Adult stem cells have shown the ability to stimulate healing of bone. Now Stanford scientists have used a protein that activates adult stem cells and progenitor cells to speed up the process of bone healing. A family of proteins called Wnt proteins are known to stimulate bone formation and tissue regeneration. Wnt proteins are difficult to isolate and hard to dissolve, so the scientists packaged the protein in liposomes, small lipid droplets similar to the membrane around cells. The Wnt proteins were planted like small flags in the outer surface of the liposome, so that when they contacted a cell they delivered their signal. The liposome technique allowed concentrated packaging of the proteins and easy delivery to target tissue. The Wnt-tagged liposomes were given to mice with damaged leg bones. Within three days, the treated mice showed 3 1/2-times more new bone growth than untreated animals, and had completely healed in four weeks, while untreated animals were still trying to heal. The Wnt protein appears to work by stimulating adult stem cells to become new bone. Because Wnt proteins can stimulate repair of a wide range of tissues, the technique might be useful not only in treatment of bone problems but also to stimulate repair of skin, heart and brain.

The study was published in Science Translational Medicine.