In a report published earlier this week in the journal Biomaterials, a team of scientists detail their work putting together a living, fully functional arm from scratch.

The limb, pictured next to this article, was that of a rat. It came complete with a perfectly shaped paw and its anatomy was so accurate it looked more like a nature-made amputated arm than a laboratory-grown one.

Further, the researchers who worked on this project say that, when zapped with electricity, the arm's muscles promptly responded by clenching and unclenching the paw.

When the limb was joined with the body of a rat under anesthesia, the rodent's body welcomed it and began feeding it blood and nutrients. Still, the scientists didn't wake the rat to test for movement or rejection.

How does one grow limbs in the lab?

Experiments of this kind are not exactly a novelty. On the contrary, windpipes, lungs, kidneys and many other organs have been engineering by scientists in recent years. Limbs, however, nobody dared experiment with.

Well, not until researcher Harald Ott at the Massachusetts General Hospital in Boston and his team came along, that is. To grow the rat arm, the scientists started by removing such a body part from a rodent belonging to this species and depleting it of all the cells comprising it.

All that was left was a collagen scaffold that was then seeded with a brand new generation of cells. It was kind of like removing all the toppings on a pizza and leaving nothing but the dough, and then adding other toppings.

To make the rat forelimbs' blood vessels more robust, the scientists used human cells to grow them. The muscles and the skin, however, were engineered from rat cells. It took less than a month for the lab-made limb to grow blood vessels and muscles. Skin grafts were then added.

“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,” researcher Harald Ott commented on the outcome of these experiments in an interview.

“This is science fiction coming to life,” added scientist Daniel Weiss at the University of Vermont College of Medicine in Burlington, as cited by New Scientist.

All in all, the team depleted around 100 donor limbs of cells and attempted to recolonize them. As detailed in the report in the journal Biomaterials, about 50 of the donor forearms used in the investigation were successfully repopulated with cells.

The goal is to make limbs for amputees

Specialist Harald Ott and fellow researchers are confident that their work growing limbs from scratch will one day benefit people left without one or more of their limbs.

Plainly put, the scientists imagine using the techniques employed to make artificial rat forearms to grow fully functional limbs for amputees. True, they have a long and rocky road ahead of them, but they hope they will one day get to work with human patients.

Unlike donor limbs, arms and maybe even legs grown from an individual's own cells would not be vulnerable to rejection, the specialists explain. Besides, they would look and feel more natural than bionic replacement limbs.