Pathogenesis of Paget disease of bone

Bone scan findings of Paget's disease of bone in patients with VCP Multisystem Proteinopathy 1

Multisystem Proteinopathy 1 (MSP1) disease is a rare genetic disorder caused by mutations in the Valosin-Containing Protein (VCP) gene with clinical features of inclusion body myopathy (IBM), frontotemporal dementia (FTD), and Paget's disease of bone (PDB). We performed bone scan imaging in twelve patients (6 females, 6 males) with confirmed VCP gene mutation six (50%) of which has myopathy alone, four (33%) with both PDB and myopathy, and two (15%) were presymptomatic carriers. We aim to characterize the PDB in diagnosed individuals, and potentially identify PDB in the myopathy and presymptomatic groups. Interestingly, two patients with previously undiagnosed PDB had positive diagnostic findings on the bone scan and subsequent radiograph imaging. Among the individuals with PDB, increased radiotracer uptake of the affected bones were of typical distribution as seen in conventional PDB and those reported in other MSP1 cohorts which are the thoracic spine and ribs (75%), pelvis (75%), shoulder (75%) and calvarium (15%). Overall, we show that technetium-99m bone scans done at regular intervals are a sensitive screening tool in patients with MSP1 associated VCP variants at risk for PDB. However, diagnostic confirmation should be coupled with clinical history, biochemical analysis, and skeletal radiographs to facilitate early treatment and prevention complications, acknowledging its limited specificity.

Optineurin regulates osteoblast function in an age-dependent fashion in a mouse model of Paget's disease of bone

Paget's disease of bone (PDB) is a degenerative disorder affecting the skull and bones. Hyperactive osteoclasts (OCs) initiate bone degradation in the early stage, followed by increased bone formation by osteoblasts (OBs) in trabecular bones during the advanced stage. This OB-OC uncoupling results in bone deformations and irregular trabecular bone patterns. Current mouse models poorly replicate the advanced-stage characteristics of PDB. Optineurin (Gene: OPTN in humans, Optn in mice, protein: OPTN) has been implicated in PDB by genetic analyses. We identified PDB-like cortical lesions associated with OC hyperactivation in an Optn knockout (Optn-/-) mouse model. However, the effects of OPTN dysfunction on OBs and trabecular bone in advanced PDB remain unclear. In this study, we used the Optn-/- mouse model to investigate trabecular bone abnormalities and OB activity in PDB. Micro-computed tomography analysis revealed severe pagetic alterations in craniofacial bones and femurs of aged Optn-/- mice, resembling clinical manifestations of PDB. Altered OB activity was observed in aged Optn-/- mice, implicating compensatory OB response in trabecular bone anomalies. To elucidate the role of OC-OB interactions in PDB, we conducted in vitro experiments using OC conditioned media (CM) to examine the effects on OB osteogenic potential. We found OC CM restored compromised osteogenic induction of Optn-/- bone marrow stromal cells (BMSCs) from young mice, suggesting OCs maintain OB activity through secreted factors. Strikingly, OC CM from aged Optn-/- mice significantly enhanced osteogenic capability of Optn-/- BMSCs, providing evidence for increased OB activity in advanced stages of PDB. We further identified TGF-β/BMP signaling pathway in mediating the effects of OC CM on OBs. Our findings provide insights into Optn's role in trabecular bone abnormalities and OB activity in PDB. This enhances understanding of PDB pathogenesis and may contribute to potential therapeutic strategies for PDB and related skeletal disorders.

Prevalence and incidence of Paget's disease of bone: Temporal trend over 20 years in the province of Quebec, Canada

BACKGROUND

Paget's disease of bone (PDB) is a focal bone disorder characterized by an increased bone remodeling and an anarchic bone structure. A decline of prevalence and incidence of PDB has been observed in some countries. No epidemiological data are available on PDB in Canada.

AIMS

We aimed at examining the evolution of the prevalence and incidence of PDB in Quebec (Canada) by analyzing health administrative databases.

METHODS

PDB case definition relied on one or more hospitalizations, or one or more physician-billing claims with a diagnosis code of PDB. To identify incident cases, a 'run-in' period of four years (1996-1999) was used to exclude prevalent cases. For each fiscal year from 2000 to 2001 to 2019-2020 (population size 2,914,480), crude age and sex-specific prevalence and incidence rates of PDB among individuals aged ≥55 years were determined, and sex-specific rates were also standardized to the 2011 age structure of the Quebec population. Generalized linear regressions were used to test for linear changes in standardized prevalence and incidence rates.

RESULTS

Over the study period, standardized prevalence of PDB has remained stable in Quebec, from 0.44 % in 2000/2001 to 0.43 % in 2019/2020 (mean change -0.002, p-value = 0.0935). For the 2019-2020 fiscal year, 13,165 men and women had been diagnosed with PDB and prevalence of PDB increased with age. Standardized incidence of PDB has decreased over time from 0.77/1000 in 2000/2001 to 0.28/1000 in 2019-2020 (mean change -0.228/year, p-value<0.0001), the incidence decreasing from 0.82/1000 to 0.37/1000 in men and from 0.76/1000 to 0.22/1000 in women, respectively. This decrease was observed in all age categories.

CONCLUSION

With the exception of a slight increase in PDB prevalence up to 0.55 % in years 2005 to 2007, the prevalence of PDB has remained stable in Quebec over the past 20 years, 13,160 men and women being currently diagnosed with PDB. The incidence has decreased over time. Our results support the epidemiological changes of PDB reported in other countries.

Genetic Screening of ZNF687 and PFN1 in a Paget's Disease of Bone Cohort Indicates an Important Role for the Nuclear Localization Signal of ZNF687

Paget's disease of bone (PDB) is a common, late-onset bone disorder, characterized by focal increases of bone turnover that can result in bone lesions. Heterozygous pathogenic variants in the Sequestosome 1 (SQSTM1) gene are found to be the main genetic cause of PDB. More recently, PFN1 and ZNF687 have been identified as causal genes in patients with a severe, early-onset, polyostotic form of PDB, and an increased likelihood to develop giant cell tumors. In our study, we screened the coding regions of PFN1 and ZNF687 in a Belgian PDB cohort (n = 188). In the PFN1 gene, no variants could be identified, supporting the observation that variants in this gene are extremely rare in PDB. However, we identified 3 non-synonymous coding variants in ZNF687. Interestingly, two of these rare variants (p.Pro937His and p.Arg939Cys) were clustering in the nuclear localization signal of the encoded ZNF687 protein, also harboring the p.Pro937Arg variant, a previously reported disease-causing variant. In conclusion, our findings support the involvement of genetic variation in ZNF687 in the pathogenesis of classical PDB, thereby expanding its mutational spectrum.

[Paget's disease of bone: 1877-2023. Etiology, and management of a disease on epidemiologic transition]

Paget's disease of bone is characterized by the alteration, in one or several bone locations, of the equilibrium between bone formation and bone resorption. This imbalance results in a disorganized, widened bone, in many cases with increased bone density, although more fragile. A genetic predisposition for Paget's disease of bone could explain between 5% and 40% of the cases. Different environmental factors should explain the rest of the cases. Paget's disease of bone was classically considered the second most common metabolic bone disease. However, in recent decades there has been a marked decrease in both incidence and clinical severity. These changes have led to believe that the influence of some environmental factor may have diminished or even disappeared. This decrease in incidence should not be an excuse for abandoning Paget's disease of bone research, but rather it should be the reason to remain searching to try to understand better its pathogenesis.

Boric Acid Inhibits RANKL-Stimulated Osteoclastogenesis In Vitro and Attenuates LPS-Induced Bone Loss In Vivo

Boron and boric acid (BA) can promote osteogenic differentiation and reduce bone resorption, which controls bone growth and maintenance of bone tissue. It has been reported that BA activates PERK-eIF2α signaling to induce cytoplasmic stress granules and cell senescence in human prostate DU-145 cells. However, whether BA can affect osteoclasts formation and LPS-induced inflammatory bone loss, and the role of the PERK-eIF2α pathway in the process, remains unknown. In vitro, RAW264.7 cells were pre-treated with boric acid (BA, 1, 10, 100 μmol/L) for 4 h, and then incubated with receptor activator of nuclear factor-kappaB ligand (RANKL, 50 ng/mL) in the presence or absence of BA for 5 days. CCK-8 and tartrate-resistant acid phosphatase (TRAP) were used to examine cell viability, osteoclastogenesis, and bone resorption; quantitative real-time PCR was performed to examine mRNA levels of c-Fos, nuclear factor of activated T cells, cytoplasmic 1 (NFATc1), TRAP, and cathepsin K; western blotting was used to examine protein expressions of glucose-regulated protein 78 (GRP78), protein kinase R (PKR)-like endoplasmic reticulum kinase (PERK), phosphorylated PERK (p-PERK), eukaryotic initiation factor 2α (eIF2α), and phosphorylated eIF2α (p-eIF2α). In vivo, lipopolysaccharide (LPS)-induced bone loss model in mice was established, and micro-computed tomography (micro-CT) scanning, bone biochemical analysis, and osteoclastogenic cytokines were detected to evaluate the effect of BA on LPS-induced bone loss. In our vitro results showed that BA treatment for 5 days inhibited osteoclasts formation as well as osteoclastic bone resorption in a dose-dependent manner. The expression of osteoclasts marker genes c-Fos, NFATc1, TRAP, and cathepsin K were attenuated by BA. Immunoblotting analysis demonstrated that BA attenuated RANKL-induced PERK-eIF2α pathway activation. The in vivo data indicated that BA significantly prevented lipopolysaccharide (LPS)-induced bone loss. Our findings strongly suggest that BA may be a promising agent for the treatment of bone destructive diseases caused by excessive osteoclastogenesis.

Non-neoplastic pathologies mimicking sarcoma - Experience from a tertiary referral centre multidisciplinary team

OBJECTIVE

Distinguishing non-neoplastic tumour-mimicking pathologies from bone and soft tissue tumours is one of the fundamental aims of a tertiary centre sarcoma multidisciplinary team (MDT) service. In this study, we aim to analyse the incidence of non-neoplastic lesions referred to a tertiary referral service as suspected sarcoma, and to analyse the spectrum of conditions comprising these tumour-mimicking pathologies.

MATERIALS AND METHODS

We conducted a retrospective observational study compiling the biopsy-proven non-neoplastic outcomes of suspected sarcoma cases referred to our MDT in the last year. We identified all referrals made to our service between 1st January 2020 and 31st December 2020 and compiled their histological diagnoses.

RESULTS

A total of 976 new cases were referred to our MDT as suspected sarcoma in one year. Of these referrals, 8.6% (84/976) received a biopsy-proven outcome of non-neoplastic pathology. These non-neoplastic outcomes were categorised into the following types of pathology: 32.1% vascular, 31.0% inflammatory, 14.3% traumatic, 6.0% degenerative, 6.0% idiopathic, 4.8% infective, 3.6% metabolic, 1.2% autoimmune, and 1.2% genetic.

CONCLUSION

A significant proportion of pathologies referred to a tertiary centre sarcoma MDT are non-neoplastic in nature. These lesions are made up of a range of pathologies, with vascular and inflammatory conditions being the most common. Our study, the first of its kind, offers clinicians an insight into tumour-mimicking pathologies encountered by a tertiary centre.

Artroplastia total de cadera en paciente con enfermedad de Paget: presentación de un caso

Introducción: La enfermedad de Paget es un trastorno metabólico de etiología desconocida, secundario a un incremento en la función de los osteoclastos y la consecuente respuesta de los osteoblastos a la formación exagerada de hueso. Compromete con mayor frecuencia el fémur proximal y, a menudo, se diagnostica incidentalmente. Se presenta el caso de una mujer con antecedente de enfermedad de Paget y pseudoartrosis de cadera izquierda, con indicaciones de prótesis total de cadera izquierda y un episodio único de luxación, sin complicaciones posteriores y una adecuada evolución. Conclusión: El manejo quirúrgico en casos de fractura de cadera permite restablecer la marcha y mejorar la calidad de vida de los pacientes con enfermedad de Paget. A pesar de ser una patología que dificulta el manejo de los pacientes, la enfermedad de Paget no es una contraindicación para la artroplastia total de cadera y permite mejorar el dolor y recuperar la funcionalidad

Profilin-1 negatively controls osteoclast migration by suppressing the protrusive structures based on branched actin filaments

BACKGROUND

Profilin-1 (Pfn1), an evolutionarily conserved actin-binding protein, is an important regulator of the cytoskeleton. We previously reported the osteoclast-specific Pfn1-conditional knockout (cKO) mice had postnatal osteolytic phenotype with craniofacial and long-bone deformities associated with increased migration of cultured osteoclasts. We hypothesized the increased cellular processes structured with branched actin filaments may underlies the mechanism of increased bone resorption in these mutant mice.

MATERIALS AND METHODS

The morphological structure and cell migration of the cultured osteoclasts were analyzed using fluorescent microscopy and time-lapse image capturing. Fractional migration distances, as well as the index of protrusive structures (%-PB) that evaluates relative border length of the protrusion were compared between the cells from control and Pfn1-cKO mice.

RESULTS

Time-lapse image analysis showed that %-PB was significantly larger in Pfn1-cKO osteoclasts. In addition, the fractional migration distance was positively correlated with the index. When the branched actin filament organization was suppressed by chemical inhibitors, the osteoclast migration was declined. Importantly, the suppression was more extensive in Pfn1-cKO than in control osteoclasts.

CONCLUSION

Our results indicated the causative involvement of the increased branched actin filament formation at least in part for their excessive migration. Our findings provide a mechanistic rationale for testing novel therapeutic approaches targeting branched actin filaments in osteolytic disorders.

Expanding the TDP-43 Proteinopathy Pathway From Neurons to Muscle: Physiological and Pathophysiological Functions

TAR DNA-binding protein 43, mostly referred to as TDP-43 (encoded by the TARDBP gene) is strongly linked to the pathogenesis of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). From the identification of TDP-43 positive aggregates in the brains and spinal cords of ALS/FTD patients, to a genetic link between TARBDP mutations and the development of TDP-43 pathology in ALS, there is strong evidence indicating that TDP-43 plays a pivotal role in the process of neuronal degeneration. What this role is, however, remains to be determined with evidence ranging from gain of toxic properties through the formation of cytotoxic aggregates, to an inability to perform its normal functions due to nuclear depletion. To add to an already complex subject, recent studies highlight a role for TDP-43 in muscle physiology and disease. We here review the biophysical, biochemical, cellular and tissue-specific properties of TDP-43 in the context of neurodegeneration and have a look at the nascent stream of evidence that positions TDP-43 in a myogenic context. By integrating the neurogenic and myogenic pathological roles of TDP-43 we provide a more comprehensive and encompassing view of the role and mechanisms associated with TDP-43 across the various cell types of the motor system, all the way from brain to limbs.

Clinical Characteristics and Pathogenic Gene Identification in Chinese Patients With Paget's Disease of Bone

OBJECTIVE

To evaluate the clinical features of sporadic Paget's disease of bone (PDB) in China and further explore the underlying genetic abnormalities of the disease.

METHODS

Clinical characteristics, biochemical indices, bone turnover markers and radiographic examinations of the patients were collected. Genomic DNA was extracted from peripheral blood and whole-exome sequencing was carried out to identify the potential pathogenic genes. The pathogenicity of the variants was thereafter investigated by bioinformatics analysis.

RESULTS

A total of 50 patients (57.20 ± 15.52 years, male/female: 1.63: 1) with PDB were included and the mean onset age was 48.34 years (48.34 ± 17.24 years). 94.0% of the patients exhibited symptomatic patterns described as bone pain (86.0%), elevated skin temperature at the lesion site (26.0%), bone deformity (22.0%) and local swelling (18.0%). The most frequently involved lesion sites were pelvis (52.0%), femur (42.0%), tibia (28.0%), skull (28.0%) and spine (18.0%), respectively. Additionally, 40.0% of them accompanied with osteoarthritis, 14.0% with pathological fractures, and the misdiagnosis rate of PDB was as high as 36.0%. Serum level of alkaline phosphatase was significantly increased, with the mean value of 284.00 U/L (quartiles, 177.00-595.00 U/L). Two heterozygous missense mutations of SQSTM1 gene (c.1211T>C, M404T) and one novel heterozygous missense mutation in HNRNPA2B1 gene (c.989C>T, p. P330L) were identified in our study. Moreover, several potential disease-causing genes were detected and markedly enriched in the pathways of neurodegeneration (including WNT16, RYR3 and RYR1 genes) and amyotrophic lateral sclerosis (ALS, including NUP205, CAPN2, and NUP214 genes).

CONCLUSION

In contrast to Western patients, Chinese patients have an earlier onset age, more severe symptoms, and lower frequency of SQSTM1 gene mutation (4.0%). Moreover, a novel heterozygous missense mutation in HNRNPA2B1 gene was identified in one male patient with isolated bone phenotype. As for other genetic factors, it was indicated that WNT16, RYR3, RYR1, NUP205, CAPN2 and NUP214 genes may be potential pathogenic genes, pathways of neurodegeneration and ALS may play a vital role in the pathogenesis of PDB.

Total Hip Replacements in Patients with Rare Pathologic Conditions Affecting Bone

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As a result of the advances in surgical technique and implant design, total hip arthroplasty (THA) is increasingly offered for the management of osteoarthritis of the hip in patients with fragile or pathologic bone.

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Posttraumatic or congenital deformities associated with fragile or pathologic bone are frequently encountered and necessitate diligent preoperative planning.

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Surgeons should be prepared to evaluate and manage intraoperative iatrogenic fracture.

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While there is limited evidence to date, components made with computer-assisted design can be considered, given the unique and highly variable patient population.

The Pathways Underlying the Multiple Roles of p62 in Inflammation and Cancer

p62 is a highly conserved, multi-domain, and multi-functional adaptor protein critically involved in several important cellular processes. Via its pronounced domain architecture, p62 binds to numerous interaction partners, thereby influencing key pathways that regulate tissue homeostasis, inflammation, and several common diseases including cancer. Via binding of ubiquitin chains, p62 acts in an anti-inflammatory manner as an adaptor for the auto-, xeno-, and mitophagy-dependent degradation of proteins, pathogens, and mitochondria. Furthermore, p62 is a negative regulator of inflammasome complexes. The transcription factor Nrf2 regulates expression of a bundle of ROS detoxifying genes. p62 activates Nrf2 by interaction with and autophagosomal degradation of the Nrf2 inhibitor Keap1. Moreover, p62 activates mTOR, the central kinase of the mTORC1 sensor complex that controls cell proliferation and differentiation. Through different mechanisms, p62 acts as a positive regulator of the transcription factor NF-κB, a central player in inflammation and cancer development. Therefore, p62 represents not only a cargo receptor for autophagy, but also a central signaling hub, linking several important pro- and anti-inflammatory pathways. This review aims to summarize knowledge about the molecular mechanisms underlying the roles of p62 in health and disease. In particular, different types of tumors are characterized by deregulated levels of p62. The elucidation of how p62 contributes to inflammation and cancer progression at the molecular level might promote the development of novel therapeutic strategies.

Paget's Disease of Bone: Osteoimmunology and Osteoclast Pathology

PURPOSE OF REVIEW

The purpose of this review is to recognize clinical features of Paget's disease of bone and to describe how the osteoclast, a myeloid-derived cell responsible for bone resorption, contributes to the disease.

RECENT FINDINGS

Recent studies have identified several variants in SQSTM1, OPTN, and other genes that may predispose individuals to Paget's disease of bone; studies of these genes and their protein products have elucidated new roles for these proteins in bone physiology. Understanding the pathologic mechanisms in the Pagetic osteoclast may lead to the identification of future treatment targets for other inflammatory and autoimmune diseases characterized by abnormal bone erosion and/or osteoclast activation.

Pattern of SQSTM1 Gene Variants in a Hungarian Cohort of Paget's Disease of Bone

Paget's disease of bone (PDB) is characterized by focal or multifocal increase in bone turnover. One of the most well-established candidate genes for susceptibility to PDB is Sequestosome 1 (SQSTM1). Mutations in SQSTM1 have been documented among Western-European, British and American patients with PDB. However, there is no information on SQSTM1 mutation status in PDB patients from the Central- and Eastern-European regions. In this study, we conducted a mutation screening for SQSTM1 gene variants in 82 PDB patients and 100 control participants in Hungary. Mutations of SQSTM1 were detected in 18 PDB patients (21.95%); associations between genotype and clinical characteristics were also analyzed. Altogether, six different exonic alterations, including two types of UTR variants in the SQSTM1 gene, were observed in our PDB patients. Similarly, to previous genetic studies on Paget's disease, our most commonly detected variant was the c.1175C > T (p.Pro392Leu) in nine cases (four in monostotic and five in polyostotic form). We have surveyed the germline SQSTM1 variant distribution among Hungarian patients with PDB. We also highlighted that the pattern of the analyzed disease-associated pathophysiological parameters could partially discriminate PDB patients with normal or mutant SQSTM1 genotype. However, our findings also underline and strengthen that not solely SQSTM1 stands in the background of the complex PDB etiology.

Toward a Mathematical Modeling of Diseases' Impact on Bone Remodeling: Technical Review

A wide variety of bone diseases have hitherto been discovered, such as osteoporosis, Paget's disease, osteopetrosis, and metastatic bone disease, which are not well defined in terms of changes in biochemical and mechanobiological regulatory factors. Some of these diseases are secondary to other pathologies, including cancer, or to some clinical treatments. To better understand bone behavior and prevent its deterioration, bone biomechanics have been the subject of mathematical modeling that exponentially increased over the last years. These models are becoming increasingly complex. The current paper provides a timely and critical analysis of previously developed bone remodeling mathematical models, particularly those addressing bone diseases. Besides, mechanistic pharmacokinetic/pharmacodynamic (PK/PD) models, which englobe bone disease and its treatment's effect on bone health. Therefore, the review starts by presenting bone remodeling cycle and mathematical models describing this process, followed by introducing some bone diseases and discussing models of pathological mechanisms affecting bone, and concludes with exhibiting the available bone treatment procedures considered in the PK/PD models.

Osteoclast Fusion: Physiological Regulation of Multinucleation through Heterogeneity-Potential Implications for Drug Sensitivity

Classically, osteoclast fusion consists of four basic steps: (1) attraction/migration, (2) recognition, (3) cell-cell adhesion, and (4) membrane fusion. In theory, this sounds like a straightforward simple linear process. However, it is not. Osteoclast fusion has to take place in a well-coordinated manner-something that is not simple. In vivo, the complex regulation of osteoclast formation takes place within the bone marrow-in time and space. The present review will focus on considering osteoclast fusion in the context of physiology and pathology. Special attention is given to: (1) regulation of osteoclast fusion in vivo, (2) heterogeneity of osteoclast fusion partners, (3) regulation of multi-nucleation, (4) implications for physiology and pathology, and (5) implications for drug sensitivity and side effects. The review will emphasize that more attention should be given to the human in vivo reality when interpreting the impact of in vitro and animal studies. This should be done in order to improve our understanding of human physiology and pathology, as well as to improve anti-resorptive treatment and reduce side effects.

Clinical phenotype of adult offspring carriers of the p.Pro392Leu mutation within the SQSTM1 gene in Paget's disease of bone

Paget's disease of bone (PDB) is a common chronic bone disorder. In the French-Canadian population, the p.Pro392Leu mutation within the SQSTM1 gene is involved in 46% of familial forms. In New Zealand, the emergence of PDB in offspring inheriting SQSTM1 mutations was reported to be delayed by a decade compared to their parents. We aimed at assessing the clinical phenotype of offspring carriers of this mutation in our French-Canadian cohort. We reviewed research records from adult offspring carriers of this mutation aged <90 years and their affected parents. In parents, we collected data on sex, age at diagnosis, number of affected bones, total serum alkaline phosphatase levels (tALPs) at diagnosis. In offspring, PDB extended phenotype assessment relying on tALPs, bone specific alkaline phosphatase levels (bALPs), procollagen type 1 amino-terminal propeptide (P1NP), whole body bone scan and skull and pelvis radiographs, was performed at inclusion from 1996 to 2009 and updated in 2016 to 2018, if not done during the past 8 years. The results showed that among the 36 offspring with an updated phenotype, four of them developed a clinical phenotype of PDB characterized by monostotic or polyostotic increased bone uptake associated with typical radiographic lesions in the affected sites, representing an incidence of 1.83 per 1000 person-years. Moreover, the age at PDB diagnosis was delayed by at least 10 years in the adult offspring carriers of the p.Pro392Leu mutation versus their affected parents. Our findings support the utility of a regular monitoring of the adult offspring without PDB but carriers of this mutation.

Catastrophic failure of cup revision hip arthroplasty due to undiagnosed Paget disease of bone: A case report

INTRODUCTION

Paget's disease of bone (PDB) is a localized chronic osteopathy, apparently not genetic in origin, and frequently diagnosed from incidental radiographic images. The disease is characterized by deformation, hypervascularity, and structural weakness of the bone and by changes in joint biomechanics. Most cases of PDB can be easily diagnosed from radiographic findings, but monostotic cases may be problematic and require invasive procedures.

PRESENTATION OF CASE

A 70-year-old woman had re-revision surgery for early catastrophic failure of an isolated cup revision hip arthroplasty because of undiagnosed PDB 21 years after the primary total hip arthroplasty. To identify the pathomechanism of early failure, we performed bone biopsy on the right iliac crest. Histopathological findings showed a mosaic pattern in the bone characteristic of PDB. Prior to the planned re-revision surgery, we treated the PDB with denosumab until the patient's serum level of alkaline phosphatase (ALP) was within the normal limits. Two months after denosumab treatment, we performed re-revision hip arthroplasty using a structural allograft and a Kerboull-type reinforcement device.

DISCUSSION

The delay in correct diagnosis of PDB was associated with the rapid destruction of pelvic bone. The preoperative use of antipagetic medication could decrease the risk of implant loosening and may be warranted to mitigate that risk.

CONCLUSION

In patients with a failed arthroplasty, thoughtful evaluation is warranted for preoperative antipagetic medication in order to reduce PDB activity and potentially decrease the risk of implant loosening. This paper offers some steps for such risk reduction in the workup before revision surgery.

The Role of Autophagy and Mitophagy in Bone Metabolic Disorders

Bone metabolic disorders include osteolysis, osteoporosis, osteoarthritis and rheumatoid arthritis. Osteoblasts and osteoclasts are two major types of cells in bone constituting homeostasis. The imbalance between bone formation by osteoblasts and bone resorption by osteoclasts has been shown to have a direct contribution to the onset of these diseases. Recent evidence indicates that autophagy and mitophagy, the selective autophagy of mitochondria, may play a vital role in regulating the proliferation, differentiation and function of osteoblasts and osteoclasts. Several signaling pathways, including PINK1/Parkin, SIRT1, MAPK8/FOXO3, Beclin-1/BECN1, p62/SQSTM1, and mTOR pathways, have been implied in the regulation of autophagy and mitophagy in these cells. Here we review the current progress about the regulation of autophagy and mitophagy in osteoblasts and osteoclasts in these bone metabolic disorders, as well as the molecular signaling activated or deactivated during this process. Together, we hope to draw attention to the role of autophagy and mitophagy in bone metabolic disorders, and their potential as a new target for the treatment of bone metabolic diseases and the requirements of further mechanism studies.

The two faces of giant cell tumor of bone

Giant cell tumor (GCT) is a bone-destructive benign neoplasm characterized by distinctive multinucleated osteoclast-like giant cells with osteolytic properties distributed among neoplastic stromal cells. GCT is locally aggressive with progressive invasion of adjacent tissues and occasionally displays malignant characteristics including lung metastasis. GCT is characterized genetically by highly recurrent somatic mutations at the G34 position of the H3F3A gene, encoding the histone variant H3.3, in stromal cells. This leads to deregulated gene expression and increased proliferation of mutation-bearing cells. However, when GCT complicates Paget disease of bone (GCT/PDB) it behaves differently, showing a more malignant phenotype with 5-year survival less than 50%. GCT/PDB is caused by a germline mutation in the ZNF687 gene, which encodes a transcription factor involved in the repression of genes surrounding DNA double-strand breaks to promote repair by homologous recombination. Identification of these driver mutations led to novel diagnostic tools for distinguishing between these two tumors and other osteoclast-rich neoplasms. Herein, we review the clinical, histological, and molecular features of GCT in different contexts focusing also on pharmacological treatments.

Mimics of axial spondyloarthritis

PURPOSE OF REVIEW

Axial spondyloarthritis (AxSpA) is a distinct clinical entity with characteristic clinical and radiographic features; however, a multitude of other metabolic, infectious and inflammatory disorders mimic it both clinically and radiographically.

RECENT FINDINGS

We present in this review article recent updates about the various disease entities and conditions that may mimic AxSpA and how to differentiate among them. The sensitivity and specificity of MRI in diagnosing AxSpA has limitations and needs to be interpreted in the context of the clinical picture. Interestingly, some recent studies have highlighted that a relatively high prevalence of bone marrow edema on pelvic MRIs in healthy volunteers which could even be categorized as having a 'positive MRI' as defined by Assessment of Spondyloarthritis International Society. Another study revealed that a substantial proportion of patients with suspected sacroiliitis were more commonly diagnosed with diseases other than inflammatory sacroiliitis. On the basis of these reports, it is prudent to request MRIs in the appropriate clinical context and interpreted with caution taking into considerations the wide differential diagnosis of such MRI changes.

SUMMARY

Highlighting the clinical pearls that differentiate disorders suspected of having sacroiliitis will lead to earlier and correct diagnosis and management; however, one must always take into considerations the radiographic and MRI findings in addition to the clinical presentations in order to make the appropriate diagnosis.

A mutation in p62 protein (p. R321C), associated to Paget's disease of bone, causes a blockade of autophagy and an activation of NF-kB pathway

Paget's disease of bone (PDB) is a bone disorder characterized by an increase in bone turnover in a disorganized way with a large increase in bone resorption followed by bone formation. The most important known genetic factor predisposing to PDB is mutation in Sequestosome1 (SQSTM1) gene. We have studied the prevalence of SQSTM1 mutations and examined genotype-phenotype correlations in a Spanish cohort of PDB patients. Also, we have characterized three PDB patients that carry the c.961C>T SQSTM1 gene mutation that it is localized in exon 6 of SQSTM1 gene and it causes the p. R321C mutation. This mutation has been reported in patients with amyotrophic lateral sclerosis and frontotemporal dementia but in our knowledge this is the first time that p62 p. R321C mutation is associated to PDB. We show that p62 p.R321C mutation could induce blockage of autophagy and cell proliferation through NF-kB pathway. These results reinforce the hypothesis of autophagy involvement in Paget's disease of bone.

Paget's Disease of Bone Affecting Peripheral Limb: Difficulties in Diagnosis: A Case Report

In terms of management of Paget's disease of bone (PDB), early diagnosis and proper management achieving remission is essential with lifelong specialist follow-up. We present the case of a 40-year-old woman with PDB affecting mainly the distal extremities (ankle and wrist). The patient visited our hospital in 2012 with heel pain. Plain radiography revealed osteoporosis, and a bone scan revealed hot uptake. Initial laboratory investigations showed normal serum calcium, 25-hydroxy-vitamin D, and parathyroid hormone levels; however, osteocalcin, C-terminal telopeptide of type I collagen, and bone alkaline phosphatase levels were elevated. A bone mineral density scan showed T- and Z-scores of −2.5 and −2.7, respectively, and bisphosphonate treatment was initiated. Biopsy performed on the calcaneal lateral wall revealed inconclusive findings. Follow-up biopsy on the left distal radius was performed 7 years later to investigate wrist pain, and this examination led to a final diagnosis as PDB. We suggest inconclusive biopsy result during the early phase of PDB and highly recommend follow-up evaluation in osteoporosis with atypical behavior.

Long-term outcomes following total hip and total knee arthroplasty in patients with Paget's disease of bone (PDB) - A national study

BACKGROUND

The incidence of total hip and total knee arthroplasty (THA/TKA) is 3.1- and 1.7-fold higher in patients with Paget's disease of bone (PDB) compared to age-matched controls. No large studies or joint registry reports exist describing outcomes following THA or TKA in PDB patients.

METHODS

The study objectives were to investigate the outcomes following THA or TKA in PDB patients using national registry data. Data were requested from the Scottish Arthroplasty Project for all PDB patients undergoing THA or TKA in Scotland from 1996 to 2013.

RESULTS

Between 1996 - 2013, 144 patients underwent primary THA and 43 patients underwent primary TKA for PDB in Scotland. Following primary THA, the most common surgical complications within one year were haematoma (1.4%), and surgical-site infection (1.4%). The overall incidence of dislocation was 2.8%. Revision THA was performed in 2.8% of patients. THA implant survival was 96.3% (CI:92.8-99.8) at 10-years, and patient survival was 50.0% (CI:39.6-60.4) at 10-years. Following TKA, only one revision surgery occurred within one year (2.3%). Revision TKA was performed in 4.7% of patients, across the whole study period. TKA implant survival was 94.5% (CI:87.1-100) at 10-years; patient survival was 38.3% (CI:16.7-59.9) at 10-years. Compared with published literature and registry data, implant longevity and patient survival are comparable between PDB patients and the general population.

CONCLUSION

This is the largest reported series of outcomes following primary THA/TKA in PDB patients. PDB patients are not at increased risk of surgical complications following primary THA or TKA compared with the general population.

A review on osteoclast diseases and osteoclastogenesis inhibitors recently developed from natural resources

Natural products have been investigated as potential candidates of novel therapeutics and play a crucial role in advanced medicinal drugs. Natural resources, including local medicinal plants (especially folk medicinal plants), animals, bacteria, and fungi have been used for more than a century, and are precious gifts from nature, providing potential medicines with high safety. Osteoclast-related diseases, such as osteoporosis, rheumatoid arthritis, Paget's disease, osteoclastoma, and periprosthetic osteolysis, are currently the most common reasons for bone inflammation, pain and fractures, resulting in low quality of life. However, the curative effects of current therapeutic drugs for these osteoclast-related diseases are limited, and long-term treatment is needed. Further, in severe cases, surgical treatments are necessary, which may cause unaffordable expenses and subsequent influences such as neuralgia, mental stress, and even development of cancer. Thus, safer inhibitors and potential drugs with enhanced curative effects and quick relief are needed to treat patients with osteoclast diseases. This review aims to introduce the main osteoclast-related diseases and some of the recently developed naturally sourced inhibitors against osteoclastogenesis, also it is desired to attract people's attention on using widely available natural resources for the evolution of new types of osteoclast inhibitors with minimal or no side-effects upon long-term treatments.

Paget's disease of bone: updates for clinicians

PURPOSE OF REVIEW

To provide clinicians an overview to the diagnosis, treatment, and management of Paget's disease, including recent guideline recommendations, with comparison of the Endocrine Society Clinical Practice Guideline (JCEM 2014) with the new Clinical Guideline review endorsed by the International Osteoporosis Foundation, the American Society of Bone and Mineral Research, the European Calcified Tissues Society, and the United Kingdom Bone Research Society (JBMR 2019).

RECENT FINDINGS

Radionuclide bone scans are recommended for assessing the extent of Paget's disease. Bisphosphonates remain the mainstay for therapy with evidence of reducing symptomatic bone pain. One 5 mg intravenous dose of zoledronic acid is the current standard therapy for Paget's disease.

SUMMARY

Paget's disease of the bone is characterized by focal increased bone remodeling activity, resulting in sclerotic or lytic lesions and poor bone quality at one or more sites. Patients may be symptomatic with bone pain, or may be asymptomatic, and identified through unexplained elevations in serum alkaline phosphatase. Diagnosis is through plain film imaging, with radionuclide bone scan to determine the extent. A single dose of IV zoledronic acid typically results in extended suppression of bone turnover and amelioration of bone pain. There remains a lack of evidence regarding efficacy of this treatment with regards to other complications of Paget's, but in general, bisphosphonate treatment is recommended.

Apoptosis and Autophagy in Picornavirus Infection

Cell death is a fundamental process in maintaining cellular homeostasis, which can be either accidental or programed. Programed cell death depends on the specific signaling pathways, resulting in either lytic or non-lytic morphology. It exists in two primary forms: apoptosis and autophagic cell death. Apoptosis is a non-lytic and selective cell death program, which is executed by caspases in response to non-self or external stimuli. In contrast, autophagy is crucial for maintaining cellular homeostasis via the degradation and recycling of cellular components. These two mechanisms also function in the defense against pathogen attack. However, picornaviruses have evolved to utilize diverse strategies and target critical components to regulate the apoptotic and autophagic processes for optimal replication and the release from the host cell. Although an increasing number of investigations have shown that the apoptosis and autophagy are altered in picornavirus infection, the mechanism by which viruses take advantage of these two processes remains unknown. In this review, we discuss the mechanisms of picornavirus executes cellular apoptosis and autophagy at the molecular level and the relationship between these interactions and viral pathogenesis.

Paget's Disease of Long Bones: Microstructural Analyses of Historical Bone Samples

Although Paget's disease of bone (PDB) is the second most common metabolic bone disease, there is only limited information about the microarchitecture of affected bones. Therefore, the aim of this study was to determine cortical and trabecular bone properties in clinically relevant locations by microcomputed tomography (µCT). Ten femora and ten tibiae affected by Paget's disease taken from the Natural History Museum Vienna were compared to 13 femora and 10 tibiae of non-affected body donors. Digitization of the cortical and trabecular bone microarchitecture was performed with an X-ray-based µCT scanner. Additionally, semi-quantitative gradings of trabecular and cortical architectural parameters of the femora and the tibiae were generated. Microcomputed tomography images showed changes in the thickness of cortices, cortical porosity, and trabecularization of cortical structures. Moreover, severe disorganization of trabecular structures, trabecular defects, and thickening of (remaining) trabeculae were detected. Numerical cortical analyses showed lower total bone volume (BV) and lower BV in the outer region (66-100%) (- 36%, p = 0.004, and - 50%, p < 0.001, respectively), lower total volume (TV) in the outer region (66-100%) (- 42%, p < 0.001), lower total bone volume fraction (BV/TV) and BV/TV in the outer region (66-100%) (- 23%, and - 12%, p < 0.001, respectively), higher BV and TV in the middle region (33-66%) and higher BV/TV in the inner region (0-33%) (123%, p = 0.011, 147%, p = 0.010, and 33%, p = 0.025, respectively) in Pagetic compared to non-affected bones. Trabecular analyses showed higher BV/TV (96%, p = 0.008) and Tb.Th (43%, p = 0.004) in Pagetic compared to non-affected bones. There is a major and consistent structural alteration of PDB at cortical and trabecular sites in weight-bearing long bones. Our findings are relevant for the differential diagnosis of PDB and for the pathogenesis of associated complications, since the disorder produces abnormalities in the structure that might lead to bone fragility.

Paget's Disease of Bone

Paget's disease of bone (PDB) is a chronic and focal bone disorder, characterized by increased osteoclast-mediated bone resorption and a subsequent compensatory increase in bone formation, resulting in a disorganized mosaic of woven and lamellar bone at one or more affected skeletal sites. As a result, bone pain, noticeable deformities, arthritis at adjacent joints, and fractures can occur. In a small proportion of cases neoplastic degeneration in osteosarcoma, or, less frequently, giant cell tumor has been also described at PDB sites. While recent epidemiological evidences clearly indicate a decrease in the prevalence and the severity of PDB, over the past 2 decades there have been consistent advances on the genetic mechanisms of disease. It is now clear that PDB is a genetically heterogeneous disorder, with mutations in at least two different genes (SQSTM1, ZNF687) and more common predisposing variants. As a counterpart to the genetic hypothesis, the focal nature of lesions, the decline in prevalence rates, and the incomplete penetrance of the disease among family members suggest that one or more environmental triggers may play a role in the pathophysiology of PDB. The exact nature of these triggers and how they might interact with the genetic factors are less understood, but recent experimental data from mice models suggest the implication of paramixoviral infections. The clinical management of PDB has also evolved considerably, with the development of potent aminobisphosphonates such as zoledronic acid which, given as a single intravenous infusion, now allows a long-term disease remission in the majority of patients.

Targeted sequencing of DCSTAMP in familial Paget's disease of bone

Paget's disease of bone (PDB) has a strong genetic component. Variants in SQSTM1 are found in up to 40% of patients with a family history of the disease, where a pattern of autosomal dominance with incomplete penetrance is apparent. By contrast, SQSTM1 variants are only found in up to 10% of patients with sporadic disease. It has been hypothesised that the remaining genetic susceptibility to PDB, particularly in familial cases, could be explained by rare genetic variants in loci previously identified by Genome Wide Association Studies. It is likely that polygenic factors are involved in many individuals. In this study we utilised whole exome sequencing to investigate predisposing genetic factors in an unsolved PDB kindred and identified a c.1189C > T p.L397F variant in DC-STAMP, also known as TM7SF4, that co-segregated with disease. DCSTAMP was identified as a gene of interest in PDB following Genome Wide Association Studies and has been previously shown to play critical roles in osteoclast fusion. The variant we identified has also been reported in association with PDB in a French-Canadian cohort however the significance of this variant was inconclusive. Targeted screening of DCSTAMP in our familial cohort of PDB patients revealed an additional 8 variants; however we did not find a significant association between any of these, including p.L397F, with PDB. Osteoclastogenesis assays from the affected proband and his unaffected brother demonstrated an increase in osteoclast number and nucleation, consistent with the pagetic phenotype. In converse to other established Paget's associated genetic variations such as SQSTM1, TNFRSF11A and OPTN, expression of the mutant DC-STAMP protein attenuated the activation of transcription factors NFκB and AP-1 when exogenously expressed. We found that the p.L397F variant did not influence the subcellular localization of the protein. Based on these findings we conclude that genetic variation in DCSTAMP is not a significant predisposing factor in our specific cohort of PDB patients and the p.L397F variant is unlikely to be a contributing factor in PDB pathogenesis.

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Variants in DC-STAMP do not appear to be significantly associated with Paget’s disease of bone in our cohort.

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The DC-STAMP p.L397F variant attenuates both NFkB and AP-1 signalling compared to the wild type protein.

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No significant differences in cellular colocalisation were found between DC-STAMP wild type and p.L397F.

Systemic Changes Affecting the Morphology of Calvarial Bone

Plastic surgeons are frequently consulted to evaluate concerns about a patient's skull. Imaging studies often reveal abnormalities in bone morphology, from increased porosity to sclerotic changes. While focal findings imply a benign or malignant neoplasm, the etiology of more diffuse findings can be more varied, making the correct diagnosis challenging. The present review summarizes the differential diagnosis of osseous lesions of the calvarium that affect the bone and contribute to changes seen on imaging studies.

p62/SQSTM1 - steering the cell through health and disease

SQSTM1 (also known as p62) is a multifunctional stress-inducible scaffold protein involved in diverse cellular processes. Its functions are tightly regulated through an extensive pattern of post-translational modifications, and include the isolation of cargos degraded by autophagy, induction of the antioxidant response by the Keap1-Nrf2 system, as well as the regulation of endosomal trafficking, apoptosis and inflammation. Accordingly, malfunction of SQSTM1 is associated with a wide range of diseases, including bone and muscle disorders, neurodegenerative and metabolic diseases, and multiple forms of cancer. In this Review, we summarize current knowledge regarding regulation, post-translational modifications and functions of SQSTM1, as well as how they are dysregulated in various pathogenic contexts.

Paget's Disease of Bone: Diagnosis and Treatment

Paget's disease of bone is a common bone disorder characterized by disorganized bone remodeling. The most likely etiology is a slow paramyxoviral infection in genetically susceptible individuals; however, the exact cause is unknown. Enhanced bone resorption due to an increased activity of osteoclasts recruits numerous osteoblasts to resorption sites, with large quantities of new bone matrix produced as a result. The accelerated bone resorption and formation are not as closely coupled as in a healthy bone; a disorganized bone tissue is formed. Many patients are asymptomatic; rising serum alkaline phosphatase or incidental finding of characteristic radiographic lesions are often the only diagnostic clues. Common clinical manifestations include bone pain, bowing of long bones, enlarged skull, and hearing loss. An elevated serum alkaline phosphatase level correlates with the disease activity. The diagnosis is confirmed by characteristic radiographic findings and by nuclear scintigraphy of the bone (the most sensitive test). Bisphosphonates, such as zoledronic acid, pamidronate, alendronate, and risedronate, are the mainstay of treatment. Patients who do not tolerate bisphosphonates can be treated with calcitonin.

Polymorphisms in genes implicated in base excision repair (BER) pathway are associated with susceptibility to Paget's disease of bone

Paget's disease of bone (PDB) is a chronic bone metabolic disorder. Currently, PDB is the second most frequent bone disorder. PDB is a focal disorder affecting the skeleton segmentally but the cause of which is unknown. It has been hypothesised that somatic mutations could be responsible for the mosaicism described in PDB patients. Therefore, our hypothesis is that defective response to DNA damage may lead to somatic mutations favouring an increased risk of PDB. So that we have analysed polymorphisms in DNA repair genes involved in the BER, NER and DSBR pathways in order to evaluate the role of these variants in modulating PDB risk. We found statistically significant differences in genotypic and allelic distribution for polymorphisms in genes implicated in the BER pathway. Our results showed that carrying the allele T of XRCC1 rs1799782 polymorphism and the allele G of APEX rs1130409 polymorphism increased the risk of developing PDB. These polymorphisms could cause a lower DNA repair efficiency and this might lead to local somatic mutations favouring bone metabolic alterations characteristic of PDB. This is the first report showing an association between polymorphism in genes implicated in the BER pathway with PDB.

Biallelic SQSTM1 mutations in early-onset, variably progressive neurodegeneration

OBJECTIVE

To characterize clinically and molecularly an early-onset, variably progressive neurodegenerative disorder characterized by a cerebellar syndrome with severe ataxia, gaze palsy, dyskinesia, dystonia, and cognitive decline affecting 11 individuals from 3 consanguineous families.

METHODS

We used whole-exome sequencing (WES) (families 1 and 2) and a combined approach based on homozygosity mapping and WES (family 3). We performed in vitro studies to explore the effect of the nontruncating SQSTM1 mutation on protein function and the effect of impaired SQSTM1 function on autophagy. We analyzed the consequences of sqstm1 down-modulation on the structural integrity of the cerebellum in vivo using zebrafish as a model.

RESULTS

We identified 3 homozygous inactivating variants, including a splice site substitution (c.301+2T>A) causing aberrant transcript processing and accelerated degradation of a resulting protein lacking exon 2, as well as 2 truncating changes (c.875_876insT and c.934_936delinsTGA). We show that loss of SQSTM1 causes impaired production of ubiquitin-positive protein aggregates in response to misfolded protein stress and decelerated autophagic flux. The consequences of sqstm1 down-modulation on the structural integrity of the cerebellum in zebrafish documented a variable but reproducible phenotype characterized by cerebellum anomalies ranging from depletion of axonal connections to complete atrophy. We provide a detailed clinical characterization of the disorder; the natural history is reported for 2 siblings who have been followed up for >20 years.

CONCLUSIONS

This study offers an accurate clinical characterization of this recently recognized neurodegenerative disorder caused by biallelic inactivating mutations in SQSTM1 and links this phenotype to defective selective autophagy.

A Diversified Spectrometric and Molecular Docking Technique to Biophysical Study of Interaction between Bovine Serum Albumin and Sodium Salt of Risedronic Acid, a Bisphosphonate for Skeletal Disorders

The binding interaction between bovine serum albumin (BSA) and sodium salt of risedronic acid (RSN) was studied by using the FT-IR (Fourier transform infrared), UV-Vis (ultraviolet–visible), fluorescence (emission and synchronous), CD (circular dichroism) spectrometric, and computational (molecular docking) techniques at 289, 297, and 305 K temperatures with physiological buffer of pH 7.40. The conformational and secondary structural changes observed for BSA from CD spectra and by curve fitting procedure were applied to Fourier self-deconvolution in FT-IR spectra. The formation of a BSA-RSN complex was confirmed from UV-Vis spectroscopy. The static type of quenching shown for RSN to BSA was verified from Stern–Volmer and modified Stern–Volmer equations. The binding constant of order 10⁵ was obtained to be confirming that there exists a strong binding interaction between BSA and RSN. Synchronous fluorescence shows that the microenvironment of tryptophan was altered, not tyrosine of BSA; in addition to this, the distance between tryptophan of BSA and RSN was found out from Forster's theory of nonradiation energy transfer. The interaction between BSA and RSN mainly occurred as a result of hydrogen bonds and van der Waals forces, the process is exothermic and spontaneous, and it was achieved through van 't Hoff equation. This interaction was affected by the presence of biologically active Fe²⁺, Ni²⁺, Ca²⁺, Mg²⁺, and Cd²⁺ ions and was also studied. The subdomain IIIA of BSA involved with RSN interaction was authenticated from molecular docking analysis.

Dok-3 and Dok-1/-2 adaptors play distinctive roles in cell fusion and proliferation during osteoclastogenesis and cooperatively protect mice from osteopenia

Bone mass is determined by coordinated acts of osteoblasts and osteoclasts, which control bone formation and resorption, respectively. Osteoclasts are multinucleated, macrophage/monocyte lineage cells from bone marrow. The Dok-family adaptors Dok-1, Dok-2 and Dok-3 are expressed in the macrophage/monocyte lineage and negatively regulate many signaling pathways, implying roles in osteoclastogenesis. Indeed, mice lacking Dok-1 and Dok-2, the closest homologues with redundant functions, develop osteopenia with increased osteoclast counts compared to the wild-type controls. Here, we demonstrate that Dok-3 knockout (KO) mice also develop osteopenia. However, Dok-3 KO, but not Dok-1/-2 double-KO (DKO), mice develop larger osteoclasts within the normal cell-count range, suggesting a distinctive role for Dok-3. Indeed, Dok-3 KO, but not Dok-1/-2 DKO, bone marrow-derived cells (BMDCs) generated larger osteoclasts with more nuclei due to augmented cell-to-cell fusion in vitro. In addition, while Dok-1/-2 DKO BMDCs generated more osteoclasts, Dok-1/-2/-3 triple-KO (TKO) BMDCs generated osteoclasts increased in both number and size. Furthermore, Dok-1/-2/-3 TKO mice showed the combined effects of Dok-3 and Dok-1/-2 deficiency: severe osteopenia with more and larger osteoclasts. Together, our findings demonstrate that Dok-3 and Dok-1/-2 play distinctive but cooperative roles in osteoclastogenesis and protect mice from osteopenia, providing physiological and pathophysiological insight into bone homeostasis.

The identification of H3F3A mutation in giant cell tumour of the clivus and the histological diagnostic algorithm of other clival lesions permit the differential diagnosis in this location

BACKGROUND

Giant Cell Tumour of Bone (GCT) is a locally aggressive primary bone tumour that usually occurs at the epiphyses of the long bones of the appendicular skeleton with a tendency to recurrence. Recurrent somatic H3F3A mutations have been described in 92% of GCT cases. GCTs involving the Clivus are extremely rare lesions and less than 15 cases are described in the literature. They represent a surgery challenge and are easily misdiagnosed. Our aim was to reveal if the genetic bases underlying Clival GCTs were the same of GCTs of long bones to improve the diagnosis and treatment.

METHODS

The targeted somatic sequencing of GCT-related genes (H3F3A, H3F3B, IDH1, IDH2 and ZNF687) was performed on Clival GCT biopsies of two different cases. Histological analyses on the same tissues were used to detect the neoplastic population and its expression profile.

RESULTS

Sanger sequencing revealed that both patients were positive for the p.Gly34Trp mutation in the H3F3A gene. Immunofluorescence assay using monoclonal antibody, specifically detecting the mutant H3.3, highlighted that the mutation only involved the mononuclear cell population and not the multinucleated giant cells. Moreover, immunohistochemistry assay showed that RANKL was highly expressed by the stromal cells within Clival GCT, mimicking what happens in GCT of the long bones. In addition, systematic literature review allowed us to generate a histology-based diagnostic algorithm of the most common clival lesions.

CONCLUSIONS

We conclude that the Clival GCT is genetically defined by somatic mutation in the H3F3A gene, linking it to the GCT of long bones. The similarity with GCTs of long bones let us to hypothesize the utility of Denosumab therapy (already effective for GCTs) in these surgically challenging cases. Moreover, H3F3A genetic screening can be combined to the histological analysis to differentiate GCTs from morphologically similar giant cell-rich sarcomas, while the histological diagnostic algorithm could help the differential diagnosis of other clival lesions.

Sargassum serratifolium attenuates RANKL-induced osteoclast differentiation and oxidative stress through inhibition of NF-κB and activation of the Nrf2/HO-1 signaling pathway

Sargassum serratifolium C. Agardh is a marine brown alga that has long been used as an ingredient for food and medicine by many people living along Asian coastlines. Recently, various beneficial effects of extracts or compounds isolated from S. serratifolium have been reported, but their efficacies against bone destruction are unclear. Therefore, in this study, we investigated the inhibitory property of an ethanol extract of S. serratifolium (EESS) on osteoclast differentiation by focusing on the receptor activator of nuclear factor-κB ligand (RANKL)-stimulated osteoclastogenesis model using RAW 264.7 macrophages. Our results demonstrated that EESS reduced RANKL-induced osteoclast differentiation in RAW 264.7 cells, by inhibiting tartrate-resistant acid phosphatase (TRAP) activity and destroying the F-actin ring formation. EESS also attenuated RANKL-induced expressions of key osteoclast-specific genes, such as nuclear factor of activated T cells cytoplasmic 1 (NFATC1), TRAP, cathepsin K and matrix metalloproteinase-9. These effects were mediated by impaired nuclear translocation of nuclear factor (NF)-κB and suppression of IκB-α degradation. In addition, EESS effectively inhibited the production of reactive oxygen species (ROS) by RANKL, which was associated with enhanced expression of nuclear translocation of nuclear factor-erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1). Overall, our findings provide evidence that EESS suppresses RANKL-induced osteoclastogenesis and oxidative stress through suppression of NF-κB and activation of Nrf2/HO-1 signaling pathway, indicating that S. serratifolium has a potential application the prevention and treatment of osteoclastogenic bone disease.

Influence Of Angiogenic Mediators And Bone Remodelling In Paget´s Disease Of Bone

Paget´s disease of bone (PDB) is characterized by increased bone resorption followed by an excessive compensatory bone formation, with an abnormal bone structure with altered mechanical properties. Pagetic bone also has a higher vascularization and marrow fibrosis. Despite of pagetic bone being a highly vascularized tissue, there are no studies on the plasma levels of angiogenic mediators in the different states of the disease; moreover, the effect of PDB treatment on plasma levels of these angiogenic mediators is not very well known. The aim of this study was to analyse plasma levels of cytokines implicated in the increased bone turnover (OPG, RANKL, sclerostin) and hypervascularization (VEGF, PGF, ENG) observed in PDB and their evolution and response to zoledronic acid treatment in 70 PDB patients, 29 with an active disease measured by plasma alkaline phosphatase (ALP). Plasma ALP concentration was higher in active PDB than in inactive PDB patients, whereas there were no differences in OPG, RANKL, sclerostin, VEGF, PGF and ENG plasma levels between active and inactive PDB patients. ALP decreased at 3 and 12 months after zoledronic acid treatment. RANKL levels were reduced and sclerostin levels were increased after 12 months of treatment. PGF levels were lower 12 months after zoledronic acid treatment, whereas there were no differences in plasma VEGF and ENG after zoledronic acid treatment. Summarizing, zoledronic acid treatment is associated to decreases in plasma levels of ALP, RANKL, sclerostin and P1GF in active PDB patients. This treatment may reduce bone turnover and might reduce the pathological vascularisation typical of pagetic bone.

Diphlorethohydroxycarmalol from Ishige okamurae Suppresses Osteoclast Differentiation by Downregulating the NF-κB Signaling Pathway

Marine algae possess a variety of beneficial effects on human health. In this study, we investigated whether diphlorethohydroxycarmalol (DPHC), isolated from Ishige okamurae, a brown alga, suppresses receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclast differentiation. DPHC significantly suppressed RANKL-induced osteoclast differentiation and macrophage-colony stimulating factor (M-CSF) expression in a dose-dependent manner. In addition, it significantly inhibited actin ring formation, the expression of osteoclast marker genes, such as tartrate-resistant acid phosphatase (TRAP), nuclear factor of activated T-cells cytoplasmic 1 (Nfatc1), cathepsin K (Ctsk), and dendritic cell-specific transmembrane protein (Dcstamp), and osteoclast-induced bone resorption. Analysis of the RANKL-mediated signaling pathway showed that the phosphorylation of both IκB and p65 was specifically inhibited by DPHC. These results suggest that DPHC substantially suppresses osteoclastogenesis by downregulating the RANK-NF-κB signaling pathway. Thus, it holds significant potential for the treatment of skeletal diseases associated with an enhanced osteoclast activity.

Dental Manifestations of Pediatric Bone Disorders

PURPOSE OF REVIEW

Several bone disorders affecting the skeleton often are manifest in the maxillofacial region. This review presents the most common bone disorders in children and their dental-oral manifestations: fibrous dysplasia, Paget's disease, osteogenesis imperfecta, renal osteodystrophy, hypophosphatasia, and osteoporosis. The specific intraoral characteristics will reviewed in detail.

RECENT FINDINGS

Recent studies confirmed the close relationship between the mandible and the maxilla with the most prevalent systemic bone disorders in children. This review will help practitioners to integrate the oral health into the systemic health and improve the multidisciplinary approach of pediatric patients between medicine and dentistry.

The Changing Presentation of Paget's Disease of Bone in Australia, A High Prevalence Region

Studies from several countries suggest that the incidence of Paget's disease of bone (PDB) and the severity of newly diagnosed cases are declining. The aim of this study was to examine secular changes in clinical presentation of PDB in Australia, which historically had the highest prevalence outside the United Kingdom. The participants were 293 patients (61% male) diagnosed between 1956 and 2013 with details recorded in the database of the Paget's Disease Research Group of Western Australia. The mean age at diagnosis was 62 years (range 28-90); 26% of participants had a family history of PDB and 11% had Sequestosome 1 (SQSTM1) mutations. After adjustment for covariates (SQSTM1 mutation status, family history, country of birth, smoking and dog exposure), there was a significant positive relationship between year of diagnosis and age at diagnosis (P < 0.001) and significant negative relationships between year of diagnosis and both pre-treatment total plasma alkaline phosphatase activity (ALP) and number of involved bones (P < 0.001 for each). Patients with SQSTM1 mutations had more extensive disease (P < 0.001) and higher pre-treatment ALP (P = 0.013). In subgroup analyses, relationships between year of diagnosis and each of age at diagnosis, number of involved bones and ALP were similar in patients with sporadic or familial disease, and in patients with and without SQSTM1 mutations. We conclude that the severity of PDB in Western Australia has declined over recent decades. This is likely to reflect altered exposure to one or more environmental agents involved in pathogenesis.

Epidemiology and pathology of Paget's disease of bone - a review

Paget's disease of bone (PDB) is a noninflammatory, metabolic, skeletal disorder characterized by localized excessive osteoclastic bone resorption that is followed by compensatory increased osteoblastic activity leading to unstructured, fibroblastic, and biomechanically unstable bone. As a result, there is deformity and enlargement of the bone with a defective and disorganized pattern. Here, we review the epidemiology, etiology, pathology, macrostructure, histology, and quantitative histomorphometry findings of PDB. Hyperosteoclastosis and poor definition of the boundary between cortical and medullary bone are the main histological findings in PDB. Additionally, Pagetic bone is also characterized by hypertrophy and alteration of trabecular parameters.

OCLI-023, a Novel Pyrimidine Compound, Suppresses Osteoclastogenesis In Vitro and Alveolar Bone Resorption In Vivo

An abnormal increase in osteoclast differentiation and activation results in various bone-resorptive diseases, including periodontitis, rheumatoid arthritis, and osteoporosis. Chemical compounds containing pyrimidine ring have been shown to regulate a variety of biological processes. Therefore, in order to identify an antiresorptive agent, we synthesized a series of pyrimidine ring-containing chemical compounds, and found that OCLI-023 suppressed the differentiation and activation of osteoclasts in vitro. OCLI-023 directly inhibited receptor activator of nuclear factor-κB ligand (RANKL)-induced differentiation of bone marrow macrophages into osteoclasts, without a cytotoxic response. OCLI-023 also downregulated the RANKL-induced mRNA expression of osteoclast markers as well as inhibited the formation of actin rings and resorption pits. OCLI-023 attenuated the RANKL-induced activation of c-Jun N-terminal kinase and nuclear factor kappa-light-chain-enhancer of activated B cell signaling pathways. In a mouse model of periodontitis, ligature induced an increase of distance between cementoenamel junction (CEJ) and alveolar bone crest (ABC) in the second molar, and OCLI-023 significantly reduced it. Histological analysis showed ligature-induced increase of osteoclast numbers was also significantly reduced by OCLI-023. These data demonstrated the inhibitory effect of OCLI-023 on osteoclast differentiation and activity of osteoclasts in vitro, as well as on ligature-induced bone loss in vivo, and OCLI-023 can be proposed as a novel anti-resorptive compound.

Rare variants in SQSTM1 and VCP genes and risk of sporadic inclusion body myositis

Genetic factors have been suggested to be involved in the pathogenesis of sporadic inclusion body myositis (sIBM). Sequestosome 1 (SQSTM1) and valosin-containing protein (VCP) are 2 key genes associated with several neurodegenerative disorders but have yet to be thoroughly investigated in sIBM. A candidate gene analysis was conducted using whole-exome sequencing data from 181 sIBM patients, and whole-transcriptome expression analysis was performed in patients with genetic variants of interest. We identified 6 rare missense variants in the SQSTM1 and VCP in 7 sIBM patients (4.0%). Two variants, the SQSTM1 p.G194R and the VCP p.R159C, were significantly overrepresented in this sIBM cohort compared with controls. Five of these variants had been previously reported in patients with degenerative diseases. The messenger RNA levels of major histocompatibility complex genes were upregulated, this elevation being more pronounced in SQSTM1 patient group. We report for the first time potentially pathogenic SQSTM1 variants and expand the spectrum of VCP variants in sIBM. These data suggest that defects in neurodegenerative pathways may confer genetic susceptibility to sIBM and reinforce the mechanistic overlap in these neurodegenerative disorders.