Lizard tails dampen hopes of regenerating human limbs

Researchers studying the anatomy of green anoles found differences between the original and regenerated tails, raising new questions for the field of regenerative medicine.
Written by Janet Fang, Contributor

If caught by a predator, the green anole lizard can drop its tail and grow another one later.

But the regenerated tail isn’t a perfect replica of the original. According to two new studies, the new tail even has a different anatomy – raising the question of whether it will ever be possible to fully regenerate injured human limbs. New Scientist reports.

After dissecting original and regenerated tails of the green anole (Anolis carolinensis), a team led by Rebecca Fisher from the University of Arizona College of Medicine found many differences, including:

  • a single long tube of cartilage runs through the new tail, rather than the chain link of vertebrae found in the original.
  • in the place of shorter, variegated muscle fibers, the new tail has long muscles stretching from tip to stump.
  • pores throughout the cartilage take the place of regular gaps in vertebrae that allow blood vessels and nerves to pass through. However, the pores only let blood vessels through, suggesting that new nerves are either trapped in the cartilage or can’t reach all the tail muscles.

The first two differences suggest that the regenerated tail would be less flexible since neither the cartilage tube nor the long muscle fibers are capable of the fine control that comes with shorter muscles and lots of small joints between bones.

The findings seem to put a damper on hopes of eventually regenerating human limbs. Jason Pomerantz, a regenerative medicine researcher at the University of California, San Francisco, says: "Even in a context that we think of as a 'good' example of regeneration, the regenerated structure is not perfect and functioning as well as the original.” The work highlights the challenge of regenerating a complicated structure.

The two studies were published the Anatomical Record this summer.

[From New Scientist]

Image: green anoles via Wikimedia

This post was originally published on Smartplanet.com

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