Scientists have come a step closer to building artificial limbs for human beings after they successful grew a tiny rat's forelimb at a laboratory at the Massachusetts General Hospital (MGH).

Dr. Harald Ott of the MGH's Department of Surgery and the Center for Regenerative Medicine recently announced in a news release that his team was able to build a functioning, artificial rat leg that circulates blood and responds to various stimuli.

"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," Ott said.

"We have shown that we can maintain the matrix of all of these tissues in their natural relationships to each other, that we can culture the entire construct over prolonged periods of time," he added.

Researchers were able to build the functional artificial leg through a technique called "decellularisation." This involves the stripping of living cells from a dead limb to expose non-living parts.

After this, cells that make up blood vessels and muscles are planted in the dead limb in a process called "recellularisation."

The limb is then placed in a specially designed bioreactor, allowed to grow for two weeks, and grafted with some skin.

The scientists then attached the limb to a living rat that was administered with anaesthesia. They later found out that the artificial leg was capable of circulating blood.

The artificial leg was also found to be able to respond to an electrical pulse, clenching and unclenching 80 percent of the time when administered with electricity.

The researchers, however, have yet to examine muscle movement when the artificial limb is attached to a living rat.

Ott also said the challenge will be in connecting the artificial limb with the nervous system.