, the older it would be.
They discovered that cartilage located in the ankles was the youngest and was regenerating at a more constant rate. Cartilage in the knees was deemed “middle-aged” and the oldest — which would regenerate at a slower rate — was in the hips.
“These findings reveal a dynamic anabolic effect in human limbs, which reflect a potential innate, albeit limited, regenerative capacity in human cartilage,” the study says.
The study points out that the presence of younger cartilage proteins would help explain why ankle injuries tend to heal quicker, while knee and hip injuries take longer to heal and could possibly develop into arthritis.
The regeneration in the cartilage was caused by molecules called microRNA. Most notably, these molecules are commonly found in animals known for being able to regrow limbs and other body parts, including salamanders, lizards, and zebrafish. Scientists have found that microRNA is a key element to encouraging the amount of cell growth needed for one of these animals to regrow a limb.
“We believe that an understanding of this ‘salamander-like’ regenerative capacity in humans, and the critically missing components of this regulatory circuit, could provide the foundation for new approaches to repair joint tissues and possibly whole human limbs,” said senior author and Duke professor Virginia Byers Kraus in a press release.
The authors say that further study of the microRNA molecules in humans could lead to significant developments in treatments for joint issues, including completely regrowing the damaged cartilage in an arthritic joint through microRNA injections.
“If we can figure out what regulators we are missing compared with salamanders, we might even be able to add the missing components back and develop a way someday to regenerate part or all of an injured human limb,” Kraus said. “We believe this is a fundamental mechanism of repair that could be applied to many tissues, not just cartilage.”
The study says that if researchers can determine the missing regenerative factors in humans, it would be possible to develop a “molecular cocktail” that could be the key to regenerating human body parts.
“We call it our ‘inner salamander’ capacity,” said lead author Ming-Feng Hsueh.