The work of a team led by Gordana Vunjak-Novakovic suggests that personalized bone grafts for human facial reconstruction may be possible in the future.

Researchers have engineered living bone tissue to repair bone loss in the jaw, a structure that is typically difficult to restore. Vunjak-Novakovic, professor of biomedical engineering and medical sciences at Columbia University, grafted customized implants into pig jaws that resulted in integration and function of the engineered graft into the recipient’s own tissue.

Birth defects and injuries can cause bone deformities in the head and face that are difficult to repair. Replacement bones must be perfectly sculpted to match the features of a person’s face. Bones of the jaw, in particular, must also be able to withstand significant force in order to chew food.

Current treatments replace missing bone with metal, bone putty derived from deceased donors or grafted bone from a person’s own body. While using the patient’s own tissue is the safest strategy, sacrificing bone from elsewhere causes a secondary injury. It can also be difficult to obtain a piece large enough to carve into an exact match. Bone putty can be useful too, but may not be structurally stable without reinforcements that must be removed in subsequent surgeries.

Researchers chose pigs to test the new bone reconstruction technique because their jaw anatomy and type of force and movement are similar to those of humans. They replaced a piece of the pig's jawbone with cow bone matrix—the material left after removing its resident cells—which served as a scaffold for the graft. Guided by imaging technology, the researchers shaped each cow bone scaffold to fit into the missing jaw bone region.

By playing with the diameter of the nanopore, the researchers were able to find the ideal compromise between current and voltage to obtain the highest possible power. Image credit: EPFL.By playing with the diameter of the nanopore, the researchers were able to find the ideal compromise between current and voltage to obtain the highest possible power. Image credit: EPFL. Next, the researchers seeded the scaffold with the pig’s own stem cells harvested from the animal's fat and placed the engineered tissue inside a bioreactor to grow for three weeks. They then implanted the engineered bone grafts into the pig and monitored the growth for six months. Over that time, the transplanted bone integrated into the pig's jaw. The grafts prompted new bone growth and strengthened the bone enough to tolerate forces needed for the pig to chew.

The researchers found that the engineered implants remodeled like natural bone. They found that the pig’s body reacted to the implant just like its own bone, breaking it down and rebuilding it as needed.

Six pigs received engineered implants, while six others received the cow bone without any stem cells. At the six-month point, all the animals had some regrowth of the missing jaw. The researchers used quantitative image analysis to determine that those pigs with the engineered implant grew the most bone.

Several features enhanced the clinical prospects of this research, according to Hunziker. First, the team isolated the stem cells from fat, which can be harvested with less discomfort than from bone marrow and yield ample cells due to abundant fat supply. They also avoided using growth factors, which are proteins that may improve bone quality but sometimes lead to excess bone growth and increase the cost of the procedure.

To contact the author of this article, email engineering360editors@globalspec.com