Osteoporosis Treatments Affect Bone Matrix Maturation in a Rat Model of Induced Cortical Remodeling

Zucker Diabetic-Sprague Dawley Rats Have Impaired Peri-Implant Bone Formation, Matrix Composition, and Implant Fixation Strength

An increasing number of patients with type 2 diabetes (T2DM) will require total joint replacement (TJR) in the next decade. T2DM patients are at increased risk for TJR failure, but the mechanisms are not well understood. The current study used the Zucker Diabetic-Sprague Dawley (ZDSD) rat model of T2DM with Sprague Dawley (SPD) controls to investigate the effects of intramedullary implant placement on osseointegration, peri-implant bone structure and matrix composition, and fixation strength at 2 and 10 weeks post-implant placement. Postoperative inflammation was assessed with circulating MCP-1 and IL-10 2 days post-implant placement. In addition to comparing the two groups, stepwise linear regression modeling was performed to determine the relative contribution of glucose, cytokines, bone formation, bone structure, and bone matrix composition on osseointegration and implant fixation strength. ZDSD rats had decreased peri-implant bone formation and reduced trabecular bone volume per total volume compared with SPD controls. The osseointegrated bone matrix of ZDSD rats had decreased mineral-to-matrix and increased crystallinity compared with SPD controls. Osseointegrated bone volume per total volume was not different between the groups, whereas implant fixation was significantly decreased in ZDSD at 2 weeks but not at 10 weeks. A combination of trabecular mineral apposition rate and postoperative MCP-1 levels explained 55.6% of the variance in osseointegration, whereas cortical thickness, osseointegration mineral apposition rate, and matrix compositional parameters explained 69.2% of the variance in implant fixation strength. The results support the growing recognition that both peri-implant structure and matrix composition affect implant fixation and suggest that postoperative inflammation may contribute to poor outcomes after TJR surgeries in T2DM patients. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

The relative contribution of bone microarchitecture and matrix composition to implant fixation strength in rats

Bone microarchitectural parameters significantly contribute to implant fixation strength but the role of bone matrix composition is not well understood. To determine the relative contribution of microarchitecture and bone matrix composition to implant fixation strength, we placed titanium implants in 12-week-old intact Sprague-Dawley rats, ovariectomized-Sprague-Dawley rats, and Zucker diabetic fatty rats. We assessed bone microarchitecture by microcomputed tomography, bone matrix composition by Raman spectroscopy, and implant fixation strength at 2, 6, and 10 weeks postimplantation. A stepwise linear regression model accounted for 83.3% of the variance in implant fixation strength with osteointegration volume/total volume (50.4%), peri-implant trabecular bone volume fraction (14.2%), cortical thickness (9.3%), peri-implant trabecular crystallinity (6.7%), and cortical area (2.8%) as the independent variables. Group comparisons indicated that osseointegration volume/total volume was significantly reduced in the ovariectomy group at Week 2 (~28%) and Week 10 (~21%) as well as in the diabetic group at Week 10 (~34%) as compared with the age matched Sprague-Dawley group. The crystallinity of the trabecular bone was significantly elevated in the ovariectomy group at Week 2 (~4%) but decreased in the diabetic group at Week 10 (~3%) with respect to the Sprague-Dawley group. Our study is the first to show that bone microarchitecture explains most of the variance in implant fixation strength, but that matrix composition is also a contributing factor. Therefore, treatment strategies aimed at improving bone-implant contact and peri-implant bone volume without compromising matrix quality should be prioritized.

Effects and mechanisms of natural plant active compounds for the treatment of osteoclast-mediated bone destructive diseases

Bone-destructive diseases, caused by overdifferentiation of osteoclasts, reduce bone mass and quality, and disrupt bone microstructure, thereby causes osteoporosis, Paget's disease, osteolytic bone metastases, and rheumatoid arthritis. Osteoclasts, the only multinucleated cells with bone resorption function, are derived from haematopoietic progenitors of the monocyte/macrophage lineage. The regulation of osteoclast differentiation is considered an effective target for the treatment of bone-destructive diseases. Natural plant-derived products have received increasing attention in recent years due to their good safety profile, the preference of natural compounds over synthetic drugs, and their potential therapeutic and preventive activity against osteoclast-mediated bone-destructive diseases. In this study, we reviewed the research progress of the potential antiosteoclast active compounds extracted from medicinal plants and their molecular mechanisms. Active compounds from natural plants that inhibit osteoclast differentiation and functions include flavonoids, terpenoids, quinones, glucosides, polyphenols, alkaloids, coumarins, lignans, and limonoids. They inhibit bone destruction by downregulating the expression of osteoclast-specific marker genes (CTSK, MMP-9, TRAP, OSCAR, DC-STAMP, V-ATPase d2, and integrin av3) and transcription factors (c-Fos, NFATc1, and c-Src), prevent the effects of local factors (ROS, LPS, and NO), and suppress the activation of various signalling pathways (MAPK, NF-κB, Akt, and Ca²⁺). Therefore, osteoclast-targeting natural products are of great value in the prevention and treatment of bone destructive diseases.