The immune system and bone

Untangling Ariadne's Thread Within the Bone Marrow Maze: A Close-Up View of Stem/Progenitor Cells' Interactome and Secretome

The bone marrow (BM) is a multifactorial, highly dynamic, still not fully "mapped," reservoir. The BM labyrinthine landscape is subject to a relentless debate on the specialized and stem/progenitor cells' scattering within designated microareas. Certainly, BM tissue plays a watchdog role in bone modeling and remodeling, hematopoiesis, immune surveillance, and endocrine response integration. Parameters like tissue topographical distinctiveness, stiffness and porosity grade, and cells' behavioral idiosyncrasies in terms of stem/progenitor cell housing, activation, and motility represent a knotty problem not easily solved. Given that the disruption of BM microdomains has been associated with a number of severe pathological disorders, the comprehension and preservation of the BM workspace at multiple levels have become mandatory. Solid evidence has showed the existence of an intricate and tightly regulated cross-talk between the BM cellular occupants. Direct physical cell-cell connections and soluble mediators, including cytokines, chemokines, growth factors, exosomes and microvesicles, orchestrate composite intracellular signaling routes. The spatiotemporal action of definite biofactors ensures a functional blood-producing organ with a physiological bone turnover and prompts the action of multipotent stromal/hematopoietic cells. Recently, significant research efforts have been addressed to build bioengineered niche-mimic models based on biofunctionalized scaffolds and organoid-like constructs. These artificial BM niches combine and transduce various aspects of bioinformatics and tissue engineering to unravel the complexities of BM organization. This chapter aims to unfold the recent breakthroughs in the understanding of a BM intramural cell-cell dialogue in a physiological and, in some cases, within an inflammatory background. BM maze is gradually being discovered, but there is still a long way to go.

Cardenolides; calotropin and gomphogenin from Calotropis procera (Aiton) mitigate bone turnover in ovariectomized osteoporotic rats: Targeting RANKL/OPG axis and estrogen receptor-alpha

The present study aimed to examine the effect of Calotropis procera (Aiton) and its major cardenolides; calotropin and gomphogenin on ovariectomy-induced osteoporosis in rats. Osteoporotic rats were orally treated with C. procera alcoholic extract (100 mg/kg), calotropin (CLT; 100 μg/kg) and gomphogenin (GPG; 100 μg/kg) for 14 consecutive days. Bone resorption/formation biomarkers; bone specific alkaline phosphatase (BALP), osteoprotegerin (OPG) and nuclear factor-κβ ligand (RANKL) as well as serum calcium and phosphorus were assessed 24 h after last doses of treatments. Serum levels of estradiol (E2) and catalase were also measured. Oral treatment with C. procera extract, CLT and GPG caused E2 restoration to normal level with a marked regulation in the RANKL/OPG axis. Serum phosphorus and calcium were up-leveled whereas BALP was downregulated. Histopathological examination, bone histomorphometric analysis and immunohistochemical staining for osteopontin (OPN) inspection further emphasized the aforementioned outcomes. The results revealed the superiority of CLT and to a lesser extent GPG osteoporotic effect over C. procera extract. Molecular docking of the two compounds on ER-α and RANKL/OPG complex showed noteworthy binding affinities which also confirmed the supremacy of CLT due to the additional hydrogen bonding of the hydroxyl groups of the sugar moiety with RANKL/OPG complex. Finally, it is concluded that CLT and GPG from C. procera hinder bone turnover by decreasing osteoclastic bone cells activity and increasing calcium mineralization thus suppressing bone remodeling and preventing bone infirmity in OVX osteoporotic rats directly via binding to RANKL/OPG complex and ER-α and indirectly through elevating level of E2.

Integrating osteoimmunology and nanoparticle-based drug delivery systems for enhanced fracture healing

Fracture healing is a complex interplay of molecular and cellular mechanisms lasting from days to weeks. The inflammatory phase is the first stage of fracture healing and is critical in setting the stage for successful healing. There has been growing interest in exploring the role of the immune system and novel therapeutic strategies, such as nanoparticle drug delivery systems in enhancing fracture healing. Advancements in nanotechnology have revolutionized drug delivery systems to the extent that they can modulate immune response during fracture healing by leveraging unique physiochemical properties. Therefore, understanding the intricate interactions between nanoparticle-based drug delivery systems and the immune response, specifically macrophages, is essential for therapeutic efficacy. This review provides a comprehensive overview of the relationship between the immune system and nanoparticles during fracture healing. Specifically, we highlight the influence of nanoparticle characteristics, such as size, surface properties, and composition, on macrophage activation, polarization, and subsequent immune responses. IMPACT STATEMENT: This review provides valuable insights into the interplay between fracture healing, the immune system, and nanoparticle-based drug delivery systems. Understanding nanoparticle-macrophage interactions can advance the development of innovative therapeutic approaches to enhance fracture healing, improve patient outcomes, and pave the way for advancements in regenerative medicine.

Engineered osteoclasts as living treatment materials for heterotopic ossification therapy

Osteoclasts (OCs), the only cells capable of remodeling bone, can demineralize calcium minerals biologically. Naive OCs have limitations for the removal of ectopic calcification, such as in heterotopic ossification (HO), due to their restricted activity, migration and poor adhesion to sites of ectopic calcification. HO is the formation of pathological mature bone within extraskeletal soft tissues, and there are currently no reliable methods for removing these unexpected calcified plaques. In the present study, we develop a chemical approach to modify OCs with tetracycline (TC) to produce engineered OCs (TC-OCs) with an enhanced capacity for targeting and adhering to ectopic calcified tissue due to a broad affinity for calcium minerals. Unlike naive OCs, TC-OCs are able to effectively remove HO both in vitro and in vivo. This achievement indicates that HO can be reversed using modified OCs and holds promise for engineering cells as "living treatment agents" for cell therapy.

Modulation of Bone and Joint Biomarkers, Gut Microbiota, and Inflammation Status by Synbiotic Supplementation and Weight-Bearing Exercise: Human Study Protocol for a Randomized Controlled Trial

BACKGROUND

There is strong evidence suggesting that prebiotics and probiotics regulate gut microbiota, reducing inflammation and thereby potentially improving bone health status. Similarly, mechanistic evidence suggests that either low-impact or high-impact weight-bearing exercises improve body composition and consequently increase bone mineral density in individuals with osteoporosis and osteoarthritis.

OBJECTIVE

This study aims to investigate the effects of a synbiotic (probiotic+prebiotic) supplementation, an exercise intervention, or a combination of both on gut microbiota, inflammation, and bone biomarkers in postmenopausal women.

METHODS

A total of 160 postmenopausal women from New Zealand will be recruited and randomized to one of four interventions or treatments for 12 weeks: control, synbiotic supplementation, exercise intervention, or synbiotic supplementation and exercise. The primary outcome measure is the bone and joint biomarkers at baseline and week 12, whereas the gut microbiota profile and inflammatory cytokine measurements will serve as the secondary outcome measures at baseline and week 12. Baseline data and exercise history will be used to assess, allocate, and stratify participants into treatment measures.

RESULTS

Recruitment of participants will begin in September 2021, and the anticipated completion date is June 2022.

CONCLUSIONS

To the best of our knowledge, this will be the first randomized controlled trial to analyze the effects of both a synbiotic supplement and an exercise intervention in postmenopausal women. On the basis of the results obtained, a combination of synbiotic supplements and exercise might serve as a noninvasive approach to manage and/or improve body composition and bone health in postmenopausal women.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry ACTRN12620000998943p; https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=380336&isClinicalTrial=False.

The role of renin angiotensin system in the pathophysiology of rheumatoid arthritis

BACKGROUND

In rheumatoid arthritis (RA) and osteoarthritis (OA), chronic inflammatory processes lead to progresive joint destruction. The renin-angiotensin system (RAS) is involved in the pathogenesis of RA and OA. The aim of this mini-review article is to summarize evidence on the role of RAS in RA and OA.

METHODS

A non-systematic search in Pubmed included terms as "rheumatoid arthritis", "renin angiotensin system", "osteopenia", "RANKL", "DKK-1", "MMP", "inflammation", "angiogenesis", "local renin-angiotensin system", "angiotensin converting enzyme", "AT2 receptor", "Ang-(1-7)", "VEGF", "angiotensine receptor blocker", "angiotensin converting enzyme inhibitors", "renin inhibitors".

RESULTS

Both RAS axes, the classical one, formed by angiotensin converting enzyme (ACE), angiotensin (Ang) II and AT1 receptor (AT1R) and the counter-regulatory one, composed by ACE2, Ang-(1-7) and the Mas receptor, modulate inflammation and tissue damage. Ang II activates pro-inflammatory mediators and oxidative stress. Conversely, Ang-(1-7) exerts anti-inflammatory actions, decreasing cytokine release, leukocyte attraction, density of vessels, tissue damage and fibrosis. Angiogenesis facilitates inflammatory cells invasion, while osteopenia causes joint dysfunction. Up-regulated osteoclastogenisis and down-regulated osteoblastogeneses were associaed with the activation of the classical RAS axis. Three different pathways, RANKL, DKK-1 and MMPs are enhanced by classical RAS activation. The treatment of RA included methotrexate and corticosteroids, which can cause side effects. Studies with angiotensin receptor blockers (ARBs), angiotensin converting enzyme inhibitors (ACEi) and renin inhibitors have been conducted in experimental and clinical RA with promising results.

CONCLUSION

The classical RAS activation is an important mechanism in RA pathogenesis and the benefit of ARB and ACEi administration should be further investigated.

JAK inhibition increases bone mass in steady-state conditions and ameliorates pathological bone loss by stimulating osteoblast function

Janus kinase (JAK)-mediated cytokine signaling has emerged as an important therapeutic target for the treatment of inflammatory diseases such as rheumatoid arthritis (RA). Accordingly, JAK inhibitors compose a new class of drugs, among which tofacitinib and baricitinib have been approved for the treatment of RA. Periarticular bone erosions contribute considerably to the pathogenesis of RA. However, although the immunomodulatory aspect of JAK inhibition (JAKi) is well defined, the current knowledge of how JAKi influences bone homeostasis is limited. Here, we assessed the effects of the JAK inhibitors tofacitinib and baricitinib on bone phenotype (i) in mice during steady-state conditions or in mice with bone loss induced by (ii) estrogen-deficiency (ovariectomy) or (iii) inflammation (arthritis) to evaluate whether effects of JAKi on bone metabolism require noninflammatory/inflammatory challenge. In all three models, JAKi increased bone mass, consistent with reducing the ratio of receptor activator of NF-κB ligand/osteoprotegerin in serum. In vitro, effects of tofacitinib and baricitinib on osteoclast and osteoblast differentiation were analyzed. JAKi significantly increased osteoblast function (P < 0.05) but showed no direct effects on osteoclasts. Additionally, mRNA sequencing and ingenuity pathway analyses were performed in osteoblasts exposed to JAKi and revealed robust up-regulation of markers for osteoblast function, such as osteocalcin and Wnt signaling. The anabolic effect of JAKi was illustrated by the stabilization of β-catenin. In humans with RA, JAKi induced bone-anabolic effects as evidenced by repair of arthritic bone erosions. Results support that JAKi is a potent therapeutic tool for increasing osteoblast function and bone formation.

B cell acute lymphoblastic leukemia cells mediate RANK-RANKL-dependent bone destruction

Although most children survive B cell acute lymphoblastic leukemia (B-ALL), they frequently experience long-term, treatment-related health problems, including osteopenia and osteonecrosis. Because some children present with fractures at ALL diagnosis, we considered the possibility that leukemic B cells contribute directly to bone pathology. To identify potential mechanisms of B-ALL-driven bone destruction, we examined the p53 ^-/-; Rag2 ^-/-; Prkdc^scid/scid triple mutant (TM) mice and p53 ^-/-; Prkdc^scid/scid double mutant (DM) mouse models of spontaneous B-ALL. In contrast to DM animals, leukemic TM mice displayed brittle bones, and the TM leukemic cells overexpressed Rankl, encoding receptor activator of nuclear factor κB ligand. RANKL is a key regulator of osteoclast differentiation and bone loss. Transfer of TM leukemic cells into immunodeficient recipient mice caused trabecular bone loss. To determine whether human B-ALL can exert similar effects, we evaluated primary human B-ALL blasts isolated at diagnosis for RANKL expression and their impact on bone pathology after their transplantation into NOD.Prkdc^scid/scidIl2rg^tm1Wjl /SzJ (NSG) recipient mice. Primary B-ALL cells conferred bone destruction evident in increased multinucleated osteoclasts, trabecular bone loss, destruction of the metaphyseal growth plate, and reduction in adipocyte mass in these patient-derived xenografts (PDXs). Treating PDX mice with the RANKL antagonist recombinant osteoprotegerin-Fc (rOPG-Fc) protected the bone from B-ALL-induced destruction even under conditions of heavy tumor burden. Our data demonstrate a critical role of the RANK-RANKL axis in causing B-ALL-mediated bone pathology and provide preclinical support for RANKL-targeted therapy trials to reduce acute and long-term bone destruction in these patients.

New insight of immuno-engineering in osteoimmunomodulation for bone regeneration

With the continuous development of bone tissue engineering, the importance of immune response in bone tissue regeneration is gradually recognized. The new bone tissue engineering products should possess immunoregulatory functions, harmonizing the interactions between the bone's immune defense and regeneration systems, and promoting tissue regeneration. This article will interpret the relationship between the bone immune system, bone tissue regeneration, as well as the immunoregulatory function of bone biomaterials and seed stem cells in bone tissue engineering. This review locates arears for foucusing efforts at providing novel designs ideas about the development of immune-mediation targeted bone tissue engineering products and the evaluation strategy for the osteoimmunomodulation property of bone biomaterials.

The Roles of Sclerostin in Immune System and the Applications of Aptamers in Immune-Related Research

Wnt signaling is one of the fundamental pathways that play a major role in almost every aspect of biological systems. In addition to the well-known influence of Wnt signaling on bone formation, its essential role in the immune system also attracted increasing attention. Sclerostin, a confirmed Wnt antagonist, is also proven to modulate the development and differentiation of normal immune cells, particularly B cells. Aptamers, single-stranded (ss) oligonucleotides, are capable of specifically binding to a variety of target molecules by virtue of their unique three-dimensional structures. With in-depth study of those functional nucleic acids, they have been gradually applied to diagnostic and therapeutic area in immune diseases due to their various advantages over antibodies. In this review, we focus on several issues including the roles of Wnt signaling and Wnt antagonist sclerostin in the immune system. For the sake of understanding, current examples of aptamers applications for the immune diseases are also discussed. At the end of this review, we propose our ideas for the future research directions.

Infection by CagA-Positive Helicobacter pylori Strains and Bone Fragility: A Prospective Cohort Study

Helicobacter pylori (HP) infection is a common and persistent disorder acting as a major cofactor for the development of upper gastrointestinal diseases and several extraintestinal disorders including osteoporosis. However, no prospective study assessed the effects of HP on bone health and fracture risk. We performed a HP screening in a population-based cohort of 1149 adults followed prospectively for up to 11 years. The presence of HP infection was assessed by serologic testing for serum antibodies to HP and the cytotoxin associated gene-A (CagA). The prevalence of HP infection did not differ among individuals with normal bone mineral density (BMD), osteoporosis, and osteopenia. However, HP infection by CagA-positive strains was significantly increased in osteoporotic (30%) and osteopenic (26%) patients respect to subjects with normal BMD (21%). Moreover, anti-CagA antibody levels were significantly and negatively associated with lumbar and femoral BMD. Consistent with these associations, patients affected by CagA-positive strains had a more than fivefold increased risk to sustain a clinical vertebral fracture (HR 5.27; 95% CI, 2.23-12.63; p < .0001) and a double risk to sustain a nonvertebral incident fracture (HR 2.09; 95% CI, 1.27-2.46; p < .005). Reduced estrogen and ghrelin levels, together with an impaired bone turnover balance after the meal were also observed in carriers of CagA-positive HP infection. HP infection by strains expressing CagA may be considered a risk factor for osteoporosis and fractures. Further studies are required to clarify in more detail the underlying pathogenetic mechanisms of this association. © 2020 American Society for Bone and Mineral Research (ASBMR).

Learning from Monocyte-Macrophage Fusion and Multinucleation: Potential Therapeutic Targets for Osteoporosis and Rheumatoid Arthritis

Excessive bone resorption by osteoclasts (OCs) covers an essential role in developing bone diseases, such as osteoporosis (OP) and rheumatoid arthritis (RA). Monocytes or macrophages fusion and multinucleation (M-FM) are key processes for generating multinucleated mature cells with essential roles in bone remodelling. Depending on the phenotypic heterogeneity of monocyte/macrophage precursors and the extracellular milieu, two distinct morphological and functional cell types can arise mature OCs and giant cells (GCs). Despite their biological relevance in several physiological and pathological responses, many gaps exist in our understanding of their formation and role in bone, including the molecular determinants of cell fusion and multinucleation. Here, we outline fusogenic molecules during M-FM involved in OCs and GCs formation in healthy conditions and during OP and RA. Moreover, we discuss the impact of the inflammatory milieu on modulating macrophages phenotype and their differentiation towards mature cells. Methodological approach envisaged searches on Scopus, Web of Science Core Collection, and EMBASE databases to select relevant studies on M-FM, osteoclastogenesis, inflammation, OP, and RA. This review intends to give a state-of-the-art description of mechanisms beyond osteoclastogenesis and M-FM, with a focus on OP and RA, and to highlight potential biological therapeutic targets to prevent extreme bone loss.

Effects of Allium hookeri on gut microbiome related to growth performance in young broiler chickens

Healthy food promotes beneficial bacteria in the gut microbiome. A few prebiotics act as food supplements to increase fermentation by beneficial bacteria, which enhance the host immune system and health. Allium hookeri is a healthy food with antioxidant and anti-inflammatory activities. A. hookeri is used as a feed supplement for broiler chickens to improve growth performance. Although the underlying mechanism is unknown, A. hookeri may alter the gut microbiome. In the current study, 16S rRNA sequencing has been carried out using samples obtained from the cecum of broiler chickens exposed to diets comprising different tissue types (leaf and root) and varying amounts (0.3% and 0.5%) of A. hookeri to investigate their impact on gut microbiome. The microbiome composition in the groups supplemented with A. hookeri leaf varied from that of the control group. Especially, exposure to 0.5% amounts of leaf resulted in differences in the abundance of genera compared with diets comprising 0.3% leaf. Exposure to a diet containing 0.5% A. hookeri leaf decreased the abundance of the following bacteria: Eubacterium nodatum, Marvinbryantia, Oscillospira, and Gelria. The modulation of gut microbiome by leaf supplement correlated with growth traits including body weight, bone strength, and infectious bursal disease antibody. The results demonstrate that A. hookeri may improve the health benefits of broiler chickens by altering the gut microbiome.

Integrative Analyses of Genes Associated With Osteoporosis in CD16+ Monocyte

BACKGROUND

Osteoporosis is a metabolic bone disease characterized by decreased bone mineral density and abnormal bone quality. Monocytes can secret cytokines for bone resorption, resulting in bone mass loss. However, the mechanism by which monocytes subpopulations lead to osteoporosis remains unclear. The aim of this study was to identify genes associated with osteoporosis in monocytes subsets.

METHODS

Three microarray datasets including GSE7158 (transcription of low/high-peak bone mass), GSE101489 (transcription of CD16+/CD16- monocyte) and GSE93883 (miRNA expression profile of primary osteoporosis) were derived from the Gene Expression Omnibus (GEO) database and analyzed with GEO2R tool to identify differentially expressed genes (DEGs). Functional enrichment was analyzed using Metascape database and GSEA software. STRING was utilized for the Protein-Protein Interaction Network construct. The hub genes were screened out using the Cytoscape software. Related miRNAs were predicted in miRWalk, miRDB, and TargetScan databases.

RESULTS

Total 368 DEGs from GSE7158 were screened out, which were mostly enriched in signaling, positive regulation of biological process and immune system process. The hub genes were clustered into two modules by PPI network analysis. We identified 15 overlapping DGEs between GSE101489 and GSE7158 microarray datasets. Moreover, all of them were up-regulated genes in both datasets. Then, nine key genes were screened out from above 15 overlapping DEGs using Cytoscape software. It is a remarkable fact that the nine genes were all in one hub gene module of GSE7158. Additionally, 183 target miRNAs were predicted according to the above nine DEGs. After cross-verification with miRNA express profile dataset for osteoporosis (GSE93883), 12 DEmiRNAs were selected. Finally, a miRNA-mRNA network was constructed with the nine key genes and 12 miRNAs, which were involved in osteoporosis.

CONCLUSION

Our analysis results constructed a gene expression framework in monocyte subsets for osteoporosis. This approach could provide a novel insight into osteoporosis.

Association of pemphigus and pemphigoid with osteoporosis and pathological fractures

Patients with pemphigus and bullous pemphigoid (BP) have potential risk factors for osteoporosis and/or fractures. To determine whether pemphigus and BP are associated with osteoporosis and fractures in the US, a cross-sectional study of 198,102,435 adults was performed, including 4506 with pemphigus and 8864 with BP from the 2006-2012 National Emergency Department Sample, a 20% sample of emergency care visits throughout the US. Pemphigus was associated with higher odds (multivariate logistic regression; adjusted odds ratio [95% confidence intervals]) of osteopenia (2.20 [1.59-3.05]), osteoporosis (2.54 [2.16-2.98]), osteomalacia (29.70 [4.05-217.83]), and pathological fractures (2.04 [1.42-2.91]). BP was associated with osteoporosis (1.55 [1.39-1.73]) and pathological fractures (1.52 [1.22-1.88]). When compared to BP, pemphigus was associated with higher odds of osteopenia (1.59 [1.06-2.41]), osteoporosis (1.38 [1.18-1.63]), and fractures (1.26 [1.04-1.53]), particularly of the ulna and radius (3.17 [1.23-8.17]). Patients with pemphigus or BP as well as long-term systemic corticosteroid use had highest odds of osteoporosis and fractures. No data were available on treatments for pemphigus or BP. Pemphigus and BP were associated with osteopenia, osteoporosis, and pathologic fractures. Patients with PEM and BP may benefit from increased screening for osteoporosis and interventions to prevent fractures.

Influence of antiretroviral therapy on bone metabolism of patients with chronic hepatitis B: a review

Hepatitis B is a major public health problem worldwide and associated with significant mortality. To prevent or delay the deleterious effects of chronic infection by the hepatitis B virus, patients should be carefully followed, and antiviral therapy indicated according to specific recommendations. Currently, available drugs inhibit viral replication and slow or stop the progression of inflammation and fibrosis of the liver. However, the drugs for oral use in the treatment of hepatitis B, jointly referred to as nucleoside/nucleotide analogs, are indicated for prolonged use and have potential side effects. The reduction in bone mineral density was associated with the use of tenofovir, already evaluated in patients infected with HIV because the drug is also part of the therapeutic arsenal for this viral infection. There are few studies on the effects of tenofovir in patients with mono hepatitis B. Therefore, this literature review proposes to examine how hepatitis B acts in the body and the mechanisms by which antiretroviral drugs (especially tenofovir) can affect bone metabolism.

Effects of oleanolic acid acetate on bone formation in an experimental periodontitis model in mice

OBJECTIVE

We evaluated the role of oleanolic acid acetate (OAA), a triterpenoid commonly used in the treatment of liver disorders, inflammatory diseases, and metastasis, in bone formation after tooth loss by periodontitis.

BACKGROUND

Periodontitis causes the sequential degradation of the alveolar bone and associated structures, resulting in tooth loss. Several studies have attempted to regenerate the bone for implantation following tooth loss.

METHODS

Maxillary left second molar was extracted from 8-week-old male mice following induction of periodontitis by ligature for 5 days. The extraction socket was treated with 50 ng/µL OAA for 1, 2, and 3 weeks. Detailed morphological changes were examined using Masson's trichrome staining, and the precise localization patterns of various signaling molecules, including CD31, F4/80, interleukin (IL)-6, and osteocalcin, were observed. The volume of bone formation was examined by Micro-CT. Osteoclasts were enumerated using tartrate-resistant acid phosphatase (TRAP) staining. For molecular dissection of signaling molecules, we employed the hanging-drop in vitro cultivation method at E14 for 1 day and examined the expression pattern of transforming growth factor (TGF)-β superfamily and Wnt signaling genes.

RESULTS

Histomorphometrical examinations showed facilitated bone formation in the extraction socket following OAA treatment. In addition, OAA-treated specimens showed the altered localization patterns of inflammatory and bone formation-related signaling molecules including CD31, F4/80, IL-6, and osteocalcin. Also, embryonic tooth germ mesenchymal tissue cultivation with OAA treatment showed the significant altered expression patterns of signaling molecules such as transforming growth factor (TGF)-β superfamily and Wnt signaling.

CONCLUSIONS

Oleanolic acid acetate induces bone formation and remodeling through proper modulation of osteoblast, osteoclast, and inflammation with regulations of TGF-β and Wnt signaling.

Activin Receptor 2 Antagonization Impairs Adipogenic and Enhances Osteogenic Differentiation in Mouse Adipose-Derived Stem Cells and Mouse Bone Marrow-Derived Stem Cells In Vitro and In Vivo

Tumors, traumata, burn injuries or surgeries can lead to critical-sized bony defects which need to be reconstructed. Mesenchymal stem cells (MSCs) have the ability to differentiate into multiple cell lineages and thus present a promising alternative for use in tissue engineering and reconstruction. However, there is an ongoing debate whether all MSCs are equivalent in their differentiation and proliferation ability. The goal of this study was to assess osteogenic and adipogenic characteristic changes of adipose-derived stem cells (ASCs) and bone marrow-derived stem cells (BMSCs) upon Myostatin inhibition with Follistatin in vitro and in vivo. We harvested ASCs from mice inguinal fat pads and BMSCs from tibiae of mice. By means of histology, real-time cell analysis, immunohistochemistry, and PCR osteogenic and adipogenic proliferation and differentiation in the presence or absence of Follistatin were analyzed. In vivo, osteogenic capacity was investigated in a tibial defect model of wild-type (WT) mice treated with mASCs and mBMSCs of Myo^-/- and WT origin. In vitro, we were able to show that inhibition of Myostatin leads to markedly reduced proliferative capacity in mBMSCs and mASCs in adipogenic differentiation and reduced proliferation in osteogenic differentiation in mASCs, whereas proliferation in mBMSCs in osteogenic differentiation was increased. Adipogenic differentiation was inhibited in mASCs and mBMSCs upon Follistatin treatment, whereas osteogenic differentiation was increased in both cell lineages. In vivo, we could demonstrate increased osteoid formation in WT mice treated with mASCs and mBMSCs of Myo^-/- origin and enhanced osteogenic differentiation and proliferation of mASCs of Myo^-/- origin. We could demonstrate that the osteogenic potential of mASCs could be raised to a level comparable to mBMSCs upon inhibition of Myostatin. Moreover, Follistatin treatment led to inhibition of adipogenesis in both lineages.

Oxidative stress as a possible pathogenic cofactor of post-menopausal osteoporosis: Existing evidence in support of the axis oestrogen deficiency-redox imbalance-bone loss

Post-menopausal osteoporosis (PO) is one of the major health issues associated with menopause-related oestrogen withdrawal. Despite the intense research and the relevant progress achieved in the last two decades, the pathogenic mechanism underlying PO is still poorly understood. As a consequence of this gap in the knowledge, such disorder and the related complications are still difficult to be effectively prevented. A wealth of experimental and epidemiological/clinical evidence suggests that the endocrine change associated to menopausal transition might lead to a derangement of redox homeostasis, that is, the prelude to the health-threaten condition of oxidative stress (OxS). In turn, this (bio)chemical stress has been widely hypothesized to contribute, most likely in synergy with inflammation, to the development of menopause-related diseases, including PO. The main aim of this review is to discuss the current literature evidence on the association between post-menopausal oestrogen withdrawal, OxS and PO. It is also aimed to provide a critical overview of the most significant epidemiological studies on the effects of dietary antioxidants on bone health and to devise a strategy to overcome the limitations emerged and controversial results.

Bone management in hematologic stem cell transplant recipients

Autologous and allogeneic hematopoietic stem cell transplantation (HSCT) is the treatment of choice for patients with some malignant and non-malignant hematological diseases. Advances in transplantation techniques and supportive care measures have substantially increased the number of long-term HSCT survivors. This has led to an increasing patient population suffering from the late effects of HSCT, of which, bone loss and its consequent fragility fractures lead to substantial morbidity. Altered bone health, with consequent fragility fractures, and chronic graft-versus-host disease (GVHD) are factors affecting long-term quality of life after HSCT. Hypogonadism, HSCT preparative regimens, nutritional factors, and glucocorticoids all contribute to accelerated bone loss and increased fracture risk. Management strategies should include bone mineral density examination, evaluation of clinical risk factors, and general dietary and physical activity measures. Evidence has accumulated permitting recommendations for more attentiveness to evaluation and monitoring of bone health, with appropriate application of osteoporosis pharmacotherapies to patients at increased risk of bone loss and fracture.

Lamins and bone disorders: current understanding and perspectives

Lamin A/C is a major constituent of the nuclear lamina implicated in a number of genetic diseases, collectively known as laminopathies. The most severe forms of laminopathies feature, among other symptoms, congenital scoliosis, osteoporosis, osteolysis or delayed cranial ossification.

Importantly, specific bone districts are typically affected in laminopathies. Spine is severely affected in LMNA-linked congenital muscular dystrophy. Mandible, terminal phalanges and clavicles undergo osteolytic processes in progeroid laminopathies and Restrictive Dermopathy, a lethal developmental laminopathy. This specificity suggests that lamin A/C regulates fine mechanisms of bone turnover, as supported by data showing that lamin A/C mutations activate non-canonical pathways of osteoclastogenesis, as the one dependent on TGF beta 2.

Here, we review current knowledge on laminopathies affecting bone and LMNA involvement in bone turnover and highlight lamin-dependent mechanisms causing bone disorders. This knowledge can be exploited to identify new therapeutic approaches not only for laminopathies, but also for other rare diseases featuring bone abnormalities.

Inactivation of mTORC1 Signaling in Osterix-Expressing Cells Impairs B-cell Differentiation

Osteoblasts provide a microenvironmental niche for B-cell commitment and maturation in the bone marrow (BM). Any abnormity of osteoblasts function may result in the defect of B lymphopoiesis. Signaling from mechanistic target of rapamycin complex 1 (mTORC1) has been implicated in regulating the expansion and differentiation of osteoblasts. Thus, we raise a hypothesis that mTORC1 signaling in osteoblasts plays a vital role in B-cell development. Inactivation of mTORC1 in osterix-expressing cells (mainly osteoblast lineage) through Osx-Cre-directed deletion of Raptor (an mTORC1-specific component) resulted in a reduction in the total B-cell population in the BM, which was due to a block in early B-cell development from the pro-B to pre-B cell stage. Further mechanistic studies revealed that this defect was the result of reduction of interleukin-7 (IL-7) expression in osterix-expressing immature osteoblasts, which caused the abnormality of IL-7/Stat5 signaling in early B lymphocytes, leading to an increased apoptosis of pre-B plus immature B cells. In vitro and in vivo studies demonstrated that the addition of exogenous IL-7 partially restored B lymphopoiesis in the BM of Raptor mutant mice. Furthermore, total BM cells cultured in conditioned media from Raptor null immature osteoblasts or media with anti-IL-7 neutralizing antibody failed to differentiate into pre-B and immature B cells, indicating that inactivation of mTORC1 in immature osteoblast cannot fully support normal B-cell development. Taken together, these findings demonstrate a novel role for mTORC1 in the regulation of bone marrow environments that support B-cell differentiation via regulating IL-7 expression. © 2017 American Society for Bone and Mineral Research.

Osteoimmunology: The Conceptual Framework Unifying the Immune and Skeletal Systems

The immune and skeletal systems share a variety of molecules, including cytokines, chemokines, hormones, receptors, and transcription factors. Bone cells interact with immune cells under physiological and pathological conditions. Osteoimmunology was created as a new interdisciplinary field in large part to highlight the shared molecules and reciprocal interactions between the two systems in both heath and disease. Receptor activator of NF-κB ligand (RANKL) plays an essential role not only in the development of immune organs and bones, but also in autoimmune diseases affecting bone, thus effectively comprising the molecule that links the two systems. Here we review the function, gene regulation, and signal transduction of osteoimmune molecules, including RANKL, in the context of osteoclastogenesis as well as multiple other regulatory functions. Osteoimmunology has become indispensable for understanding the pathogenesis of a number of diseases such as rheumatoid arthritis (RA). We review the various osteoimmune pathologies, including the bone destruction in RA, in which pathogenic helper T cell subsets [such as IL-17-expressing helper T (Th17) cells] induce bone erosion through aberrant RANKL expression. We also focus on cellular interactions and the identification of the communication factors in the bone marrow, discussing the contribution of bone cells to the maintenance and regulation of hematopoietic stem and progenitors cells. Thus the time has come for a basic reappraisal of the framework for understanding both the immune and bone systems. The concept of a unified osteoimmune system will be absolutely indispensable for basic and translational approaches to diseases related to bone and/or the immune system.

CD8+ T cells mediate the regenerative PTH effect in hPDL cells via Wnt10b signaling

It was the aim of the present investigation to examine whether the stimulating effect of parathyroid hormone (PTH) on human periodontal ligament (hPDL) cell proliferation and differentiation would be enhanced by hPDL/T-cell interaction involving Wnt10b signaling as a mediating pathway. hPDL cells were cultured from healthy premolar tissues of three adolescent orthodontic patients and exposed to PTH(1-34) in monocultures or co-cultures with CD8⁺ T cells. At harvest, proliferation, alkaline phosphatase-specific activity (ALP), and osteocalcin production were determined by immunofluorescence cytochemistry, real-time PCR, biochemical assay, and ELISA. Wnt10b signaling was analyzed by the use of a specific WNT10b neutralizing antibody. PTH(1-34) stimulation of T cells significantly increased Wnt10b expression and production. Wnt10b exposure of hPDL cells enhanced proliferation and differentiation. PDL cells co-cultured with T cells showed a Wnt10b-dependent regulation of proliferation and differentiation parameters. The addition of a Wnt10b-neutralizing Ab to the co-culture medium resulted in a significant inhibition of the PTH(1-34) effect on proliferation, ALP-specific activity, and osteocalcin protein expression. Our findings provide novel insight into the mechanism of action of PTH on hPDL cells and establish the interplay of T cells and hPDL cells via the Wnt10b pathway as a modulating factor for the anabolic properties of the hormone in periodontal regeneration.

Synergistic attenuation of ovariectomy-induced bone loss by combined use of fish oil and 17β-oestradiol

Oestrogen and n-3 PUFA, especially EPA and DHA, have been reported to have beneficial effects on bone loss. Thus, the purpose of the present study was to investigate the synergistic bone-protective mechanism of combined treatments of EPA+DHA supplementation and oestrogen injection in ovariectomised rats. Rats were fed a modified American Institute of Nutrition-93G diet with 0 %, 1 % or 2 % n-3 PUFA (EPA+DHA) relative to the total energy intake for 12 weeks. Rats were surgically ovariectomised at week 8, and after a 1-week recovery period rats were injected with either 17β-oestradiol-3-benzoate (E2) or maize oil for the last 3 weeks. Combined use of n-3 PUFA and E2 synergistically increased femoral cortical bone volume, bone mineral content and the bone expression of runt-related transcription factor 2 (RUNX2), but decreased the bone expression of IL-1β. Both n-3 PUFA and E2 decreased the bone expressions of IL-7, TNF-α and PPAR-γ, and increased the bone expression of oestrogen receptor-α. n-3 PUFA in the presence of E2 and E2 alone significantly decreased the bone expressions of IL-1β and IL-6 and increased the bone expression of RUNX2. E2 significantly decreased the serum levels of bone turnover markers and the bone expression of receptor activator of NF-κB ligand, but decreased the bone expression of osteoprotegerin. The combined use of n-3 PUFA and E2 exerted synergistic bone-protective efficacy through up-regulation of RUNX2, an essential transcription factor for bone formation, as well as the suppression of bone-resorbing cytokine IL-1β.

Influence of Synbiotics on Selected Oxidative Stress Parameters

The aim of the present study was to assess synbiotic (Lactobacillus casei + inulin) influence on oxidative stress parameters such as concentrations of malondialdehyde (MDA), hydrogen peroxide (H₂O₂), glutathione, and free sulfhydryl groups content. Experiments were carried out on healthy volunteers (n = 32). The subjects were divided into women group (n = 16) and men group (n = 16) and randomly assigned to synbiotic and control groups. Blood samples were collected before synbiotic supplementation and after 7 wks, at the end of the study. The administration of synbiotic resulted in a significant decrease in MDA (p < 0.01), H₂O₂ (p < 0.01), and GSSG concentrations (p < 0.05) as compared with the control groups and significant increase in the concentrations of GSHt (p < 0.001), GSH (p < 0.01), and -SH group content (p < 0.05) versus control. Synbiotics containing L. casei plus inulin may have positive influence on selected oxidative stress markers.

Activation of mTORC1 in B Lymphocytes Promotes Osteoclast Formation via Regulation of β-Catenin and RANKL/OPG

The cytokine receptor activator of nuclear factor-κB ligand (RANKL) induces osteoclast formation from monocyte/macrophage lineage cells. However, the mechanisms by which RANKL expression is controlled in cells that support osteoclast differentiation are still unclear. We show that deletion of TSC1 (tuberous sclerosis complex 1) in murine B cells causes constitutive activation of mechanistic target of rapamycin complex 1 (mTORC1) and stimulates RANKL but represses osteoprotegerin (OPG) expression and subsequently promotes osteoclast formation and causes osteoporosis in mice. Furthermore, the regulation of RANKL/OPG and stimulation of osteoclastogenesis by mTORC1 was confirmed in a variety of RANKL-expressing cells and in vivo. Mechanistically, mTORC1 controls RANKL/OPG expression through negative feedback inactivation of Akt, destabilization of β-catenin mRNA, and downregulation of β-catenin. Our findings demonstrate that mTORC1 activation-stimulated RANKL expression in B cells is sufficient to induce bone loss and osteoporosis. The study also established a link between mTORC1 and the RANKL/OPG axis via negative regulation of β-catenin. © 2016 American Society for Bone and Mineral Research.

Impact of Strength Training on Bone Mineral Density in Patients Infected With HIV Exhibiting Lipodystrophy

This study aimed to evaluate the impact of strength training on bone mineral density (BMD) in individuals harboring HIV exhibiting lipodystrophy. The study included 20 subjects (16 men) aged 50.60 ± 6.40 years with reduced BMD, presenting positive serology for HIV, using highly active antiretroviral therapy, and performing no regular practice of physical exercise before being enrolled in the study. Bone mineral density levels were evaluated by dual-energy x-ray absorptiometry in the lumbar spine, femoral neck, and 1/3 radius, before and after 36 sessions (12 weeks) of strength training. Compared with pre-exercise period, the results showed increased BMD in lumbar spine (3.28%; p = 0.012), femoral neck (8.45%; p = 0.044), and 1/3 radius (5.41%; p = 0.035). This is the first study evaluating the impact of strength training in patients living with HIV and exhibiting lipodystrophy, showing an increased BMD in all the regions measured (lumbar spine, femoral neck, and 1/3 radius). This study showed the beneficial impact of the strength training on BMD increase in patients living with HIV as an effective and available approach to improve bone health.

Dry Extract of Matricaria recutita L. (Chamomile) Prevents Ligature-Induced Alveolar Bone Resorption in Rats via Inhibition of Tumor Necrosis Factor-α and Interleukin-1β

BACKGROUND

Matricaria recutita L. (chamomile) has demonstrated anti-inflammatory activity. Accordingly, the ability of the Matricaria recutita extract (MRE) to inhibit proinflammatory cytokines and its influence on alveolar bone resorption (ABR) in rats.

METHODS

Wistar rats were subjected to ABR by ligature with nylon thread in the second upper-left molar, with contralateral hemiarcade as control. Rats received polysorbate TW80 (vehicle) or MRE (10, 30, and 90 mg/kg) 1 hour before ligature and daily until day 11. The periodontium was analyzed by macroscopy, histometry, histopathology, and immunohistochemistry for the receptor activator of nuclear factor-kappa B ligand (RANKL), osteoprotegerin (OPG), and tartrate-resistant acid phosphatase (TRAP). The gingival tissue was used to quantify the myeloperoxidase (MPO) activity and tumor necrosis factor (TNF)-α and interleukin (IL)-1β levels by enzyme-linked immunosorbent assay. Blood samples were collected to evaluate bone-specific alkaline phosphatase (BALP), leukogram, and dosages of aspartate and alanine transaminases, urea, and creatinine. Aspects of liver, kidneys, spleen, and body mass variations were also evaluated.

RESULTS

The 11 days of ligature induced bone resorption, low levels of BALP, leukocyte infiltration; increase of MPO, TNF-α, and IL-1β; immunostaining increase for RANKL and TRAP; reduction of OPG and leukocytosis, which were significantly prevented by MRE, except for the low levels of BALP and the leukocytosis. Additionally, MRE did not alter organs or body weights of rats.

CONCLUSION

MRE prevented the inflammation and ABR by reducing TNF-α and IL-1β, preventing the osteoclast activation via the RANKL-OPG axis, without interfering with bone anabolism.

FOXO1 deletion reduces dendritic cell function and enhances susceptibility to periodontitis

The host response plays both protective and destructive roles in periodontitis. FOXO1 is a transcription factor that is activated in dendritic cells (DCs), but its function in vivo has not been examined. We investigated the role of FOXO1 in activating DCs in experimental (CD11c.Cre(+).FOXO1(L/L)) compared with matched control mice (CD11c.Cre(-).FOXO1(L/L)) in response to oral pathogens. Lineage-specific FOXO1 deletion reduced the recruitment of DCs to oral mucosal epithelium by approximately 40%. FOXO1 was needed for expression of genes that regulate migration, including integrins αν and β3 and matrix metalloproteinase-2. Ablation of FOXO1 in DCs significantly decreased IL-12 produced by DCs in mucosal surfaces. Moreover, FOXO1 deletion reduced migration of DCs to lymph nodes, reduced capacity of DCs to induce formation of plasma cells, and reduced production of bacteria-specific antibody. The decrease in DC function in the experimental mice led to increased susceptibility to periodontitis through a mechanism that involved a compensatory increase in osteoclastogenic factors, IL-1β, IL-17, and RANKL. Thus, we reveal a critical role for FOXO1 in DC recruitment to oral mucosal epithelium and activation of adaptive immunity induced by oral inoculation of bacteria.

Molecular mechanisms of osteoporotic hip fractures in elderly women

A common manifestation of age-related bone loss and resultant osteoporosis are fractures of the hip. Age-related osteoporosis is thought to be determined by a number of intrinsic factors including genetics, hormonal changes, changes in levels of oxidative stress, or an inflammatory status associated with the aging process. The aim of this study was to investigate gene expression and bone architecture in bone samples derived from elderly osteoporotic women with hip fractures (OP) in comparison to bone samples from age matched women with osteoarthritis of the hip (OA). Femoral heads and adjacent neck tissue were collected from 10 women with low-trauma hip fractures (mean age 83±6) and consecutive surgical hip replacement. Ten bone samples from patients undergoing hip replacement due to osteoarthritis (mean age 80±5) served as controls. One half of each bone sample was subjected to gene expression analysis. The second half of each bone sample was analyzed by microcomputed tomography. From each half, samples from four different regions, the central and subcortical region of the femoral head and neck, were analyzed. We could show a significantly decreased expression of the osteoblast related genes RUNX2, Osterix, Sclerostin, WNT10B, and Osteocalcin, a significantly increased ratio of RANKL to Osteoprotegerin, and a significantly increased expression of the enzymes superoxide dismutase 2 (SOD2) and glutathione peroxidase GPX3, and of the inflammatory cytokine IL6 in bone samples from hip fracture patients compared to controls. Major microstructural changes in OP bone were seen in the neck and were characterized by a significant decrease of bone volume, trabecular number, and connectivity density and a significant increase of trabecular separation. In conclusion, our data give evidence for a decreased expression of osteoblast related genes and increased expression of osteoclast related genes. Furthermore, increased expression of SOD2 and GPX3 suggest increased antioxidative activity in bone samples from elderly osteoporotic women with hip fractures.

Enhancement of osteogenesis post-splenectomy does not attenuate bone loss in ovariectomized rats

The roles of different immune cell populations and cytokines in bone metabolism have been extensively investigated. However, the influence of whole immune organ removal on osteopathology remains unknown. In the current study, we investigated the effects of splenectomy on bone metabolism and microarchitecture in rats with or without concurrent ovariectomy. Ovariectomized (OVX) rats were used as osteoporosis model. Sixty 12-week-old female rats were randomized into 4 groups (n = 15): sham, splenectomized (SP), ovariectomized, as well as ovariectomized and splenectomized (OVX + SP). Bone microarchitecture was assessed by micro CT analysis at 4 week and 12 week post-operation, respectively. Bone pathology and metabolism were evaluated via immunohistochemical staining. The serum levels of alkaline phosphatase (ALP), tumor necrosis factor-alpha (TNF-α), tartrate-resistant acid phosphatase 5b (Tracp5b), and C-terminal telopeptide (CTx) were analyzed at 4 and 12 weeks post-operation. Removal of the spleen led to alterations in the homeostasis of bone metabolism and increased bone formation in rats. In this study, our findings indicate that the spleen is involved in skeletal metabolism.

Increased NF-κB Activity and Decreased Wnt/β-Catenin Signaling Mediate Reduced Osteoblast Differentiation and Function in ΔF508 Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) Mice

The prevalent human ΔF508 mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) is associated with reduced bone formation and bone loss in mice. The molecular mechanisms by which the ΔF508-CFTR mutation causes alterations in bone formation are poorly known. In this study, we analyzed the osteoblast phenotype in ΔF508-CFTR mice and characterized the signaling mechanisms underlying this phenotype. Ex vivo studies showed that the ΔF508-CFTR mutation negatively impacted the differentiation of bone marrow stromal cells into osteoblasts and the activity of osteoblasts, demonstrating that the ΔF508-CFTR mutation alters both osteoblast differentiation and function. Treatment with a CFTR corrector rescued the abnormal collagen gene expression in ΔF508-CFTR osteoblasts. Mechanistic analysis revealed that NF-κB signaling and transcriptional activity were increased in mutant osteoblasts. Functional studies showed that the activation of NF-κB transcriptional activity in mutant osteoblasts resulted in increased β-catenin phosphorylation, reduced osteoblast β-catenin expression, and altered expression of Wnt/β-catenin target genes. Pharmacological inhibition of NF-κB activity or activation of canonical Wnt signaling rescued Wnt target gene expression and corrected osteoblast differentiation and function in bone marrow stromal cells and osteoblasts from ΔF508-CFTR mice. Overall, the results show that the ΔF508-CFTR mutation impairs osteoblast differentiation and function as a result of overactive NF-κB and reduced Wnt/β-catenin signaling. Moreover, the data indicate that pharmacological inhibition of NF-κB or activation of Wnt/β-catenin signaling can rescue the abnormal osteoblast differentiation and function induced by the prevalent ΔF508-CFTR mutation, suggesting novel therapeutic strategies to correct the osteoblast dysfunctions in cystic fibrosis.

The Impact of Immune System in Regulating Bone Metastasis Formation by Osteotropic Tumors

Bone metastases are frequent and debilitating consequence for many tumors, such as breast, lung, prostate, and kidney cancer. Many studies report the importance of the immune system in the pathogenesis of bone metastasis. Indeed, bone and immune system are strictly linked to each other because bone regulates the hematopoietic stem cells from which all cells of the immune system derive, and many immunoregulatory cytokines influence the fate of bone cells. Furthermore, both cytokines and factors produced by immune and bone cells promote the growth of tumor cells in bone, contributing to supporting the vicious cycle of bone metastasis. This review summarizes the current knowledge on the interactions among bone, immune, and tumor cells aiming to provide an overview of the osteoimmunology field in bone metastasis from solid tumors.

Bone-immune cell crosstalk: bone diseases

Bone diseases are associated with great morbidity; thus, the understanding of the mechanisms leading to their development represents a great challenge to improve bone health. Recent reports suggest that a large number of molecules produced by immune cells affect bone cell activity. However, the mechanisms are incompletely understood. This review aims to shed new lights into the mechanisms of bone diseases involving immune cells. In particular, we focused our attention on the major pathogenic mechanism underlying periodontal disease, psoriatic arthritis, postmenopausal osteoporosis, glucocorticoid-induced osteoporosis, metastatic solid tumors, and multiple myeloma.

High-sensitivity C-reactive protein is an independent risk factor for non-vertebral fractures in women and men: The Tromsø Study

Low-grade inflammation is associated with fractures, while the relationship between inflammation and bone mineral density (BMD) is less clear. Moreover, any gender differences in the sensitivity to inflammation are still poorly elucidated. We therefore tested the hypothesis that high-sensitivity C-reactive protein (CRP) is an independent risk factor for low BMD and non-vertebral fractures, in both genders, and whether there are gender differences in these associations. CRP levels and BMD at the total hip and femoral neck were measured in 1902 women and 1648 men between 55 and 74 years of age, at baseline in the Tromsø Study, Norway, in 2001-2002. Non-vertebral fractures were registered from hospital X-ray archives during an average of 7.2 years follow-up. Linear regression analyses were used for CRP association with BMD and Cox proportional hazards model for fracture prediction by CRP. During 25 595 person-years follow-up, 366 (19%) women and 126 (8%) men suffered a non-vertebral fracture. There was no association between CRP and BMD in women, but an inverse association in men (p=0.001) after adjustment for age and body mass index. Each standard deviation (SD) increase in log-CRP was associated with an increased risk for non-vertebral fracture by 13% in women and 22% in men (hazard ratios (HRs) 1.13, 95% confidence interval (CI) 1.02-1.26, p=0.026 and 1.22, 95% CI=1.00-1.48, p=0.046, respectively). After adjustment for BMD and other risk factors, women with CRP in the upper tertile exhibited 39% higher risk for fracture than those in the lowest tertile of CRP (HR = 1.39, 95% CI = 1.06-1.83, p = 0.017), while men in the upper tertile exhibited 80% higher risk (HR=1.80, 95% CI=1.10-2.94, p=0.019). In summary, CRP was not associated with BMD in women but inversely associated in men, and predicted fractures in both genders. We infer that inflammation influence fracture risk in both women and men, although the biological mechanisms may differ between the genders.

Vitamin D and skeletal health in autoimmune bullous skin diseases: a case control study

Background

The presence of hypovitaminosis D in patients with autoimmune bullous skin diseases, such as pemphigus vulgaris (PV) and bullous pemphigoid (BP), is debated. In a previous study we found an increased prevalence of vertebral fractures (VFx) and hypovitaminosis D in PV and BP patients. The present study extends the sample size of the previous one, for investigating the 25-hydroxyvitamin D (25OHVitD) levels in relation with the skeletal health and disease intensity in these patients.

Methods

The previous study was performed in 13 PV and 15 BP patients and 28 controls. Data from 39 additional patients (22 PV and 17 BP) were now added. Eventually, we studied 67 patients (35 PV, 32 BP, 51 females), aged 64.7 ± 16.9 years and 67 age- gender- and body mass index-matched controls. In all subjects, serum 25OHVitD, calcium and alkaline phosphatase (ALP) levels were measured, bone mineral density (BMD) was evaluated by Dual-energy X-ray. Absorptiometry at lumbar spine (LS) and femoral neck (FN) and the presence of VFx were ascertained by visual assessment from spinal radiographs. In patients, the disease intensity was evaluated by the autoimmune bullous skin disorder intensity score (ABSIS).

Results

As compared with controls, both PV and BP patients showed lower 25OHVitD (22.2 ± 11.1 vs 13.9 ± 8.3 ng/mL, p < 0.001 and 22.4 ± 14.9 vs 9.5 ± 7.7 ng/mL, p < 0.0001, respectively) and higher prevalence of severe hypovitaminosis D (22.9 vs 48.6%, p < 0.02 and 31.1 vs 75.0%, p < 0.0001, respectively) and VFx (28.6 vs 57.1%, p = 0.03 and 34.4 vs 62.5%, P = 0.02, respectively). In both PV and BP patients, LS and FN BMD did not differ from controls. In the whole patients’ group, ABSIS score was inversely associated with 25OHVitD levels (R = −0.36, p < 0.005), regardless of age (β = −3.2, P = 0.009).

Conclusions

PV and BP patients have an increased prevalence of hypovitaminosis D and VFx. The extended study shows, for the first time, that the 25OHVitD levels are inversely associated with disease intensity and that VFx occur in spite of a not reduced BMD.

Electronic supplementary material

The online version of this article (doi:10.1186/s13023-015-0230-0) contains supplementary material, which is available to authorized users.

High-sensitivity CRP is an independent risk factor for all fractures and vertebral fractures in elderly men: the MrOS Sweden study

Epidemiological studies have shown low-grade inflammation measured by high-sensitivity C-reactive protein (hs-CRP) to be associated with fracture risk in women. However, it is still unclear whether hs-CRP is also associated with fracture risk in men. We therefore measured serum levels of hs-CRP in 2910 men, mean age 75 years, included in the prospective population-based MrOS Sweden cohort. Study participants were divided into tertile groups based on hs-CRP level. Fractures occurring after the baseline visit were validated (average follow-up 5.4 years). The incidence for having at least one fracture after baseline was 23.9 per 1000 person-years. In Cox proportional hazard regression analyses adjusted for age, hs-CRP was related to fracture risk. The hazard ratio (HR) of fracture for the highest tertile of hs-CRP, compared with the lowest and the medium tertiles combined, was 1.48 (95% CI, 1.20-1.82). Multivariate adjustment for other risk factors for fractures had no major effect on the associations between hs-CRP and fracture. Results were essentially unchanged after exclusion of subjects with hs-CRP levels greater than 7.5 mg/L, as well as after exclusion of subjects with a first fracture within 3 years of follow-up, supporting that the associations between hs-CRP and fracture risk were not merely a reflection of a poor health status at the time of serum sampling. Femoral neck bone mineral density (BMD) was not associated with hs-CRP, and the predictive role of hs-CRP for fracture risk was essentially unchanged when femoral neck BMD was added to the model (HR, 1.37; 95% CI, 1.09-1.72). Exploratory subanalyses of fracture type demonstrated that hs-CRP was clearly associated with clinical vertebral fractures (HR, 1.61; 95% CI, 1.12-2.29). We demonstrate, using a large prospective population-based study, that elderly men with high hs-CRP have increased risk of fractures, and that these fractures are mainly vertebral. The association between hs-CRP and fractures was independent of BMD. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

Subchondral chitosan/blood implant-guided bone plate resorption and woven bone repair is coupled to hyaline cartilage regeneration from microdrill holes in aged rabbit knees

OBJECTIVE

Little is known of how to routinely elicit hyaline cartilage repair tissue in middle-aged patients. We tested the hypothesis that in skeletally aged rabbit knees, microdrill holes can be stimulated to remodel the bone plate and induce a more integrated, voluminous and hyaline cartilage repair tissue when treated by subchondral chitosan/blood implants.

DESIGN

New Zealand White rabbits (13 or 32 months old, N = 7) received two 1.5 mm diameter, 2 mm depth drill holes in each knee, either left to bleed as surgical controls or press-fit with a 10 kDa (distal hole: 10K) or 40 kDa (proximal hole: 40K) chitosan/blood implant with fluorescent chitosan tracer. Post-operative knee effusion was documented. Repair tissues at day 0 (N = 1) and day 70 post-surgery (N = 6) were analyzed by micro-computed tomography, and by histological scoring and histomorphometry (SafO, Col-2, and Col-1) at day 70.

RESULTS

All chitosan implants were completely cleared after 70 days, without increasing transient post-operative knee effusion compared to controls. Proximal control holes had worse osteochondral repair than distal holes. Both implant formulations induced bone remodeling and improved lateral integration of the bone plate at the hole edge. The 40K implant inhibited further bone repair inside 50% of the proximal holes, while the 10K implant specifically induced a "wound bloom" reaction, characterized by decreased bone plate density in a limited zone beyond the initial hole edge, and increased woven bone (WB) plate repair inside the initial hole (P = 0.016), which was accompanied by a more voluminous and hyaline cartilage repair (P < 0.05 vs control defects).

CONCLUSION

In a challenging aged rabbit model, bone marrow-derived hyaline cartilage repair can be promoted by treating acute drill holes with a biodegradable subchondral implant that elicits bone plate resorption followed by anabolic WB repair within a 70-day repair period.

Methanol Extract of Euchelus asper Prevents Bone Resorption in Ovariectomised Mice Model

Marine molluscs are widely distributed throughout the world and many bioactive compounds exhibiting antiviral, antitumor, antileukemic, and antibacterial activity have been reported worldwide. The present study was designed to investigate the beneficial effect of methanol extract of Euchelus asper (EAME) on estrogen deficiency induced osteoporosis in ovariectomised mice model. Forty-two female Swiss albino mice were randomly assigned into Sham operated (Sham) group and six ovariectomised (OVX) subgroups such as OVX with vehicle (OVX); OVX with estradiol (2 mg/kg/day); OVX with EAME of graded doses (25, 50, 100, and 200 mg/kg/day). Bone turnover markers like serum alkaline phosphatase (ALP), serum acid phosphatase (ACP), serum calcium, and histological investigations of tibia and uterus were analysed. Metaphyseal DNA content of the femur bone was also studied. Antiosteoclastogenic activity of EAME was examined. Administration of EAME was able to reduce the increased bone turnover markers in the ovariectomised mice. Histomorphometric analysis revealed an increase in bone trabeculation and restoration of trabecular separation by EAME treatment. Metaphyseal DNA content of the femur of the OVX mice was increased by EAME administration. EAME also showed a potent antiosteoclastogenic behaviour. Thus, the present study reveals that EAME was able to successfully reduce the estrogen deficiency induced bone loss.

Nutrient element-based bioceramic coatings on titanium alloy stimulating osteogenesis by inducing beneficial osteoimmmunomodulation

Nutrient element-based Sr₂ZnSi₂O₇ coatings induce favorable osteoimmunomodulation. Material chemistry of Sr₂ZnSi₂O₇ coating modulates the immune environment to induce osteogenic differentiation of BMSCs by activating BMP2 signalling pathway.

Osteoimmunology and bone homeostasis: relevance to spondyloarthritis

The seronegative spondyloarthopathies (SpA) share certain common articular and peri-articular features that differ from rheumatoid arthritis (RA) and other forms of inflammatory arthritis. These include the tendency of the SpAs to involve the axial skeleton in addition to the diarthrodial joints, and the prominent involvement of the extra-articular entheses (sites of ligamentous and tendon insertion), which are not common sites of primary pathology in RA and other inflammatory arthropathies. The differential anatomic sites of bone pathology in the SpAs in comparison to the other forms of arthritis suggest that the underlying pathogenic processes and cellular and molecular mechanisms that account for the peri-articular bone pathology involve different underlying disease mechanisms. This review will highlight the molecular and cellular processes that are involved in the pathogenesis of the skeletal pathology in the SpAs, and provide evidence that many of the factors involved in regulation of bone cell function exhibit potent immune-regulatory activity, providing support for the general concept of osteoimmunology.

Osteogenic differentiation of bone marrow MSCs by β-tricalcium phosphate stimulating macrophages via BMP2 signalling pathway

Immune reactions play important roles in determining the in vivo fate of bone substitute materials, either in new bone formation or inflammatory fibrous tissue encapsulation. The paradigm for the development of bone substitute materials has been shifted from inert to immunomodulatory materials, emphasizing the importance of immune cells in the material evaluation. Macrophages, the major effector cells in the immune reaction to implants, are indispensable for osteogenesis and their heterogeneity and plasticity render macrophages a primer target for immune system modulation. However, there are very few reports about the effects of macrophages on biomaterial-regulated osteogenesis. In this study, we used β-tricalcium phosphate (β-TCP) as a model biomaterial to investigate the role of macrophages on the material stimulated osteogenesis. The macrophage phenotype switched to M2 extreme in response to β-TCP extracts, which was related to the activation of calcium-sensing receptor (CaSR) pathway. Bone morphogenetic protein 2 (BMP2) was also significantly upregulated by the β-TCP stimulation, indicating that macrophage may participate in the β-TCP stimulated osteogenesis. Interestingly, when macrophage-conditioned β-TCP extracts were applied to bone marrow mesenchymal stem cells (BMSCs), the osteogenic differentiation of BMSCs was significantly enhanced, indicating the important role of macrophages in biomaterial-induced osteogenesis. These findings provided valuable insights into the mechanism of material-stimulated osteogenesis, and a strategy to optimize the evaluation system for the in vitro osteogenesis capacity of bone substitute materials.