When someone is missing bone in their face due to injury or illness, the current treatment involves transplanting a piece of bone extracted from the leg, leaving a deficit there. Now, however, scientists have succeeded in growing extra bone within sheep's bodies, that's preformed to the shape required.

Led by Prof. Antonios Mikos from Texas-based Rice University, a multi-institution team started by removing sections of bone from the mandibles (jawbones) of six sheep, then temporarily filling the resulting gaps with spacers. The scientists also created 3D-printed molds in the shape of the pieces of bone that had been removed.

Called bioreactors, those molds were then filled with either a biocompatible ceramic or crushed bone, and then surgically implanted on the sheeps' ribs. At the implant sites, the ribs' periosteum – which is a layer of vascularized connective tissue – was exposed.

Over the next nine weeks, bone cells from the ribs proceeded to migrate into the ceramic and crushed bone, gradually replacing those materials until nothing but live bone remained. The researchers then proceeded to remove the bioreactors from the ribs, and to remove the spacers from the animals' mandibles. They then implanted the pieces of form-fitting newly-grown bone in the corresponding gaps. The material grown using the crushed bone proved to be the most like natural bone, so it ended up being used for all the implants.

After a further 12 weeks, it was found that the bioreactor-grown bone had "knitted" to the adjacent mandible bone, and soft tissue had grown over the wound site.

"We have been gratified to contribute a regenerative solution for the potential treatment of craniofacial defects," says Mikos. "This work is testament to the value of team science."

A paper on the research was recently published in the journal Proceedings of the National Academy of Sciences.