First biolimb ever: Rat forearm grown in lab

Brett Smith for redOrbit.com – Your Universe Online
In a development that could be a huge step forward for amputees, researchers at Massachusetts General Hospital in Boston have, for the first time ever, grown a rat forearm in the lab, according to a report in New Scientist.

“We’re focusing on the forearm and hand to use it as a model system and proof of principle,” said Dr. Harald Ott, a thoracic surgeon at MGH. “But the techniques would apply equally to legs, arms, and other extremities.” (Other extremities, you say?)
Currently, amputees may get a replacement limb that looks fine, but doesn’t even approach the function of an actual limb. A few hand transplants have been successfully performed, but the patients must commit to a lifetime of immunosuppressant drugs to keep their body from rejecting the new hand.
A new limb grown from the technology being developed at MGH would circumvent the need for immunosuppressant drugs as the limb would be grown from an amputee’s own cells.
Growing a rat limb
“This is the first attempt to make a biolimb, and I’m not aware of any other technology able to generate a composite tissue of this complexity,” Ott said.
In the first “decellularization” step of the process, organs from deceased donors are treated with chemicals that strip off the soft tissue, making just the “scaffold” of the organ, built mostly from the inert protein collagen. This maintains all the sophisticated architecture in the original body organ. With the rat forearm, this involved the collagen structures that define blood vessels, tendons, ligaments, muscles, and bones.
In the next step, the organ scaffold is ‘recellularized’ by seeding it with cells from the recipient. The scaffold is then grown in a bioreactor that permits new tissue to grow and takeover the scaffold. Since the grown soft tissue is from the recipient’s own cells – the recipient will not reject the limb when it is attached.
Future steps include nervous system
The MGH team has already decellularized around 100 rat forelimbs and recellularized at least half of them. Ott said his team still needs to figure out how to seed the limb with bone, cartilage, and other cells to see if these tissues can be properly regenerated. The team then needs to start working on a nervous system for the limb.
“It’s a notable step forward, and based on sound science, but there are some technical challenges that Harald’s group has to tackle,” Steve Badylak, an who is expert doing similar work with pig limbs at the University of Pittsburgh, told New Scientist. “Of these, the circulation is probably the biggest challenge, and making sure even the tiniest capillaries are successfully lined with endothelial cells so that they don’t collapse and cause clots.”
“But this is really an engineering approach, taking known fundamental principles of biology and applying them as an engineer would,” Badylak added.
Ott said if his team is successful, it could bring relief to the 1.5 million amputees living in the US and millions of others worldwide.
“At present, if you lose an arm, a leg, or soft tissue as part of cancer treatment or burns, you have very limited options,” he said.
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