Gene therapy and stem cells prompt bone to regrow itself

Bone grafts, though imperfect, are used to repair fractures so severe the bone cannot mend the breach on its own. A Cedars-Sinai-led team has developed a combination treatment using ultrasound, stem cells and gene therapy that could replace this method.

Bone grafted either from the patient, usually from the hip or from a donor, is designed to act as a scaffold for the broken bone to heal and to be reabsorbed over time. But both types of grafts can cause problems. Some patients do not have enough healthy bone for a graft. In other cases, taking bone from the hip can lead to new injuries or infection. And donor grafts may not integrate properly into the bone, failing to fix the break.

The Cedars-Sinai investigators, led by Dan Gazit, injected a collagen matrix into the fractured leg bones of lab animals, according to a statement. Over two weeks, this matrix “recruited” stem cells from the fractured leg. Then, to kickstart healing, the team used an ultrasound pulse and microbubbles to deliver a bone-inducing gene. Eight weeks later, the fracture was healed in all animals that underwent the treatment. (See video below.)

“We’re combining an engineering approach with a biological approach to advance regenerative engineering, which we believe is the future of medicine,” Gazit said.

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It is difficult to pin down exact numbers for bone graft procedures, but the team said more than 2 million procedures are performed around the world annually. Grand View Research valued the bone graft market at $2.3 billion in 2015 and projected it will grow beyond $3.6 billion by 2024.

“This study is the first to demonstrate that ultrasound-mediated gene delivery to an animal’s own stem cells can effectively be used to treat nonhealing bone fractures,” said Gadi Pelled, an assistant professor of surgery at Cedars-Sinai, in the statement. “It addresses a major orthopedic unmet need and offers new possibilities for clinical translation.”