Artificial limbs have been grown in a laboratory for the first time, producing body parts for rats. This could be a significant step toward the manufacture of artificial biological limbs for people who have lost appendages due to injury or disease.

A new technique capable of creating entire organs was used to manufacture the artificial limbs. The appendages created by the process are complete, with functioning muscles and blood vessels.

"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 of these tissues in their natural relationships to each other," said Harald Ott of the Department of Surgery and the Center for Regenerative Medicine at Mass General Hospital.

In addition to forming limbs of the rodents, researchers were able to show that the same process would be capable of producing primate limbs.

Roughly 1.5 million people living in the United States have lost one or more limbs. Mechanical prosthetic devices are often unattractive, and difficult to manage. By developing this technique further researchers hope to be able, one day, to produce biological limbs for human subjects.

Some patients have undergone surgery to have a donated hand placed on their wrist, replacing a missing extremity. However, this procedure requires the patient to undergo long-term immunosuppressive therapy, to prevent their bodies from rejecting the new hand. This can have a wide range of health problems, leading to diseases and infections.

The critical hurdle in growing limbs has been developing a matrix to provide the structure over which tissues and muscles could form. The progenitor cells for these structures can be harvested easily from patients, tricking the body into not recognizing the new limb as a foreign object.

Living cells were stripped from a donor organ but the vascular and nerve matrix was maintained. Then progenitor cells and vascular cells were added. After muscles were grown on the matrix, electrical stimulation of the structures resulted in contractions roughly 80 percent as strong those seen in newborn rats. These signals were able to cause movement within the wrists and paws of the artificial limbs. Vascular systems in the artificial biological limbs were able to fill with blood, and supply continued circulation.

In patients receiving transplanted hands, nerves have formed between the new extremity and the wrist or forearm where it is attached. Researchers hope a similar process will also take place with laboratory-grown biological limbs.

"Additional next steps will be replicating our success in muscle regeneration with human cells and expanding that to other tissue types, such as bone, cartilage and connective tissue," Ott told the press.

Development of the world's first artificial limbs for rat was published in the journal Biomaterials.

Photo: Staffan Vilcans | Flickr

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