The tissue engineering of bone is fairly advanced in comparison to that of most of the rest of our biology. In part, it is an easier problem from a mechanical point of view, as the medical community has decades of experience in the nuts and bolts of replacing lost bone with other substances. So replacing bone with freshly grown new bone is in many ways an easier proposition that what already takes place in hospitals around the world. If labs can generate the bone tissue, there is a commercial network of medical providers ready and waiting to make use of it.
A recent popular science article gives us an idea as to the present state of the art here:
Gordana Vunjak-Novakovic, a professor of biomedical engineering at Columbia University, has solved one of many problems on the way to successful bone implants: how to grow new bones in the anatomical shape of the original. ... "We are starting studies with large animals that will establish safety and feasibility before commercialization," she said.
Dr. Vunjak-Novakovic, Dr. Warren L. Grayson and other members of the team used digital images of the joint to guide a machine that carved a three-dimensional replica, called a scaffold, from cleansed bone material. The team turned the bare scaffold into living tissue by putting it into a chamber molded to its exact shape, and adding human cells, typically isolated from bone marrow or liposuctioned fat. A steady source of oxygen, growth hormones, sugar and other nutrients was piped into the chamber, or bioreactor, so the bone would flourish.
This is another example of a form of recellularization, demonstrated in heart tissue engineering and treachea transplants in recent years. It doesn't remove the need for donor organs, but it can allow a patient's own cells to produce the final tissue for implantation, thereby eliminating any concern of rejection by the immune system. But back to the article:
Professor Hollister at Michigan is also working on creating bones of a jaw joint. But instead of using a bioreactor to grow them, he plans to use the human body as the incubator. The scaffold for the new bone, designed from a CT scan and printed directly using a laser system, is filled with cells from bone marrow or fat that are taken from the patient to prevent immune-system reactions. "Then we will let the patient’s body naturally heal and reconstruct the tissue as the implant is resorbed by the body," he said.
Many of the components to generate good bones are in place, said David L. Kaplan, professor and chairman of the department of biomedical engineering at Tufts University. "The technology is here," he said, "to control the size, shape and functional features of human tissue in the lab."
Promising advances are taking place here and now in regenerative medicine and tissue engineering. It's a very active, exciting field of human endeavor.