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en: Cell cycle checkpoint factor p15Ink4b is a novel regulator of osteoclast differentiation.

en: Osteoclasts are specialized cells essential for bone resorption, a crucial process in bone remodeling, and dysregulation of osteoclastogenesis can lead to pathological bone loss such as osteoporosis and rheumatoid arthritis. Therefore, understanding the precise mechanisms governing osteoclast differentiation is crucial for developing effective therapies for skeletal diseases. In osteoclastogenesis, as well as other differentiated cells, it is well understood that cell cycle arrest is essential for terminal differentiation and is tightly regulated by CDK inhibitors such as Cip/Kip family and Ink4 family protein. In this manuscript, we identified p15Ink4b, a member of the Ink4 family, as a novel regulator of osteoclastogenesis by comprehensive single-cell RNA sequence data reanalyzing. Furthermore, histological analysis and in vitro osteoclast differentiation assay revealed that p15Ink4b functionally regulates osteoclastogenesis. Our findings may not only provide insights into the molecular mechanisms of osteoclast differentiation but also underscore the potential of harnessing cell cycle mechanisms to develop novel therapeutic strategies for bone diseases.

en: Scientific reports

ja: Scientific reports


en: Methylglyoxal compromises callus mineralization and impairs fracture healing through suppression of osteoblast terminal differentiation.

en: Impaired fracture healing in diabetic patients leads to prolonged morbidity and increased healthcare costs. Methylglyoxal (MG), a reactive metabolite elevated in diabetes, is implicated in various complications, but its direct impact on bone healing remains unclear. Here, using a non-diabetic murine tibial fracture model, we demonstrate that MG directly impairs fracture healing. Micro-computed tomography revealed decreased volumetric bone mineral density in the callus, while callus volume remained unchanged, resulting in a brittle bone structure. This was accompanied by reduced expression of osteocalcin and bone sialoprotein, both critical for mineralization. Biomechanical analysis indicated that MG reduced the mechanical resilience of the fracture site without altering its elastic strength, suggesting that the impairment was not primarily due to the accumulation of advanced glycation end-products in the bone extracellular matrix. In vitro studies confirmed that non-cytotoxic concentrations of MG inhibited osteoblast maturation and mineralization. Transcriptomic analysis identified downregulation of Osterix, a key transcription factor for osteoblast maturation, without altering Runx2 levels, leading to decreased expression of key mineralization-related factors like osteocalcin. These findings align with clinical observations of reduced circulating osteocalcin levels in diabetic patients, suggesting that the detrimental effects of MG on osteoblasts may extend beyond bone metabolism. Our study highlights MG and MG-sensitive pathways as potential therapeutic targets for improving bone repair in individuals with diabetes and other conditions characterized by elevated MG levels.

en: Biochemical and biophysical research communications