Researchers in Illinois say they were able to regrow bone to repair a hole in a mouse’s skull.

The researchers, based at Northwestern University and the University of Chicago, think their work could lead to significant improvement in the care of people with severe skull or face trauma. They say they were able to regenerate skull bone and supporting blood vessels just where they needed to go, surpassing previous bone regrowth methods in speed.

Surgeons often treat skull and facial injuries by grafting bone from other parts of the body of the people they are treating. They harvest bone from the pelvis, ribs or elsewhere. The bone grafting is painful, and it becomes increasingly difficult the larger the graft becomes or the more contoured it needs to be.

The Northwestern University and University of Chicago researchers think their work could someday make such bone grafting obsolete. Their method involved harvesting mouse skull cells and engineering them to produce a protein, BMP9, that promotes bone growth. They then delivered and contained the new cells in the affected area using a hydrogel. The hydrogel, developed by Northwestern biomedical engineering and surgery professor Guillermo Ameer, acted as a temporary scaffold while the engineered skull cells did their job.

Regrowing bone in vivo using the BMP9 promises a therapy that might be more “surgeon friendly, if you will, and not too complicated to scale up for the patients,” Ameer said.

Ameer’s scaffolding hydrogel is a material based on citric acid, dubbed PPCN-g. The hydrogel is a liquid but turns into a gel-like elastic material when warmed to body temperature.

“When applied, the liquid, which contains cells capable of producing bone, will conform to the shape of the bone defect to make a perfect fit,” Ameer said. “It then stays in place as a gel, localizing the cells to the site for the duration of the repair.” The PPCN-g reabsorbs into body as the bone regrows.

“What we found is that these cells make natural-looking bone in the presence of the PPCN-g,” Ameer said. “The new bone is very similar to normal bone in that location.”

It could still take years to get the technology used in humans, Ameer said. But he added: “We did show proof of concept that we can heal large defects in the skull that would normally not heal on their own using a protein, cells and a new material that come together in a completely new way. Our team is very excited about these findings and the future of reconstructive surgery.”

The China Scholarship Council, National Institute of Dental and Craniofacial Research, Chicago Community Trust and National Center for Advancing Translational Sciences supported the research, which was published last week in the journal PLOS One.

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