The next step will be learning how to regrow nerves, bone, cartilage, and connective tissue. That could prove to be a significant challenge, but hopefully not an insurmountable one. "In clinical limb transplantation, nerves do grow back into the graft, enabling both motion and sensation," Harald Ott, study author and surgeon at Mass General, said in a statement. "We have learned that this process is largely guided by the nerve matrix within the graft. We hope in future work to show that the same will apply to bioartificial grafts."