From left: Charles Chan, Owen Marecic and Michael Longaker

By Christopher Vaughan

Stanford stem cell researcher Michael Longaker, MD and his colleagues announced that they have discovered the stem cell responsible for healing bone fractures in mice. The identification of the bone repair stem cell in mice and eventually in humans could lead to improved healing after bones are broken. The research was recently published in the Proceedings of the National Academy of Sciences.
            “The dream is that we might be able to do cellular therapy for bone breaks,” says postdoctoral fellow Charles Chan, PhD, one of the scientists who took part in the research. “Right now bone breaks can take months to heal and we have very little we can do to affect that process.”
            Earlier this year, Longaker and his colleagues announced that they had identified the primary stem cell that gives rise to the myriad cell types of the skeletal system in mice. This primary skeletal stem cell produces bone, cartilage and a biological important cell type called stromal cells. The latest research is part of a larger effort to map all the cell types in the skeletal system.
            One of the surprises of this research was that the stem cell responsible for repairing bone breaks is different than the cell responsible for maintaining bone, says Longaker, who is also co-director of the Stanford Institute for Stem Cell Biology and Regenerative Medicine. “Only when we understand all the players can we see how they work and interact to impact the disease, healing and maintenance of the skeletal system,” he says.
            The research is especially important for people who have conditions that inhibit bone healing, like osteoporosis or diabetes, Longaker says. “We are excited because this extends the story from bone maintenance to response to bone injury.”
            The research is also notable because the paper’s first author is Owen Marecic, a former All-American Stanford football player who would sometimes play both offense and defense during the same game at Stanford. Marecic has always been interested in pursuing a career in medicine, and after playing for the Cleveland Browns and the San Francisco 49ers he decided to retire as an athlete. He is now preparing himself for medical school, where he wants to study to become an orthopedic surgeon. “He was joking that he has had more experience breaking bones than healing them,” Chan says.
            Longaker and the other researchers were impressed with how quickly Marecic came up to speed in the lab. “It’s really unusual for someone to hit the ground running and become a first author on a high-impact paper,” Longaker says. Marecic in part credits his experience working on teams, and also sees team analogies in how his research subject behaves in the body. “A team is okay if all of the players know their role and are taking care of business,” Marecic says. “The cell we found probably functions in a similar way, saying ‘Get me to an injury environment and let me go to work.’”