In a step towards personalized bone grafts to treat traumatic injury or congenital defects, a study, led by Darja Marolt, PhD, and Giuseppe Maria de Peppo, PhD, and published in the Proceedings of the National Academy of Sciences, reports the generation of patient-specific bone substitutes from skin cells for repair of large bone defects. This advance will facilitate the development of customizable, three-dimensional bone grafts on-demand, matched to fit the exact needs and immune profile of a patient. Taking skin cells, the NYSCF scientists utilized an advanced technique called “reprogramming” to revert adult cells into an embryonic-like state. The researchers differentiated the resultant induced pluripotent stem (iPS) cells into bone-forming progenitors and then seeded these cells onto a three-dimensional scaffold, which was placed into an artificial, biologically active environment, a bioreactor. Analysis revealed that, even in vitro, bone formed; and, when implanted in mice, the bone matured into typical dense, mineral-rich tissue. Next steps for this proof-of-concept research include protocol optimization and long-term safety trials in animal models.