Not long after the first artificially intelligent prostheses are hitting the consumer market, a team of bioengineers has taken the first step towards creating "bioartificial" replacement limbs for amputees.
Spring-boarding off the techniques used to create bioartificial organs, they created a rat forelimb that boasts functioning vascular and muscle tissue.
"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," says senior author of the paper on the project Harald Ott, MD, of the Massachusetts General Hospital (MGH) Department of Surgery and the Center for Regenerative Medicine.
While donor hand transplants exist, they require lifelong immunosuppressive therapy, which carries health risks and impracticalities, despite improvements to the quality of life.
It's possible to use progenitor cells necessary to regenerate the many tissues in a limb that come from the recipient, yet the missing link has been, quite literally, the matrix that connects cells and helps them grow -- until now.
"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, and that we can repopulate the vascular system and musculature," says Dr. Ott.
The new method employs a detergent, bathing donor cells in it until all that remains is the matrix.
Next, the research team repopulates the stripped-down donor matrix with the recipient's progenitor cells specific to the organ being duplicated.
Dr. Ott and his team have regenerated kidneys, livers, hearts and lungs from animal models, yet this is the first occurrence in which scientists have created a bioartificial limb with all its complex tissues.
Using this technique, Dr. Ott and his colleagues at MGH perfused the detergent through the vascular system, ridding the forelimb from cellular material over the course of a week.
The remaining matrix -- the preliminary structure to all the various tissues in the limb -- was free of cells and waiting for muscle and vascular cells that had been cultivated in the lab.
Veins and arteries were then regenerated when vascular cells were injected into the limb's main artery.
The team injected muscle progenitors into sheaths in the matrix that house each muscle and electrical stimulation was successfully applied, giving the limb 80 percent of the strength of a newborn rat.
More than 1.5 million people in the US have lost a limb, according to the researchers, who aim to make advances in both function and appearance of prosthetics.
The paper was published in the journal Biomaterials.