Radiofrequency Echographic Multispectrometry (REMS) can Overcome the Effects of Structural Internal Artifacts and Evaluate Bone Fragility Accurately.

PURPOSE: This study measured bone mineral density (BMD) in a Japanese population using the novel non-ionizing system using radiofrequency echographic multispectrometry (REMS) and compared the results with those obtained using traditional dual-energy X-ray absorptiometry (DXA). We aimed to identify any discrepancies between measurements obtained using these instruments and identify the influencing factors. METHODS: This cross-sectional study examined patients with osteoporosis treated at a single center from April to August 2023. We examined BMD assessment by DXA and REMS in lumbar spine and proximal femur. Patients were categorized into two groups: those with discrepancies between lumbar spine BMD measured by DXA and REMS, and those without. Semiquantitative evaluation of vertebral fractures and abdominal aortic calcification scoring were also performed and compared between the two groups, along with various patient characteristics. RESULTS: A total of 70 patients (88.6% female; mean age 78.39 ± 9.50 years) undergoing osteoporosis treatment were included in the study. A significant difference was noted between DXA and REMS measurement of BMD and T-scores, with REMS recording consistently lower values. The discrepancy group exhibited a higher incidence of multiple vertebral fractures and increased vascular calcification than the non-discrepancy group. Multivariate analysis indicated that diabetes mellitus, severe vertebral fractures, and increased abdominal aortic calcification scores were significantly associated with discrepancies in lumbar spine T-scores. CONCLUSION: This study suggests that REMS may offer a more accurate measurement of BMD, overcoming the overestimation of BMD by DXA owing to factors such as vertebral deformities, abdominal aortic calcification, and diabetes mellitus.

Dynamic transcriptome analysis of osteal macrophages identifies distinct subset with senescence features in experimental osteoporosis.

Given the potential fundamental function of osteal macrophages in bone pathophysiology, we study here their precise function in experimental osteoporosis. Gene profiling of osteal macrophages from ovariectomized mice demonstrated the upregulation of genes that were involved in oxidative stress, cell senescence and apoptotic process. A scRNA-seq analysis revealed that osteal macrophages were heterogenously clustered into 6 subsets that expressed proliferative, inflammatory, anti-inflammatory and efferocytosis gene signatures. Importantly, postmenopausal mice exhibited a 20-fold increase in subset-3 that showed a typical gene signature of cell senescence and inflammation. These findings suggest that the decreased production of estrogen due to postmenopause altered the osteal macrophages subsets, resulting in a shift toward cell senescence and inflammatory conditions in the bone microenvironment. Furthermore, adoptive macrophage transfer onto calvarial bone was performed and mice that received oxidative-stressed macrophages exhibited greater osteolytic lesions than control macrophages, suggesting the role of these cells in development of inflammaging in bone microenvironment. Consistently, depletion of senescent cells and oxidative-stressed macrophages subset alleviated the excessive bone loss in postmenopausal mice. Our data provided a new insight into the pathogenesis of osteoporosis and sheds light on a new therapeutic approach for the treatment/prevention of postmenopausal osteoporosis.

Noncanonical Pyroptosis Triggered by Macrophage-Derived Extracellular Vesicles in Chondrocytes Leading to Cartilage Catabolism in Osteoarthritis.

OBJECTIVE: The severity of osteoarthritis (OA) and cartilage degeneration is highly correlated with the development of synovitis, which is mediated by the activity of inflammatory macrophages. A better understanding of intercellular communication between inflammatory macrophages and chondrocytes should aid in the discovery of novel therapeutic targets. We undertook this study to explore the pathologic role of inflammatory macrophage extracellular vesicles (EVs) in cartilage degeneration. METHODS: Macrophages were stimulated by treatment with bacterial lipopolysaccharides to mimic the state of inflammatory macrophages, and the resulting EVs were harvested for chondrocyte stimulation in vitro and for intraarticular injection in a mouse model. The stimulated chondrocytes were further subjected to RNA-sequencing analysis and other functional assays. The action of caspase 11 was disrupted in vitro using a specific small interfering RNA or wedelolactone, and in experimental murine OA models by intraarticular injection of wedelolactone. RESULTS: Stimulated chondrocytes exhibited a significant elevation in the expression of chondrocyte catabolic factors. Consistent with these results, RNA-sequencing analyses of stimulated chondrocytes indicated that up-regulated genes were mainly categorized into apoptotic process and tumor necrosis factor signaling pathways, which suggests the induction of apoptotic process. Moreover, these chondrocytes exhibited a significant elevation in the expression of pyroptosis-related molecules that were correlated with the expression of chondrocyte catabolic factors. The disruption of caspase 11 significantly alleviated pyroptotic and catabolic processes in stimulated chondrocytes and pathologic changes in collagenase-induced and joint instability-induced OA models. CONCLUSION: Our results provide new insight into the pathologic mechanisms of OA and suggest that noncanonical pyroptosis in chondrocytes represents an attractive therapeutic target for treatment.