Research scientists at Massachusetts General Hospital have taken a huge step forward in medical science, as they’ve developed an artificial rat limb in a lab setting. The rat forelimb is complete with functioning vascular and muscle tissue, and opens the door for further experiments that could be applied to artificially growing limbs for primates in the future.

Senior researcher Dr. Harald Ott discussed in a press release the difficulty of growing artificial limbs. Every limb contains muscle, bone, cartilage, ligaments, nerves, and several other integral parts, and according to Ott, “each of which has to be rebuilt and requires a specific supporting structure called the matrix.” The successful development of the limb proved, “that we can culture the entire construct over prolonged periods of time,” according to Ott.

The experiment involved living cells taken from a donor organ that were stripped and repopulated with progenitor cells for each specific organ. Through this method, Ott and his team were able to remove cellular materials from dead rats while preserving the vasculature and nerve matrix.

After injecting muscle progenitors into the matrix sheaths of each muscle, vascular cells were present along blood vessel walls, while muscle cells aligned appropriately throughout the muscle matrix.

The limbs were tested for functionality, at which point muscle fibers contracted while the digital joints of the rats’ paws flexed with electrical stimulation. The next step in research is growing nerves within a limb and reintegrating them into the nervous system of the recipient.

Obviously, there is a long way to go until artificial limbs may be attached to humans, but this breakthrough is an exciting step in the right direction.