Osteoclast responses to lipopolysaccharide, parathyroid hormone and bisphosphonates in neonatal murine calvaria analyzed by laser scanning confocal microscopy

A novel nano delivery system targeting different stages of osteoclasts

Osteoclast (OC) abnormalities represent osteoporosis's critical mechanism (OP). OCs undergo multiple processes that range from monocytic to functional. Different drugs target OCs at different developmental stages; however, almost no Suitable drug-targeted delivery systems exist. Therefore, we designed two dual-targeting nanoparticles to target OCs at different functional stages. Using the calcitonin gene-related peptide receptor (CGRPR), which OC precursors highly express, and specific TRAPpeptides screened in the bone resorption lacuna, where mature OCs function, respectively, two types of dual-targeted nanoparticles were constructed. Afterwards, nanoparticles were grafted with hyaluronic acid (HA), which specifically binds to CD44 on the surface of the OCs. In vivo and in vitro experiments show that both nanoparticles have noticeable targeting effects on OCs. This suggests that dual-targeting nanoparticles designed for different functional periods of OC can be well targeted to the corresponding OC, and further promote the more precise delivery of drugs used to treat OP.

Structure-Dependent Effects of Bisphosphonates on Inflammatory Responses in Cultured Neonatal Mouse Calvaria

Bisphosphonates (BPs) are classified into two groups, according to their side chain structures, as nitrogen-containing BPs (NBPs) and non-nitrogen-containing BPs (non-NBPs). In this study, we examined the effects of NBPs and non-NBPs on inflammatory responses, by quantifying the inflammatory mediators, prostaglandin E₂ (PGE₂) and nitric oxide (NO), in cultured neonatal mouse calvaria. All examined NBPs (pamidronate, alendronate, incadronate, risedronate, zoledronate) stimulated lipopolysaccharide (LPS)-induced PGE₂ and NO production by upregulating COX-2 and iNOS mRNA expression, whereas non-NBPs (etidronate, clodronate, tiludronate) suppressed PGE₂ and NO production, by downregulating gene expression. Additionally, [4-(methylthio) phenylthio] methane bisphosphonate (MPMBP), a novel non-NBP with an antioxidant methylthio phenylthio group in its side chain, exhibited the most potent anti-inflammatory activity among non-NBPs. Furthermore, results of immunohistochemistry showed that the nuclear translocation of NF-κB/p65 and tyrosine nitration of cytoplasmic protein were stimulated by zoledronate, while MPMBP inhibited these phenomena, by acting as a superoxide anion (O₂⁻) scavenger. These findings indicate that MPMBP can act as an efficacious agent that causes fewer adverse effects in patients with inflammatory bone diseases, including periodontitis and rheumatoid arthritis.

Anti-resorptive agents reduce the size of resorption cavities: a three-dimensional dynamic bone histomorphometry study

Alterations in resorption cavities and bone remodeling events during anti-resorptive treatment are believed to contribute to reductions in fracture risk. Here, we examine changes in the size of individual remodeling events associated with treatment with a selective estrogen receptor modulator (raloxifene) or a bisphosphonate (risedronate). Adult female rats (6months of age) were submitted to ovariectomy (n=17) or sham surgery (SHAM, n=5). One month after surgery, the ovariectomized animals were separated into three groups: untreated (OVX, n=5), raloxifene treated (OVX+Ral, n=6) and risedronate treated (OVX+Ris, n=6). At 10months of age, the lumbar vertebrae were submitted to three-dimensional dynamic bone histomorphometry to examine the size (depth, breadth and volume) of individual resorption cavities and formation events. Maximum resorption cavity depth did not differ between the SHAM (23.66±1.87μm, mean±SD) and OVX (22.88±3.69μm) groups but was smaller in the OVX+Ral (14.96±2.30μm) and OVX+Ris (14.94±2.70μm) groups (p<0.01). Anti-resorptive treatment was associated with reductions in the surface area of resorption cavities and the volume occupied by each resorption cavity (p<0.01 each). The surface area and volume of individual formation events (double-labeled events) in the OVX+Ris group were reduced as compared to other groups (p<0.02). Raloxifene treated animals showed similar amounts of bone remodeling (ES/BS and dLS/BS) compared to sham-operated controls but smaller cavity size (depth, breadth and volume). The current study shows that anti-resorptive agents influence the size of resorption cavities and individual remodeling events and that the effect of anti-resorptives on individual remodeling events may not always be directly related to the degree of suppression of bone remodeling.

Evolution of bisphosphonate-related osteonecrosis of the jaw in patients with multiple myeloma and Waldenstrom's macroglobulinemia: a retrospective multicentric study

Bisphosphonates (BPs) are used intravenously to treat cancer-related conditions for the prevention of pathological fractures. Osteonecrosis of the jaw (BRONJ) is a rare complication reported in 4-15% of patients. We studied, retrospectively, 55 patients with multiple myeloma or Waldenstrom's macroglobulinemia followed up from different haematological departments who developed BRONJ. All patients were treated with BPs for bone lesions and/or fractures. The most common trigger for BRONJ was dental alveolar surgery. After a median observation of 26 months, no death caused by BRONJ complication was reported. In all, 51 patients were treated with antibiotic therapy, and in 6 patients, this was performed in association with surgical debridement of necrotic bone, in 16 with hyperbaric O(2) therapy/ozonotherapy and curettage and in 12 with sequestrectomy and O(2)/hyperbaric therapy. Complete response was observed in 20 cases, partial response in 21, unchanged in 9 and worsening in 3. The association of surgical treatment with antibiotic therapy seems to be more effective in eradicating the necrotic bone than antibiotic treatment alone. O(2) hyperbaric/ozonotherapy is a very effective treatment. The cumulative dosage of BPs is important for the evolution of BRONJ. Because the most common trigger for BRONJ was dental extractions, all patients, before BP treatment, must achieve an optimal periodontal health.

Microglial expression of alphavbeta3 and alphavbeta5 integrins is regulated by cytokines and the extracellular matrix: beta5 integrin null microglia show no defects in adhesion or MMP-9 expression on vitronectin

As the primary immune effector cells in the CNS, microglia play a central role in regulating inflammation. The extracellular matrix (ECM) protein vitronectin is a strong inducer of microglial activation, switching microglia from a resting into an activated potentially destructive phenotype. As the activating effect of vitronectin is mediated by alphav integrins, the aim of the current study was to evaluate the requirement of the alphavbeta5 integrin in mediating microglial adhesion and activation to vitronectin, by studying these events in beta5 integrin-null murine microglia. Surprisingly, beta5 integrin null microglia were not defective in adhesion to vitronectin. Further analysis showed that microglia express the alphavbeta3 integrin, in addition to alphavbeta5. Flow cytometry revealed that microglial alphav integrin expression is regulated by cytokines and ECM proteins. alphavbeta3 integrin expression was downregulated by IFN-gamma, TNF, LPS, and TGF-beta1. alphavbeta5 expression was also reduced by IFN-gamma, TNF, and LPS, but strongly increased by the antiactivating factors TGF-beta1 and laminin. Gel zymography revealed that beta5 integrin null microglia showed no deficiency in their expression of matrix metalloproteinase (MMP)-9 in response to vitronectin. Taken together, these data show that microglia express two different alphav integrins, alphavbeta3 and alphavbeta5, and that expression of these integrins is independently regulated by cytokines and ECM proteins. Furthermore, it reveals that the alphavbeta5 integrin is not essential for mediating microglial adhesion and MMP-9 expression in response to vitronectin.

Current topics in pharmacological research on bone metabolism: inhibitory effects of bisphosphonates on the differentiation and activity of osteoclasts

Despite the extensive use of bisphosphonates (BPs) in the treatment of metabolic bone diseases associated with increased osteoclastic bone resorption, the precise mechanism of their action on bone metabolism is still unclear. To clarify at which stages of osteoclast differentiation and activation that BPs influence, we examined the osteoclasts generated from mononuclear precursors and osteoclasts in the calvaria by laser scanning confocal microscopy. The studies showed that BPs inhibit lipopolysaccharide- or parathyroid hormone-induced osteoclast differentiation, fusion, attachment, actin ring formation, and activation and that both beta3 integrin and osteopontin have an important role in cytoskeletal rearrangements associated with cell attachment and resorption in osteoclasts.