Mass. General researchers grow muscular rat arms in a dish

A re-engineered rat limb grown at Harald Ott's lab at the Mass. General Hospital  Center for Regenerative Medicine.
A re-engineered rat limb grown at Harald Ott's lab at the Mass. General Hospital Center for Regenerative Medicine.

It sounds like something that involves a hex and a healthy dose of Skele-Gro.

In a step toward a future in which custom-grown limbs are transplanted in people, Boston researchers have regrown muscles on the chopped-off arms of rats. When they were re-attached to the rodents, vascular channels filled with blood. And when a low current was applied to the muscles, they twitched.

About a decade ago, researchers discovered that they could use a soapy solution to gently flush out living cells from organs like the heart or a liver — kind of like squeezing out the water from a soaked sponge — and retain the rest of the structure that kept them in place. Then, when they seeded new cells on the scaffold, the cells filled out the organ and reclaimed much of its function.

“You move everybody out, and then you move new living cells into that framework,” said Harald Ott, a researcher at Massachusetts General Hospital who led the new work.

Ott’s lab has successfully used this method to regenerate rat livers, and even a whole kidney that produced urine. The idea is that donor organs could be replenished with cells from the person in need of a transplant to reduce the chance of rejection. The latest study, demonstrated in the forearms of rats, is a first attempt on a limb.

Ott and team showed that it was possible to remove the cells from a rat and baboon forearms — which typically have layered and complex tissue — and still retain a scaffold. They published their results in the journal Biomaterials this week.

When the young mouse muscle cells that were added to the rat arms found their place along the matrix, they grew. In some samples, the researchers were able to grow blood vessels.

It wasn’t perfect — the muscle was too weak to move the arm, Ott said. As next steps, he intends to add other kinds of forearm cells to the mix. The idea would be to regenerate the arm in layers: first bone from bone cells, then muscle from “myoblasts,” then blood vessels, and finally nerves.

Before it can be applied to human limbs, the team will need to demonstrate that human cells can find their place on the empty canvas of a primate’s arm. “There’s no reason why it shouldn’t work,” Ott said. But they still need to show it can be done.

Nidhi Subbaraman writes about science and research. Email her at
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