Summary Osteomyelitis is a common manifestation of invasive Staphylococcus aureus infection. Pathogen-induced bone destruction limits antimicrobial penetration to the infectious focus and compromises treatment of osteomyelitis. To investigate mechanisms of S. aureus-induced bone destruction, we developed a murine model of osteomyelitis. Micro-computed tomography of infected femurs revealed that S. aureus triggers profound alterations in bone turnover. The bacterial regulatory locus sae was found to be critical for osteomyelitis pathogenesis, as Sae-regulated factors promote pathologic bone remodeling and intraosseous bacterial survival. Exoproteome analyses revealed the Sae-regulated protease aureolysin as a major determinant of the S. aureus secretome and identified the phenol soluble modulins as aureolysin-degraded, osteolytic peptides that trigger osteoblast cell death and bone destruction. These studies establish a murine model for pathogen-induced bone remodeling, define Sae as critical for osteomyelitis pathogenesis, and identify protease-dependent exoproteome remodeling as a major determinant of the staphylococcal virulence repertoire.

The activation of sympathetic nerves by psychosocial stress creates a favorable environment in bone for the establishment of cancer cells in a mouse model of breast cancer.

The effects of type 1 diabetes on de novo bone formation during tibial distraction osteogenesis (DO) and on intact trabecular and cortical bone were studied using nonobese diabetic (NOD) mice and comparably aged nondiabetic NOD mice. Diabetic mice received treatment with insulin, vehicle, or no treatment during a 14-day DO procedure. Distracted tibiae were analyzed radiographically, histologically, and by microcomputed tomography (CT). Contralateral tibiae were analyzed using CT. Serum levels of insulin, osteocalcin, and cross-linked C-telopeptide of type I collagen were measured. Total new bone in the DO gap was reduced histologically (P < 0.001) and radiographically (P < 0.05) in diabetic mice compared with nondiabetic mice but preserved by insulin treatment. Serum osteocalcin concentrations were also reduced in diabetic mice (P < 0.001) and normalized with insulin treatment. Evaluation of the contralateral tibiae by CT and mechanical testing demonstrated reductions in trabecular bone volume and thickness, cortical thickness, cortical strength, and an increase in endosteal perimeter in diabetic animals, which were prevented by insulin treatment. These studies demonstrate that bone formation during DO is impaired in a model of type 1 diabetes and preserved by systemic insulin administration. Diabetes 54:2875-2881, 2005 T ype 1 diabetes is associated with several disorders of skeletal health, including decreased bone density, an increased risk for osteoporosis (1-6), and fragility fracture (7-9), as well as poor bone healing and regeneration characteristics (10), conditions which all rely, in part, upon an intramembranous component to bone formation. Increasing evidence suggests that skeletal abnormalities in type 1 diabetes may, in part, result from the detrimental effects of type 1 diabetes on bone formation. For example, decreased expression of transcription factors that regulate osteoblast differentiation have been demonstrated in animal models of type 1 diabetes (11). Numerous reports of bone histology in diabetic animals demonstrate decreased osteoblast number, osteoid volume, and mineral apposition rates (rev. in 12). In diabetic rats, plasma osteocalcin concentrations, a marker of osteoblast activity, acutely decline beginning on the 1st day of glucosuria (13). Similarly, serum concentrations of osteocalcin in children with newly diagnosed type 1 diabetes are significantly lower at the onset of disease (14). Serum markers correlated with bone formation (IGF-I, alkaline phosphatase, and osteocalcin) also are significantly lower in diabetic patients with osteopenia compared with those without osteopenia (2), and studies have demonstrated that lower bone mineral density (BMD) in type 1 diabetes is correlated with decreased markers of bone formation and more exaggerated dysregulation of the IGF system (15).The present study was designed to test the hypothesis that type 1 diabetes specifically impedes intramembranous bone formation by using a model of tibial distraction osteogenesis uniquely modified for use ...