Histamine promotes osteoclastogenesis through the differential expression of histamine receptors on osteoclasts and osteoblasts

Novel insights on the biology and immunologic effects of histamine: A road map for allergists and mast cell biologists

Histamine (C5H9N3, molecular weight 111.15 g/mol) is a well-studied endogenous biogenic amine composed of an imidazole ring attached to an ethylamine side chain. It has a limited half-life of a few minutes within tissues and in circulation. Several cell types including mast cells (MCs), basophils, platelets, histaminergic neurons, and enterochromaffin cells produce varying amounts of histamine using histidine decarboxylase. However, only MCs and basophils have complex mechanisms to pack and store histamine in granules along with other mediators using serglycin and its carried glycosaminoglycan side chains. Relatively low granule pH (∼5.5) supports the binding of stored histamine to heparin, whereas exposure to neutral pH after degranulation weakens the binding and histamine becomes liberated. Histamine exerts multifaceted regulatory biofunctions by engaging its 4 types of heptahelical G protein-coupled receptors (H1R-H4R), which have different expression profiles and functions. MCs express H1R, H2R, and H4R, which gives them a dual role in histamine biology as producers and responsive target cells. Histamine plays a role in a variety of physiologic and pathologic processes such as cell proliferation, differentiation, hematopoiesis, vascular permeability, embryogenesis, tissue regeneration, and wound healing. The emergence of histamine receptor-deficient mouse models and the development of multiple histamine receptor agonists and antagonists have helped researchers better understand these physiologic and pathogenic functions of histamine. We review the biology of histamine with a focus on immunologic aspects and the role of histamine in allergy and MC biology.

Synovial mast cells and osteoarthritis: Current understandings and future perspectives

Osteoarthritis (OA) is a prevalent joint disease worldwide that significantly impacts the quality of life of individuals, particularly those in middle-aged and elderly populations. OA was initially considered as non-inflammatory arthritis, but recent studies have identified a substantial number of immune responses in OA, leading to the recognition of inflammation as a key factor in its pathogenesis. An increasing number of studies have found that mast cell (MC) and MC-secreted inflammatory mediators and cytokines are notably increased in the synovial fluid of OA patients, indicating a potential association between MCs and the onset and progression of synovial inflammation. The present review aims to summarize the significance and mechanism of MCs in the pathogenesis of OA. Meanwhile, we also discuss the clinical potential of using MCs as therapeutic target for OA therapy. Modulating the activities of MCs or the mediators of MCs in the synovial fluid inflammatory microenvironment will be promising new options for the treatment of OA.

Osteoporosis in Systemic Mastocytosis: A Scoping Review

Background: Mastocytosis (MS) is a rare disease that can involve various organs, including the bone. Given the incidence of the disease in the global population, MS poses a challenge for physicians, and early therapeutic intervention in the initial stages could significantly impact the quality of life of affected patients. Objective: The aim of this scoping review was to provide an overview of secondary osteoporosis in systemic mastocytosis (SM), focusing on the heterogeneity of its manifestations, the benefits of early diagnosis, and appropriate pharmacological treatment. Design: A technical expert panel (TEP) consisting of 8 physicians with expertise in metabolic bone diseases conducted the review following the PRISMA-ScR model. A strength of this study is that it provides various therapeutic approaches for patients with bone involvement in SM, although the limited available literature on the topic constituted a limitation. The TEP sought evidence regarding the following diagnostic and therapeutic modalities in the management of SM: "bisphosphonate therapy", "zoledronic acid therapy", "denosumab therapy", "IFN-alpha therapy", and "IFN-alpha therapy in combination with pamidronate". Results: Clinical data showed a correlation between densitometric outcomes, serum tryptase levels, and mast cell infiltration in the bone marrow, between increased bone mineral density and the presence of osteosclerosis in cases of advanced SM, between the severity of osteoporosis and hypertryptasemia, and also provided results on the long-term effects of bisphosphonate therapy, the therapeutic efficacy of zoledronic acid administration, the positive effect of denosumab on the reduction of serum tryptase levels (even if is proved in a limited numbers of cases) and the prevention of new fractures, and the effect of IFN-alpha in more severe cases of SM, either alone or in combination with pamidronate. Conclusions: Studies have demonstrated the effectiveness of various treatments depending on the form of mastocytosis, whether indolent systemic or advanced systemic, in the prognosis of the disease. However, this role should be further investigated in additional clinical studies, considering the limited data on the use of these interventions.

Association between Chronic Atrophic Gastritis and Bone Mineral Density among Women Older than 40 Years of Age in Korea

BACKGROUND

Chronic atrophic gastritis causes hypochlorhydria, hypergastrinemia, and malabsorption of nutrients, leading to lower bone mineral density. The few studies that investigated the association between chronic atrophic gastritis and bone mineral density have reported inconsistent findings. As such, the present study assessed the association between chronic atrophic gastritis and bone mineral density among a large sample of women >40 years of age in Korea.

METHODS

Data from 8,748 women >40 years of age who underwent esophagogastroduodenoscopy and bone densitometry were analyzed. Chronic atrophic gastritis was diagnosed using esophagogastroduodenoscopy. Bone mineral density of the lumbar vertebrae (L), femur neck, and femur total, measured using dual-energy X-ray absorptiometry, were the primary outcome variables. Low bone mineral density, which could be diagnosed as osteoporosis or osteopenia, was defined and analyzed as a secondary outcome. Linear regression was used to calculate adjusted mean values of bone mineral density. The association between low bone mineral density and chronic atrophic gastritis was analyzed using multiple logistic regression.

RESULTS

The adjusted mean bone mineral density for L1-L4 was 1.063±0.003, femur neck (0.826±0.002), and femur total (0.890±0.002) were significantly lower in patients with chronic atrophic gastritis than others (1.073±0.002, 0.836±0.001, 0.898±0.002, respectively; all P<0.01). Women with chronic atrophic gastritis exhibited an increased likelihood for osteopenia or osteoporosis, even after adjusting for age and other confounding factors (odds ratio, 1.25; 95% confidence interval, 1.13-1.40; P<0.01). However, subgroup analysis revealed statistical significance only in postmenopausal women (odds ratio, 1.27; P<0.001).

CONCLUSION

Chronic atrophic gastritis was associated with lower bone mineral density and a higher risk for osteopenia or osteoporosis among postmenopausal women.

Gut hormone analogues and skeletal health in diabetes and obesity: Evidence from preclinical models

Diabetes mellitus and obesity are rapidly growing worldwide. Aside from metabolic disturbances, these two disorders also affect bone with a higher prevalence of bone fractures. In the last decade, a growing body of evidence suggested that several gut hormones, including ghrelin, gastrin, glucose-dependent insulinotropic polypeptide (GIP), glucagon, and glucagon-like peptide-1 and 2 (GLP-1 and GLP-2, respectively) may affect bone physiology. Several gut hormone analogues have been developed for the treatment of type 2 diabetes and obesity, and could represent a new alternative in the therapeutic arsenal against bone fragility. In the present review, a summary of the physiological roles of these gut hormones and their analogues is presented at the cellular level but also in several preclinical models of bone fragility disorders including type 2 diabetes mellitus, especially on bone mineral density, microarchitecture and bone material properties. The present review also summarizes the impact of GLP-1 receptor agonists approved for the treatment of type 2 diabetes mellitus and the more recent dual or triple analogue on bone physiology and strength.

Effects of the DL76 Antagonist/Inverse Agonist of Histamine H3 Receptors on Experimental Periodontitis in Rats: Morphological Studies

BACKGROUND

Periodontitis preceded by gingivitis is the most common form of periodontal disease and occurs due to the interaction of microorganisms present in the complex bacterial aggregates of dental plaque biofilm and their metabolism products with periodontal tissues. Histamine is a heterocyclic biogenic amine acting via four types of receptors. Histamine H3 receptors act as presynaptic auto/heteroreceptors to regulate the release of histamine and other neurotransmitters.

AIM

Since the nervous system is able to regulate the progression of the inflammatory process and bone metabolism, the aim of this study was to investigate the effects of DL76, which acts as an antagonist/inverse agonist of H3 receptors, on the course of experimental periodontitis.

MATERIALS AND METHODS

This study was conducted in 24 mature male Wistar rats weighing 245-360 g, aged 6-8 weeks. A silk ligature was placed on the second maxillary molar of the right maxilla under general anesthesia. From the day of ligating, DL76 and 0.9% NaCl solutions were administered subcutaneously for 28 days in the experimental and control groups, respectively. After the experiment, histopathological, immunohistochemical and radiological examinations were performed.

RESULTS

Ligation led to the development of the inflammatory process with lymphocytic infiltration, increased epithelial RANKL and OPG expression as well as bone resorption. DL76 evoked a reduction in (1) lymphocytic infiltration, (2) RANKL and OPG expression as well as (3) bone resorption since the medians of the mesial and distal interdental spaces in the molars with induced periodontitis were 3.56-fold and 10-fold lower compared to the corresponding values in saline-treated animals with periodontitis.

CONCLUSION

DL76 is able to inhibit the progression of experimental periodontitis in rats, as demonstrated by a reduction in the inflammatory cell infiltration, a decrease in the RANKL/RANK OPG pathway expression and a reduction in the alveolar bone resorption.

Intracranial invasion of a mast cell tumour in a dog: A case report and review of the literature

An 11-year-old, female-neutered beagle was presented with a growing soft tissue mass arising within the deep tissues of the left cranial cervical region. At presentation, facial asymmetry was evident along with palpable lymphadenomegaly. Magnetic resonance imaging demonstrated a locally invasive cervical mass with intracranial invasion through focal osteolysis of the occipital bone. After antihistamine administration, cytology confirmed mast cell tumour (MCT) with metastasis to local lymph nodes and liver. The owner chose to pursue lomustine and prednisolone, which were dispensed, but, before home administration, prolonged seizures/status epilepticus occurred prompting euthanasia. Postmortem examination confirmed a high-grade MCT associated with, and infiltrating through, muscle, calvarium, dura mata, leptomeninges and the underlying brain. We present the clinical, imaging, and pathological findings of an unprecedented case of extracranial MCT tumour causing osteolysis of an imperforate flat bone (occipital bone) and intracranial invasion.

Assessment of Bone Microarchitecture in Patients with Systemic Mastocytosis and its Association with Clinical and Biochemical Parameters of the Disease

Patients with systemic mastocytosis (SM) are at high risk of bone deterioration. However, the evaluation of bone microarchitecture in this disease remains unclear. We aimed to assess bone microarchitecture in patients with SM. This was a cross-sectional study of 21 adult patients with SM conducted in a quaternary referral hospital in Sao Paulo, Brazil. A healthy, age-, weight-, and sex-matched cohort of 63 participants was used to provide reference values for bone microarchitecture, assessed by high resolution peripheral quantitative computed tomography (HR-pQCT). Total volumetric bone mineral density (vBMD), cortical vBMD, and cortical thickness at the radius were significantly lower in the control group compared with the SM group (all P < 0.001). Patients with aggressive SM had significantly lower trabecular number (Tb.N) (P = 0.035) and estimated failure load (F.load) (P = 0.032) at the tibia compared with those with indolent SM. Handgrip strength was significantly higher in patients who had more Tb.N at the radius (ρ, 0.46; P = 0.036) and tibia (ρ, 0.49; P = 0.002), and lower who had more trabecular separation at the radius (ρ, -0.46; P = 0.035) and tibia (ρ, -0.52; P = 0.016). Strong and positive associations between F.load (ρ, 0.75; P < 0.001) and stiffness (ρ, 0.70; P < 0.001) at the radius, and between F.load at the tibia (ρ, 0.45; P = 0.038) were observed with handgrip strength. In this cross-sectional study, aggressive SM was more susceptible to bone deterioration compared with indolent SM. In addition, the findings demonstrated that handgrip strength was associated with bone microarchitecture and bone strength.

Bone and Cytokine Markers Associated With Bone Disease in Systemic Mastocytosis

BACKGROUND

Mastocytosis encompasses a heterogeneous group of diseases characterized by tissue accumulation of clonal mast cells, which frequently includes bone involvement. Several cytokines have been shown to play a role in the pathogenesis of bone mass loss in systemic mastocytosis (SM), but their role in SM-associated osteosclerosis remains unknown.

OBJECTIVE

To investigate the potential association between cytokine and bone remodeling markers with bone disease in SM, aiming at identifying biomarker profiles associated with bone loss and/or osteosclerosis.

METHODS

A total of 120 adult patients with SM, divided into 3 age and sex-matched groups according to their bone status were studied: (1) healthy bone (n = 46), (2) significant bone loss (n = 47), and (3) diffuse bone sclerosis (n = 27). Plasma levels of cytokines and serum baseline tryptase and bone turnover marker levels were measured at diagnosis.

RESULTS

Bone loss was associated with significantly higher levels of serum baseline tryptase (P = .01), IFN-γ (P = .05), IL-1β (P = .05), and IL-6 (P = .05) versus those found in patients with healthy bone. In contrast, patients with diffuse bone sclerosis showed significantly higher levels of serum baseline tryptase (P < .001), C-terminal telopeptide (P < .001), amino-terminal propeptide of type I procollagen (P < .001), osteocalcin (P < .001), bone alkaline phosphatase (P < .001), osteopontin (P < .01), and the C-C Motif Chemokine Ligand 5/RANTES chemokine (P = .01), together with lower IFN-γ (P = .03) and RANK-ligand (P = .04) plasma levels versus healthy bone cases.

CONCLUSIONS

SM with bone mass loss is associated with a proinflammatory cytokine profile in plasma, whereas diffuse bone sclerosis shows increased serum/plasma levels of biomarkers related to bone formation and turnover, in association with an immunosuppressive cytokine secretion profile.

Oral administration of live combined Bacillus subtilis and Enterococcus faecium alleviates colonic oxidative stress and inflammation in osteoarthritic rats by improving fecal microbiome metabolism and enhancing the colonic barrier

Osteoarthritis (OA) causes intestinal damage. The protective effect of probiotics on the intestine is indeed effective; however, the mechanism of protection against intestinal damage in OA is not clear. In this study, we used meniscal/ligamentous injury (MLI) to mimic OA in rats and explored the colonic protective effects of Bacillus subtilis and Enterococcus faecium on OA. Our study showed that treatment with B. subtilis and E. faecium attenuated colonic injury and reduced inflammatory and oxidative stress factors in the serum of osteoarthritic rats. α- and ß diversity of the fecal flora were not different among groups; no significant differences were observed in the abundances of taxa at the phylum and genus levels. We observed the presence of the depression-related genera Alistipes and Paraprevotella. Analysis of fecal untargeted metabolism revealed that histamine level was significantly reduced in the colon of OA rats, affecting intestinal function. Compared to that in the control group, the enriched metabolic pathways in the OA group were primarily for energy metabolisms, such as pantothenate and CoA biosynthesis, and beta-alanine metabolism. The treatment group had enriched linoleic acid metabolism, fatty acid biosynthesis, and primary bile acid biosynthesis, which were different from those in the control group. The differences in the metabolic pathways between the treatment and OA groups were more evident, primarily in symptom-related metabolic pathways such as Huntington's disease, spinocerebellar ataxia, energy-related central carbon metabolism in cancer, pantothenate and CoA biosynthesis metabolic pathways, as well as some neurotransmission and amino acid transport, and uptake- and synthesis-related metabolic pathways. On further investigation, we found that B. subtilis and E. faecium treatment enhanced the colonic barrier of OA rats, with elevated expressions of tight junction proteins occludin and Zonula occludens 1 and MUC2 mRNA. Intestinal permeability was reduced, and serum LPS levels were downregulated in the treatment group. B. subtilis and E. faecium also regulated the oxidative stress pathway Keap1/Nrf2, promoted the expression of the downstream protective proteins HO-1 and Gpx4, and reduced intestinal apoptosis. Hence, B. subtilis and E. faecium alleviate colonic oxidative stress and inflammation in OA rats by improving fecal metabolism and enhancing the colonic barrier.

Human mast cells induce osteoclastogenesis through cell surface RANKL

OBJECTIVES

We employed the co-culture of CD34⁺ stem cell-derived human mast cells (HMC) and human monocyte-derived osteoclast precursors to evaluate if mast cells contribute to the pathogenesis of osteoporosis through regulation of osteoclast proliferation and activation.

METHODS

Mature HMC and osteoclast precursors were cultured from monocytes isolated from human buffy coat. The osteoclast precursors were incubated with HMC or receptor activator of nuclear factor kappa-B ligand (RANKL) for a week prior to determination of osteoclast maturation through characterization by their morphology and tartrate resistant acid phosphatase (TRAP) expression. The bone absorption activity was determined by pit formation on osteo-assay plate.

RESULTS

Mature osteoclasts were identified following co-culture of osteoclast precursors with HMC for one week in the absence of RANKL and they were capable of bone resorption. These actions of HMC on osteoclasts were not affected by mast cell activators such anti-IgE or substance P but could be reversed by osteoprotegerin (OPG) in the co-culture system suggesting the involvement of RANKL. The expression of RANKL on the cell surface of HMC was confirmed by flow cytometry and the density was not affected by activation of HMC.

CONCLUSION

Our study provided direct evidence confirming the initiation of osteoclast proliferation and activation by mast cells through cell surface RANKL suggesting that mast cells may contribute to bone destruction in pathological conditions such as osteoporosis.

Outcomes associated with proton pump inhibitors and distal radius fractures: A post-hoc comparative analysis

Long-term, high-dose, daily proton pump inhibitors (PPI) may impact outcomes associated with distal radius fractures (DRF). The hypothesis was that differences existed in patient demographics, but there existed no differences in injury patterns, interventions, post-operative complications, and patient-reported outcomes between patients not on a PPI and patients on a PPI with a DRF. METHODS: An IRB-approved, post-hoc analysis of patients with DRF from 2012 through 2018 was performed. Patients included were age ≥18 years, sustained a DRF, had completed medical and medication records, Quick Disabilities of the Arm, Shoulder and Hand (DASH) scores, Global Assessment of Functioning (GAF) scores, visual analogue scale (VAS) pain scores, and a minimum of 1-year follow-up. Patients were stratified into two cohorts. Cohort one patients had no prescription or over-the-counter PPI use (no PPI cohort). Cohort two patients had adherence to a long-term, high-dose, daily PPI (PPI cohort). RESULTS: Two hundred and eighty-one DRF patients were included. Of these 281 patients, 240 were in the no PPI cohort and 41 were in the PPI cohort. Patients in the PPI cohort had more median nerve injuries (12% versus 3%, p = 0.025) and radial shaft fractures (5% versus 0%, p = 0.020), less contralateral upper extremity injuries (0% versus 4%, p = 0.001), and more post-operative nonunions (7% versus 1%, p = 0.029) compared to patients in the no PPI cohort. The results obtained suggest that a CONCLUSIONS: Long-term, high-dose, daily PPI's may be associated with more median nerve injuries and radial shaft fractures, less contralateral upper extremity injuries, and more post-operative nonunions compared to DRF patients not on a PPI.

The Rising Era of “Immunoporosis”: Role of Immune System in the Pathophysiology of Osteoporosis

Discoveries in the last few years have emphasized the existence of an enormous breadth of communication between bone and the immune system in maintaining skeletal homeostasis. Originally, the discovery of various factors was assigned to the immune system viz. interleukin (IL)-6, IL-10, IL-17, tumor necrosis factor (TNF)-α, receptor activator of nuclear factor kappa B ligand (RANKL), nuclear factor of activated T cells (NFATc1), etc., but now these factors have also been shown to have a significant impact on osteoblasts (OBs) and osteoclasts (OCs) biology. These discoveries led to an alteration in the approach for the treatment of several bone pathologies including osteoporosis. Osteoporosis is an inflammatory bone anomaly affecting more than 500 million people globally. In 2018, to highlight the importance of the immune system in the pathophysiology of osteoporosis, our group coined the term “immunoporosis”. In the present review, we exhaustively revisit the characteristics, mechanism of action, and function of both innate and adaptive immune cells with the goal of understanding the potential of immune cells in osteoporosis. We also highlight the Immunoporotic role of gut microbiota (GM) for the treatment and management of osteoporosis. Importantly, we further discuss whether an immune cell-based strategy to treat and manage osteoporosis is feasible and relevant in clinical settings.

Mast Cells Trigger Disturbed Bone Healing in Osteoporotic Mice

Mast cells are important tissue-resident sensor and effector immune cells but also play a major role in osteoporosis development. Mast cells are increased in numbers in the bone marrow of postmenopausal osteoporotic patients, and mast cell-deficient mice are protected from ovariectomy (OVX)-induced bone loss. In this study, we showed that mast cell-deficient Mcpt5-Cre R-DTA mice were protected from OVX-induced disturbed fracture healing, indicating a critical role for mast cells in the pathomechanisms of impaired bone repair under estrogen-deficient conditions. We revealed that mast cells trigger the fracture-induced inflammatory response by releasing inflammatory mediators, including interleukin-6, midkine (Mdk), and C-X-C motif chemokine ligand 10 (CXCL10), and promote neutrophil infiltration into the fracture site in OVX mice. Furthermore, mast cells were responsible for reduced osteoblast and increased osteoclast activities in OVX mice callus, as well as increased receptor activator of NF-κB ligand serum levels in OVX mice. Additional in vitro studies with human cells showed that mast cells stimulate osteoclastogenesis by releasing the osteoclastogenic mediators Mdk and CXCL10 in an estrogen-dependent manner, which was mediated via the estrogen receptor alpha on mast cells. In conclusion, mast cells negatively affect the healing of bone fractures under estrogen-deficient conditions. Hence, targeting mast cells might provide a therapeutic strategy to improve disturbed bone repair in postmenopausal osteoporosis. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Antihistamines Potentiate Dexamethasone Anti-Inflammatory Effects. Impact on Glucocorticoid Receptor-Mediated Expression of Inflammation-Related Genes

Antihistamines and glucocorticoids (GCs) are often used together in the clinic to treat several inflammation-related situations. Although there is no rationale for this association, clinical practice has assumed that, due to their concomitant anti-inflammatory effects, there should be an intrinsic benefit to their co-administration. In this work, we evaluated the effects of the co-treatment of several antihistamines on dexamethasone-induced glucocorticoid receptor transcriptional activity on the expression of various inflammation-related genes in A549 and U937 cell lines. Our results show that all antihistamines potentiate GCs' anti-inflammatory effects, presenting ligand-, cell- and gene-dependent effects. Given that treatment with GCs has strong adverse effects, particularly on bone metabolism, we also examined the impact of antihistamine co-treatment on the expression of bone metabolism markers. Using MC3T3-E1 pre-osteoblastic cells, we observed that, though the antihistamine azelastine reduces the expression of dexamethasone-induced bone loss molecular markers, it potentiates osteoblast apoptosis. Our results suggest that the synergistic effect could contribute to reducing GC clinical doses, ineffective by itself but effective in combination with an antihistamine. This could result in a therapeutic advantage, as the addition of an antihistamine may reinforce the wanted effects of GCs, while related adverse effects could be diminished or at least mitigated. By modulating the patterns of gene activation/repression mediated by GR, antihistamines could enhance only the desired effects of GCs, allowing their effective dose to be reduced. Further research is needed to correctly determine the clinical scope, benefits, and potential risks of this therapeutic strategy.

Cell Interplay in Osteoarthritis

Osteoarthritis (OA) is a common chronic disease and a significant health concern that needs to be urgently solved. OA affects the cartilage and entire joint tissues, including the subchondral bone, synovium, and infrapatellar fat pads. The physiological and pathological changes in these tissues affect the occurrence and development of OA. Understanding complex crosstalk among different joint tissues and their roles in OA initiation and progression is critical in elucidating the pathogenic mechanism of OA. In this review, we begin with an overview of the role of chondrocytes, synovial cells (synovial fibroblasts and macrophages), mast cells, osteoblasts, osteoclasts, various stem cells, and engineered cells (induced pluripotent stem cells) in OA pathogenesis. Then, we discuss the various mechanisms by which these cells communicate, including paracrine signaling, local microenvironment, co-culture, extracellular vesicles (exosomes), and cell tissue engineering. We particularly focus on the therapeutic potential and clinical applications of stem cell-derived extracellular vesicles, which serve as modulators of cell-to-cell communication, in the field of regenerative medicine, such as cartilage repair. Finally, the challenges and limitations related to exosome-based treatment for OA are discussed. This article provides a comprehensive summary of key cells that might be targets of future therapies for OA.

Bothrops moojeni Venom and Its Components Strongly Affect Osteoclasts' Maturation and Protein Patterns

Osteoclasts (OCs) are important for bone maintenance, calcium balance, and tissue regeneration regulation and are involved in different inflammatory diseases. Our study aimed to evaluate the effect of Bothrops moojeni's venom and its low and high molecular mass (HMM and LMM) fractions on human peripheral blood mononuclear cell (PBMC)-derived OCs' in vitro differentiation. Bothrops moojeni, a Brazilian lanced-head viper, presents a rich but not well-explored, venom composition. This venom is a potent inducer of inflammation, which can be used as a tool to investigate the inflammatory process. Human PBMCs were isolated and induced to OC differentiation following routine protocol. On the fourth day of differentiation, the venom was added at different concentrations (5, 0.5, and 0.05 µg/mL). We observed a significant reduction of TRAP+ (tartrate-resistant acid phosphatase) OCs at the concentration of 5 µg/mL. We evaluated the F-actin-rich OCs structure's integrity; disruption of its integrity reflects bone adsorption capacity. F-actin rings phalloidin staining demonstrated that venom provoked their disruption in treated OCs. HMM, fraction reduces TRAP+ OCs at a concentration of 5 µg/mL and LMM fraction at 1 µg/mL, respectively. Our results indicate morphological changes that the venom induced cause in OCs. We analyzed the pattern of soluble proteins found in the conditioned cell culture medium OCs treated with venom and its fractions using mass spectrometry (LC-MS/IT-Tof). The proteomic analyses indicate the possible pathways and molecular mechanisms involved in OC reduction after the treatment.

Comparison of fracture risk between proton pump inhibitors and histamine-2 receptor antagonists in ANCA-associated vasculitis patients: a nested case-control study

OBJECTIVE

Whether acid suppressants [proton pump inhibitors (PPIs) and histamine-2 receptor antagonists (H2RAs)] are associated with bone fractures in patients with ANCA-associated vasculitis (AAV) treated with glucocorticoids remains unclear. This study compared PPIs with H2RAs in terms of the risk of bone fractures in patients with AAV who received in-hospital induction therapy with glucocorticoids.

METHODS

We retrospectively identified 149 patients with fractures among 22 821 patients newly diagnosed with AAV in 1730 hospitals using a nationwide inpatient database from July 2010 to March 2018. We conducted 1:4 case-control matching. Age, sex, duration of AAV treatment and fiscal year were matched between the cases and controls. A conditional logistic regression analysis was conducted to assess the association between acid suppressants and fractures.

RESULTS

Of all enrolled patients with fractures, the median age was 77 years, and 99 (66%) were female. The median duration from AAV treatment to fracture was 52 days. The proportion of patients using PPIs was 91.3% (136 of 149) and 80.2% (478 of 596) in the case and control groups, respectively. Compared with H2RA use, PPI use was significantly associated with fractures after adjustment for age, sex, BMI, smoking habit, Charlson comorbidity index, renal failure, bisphosphonate and same fiscal year according to a multivariate analysis (adjusted odds ratio, 3.76; 95% CI: 1.37, 10.3).

CONCLUSION

PPI users had a higher risk of fractures than H2RA users among mostly advanced-age patients with AAV with remission induction therapy.

Mast cells contribute to alveolar bone loss in Spontaneously Hypertensive Rats with periodontal disease regulating cytokines production

Mast cells (MCs) play a pivotal role in inflammatory responses and had been studied in inflammatory bone disorders, however, their role in alveolar bone loss induced by periodontal disease (PD) is not yet fully understood. We, therefore, aimed to evaluate the effects of MCs depletion in the PD-induced alveolar bone loss in Wistar (W) and Spontaneously Hypertensive Rats (SHRs). PD was induced by ligating the lower first molars with silk thread one day after the MCs depletion, by the pre-treatment with compound 48/80 for 4 days. After 15 days of PD induction, the hemi-mandibles were surgically collected for qRT-PCR, histological analyses, immunostaining, and ELISA. Systolic blood pressure (SBP) was verified by tail plethysmography to confirm the hypertensive status, and SHR presented SBP >150 mmHg, and previous MC depletion alone or associated with PD did not alter this parameter. SHRs showed a more severe alveolar bone loss compared to W, and MC depletion significantly inhibited this response in both strains, with a more significant response in SHRs. MCs were less abundant in 48/80+PD groups, thus validating the previous MCs depletion in our model. PD increased the number of MC in the gingival tissue of SHR. Cytokine production (TNF-α, IL-6, IL-1β, and CXCL3) was constitutively higher in SHR and increased further after PD, which was also significantly reduced in the MCs-depleted animals. PD led to an increased expression of Opn, Rankl, Rank, Vtn, Itga5, Itgb5, Trap, and Ctsk in the mandible of W and SHRs, which was reversed in MCs-depleted animals. These results suggest that MCs significantly contributes to the PD-induced alveolar bone resorption, especially in the SHR, which is associated with a more severe PD progression compared to Wistar, partly explained by these cells contribution to the inflammatory status and mediator production, stimulating osteoclast-related response markers, which were reduced after MC depletion in our experimental model.

Proton Pump Inhibitors and Fractures in Adults: A Critical Appraisal and Review of the Literature

Despite the large number of patients worldwide being on proton pump inhibitors (PPIs) for acid-related gastrointestinal disorders, uncertainty remains over their long-term safety. Particularly, the potential side effects of these drugs on bone health have been evaluated in the last years. The purpose of our narrative review is to gather and discuss results of clinical studies focusing on the interactions between PPIs and fracture risk. Data generated mainly from nested case-control studies and meta-analysis suggest that long-term/high-dose PPIs users are characterized by an increased risk of fragility fractures, mainly hip fractures. However, in these studies, the PPIs-induced bone impairment is often not adjusted for different confounding variables that could potentially affect bone health, and exposure to PPIs was reported using medical prescriptions without adherence evaluation. The mechanisms of the PPI-related bone damage are still unclear, but impaired micronutrients absorption, hypergastrinemia, and increased secretion of histamine may play a role. Clinicians should pay attention when prescribing PPIs to subjects with a preexistent high risk of fractures and consider antiosteoporotic drugs to manage this additive effect on the bone. However, further studies are needed to clarify PPIs action on the bone.

Effects of Histamine Receptor Antagonist Cetirizine on Orthodontic Tooth Movement

Many patients regularly take histamine receptor antagonists, such as cetirizine, to prevent allergic reactions, but these antiallergic drugs may have inadvertent effects on orthodontic treatment. In previous studies, histamine has been shown to modulate the sterile inflammatory reaction underlying orthodontic tooth movement. Pertinent effects of histamine antagonization via cetirizine during orthodontic treatment, however, have not been adequately investigated. We thus treated male Fischer344 rats either with tap water (control group) or cetirizine by daily oral gavage corresponding to the clinically used human dosage adjusted to the rat metabolism (0.87 mg/kg) or to a previously published high dosage of cetirizine (3 mg/kg). Experimental anterior movement of the first upper left molar was induced by insertion of a nickel-titanium (NiTi) coil spring (0.25 N) between the molar and the upper incisors. Cone-beam computed tomography (CBCT), micro-computed tomography (µCT) images, as well as histological hematoxylin-eosin (HE), and tartrate-resistant acid phosphatase (TRAP) stainings were used to assess the extent of tooth movement, cranial growth, periodontal bone loss, root resorptions, and osteoclast activity in the periodontal ligament. Both investigated cetirizine dosages had no impact on the weight gain of the animals and, thus, animal welfare. Neither the extent of tooth movement, nor cranial growth, nor root resorption, nor periodontal bone loss were significantly influenced by the cetirizine dosages investigated. We, thus, conclude that histamine receptor antagonist cetirizine can be used during orthodontic treatment to prevent allergic reactions without clinically relevant side effects on orthodontic tooth movement.

The Skeletal Effects of Short-Term Triple Therapy in a Rat Model of Gastric Ulcer Induced by Helicobacter pylori Infection

Purpose

Triple therapy is the standard therapy to eradicate Helicobacter pylori (H.pylori) infection. Chronic use of proton pump inhibitors (PPIs), a component of triple therapy, is associated with osteoporosis. However, the skeletal effects of short-term triple therapy containing PPI remain elusive. This study aims to determine the skeletal effect of short-term triple therapy in a rat model of gastric ulcer induced by H. pylori.

Methods

Three-month-old male Sprague Dawley rats were assigned to normal control, H. pylori-inoculated group (negative control) and H. pylori-inoculated group receiving triple therapy consisting of omeprazole [2.035 mg/kg body weight (b.w)], amoxicillin (102.80 mg/kg b.w) and clarithromycin (51.37 mg/kg b.w) (n=6/group). H. pylori infection developed for four weeks after inoculation, followed by two-week triple therapy. At the end of the treatment period, femoral bones of the rats were harvested for analysis. Bone mineral density and content of the femurs were determined using dual-energy X-ray absorptiometry, while bone strength was measured with a universal mechanical tester.

Results

Bone mineral content was significantly lower in the negative control group compared to the triple therapy group (p=0.014). Triple therapy decreased strain (vs negative control, p=0.002) and displacement of the femur (vs normal control, p=0.004; vs untreated control, p=0.005). No significant difference was observed in other parameters among the study groups (p>0.05).

Conclusion

Short-term triple therapy increases bone mineral content but decreases bone strength of rats. Skeletal prophylaxis should be considered for patients on short-term triple therapy containing PPI.

Systemic mastocytosis revisited with an emphasis on skeletal manifestations

Systemic mastocytosis (SM) is a rare form of mastocytosis that can affect various organ systems. Bone involvement is the most common and prominent imaging feature in patients with SM regardless of the subtype. Furthermore, bone involvement is a prognostic factor as it may entail an aggressive course of the disease. Diagnosis is established by bone marrow biopsy complemented by imaging modalities such as radiography, CT, and magnetic resonance (MR) imaging. The radiographic and CT appearances are that of sclerotic, lytic, or mixed patterns with focal or diffuse distribution, involving primarily the axial skeleton and the ends of the long bones. Bone marrow infiltration is best recognized on MR imaging. Osteoporosis is common in SM; thus, a bone mineral density measurement at lumbar spine and proximal femur by dual-energy X-ray absorptiometry should be obtained. Imaging plays a huge part in the diagnostic process; when skeletal imaging findings are carefully interpreted and correlated with clinical features, they can lead to the suspicion of SM. The primary aims of this review article were to focus on the role of imaging in detection and characterization of skeletal patterns of SM and to discuss relevant clinical features that could facilitate prompt and correct diagnosis.

A critical assessment of the potential of pharmacological modulation of aldehyde dehydrogenases to treat the diseases of bone loss

Chronic alcoholism (CA) decreases bone mass and increases the risk of hip fracture. Alcohol and its main metabolite, acetaldehyde impairs osteoblastogenesis by increasing oxidative stress. Aldehyde dehydrogenase (ALDH) is the rate-limiting enzyme in clearing acetaldehyde from the body. The clinical relevance of ALDH in skeletal function has been established by the discovery of single nucleotide polymorphism, SNP (rs671) in the ALDH2 gene giving rise to an inactive form of the enzyme (ALDH2*2) that causes increased serum acetaldehyde and osteoporosis in the affected individuals. Subsequent mouse genetics studies have replicated human phenotype in mice and confirmed the non-redundant role of ALDH2 in bone homeostasis. The activity of ALDH2 is amenable to pharmacological modulation. ALDH2 inhibition by disulfiram (DSF) and activation by alda-1 cause reduction and induction of bone formation, respectively. DSF also inhibits peak bone mass accrual in growing rats. On the other hand, DSF showed an anti-osteoclastogenic effect and protected mice from alcohol-induced osteopenia by inhibiting ALDH1a1 in bone marrow monocytes. Besides DSF, there are several classes of ALDH inhibitors with disparate skeletal effects. Alda-1, the ALDH2 activator induced osteoblast differentiation by increasing bone morphogenic protein 2 (BMP2) expression via ALDH2 activation. Alda-1 also restored ovariectomy-induced bone loss. The scope of structure-activity based studies with ALDH2 and the alda-1-like molecule could lead to the discovery of novel osteoanabolic molecules. This review will critically discuss the molecular mechanism of the ethanol and its principal metabolite, acetaldehyde in the context of ALDH2 in bone cells, and skeletal homeostasis.

Effects of histamine on human periodontal ligament fibroblasts under simulated orthodontic pressure

As type-I-allergies show an increasing prevalence in the general populace, orthodontic patients may also be affected by histamine release during treatment. Human periodontal ligament fibroblasts (PDLF) are regulators of orthodontic tooth movement. However, the impact of histamine on PDLF in this regard is unknown. Therefore PDLF were incubated without or with an orthodontic compressive force of 2g/cm² with and without additional histamine. To assess the role of histamine-1-receptor (H1R) H1R-antagonist cetirizine was used. Expression of histamine receptors and important mediators of orthodontic tooth movement were investigated. PDLF expressed histamine receptors H1R, H2R and H4R, but not H3R. Histamine increased the expression of H1R, H2R and H4R as well as of interleukin-6, cyclooxygenase-2, and prostaglandin-E2 secretion even without pressure application and induced receptor activator of NF-kB ligand (RANKL) protein expression with unchanged osteoprotegerin secretion. These effects were not observed in presence of H1R antagonist cetirizine. By expressing histamine receptors, PDLF seem to be able to respond to fluctuating histamine levels in the periodontal tissue. Increased histamine concentration was associated with enhanced expression of proinflammatory mediators and RANKL, suggesting an inductive effect of histamine on PDLF-mediated osteoclastogenesis and orthodontic tooth movement. Since cetirizine inhibited these effects, they seem to be mainly mediated via histamine receptor H1R.

Fracture Risk Reduction by Bisphosphonates in Mastocytosis?

BACKGROUND

Fragility fractures (FFxs) and osteoporosis are frequent manifestations of indolent systemic mastocytosis (ISM). So far, the effect of antiosteoporotic therapy on FFxs has scarcely been investigated.

OBJECTIVE

This study evaluates the long-term effect of bisphosphonate treatment on FFxs, bone mineral density (BMD), and bone resorption in patients with ISM in daily clinical practice.

METHODS

Patients with ISM who received bisphosphonates because of osteoporosis and/or FFxs were retrospectively analyzed (n = 58). Fractures were recorded by vertebral fracture assessment, X-rays of the thoracolumbar spine, medical records, and a questionnaire. Five-year analysis (n = 30) was made by comparing observed 5-year FFx risk with MastFx-predicted FFx risk for patients with ISM not treated with antiosteoporotic drugs and analyzing 5-year change in BMD and serum collagen C telopeptide (sCTx) Z-scores.

RESULTS

During the median follow-up of 7.3 years, 14 of 58 patients suffered 40 FFxs. Five- and 10-year FFx-free survival were 81.9% (standard error [SE], 5.5%) and 67.0% (SE, 7.7%), respectively. FFx risk was significantly higher in patients with previous vertebral FFxs (P = .004), lower femoral BMD at baseline (P = .042), and history of anaphylaxis (P = .028). No 5-year FFx risk reduction could be proven, possibly due to the small sample size. The lumbar BMD Z-score significantly increased from median (interquartile range [IQR]) -2.20 (-2.80 to -1.50) to -1.50 (-2.30 to -0.60) (P < .001, n = 27). The sCTx Z-score decreased from median 0.71 (IQR, -0.59 to 2.39) to -0.95 (-1.30 to -0.16) (P = .008, n = 15).

CONCLUSION

Bisphosphonates significantly increase BMD and decrease sCTx in patients with ISM. However, FFxs still frequently occur. Especially patients with previous FFxs remain at high risk of new FFxs.

Ranitidine Impairs Bone Healing and Implant Osseointegration in Rats' Tibiae

PURPOSE

Ranitidine has been found to have an impact on bone metabolism by suppressing osteoclastogenesis. We hypothesized that the use of ranitidine would impair bone healing and implant osseointegration. This study investigated the effect of postoperative administration of ranitidine on bone healing and osseointegration in rats.

MATERIALS AND METHODS

Twenty-two Sprague-Dawley rats underwent surgery to create a unicortical bone defect in each tibia. A titanium implant was placed on the right tibial defect, whereas the contralateral defect was left unfilled. After surgery, the rats were randomly divided into 2 groups receiving a daily dose of ranitidine or saline solution for 14 days and then euthanized for assessment of bone healing and osseointegration using micro-computed tomography (CT) and histomorphometry.

RESULTS

Micro-CT analysis of the bone defect showed a larger bone defect volume in the ranitidine group (0.82 ± 0.13 μL vs 0.66 ± 0.16 μL, P = .034), thinner cortical thickness (0.54 ± 0.07 mm vs 0.63 ± 0.11 mm, P = .026), and less bone regeneration at the defect site (40% ± 12% vs 57% ± 11%, P = .003). Implant-site micro-CT analysis showed less osseointegration in the ranitidine group (34.1% ± 2.7% vs 43.5% ± 2.1%, P = .014), and implant-site histologic analysis showed less medullary (P = .021), cortical (P = .001), and total (P = .003) bone-implant contact and less peri-implant bone volume-tissue volume (P = .002) in the ranitidine group. Histologic analysis for osteoclastic activity showed a lower number of osteoclasts in the ranitidine group (4.8 ± 2.4 mm^-2 vs 9.1 ± 2.1 mm^-2, P = .026).

CONCLUSIONS

The postoperative use of ranitidine impaired bone healing and osseointegration.

Hematological Diseases and Osteoporosis

Secondary osteoporosis is a common clinical problem faced by bone specialists, with a higher frequency in men than in women. One of several causes of secondary osteoporosis is hematological disease. There are numerous hematological diseases that can have a deleterious impact on bone health. In the literature, there is an abundance of evidence of bone involvement in patients affected by multiple myeloma, systemic mastocytosis, thalassemia, and hemophilia; some skeletal disorders are also reported in sickle cell disease. Recently, monoclonal gammopathy of undetermined significance appears to increase fracture risk, predominantly in male subjects. The pathogenetic mechanisms responsible for these bone loss effects have not yet been completely clarified. Many soluble factors, in particular cytokines that regulate bone metabolism, appear to play an important role. An integrated approach to these hematological diseases, with the help of a bone specialist, could reduce the bone fracture rate and improve the quality of life of these patients.

The Role of Mast Cells in Bone Metabolism and Bone Disorders

Mast cells (MCs) are important sensor and effector cells of the immune system that are involved in many physiological and pathological conditions. Increasing evidence suggests that they also play an important role in bone metabolism and bone disorders. MCs are located in the bone marrow and secrete a wide spectrum of mediators, which can be rapidly released upon activation of mature MCs following their differentiation in mucosal or connective tissues. Many of these mediators can exert osteocatabolic effects by promoting osteoclast formation [e.g., histamine, tumor necrosis factor (TNF), interleukin-6 (IL-6)] and/or by inhibiting osteoblast activity (e.g., IL-1, TNF). By contrast, MCs could potentially act in an osteoprotective manner by stimulating osteoblasts (e.g., transforming growth factor-β) or reducing osteoclastogenesis (e.g., IL-12, interferon-γ). Experimental studies investigating MC functions in physiological bone turnover using MC-deficient mouse lines give contradictory results, reporting delayed or increased bone turnover or no influence depending on the mouse model used. By contrast, the involvement of MCs in various pathological conditions affecting bone is evident. MCs may contribute to the pathogenesis of primary and secondary osteoporosis as well as inflammatory disorders, including rheumatoid arthritis and osteoarthritis, because increased numbers of MCs were found in patients suffering from these diseases. The clinical observations could be largely confirmed in experimental studies using MC-deficient mouse models, which also provide mechanistic insights. MCs also regulate bone healing after fracture by influencing the inflammatory response toward the fracture, vascularization, bone formation, and callus remodeling by osteoclasts. This review summarizes the current view and understanding of the role of MCs on bone in both physiological and pathological conditions.

The effect of cetirizine, a histamine 1 receptor antagonist, on bone remodeling after calvarial suture expansion

Objective

The objective of this study was to evaluate the effects of cetirizine, a histamine 1 receptor antagonist, on bone remodeling after calvarial suture expansion.

Methods

Sixty male Sprague–Dawley rats were divided into 4 groups; the phosphate-buffered saline (PBS)-injected no expansion group, cetirizine-injected no expansion group, PBS-injected expansion group, and cetirizine-injected expansion group, and were observed at 7, 14, and 28 days. Five rats per group were examined at each observation day. Daily injections of cetirizine or PBS were administered to the relevant groups starting 2 weeks prior to expander insertion. A rapid expander was inserted in the calvarial bone to deliver 100 cN of force to the parietal suture. The specimens were prepared for hematoxylin and eosin and tartrate-resistant acid phosphatase (TRAP) staining. Suture opening and bone regeneration were evaluated using microcomputed tomography and bone histomorphometric analysis. Serum blood levels of osteocalcin and carboxy-terminal collagen crosslinks (CTX) were also evaluated.

Results

TRAP-positive cell counts and CTX levels decreased while osteocalcin levels increased in the cetirizine-injected expansion group at observation day 28. In the expansion groups, the mineralized area gradually increased throughout the observation period. At day 28, the cetirizine-injected expansion group showed greater bone volume density, greater mineralized area, and narrower average suture width than did the PBS-injected expansion group.

Conclusions

Cetirizine injection facilitated bone formation after suture expansion, mostly by suppressing osteoclastic activity. Histamine 1 receptor antagonists may aid in bone formation after calvarial suture expansion in the rat model.

Does Allergy Break Bones? Osteoporosis and Its Connection to Allergy

: Osteoporosis and allergic diseases are important causes of morbidity, and traditionally their coexistence has been attributed to causality, to independent processes, and they were considered unrelated. However, the increasing knowledge in the field of osteoimmunology and an increasing number of epidemiological and biological studies have provided support to a correlation between bone and allergy that share pathways, cells, cytokines and mediators. If the link between allergic pathology and bone alterations appears more subtle, there are conditions such as mastocytosis and hypereosinophilic or hyper-IgE syndromes characterized by the proliferation of cells or hyper-production of molecules that play a key role in allergies, in which this link is at least clinically more evident, and the diseases are accompanied by frank skeletal involvement, offering multiple speculation cues. The pathophysiological connection of allergy and osteoporosis is currently an intriguing area of research. The aim of this review is to summarize and bring together the current knowledge and pursue an opportunity to stimulate further investigation.

Effects of loratadine, a histamine H1 receptor antagonist, on the skeletal system of young male rats

Background

Histamine H₁ receptor antagonists are widely used in the treatment of allergic diseases. H₁ receptors are expressed on bone cells and histamine takes part in regulation of bone metabolism. Loratadine is often prescribed to children.

Purpose

The aim of the present study was to investigate the effects of loratadine on the skeletal system of young rats.

Material and methods

Loratadine (0.5, 5, and 50 mg/kg p.o. daily) was administered for 4 weeks to male Wistar rats, 6-week-old at the start of the experiment. Bone mass, mass of bone mineral, calcium, and phosphorus content in the bone mineral of the tibia, femur, and L-4 vertebra, histomorphometric parameters of the femur, mechanical properties of the proximal tibial metaphysis, femoral diaphysis and femoral neck, and serum levels of bone turnover markers were examined.

Results

Loratadine at 0.5 and 5 mg/kg did not significantly affect the skeletal system of young rats. At 50 mg/kg, loratadine decreased the femoral length, increased content of calcium and phosphorus in the bone mineral of the vertebra, and tended to improve mechanical properties of the tibial metaphysis.

Conclusion

High-dose loratadine slightly but significantly affected development of the skeletal system in rapidly growing rats.

Higher prevalence of vertebral fractures in systemic mastocytosis, but not in cutaneous mastocytosis and idiopathic mast cell activation syndrome

Little is known about osteoporosis in mast cell disorders (MCDs) not related to systemic mastocytosis. We described osteoporosis and fractures in MCDs and showed that systemic mastocytosis was the only studied MCDs associated with osteoporotic vertebral fractures.

INTRODUCTION

To describe osteoporosis (OP) and fragility fractures in mast cell disorders (MCDs).

METHODS

We retrospectively analyzed data concerning all successive patients with systemic mastocytosis (SM), cutaneous mastocytosis (CM), and mast cell activation syndromes (MCAS) diagnosed in our mastocytosis expert center between 2004 and 2015. We collected data concerning demographic profiles, clinical signs of MCD, osteoporosis, fractures, densitometry, and biological assessment of MCD. We compared CM and MCAS patients with SM patients with regard to the characteristics of OP and fragility fractures.

RESULTS

We assessed 89 SM patients, 20 CM patients, and 20 MCAS patients. Osteoporosis was less frequent in CM (15.0%) and MCAS (10.0%) than in SM (44.9%). Similarly, fractures were less frequent in non-SM MCDs, respectively 5.0%, 5.0%, and 28.1%. SM patients displayed high prevalence of vertebral fractures (22.5%), mostly multiple. Conversely, in non-SM patients, vertebral fractures appeared to be uncommon (5%) and more frequently associated with risk factors for osteoporosis.

CONCLUSIONS

SM is associated with multiple vertebral osteoporotic fractures, whereas CM and MCAS do not appear to be associated with this phenotype.

Proton Pump Inhibitors and Fracture Risk: A Review of Current Evidence and Mechanisms Involved

The number of patients with gastroesophageal problems taking proton pump inhibitors (PPIs) is increasing. Several studies suggested a possible association between PPIs and fracture risk, especially hip fractures, but the relationship remains contentious. This review aimed to investigate the longitudinal studies published in the last five years on the relationship between PPIs and fracture risk. The mechanism underlying this relationship was also explored. Overall, PPIs were positively associated with elevated fracture risk in multiple studies (n = 14), although some studies reported no significant relationship (n = 4). Increased gastrin production and hypochlorhydria are the two main mechanisms that affect bone remodeling, mineral absorption, and muscle strength, contributing to increased fracture risk among PPI users. As a conclusion, there is a potential relationship between PPIs and fracture risks. Therefore, patients on long-term PPI treatment should pay attention to bone health status and consider prophylaxis to decrease fracture risk.

Mast Cells in Early Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease characterized by inflammation of the synovial membrane, with thickening of the synovial layer, cellular hyperplasia, and infiltration of immune cells. Mast cells (MCs) are cells of the innate immunity present in healthy synovia and part of the cellular hyperplasia characterizing RA synovitis. Although their presence in synovia has been well described, the exact functions and the correlation of MCs with disease development and progression have been debated, particularly because of contradictory data obtained in animal models and from patients with longstanding disease. Here, we present a revision of the literature on MCs in RA, including the most recent observations obtained from patients with early RA, indicating MCs as relevant markers of disease severity in early RA.

Bone Disease in Mastocytosis

Systemic mastocytosis can give very different bone pictures: from osteosclerosis to osteoporosis. Osteoporosis is one of the most frequent manifestations particularly in adults and the most clinical relevant. It is often complicated by a high recurrence of mainly vertebral fragility fractures. The main factor of bone loss is the osteoclast with a relative or absolute predominance of bone resorption. The RANK-RANKL pathway seems of key importance, but histamine and other cytokines also play a significant role in the process. The predominance of resorption made bisphosphonates, as anti-resorptive drugs, the most rational treatment of bone involvement in systemic mastocytosis.

Mast Cells Are Critical Regulators of Bone Fracture-Induced Inflammation and Osteoclast Formation and Activity

Mast cells, important sensor and effector cells of the immune system, may influence bone metabolism as their number is increased in osteoporotic patients. They are also present during bone fracture healing with currently unknown functions. Using a novel c-Kit-independent mouse model of mast cell deficiency, we demonstrated that mast cells did not affect physiological bone turnover. However, they triggered local and systemic inflammation after fracture by inducing release of inflammatory mediators and the recruitment of innate immune cells. In later healing stages, mast cells accumulated and regulated osteoclast activity to remodel the bony fracture callus. Furthermore, they were essential to induce osteoclast formation after ovariectomy. Additional in vitro studies revealed that they promote osteoclastogenesis via granular mediators, mainly histamine. In conclusion, mast cells are redundant in physiologic bone turnover but exert crucial functions after challenging the system, implicating mast cells as a potential target for treating inflammatory bone disorders. © 2017 American Society for Bone and Mineral Research.

Prevalence and risk factors for fragility fracture in systemic mastocytosis

OBJECTIVES

Systemic mastocytosis (SM) is characterized by the accumulation of mast cells in tissues other than the skin. Bone involvement although frequent has not been thoroughly evaluated. Primary objective was to determine risk factors associated with fragility fractures (FF) in SM. Secondary objectives were to evaluate the ability of bone marrow tryptase (BMT) level to identify patients with FF, and to describe bone involvement in SM.

METHODS

We analyzed retrospectively all consecutive patients seen in our expert center, with a diagnosis of SM according to the 2001 WHO criteria, and with complete bone assessment. We collected data about lifetime fractures, types of cutaneous manifestations, degranulation symptoms, blood and BMT levels, bone mineral density assessed by densitometry and KIT mutation. We performed a univariate analysis investigating the factors associated with FF and then a logistic multivariable regression analysis. We assessed the ability of bone marrow tryptase to identify patients with FF.

RESULTS

Eighty-nine patients with SM were included. Thirty-six patients (40.4%) suffered from osteoporosis and twenty-five (28.1%) experienced lifetime FF. Univariate analysis identified age at diagnosis and disease onset, presence of telangiectasia macularis eruptiva perstans, digestive symptoms, mast cells activation symptoms, elevated BMT, low femoral and lumbar BMD, as associated with FF. Multivariate analysis identified elevated BMT, low femoral T score and older age at diagnosis as independently associated with FF.

CONCLUSIONS

Low femoral T-score, BMT level, and older age at diagnosis are markers associated with FF in SM. BMT may represent an important biomarker to predict FF in SM patients.

Mast Cell Mediators Inhibit Osteoblastic Differentiation and Extracellular Matrix Mineralization

Mast cells are multifunctional immune cells that participate in many important processes such as defense against pathogens, allergic reactions, and tissue repair. These cells perform their functions through the release of a wide variety of mediators. This release occurs mainly through cross-linking IgE (immunoglobulin E) bound to high affinity IgE receptors by multivalent antigens. The abundance of mast cells in connective tissue, surrounding blood vessels, and their involvement in the early stages of bone repair support the possibility of physiological and pathological interactions between mast cells and osteoblasts. However, the participation of mast cell mediators in osteogenesis is not fully understood. Therefore, the objective of this work was to investigate the role of mast cell mediators in the acquisition of the osteogenic phenotype in vitro. The results show that pooled mast cell mediators can affect proliferation, morphology, and cytoskeleton of osteoblastic cells, and impair the activity and expression of alkaline phosphatase as well as the expression of bone sialoprotein. Also, mast cell mediators inhibit the expression of mRNA for those proteins and inhibit the formation and maturation of calcium nodules and consequently inhibit mineralization. Therefore, mast cell mediators can modulate osteogenesis and are potential therapeutic targets for treatments of bone disorders.

Coordination of early cellular reactions during activation of bone resorption in the rat mandible periosteum: An immunohistochemical study

The activation step of bone remodeling remains poorly characterized. Activation comprises determination of the site to be remodeled, osteoclast precursor recruitment, their migration to the site of remodeling, and differentiation. These actions involve different compartments and cell types. The aim of this study was to investigate events and cell types involved during activation. We used a bone remodeling model in rats where extractions of the upper jaw molars initiate remodeling of the antagonist lower jaw (mandible) cortex along the periosteum. In this model osteoclastic resorption peaks 4 days after extractions. We previously reported that mast cell activation in the periosteum fibrous compartment is an early event of activation, associated with recruitment of circulating monocyte osteoclast precursors. By using immunohistochemistry, we observed 9 hours after induction a spatially oriented expression of InterCellular Adhesion Molecule-1 in the vessels that was inhibited by antagonists of histamine receptors 1 and 2. It was followed at 12 hours by the recruitment of ED1+ monocytes. In parallel, at 9 hours, Vascular Cellular Adhesion Molecule-1+ fibroblast-like cells scattered in the fibrous compartment of the periosteum between the vessels and the osteogenic compartment increased; these cells may be implicated in osteoclast precursor migration. Receptor Activator of NF KappaB Ligand+ cells increased at 12 hours in the osteogenic compartment and reached a peak at 18 hours. At 24 hours the numbers of osteogenic cells and subjacent osteocytes expressing semaphorin 3a, a repulsive for osteoclast precursors, decreased before returning to baseline at 48 hours. These data show that during activation the two periosteum compartments and several cell types are coordinated to recruit and guide osteoclast precursors towards the bone surface.

Muscle paralysis induces bone marrow inflammation and predisposition to formation of giant osteoclasts

Transient muscle paralysis engendered by a single injection of botulinum toxin A (BTxA) rapidly induces profound focal bone resorption within the medullary cavity of adjacent bones. While initially conceived as a model of mechanical disuse, osteoclastic resorption in this model is disproportionately severe compared with the modest gait defect that is created. Preliminary studies of bone marrow following muscle paralysis suggested acute upregulation of inflammatory cytokines, including TNF-α and IL-1. We therefore hypothesized that BTxA-induced muscle paralysis would rapidly alter the inflammatory microenvironment and the osteoclastic potential of bone marrow. We tested this hypothesis by defining the time course of inflammatory cell infiltration, osteoinflammatory cytokine expression, and alteration in osteoclastogenic potential in the tibia bone marrow following transient muscle paralysis of the calf muscles. Our findings identified inflammatory cell infiltration within 24 h of muscle paralysis. By 72 h, osteoclast fusion and pro-osteoclastic inflammatory gene expression were upregulated in tibia bone marrow. These alterations coincided with bone marrow becoming permissive to the formation of osteoclasts of greater size and greater nuclei numbers. Taken together, our data are consistent with the thesis that transient calf muscle paralysis induces acute inflammation within the marrow of the adjacent tibia and that these alterations are temporally consistent with a role in mediating muscle paralysis-induced bone resorption.

Suppression of osteogenic differentiation in mesenchymal stem cells from patients with ossification of the posterior longitudinal ligament by a histamine-2-receptor antagonist

Mesenchymal stem cells (MSCs) in ossification of the posterior longitudinal ligament (OPLL) patients have a high propensity toward osteogenesis. Histamine receptor H2 (H2R) antagonists (H2 blockers) like famotidine decrease ossification in patients, by an unclear mechanism. To confirm that MSCs express H2R and to clarify how H2 blockers suppress osteogenic differentiation, we used spinal-ligament MSCs from patients with OPLL or with cervical spondylotic myelopathy (CSM) (control). The MSCs were treated with 10, 30, or 100nM famotidine for 7 or 21 days. Flow cytometry revealed that cells from both groups expressed MSC surface markers CD44, CD90, and CD105 (> 97.5%) but not CD34 or CD45 (< 2.5%). Immunoblotting showed that the MSCs from both groups expressed H2R, but those from OPLL patients expressed it at higher levels. Real-time qPCR indicated the H2R expression was significantly suppressed by 30nM famotidine for 7 days or by 30 or 100nM for 21 days. However, histidine decarboxylase, a key enzyme in histamine production, did not change significantly after famotidine addition. Famotidine treatment at 100nM for 21 days significantly suppressed mRNA expression of the osteogenic markers osteocalcin (OCN), bone morphogenetic protein 2 (BMP2), and runt-related transcription factor 2 (RUNX2) only in OPLL-derived MSCs. Immunoblots showed that famotidine suppressed BMP2 and OCN in the OPLL group and H2R and RUNX2 in both groups. These results suggest famotidine inhibits osteogenic differentiation in OPLL-derived MSCs by acting as an H2R antagonist, but also by decreasing H2R expression, and support the clinical use of famotidine to treat OPLL.

Histamine and Histamine H4 Receptor Promotes Osteoclastogenesis in Rheumatoid Arthritis

Histamine H4 receptor (H4R) has immune-modulatory and chemotaxic effects in various immune cells. This study aimed to determine the osteoclastogenic role of H4R in rheumatoid arthritis (RA). The concentration of histamine in synovial fluid (SF) and sera in patients with RA was measured using ELISA. After RA SF and peripheral blood (PB) CD14+ monocytes were treated with histamine, IL-17, IL-21 and IL-22, and a H4R antagonist (JNJ7777120), the gene expression H4R and RANKL was determined by real-time PCR. Osteoclastogenesis was assessed by counting TRAP–positive multinucleated cells in PB CD14+ monocytes cultured with histamine, Th17 cytokines and JNJ7777120. SF and serum concentration of histamine was higher in RA, compared with osteoarthritis and healthy controls. The expression of H4R was increased in PB monocytes in RA patients. Histamine, IL-6, IL-17, IL-21 and IL-22 induced the expression of H4R in monocytes. Histamine, IL-17, and IL-22 stimulated RANKL expression in RA monocytes and JNJ7777120 reduced the RANKL expression. Histamine and Th17 cytokines induced the osteoclast differentiation from monocytes and JNJ7777120 decreased the osteoclastogenesis. H4R mediates RANKL expression and osteoclast differentiation induced by histamine and Th17 cytokines. The blockage of H4R could be a new therapeutic modality for prevention of bone destruction in RA.

Prevalence, pathogenesis, and treatment options for mastocytosis-related osteoporosis

Mastocytosis is a rare condition characterized by abnormal mast cell proliferation and a broad spectrum of manifestations, including various organs and tissues. Osteoporosis is one of the most frequent manifestations of systemic mastocytosis, particularly in adults. Osteoporosis secondary to systemic mastocytosis is a cause of unexplained low bone mineral density that should be investigated when accompanied by suspicious clinical elements. Bone involvement is often complicated by a high recurrence of fragility fractures, mainly vertebral, leading to severe disability. The mechanism of bone loss is the result of different pathways, not yet fully discovered. The main actor is the osteoclast with a relative or absolute predominance of bone resorption. Among the stimuli that drive osteoclast activity, the most important one seems to be the RANK-RANKL signaling, but also histamine and other cytokines play a significant role in the process. The central role of osteoclasts made bisphosphonates, as anti-resorptive drugs, the most rational treatment for bone involvement in systemic mastocytosis. There are a few small studies supporting this approach, with large heterogeneity of drug and administration scheme. Currently, zoledronate has the best evidence in terms of gain in bone mineral density and bone turnover suppression, two surrogate markers of anti-fracture efficacy.

Skeletal effects of a gastrin receptor antagonist in H+/K+ATPase beta subunit KO mice

Epidemiological studies suggest an increased fracture risk in patients taking proton pump inhibitors (PPIs) for long term. The underlying mechanism, however, has been disputed. By binding to the gastric proton pump, PPIs inhibit gastric acid secretion. We have previously shown that proton pump (H(+)/K(+)ATPase beta subunit) KO mice exhibit reduced bone mineral density (BMD) and inferior bone strength compared with WT mice. Patients using PPIs as well as these KO mice exhibit gastric hypoacidity, and subsequently increased serum concentrations of the hormone gastrin. In this study, we wanted to examine whether inhibition of the gastrin/CCK2 receptor influences bone quality in these mice. KO and WT mice were given either the gastrin/CCK2 receptor antagonist netazepide dissolved in polyethylene glycol (PEG) or only PEG for 1year. We found significantly lower bone mineral content and BMD, as well as inferior bone microarchitecture in KO mice compared with WT. Biomechanical properties by three-point bending test also proved inferior in KO mice. KO mice receiving netazepide exhibited significantly higher cortical thickness, cortical area fraction, trabecular thickness and trabecular BMD by micro-CT compared with the control group. Three-point bending test also showed higher Young's modulus of elasticity in the netazepide KO group compared with control mice. In conclusion, we observed that the gastrin receptor antagonist netazepide slightly improved bone quality in this mouse model, suggesting that hypergastrinemia may contribute to deteriorated bone quality during acid inhibition.

Effects of the Histamine 1 Receptor Antagonist Cetirizine on the Osteoporotic Phenotype in H(+) /K(+) ATPase Beta Subunit KO Mice

Epidemiological studies suggest increased fracture risk in patients using proton pump inhibitors (PPIs). We have previously shown that the H(+) /K(+) ATPase beta subunit knockout (KO) mouse, which is a model of PPI-use, have lower bone mineral density (BMD) and impaired bone quality compared to wild type (WT) mice. Like PPI users, these KO mice display elevated gastric pH and hypergastrinemia, which in turn stimulates gastric histamine release. Previous studies have suggested a negative effect of histamine on bone, thus, we wanted to study whether a histamine 1 receptor (H1R) antagonist could improve bone quality in KO mice. Female KO and WT mice aged 8 weeks received either an H1R antagonist (cetirizine) or polyethylene glycol (PEG) for 6 months. At the end of the study, KO mice displayed elevated plasma histamine levels compared to WT. As demonstrated previously, the KO mice also exhibited lower whole body BMD, reduced mechanical bone strength, and impaired bone quality assessed by μCT. No significant differences, however, were found between the KO groups receiving cetirizine or PEG for any of the measured bone parameters. In vitro gene expression analyses of histamine receptors revealed the presence of H1R and H2R both in osteoblasts and osteoclasts, and H3R in late stage osteoblasts. In conclusion, administration of the H1R antagonist cetirizine in a concentration of 3 mg/kg did not rescue the osteoporotic phenotype in H(+) /K(+) ATPase beta subunit KO mice. It can, however, not be ruled out that histamine may influence bone via other receptors. J. Cell. Biochem. 117: 2089-2096, 2016. © 2016 Wiley Periodicals, Inc.

Periosteum Metabolism and Nerve Fiber Positioning Depend on Interactions between Osteoblasts and Peripheral Innervation in Rat Mandible

The sympathetic nervous system controls bone remodeling by regulating bone formation and resorption. How nerves and bone cells influence each other remains elusive. Here we modulated the content or activity of the neuropeptide Vasoactive Intestinal Peptide to investigate nerve-bone cell interplays in the mandible periosteum by assessing factors involved in nerve and bone behaviors. Young adult rats were chemically sympathectomized or treated with Vasoactive Intestinal Peptide or Vasoactive Intestinal Peptide_10-28, a receptor antagonist. Sympathectomy depleted the osteogenic layer of the periosteum in neurotrophic proNerve Growth Factor and neurorepulsive semaphorin3a; sensory Calcitonin-Gene Related Peptide-positive fibers invaded this layer physiologically devoid of sensory fibers. In the periosteum non-osteogenic layer, sympathectomy activated mast cells to release mature Nerve Growth Factor while Calcitonin-Gene Related Peptide-positive fibers increased. Vasoactive Intestinal Peptide treatment reversed sympathectomy effects. Treating intact animals with Vasoactive Intestinal Peptide increased proNerve Growth Factor expression and stabilized mast cells. Vasoactive Intestinal Peptide_10-28 treatment mimicked sympathectomy effects. Our data suggest that sympathetic Vasoactive Intestinal Peptide modulate the interactions between nervous fibers and bone cells by tuning expressions by osteogenic cells of factors responsible for mandible periosteum maintenance while osteogenic cells keep nervous fibers at a distance from the bone surface.