Bone fractures in patients with diabetes mellitus often do not heal as well as those in people without diabetes mellitus; however, the mechanisms underlying this impaired healing have been unclear. A recently published paper analysed the function of skeletal stem cells in mouse models of diabetes mellitus to try and determine what factors impair bone repair. The authors found that high serum levels of tumour necrosis factor in diabetic mice repressed the expression of Indian hedgehog (Ihh) in skeletal stem cells. Repressing hedgehog signalling during fracture repair suppressed the expansion of skeletal stem cells that usual happens after injury, which resulted in impaired healing. Importantly, the effects could be reversed with exogenous administration of Ihh.