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This Rat Limb Was Grown in the Lab

Researchers stripped cells from a rat's arm, then used it as a base to grow new ones.

by Emiko Jozuka
Jun 4 2015, 11:55am

A suspension of muscle progenitor cells is injected into the cell-free matrix of a decellularized rat limb. Image: Bernhard Jank, MD, Ott Laboratory, Massachusetts General Hospital Center for Regenerative Medicine

The naked little animal arm in this video is no ordinary limb. According to a report by the New Scientist, it's the world's first bioengineered rat limb grown in a lab from living cells.

In a study published in the journal Biomaterials, a team of researchers from the Ott Laboratory at Massachusetts General Hospital MGH explained how they grew the rat limb in a bid to push forward the development of bioartificial limbs, which might some day be suitable for transplantation.

Bioengineering techniques have been used previously to grow individual organs like hearts and lungs. But what's particularly cool about this experiment is that the researchers have been able to grow a whole animal limb.

The stem cells needed to grow tissue can be provided by a donor. What researchers hadn't been able to work out until now, however, is how to construct a supporting structure known as the "matrix" or "scaffold", which holds together all the things like bone, blood, cartilage, nerves, and muscle which make up limbs.

To make the new limb, the researchers used a technique called "decellularization" to strip the cellular materials from the forelimb of a dead rat, while leaving the nerve matrix and the primary blood vessels intact (this is what's shown in the video). Next up, the researchers injected muscle stem cells into the decellularized rat limb, which provides the structure onto which the new cells can grow. This is then cultured in a bioreactor.

A suspension of muscle progenitor cells is injected into the cell-free matrix of a decellularized rat limb. Image: Bernhard Jank, MD, Ott Laboratory, Massachusetts General Hospital Center for Regenerative Medicine

"The composite nature of our limbs makes building a functional biological replacement particularly challenging," explained Harald Ott, MD of the MGH Department of Surgery and the Center for Regenerative Medicine in a press release.

"We have shown that we can maintain the matrix of all of these tissues in their natural relationship 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," he added.

According to the non-profit organisation Amputee Coalition, there are nearly two million amputees in the US. Both prosthetic technology and donor hand transplants are an option. Patients still have to face the lifelong risks of immunosuppressive therapy after transplant procedures, and prosthetics can have limitations in design and function. If limbs could be bioengineered in the future for those that need them, such setbacks could be reduced.