Scientists 'Grow' a Limb in the Lab

Scientists may have managed to grow an arm. Researchers have used an experimental approach to engineer rat forelimbs with functioning vascular and muscle tissue. In addition, the researchers provided evidence that the same approach could be applied to the limbs of primates.

"The composite nature of our limbs makes building a functional biological replacement particularly challenging," said Harald Ott, one of the researchers, in a news release. "Limbs contain muscles, bone, cartilage, blood vessels, tendons, ligaments and nerves-each of which has to be rebuilt and requires a specific supporting structure called the matrix. We have shown that we can maintain the matrix of all these tissues in their natural relationships to each other, that we can culture the entire construct over prolonged periods of time, and that we can repopulate the vascular system and musculature."

In this latest study, the researchers stripped living cells from a donor organ with a detergent solution. Then, the remaining matrix was repopulated with progenitor cells appropriate to the specific organ. This decellularization technique is used to regenerate kidneys, livers, hears and lungs from animal models. This, however, is the first time that it's been used to engineer the more complex tissues of a limb.

The limb also functioned, as well. Electrical stimulation caused the muscle fibers to contract with a strength 80 percent of what would be seen in newborn animals. In addition, vascular systems of bioengineered forelimbs transplanted into recipient animals quickly filled with blood which continued to circulate, and electrical stimulation of muscles within transplanted grafts flexed the wrists and digital joints of the animals' paws.

"In clinical limb transplantation, nerves do grow back into the graft, enabling both motion and sensation, and we have learned that this process is largely guided by the nerve matrix within the graft," said Ott. "We hope in future work to show that the same will apply to bioartificial grafts."

The findings are published in the journal Biomaterials.

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