T cell Associated Cytokines Influence Bone Metabolism in A Glucose Dependent Manner: Implications for Fracture Healing in Type 1 Diabetes Mellitus

Type 1 diabetes mellitus (T1D) is a chronic metabolic disorder defined by autoimmune-mediated destruction of insulin-producing pancreatic β islet cells, resulting in insulin deficiency, dysregulated glucose metabolism, and systemic metabolic stress. These metabolic disturbances contribute to cumulative tissue damage and are associated with numerous long-term complications that impair quality of life and increase mortality. Among these complications, delayed or impaired healing following acute injuries such as bone fractures is well documented. Individuals with T1D that experience fracture injury may have prolonged healing times, compromised bone structural integrity, and, in severe cases, non-union fractures that result in persistent disability. Notably, suboptimal fracture healing may occur even in patients with well-controlled glycemia, suggesting contributions beyond metabolic disfunction alone. In this context, we hypothesized that T cell-specific immune dysregulation intrinsic to T1D contributes to impaired fracture healing independently of, or in conjunction with, metabolic dysfunction. To investigate the functional consequences of this T cell mediated immune dysregulation on bone metabolism, we first developed and characterized a cost-effective, reproducible, immortalized cell line–derived three-dimensional (3D) in vitro model of murine bone metabolism and homeostasis. This model recapitulates key features of bone formation and remodeling, as demonstrated by the temporal dynamics of established osteoblast and osteoclast biomarkers. Secondly, using a combination of in vivo and ex vivo murine models of T1D, we identified leukemia inhibitory factor (LIF) and interferon gamma (IFNγ) as T cell–associated cytokines whose expression is modulated by the diabetic phenotype during the acute fracture response. Finally, leveraging the 3D in vitro bone organoid system, we demonstrated that IFNγ alters patterns of osteogenic gene expression, decreases bone matrix formation, and delays resorption kinetics in a glucose-dependent manner. Conversely, when combined with IFNγ, LIF is able to reverse these negative effects by rebalancing osteogenic factors, rescuing osteoblast function and resorption kinetics in the setting of elevated glucose. Collectively, these data identify LIF as a potential immune-metabolic rheostat that modulates bone homeostasis during inflammatory stress and metabolic dysregulation. This work provides mechanistic insight into how diabetes-associated immune alterations may impair fracture healing and establishes a versatile experimental framework for studying osteoimmunological interactions relevant to diabetic bone disease.