Paget disease of bone

Preliminary investigation reveals novel pathological consequences of bluetongue virus-1 infection in the endocrine glands of pregnant Indian sheep

Bluetongue virus (BTV), a major peril to the sheep industry, infects a wide range of the cells in the infected animals including mononuclear, dendritic and epithelial cells. However, little is known about its tropism for the secretory epithelial cells of endocrine glands and the pathogenesis it induces. The aim of the study was to assess the BTV load, antigen distribution in the tissue of the pituitary, thyroid as well as adrenal glands and associated histopathological consequences. BTV antigens were localized using immunohistochemistry in the thyroid's epithelial cells, zona fasciculata and zona reticularis cells and the anterior pituitary epithelial cells. The real-time PCR portrayed the high viral load in adrenals at 7th days postinoculation (DPI) and in thyroid and pituitary glands at 15th DPI. Serum examination revealed variation in the T-3 and T-4 of infected animals in comparison to the control group. Caspase-3 immunolocalization revealed BTV-1 induces apoptosis in the affected cells of endocrine gland of infected animals. Further, this study signifies the tropism of BTV in the novel sites (endocrine glands) of the host that might be one of the reasons for the poor performance of infected animals.

Selenoprotein W engages in overactive osteoclast differentiation in multiple myeloma

BACKGROUND

Patients with multiple myeloma exhibit malignant osteolytic bone disease due to excessive osteoclast formation and function. We recently identified that osteoclastogenic stimulator selenoprotein W (SELENOW) is upregulated via ERK signaling and downregulated via p38 signaling during receptor activator of nuclear factor (NF)-κΒ ligand (RANKL)-induced osteoclast differentiation. In the intrinsic physiological process, RANKL-induced downregulation of SELENOW maintains proper osteoclast differentiation; in contrast, forced overexpression of SELENOW leads to overactive osteoclast formation and function.

METHODS AND RESULTS

We observed that SELENOW is highly expressed in multiple myeloma-derived peripheral blood mononuclear cells (PBMCs) and mature osteoclasts when compared to healthy controls. Also, the level of tumor necrosis factor alpha (TNFα), a pathological osteoclastogenic factor, is increased in the PBMCs and serum of patients with multiple myeloma. ERK activation by TNFα was more marked and sustained than that by RANKL, allowing SELENOW upregulation. Excessive expression of SELENOW in osteoclast progenitors and mature osteoclasts derived from multiple myeloma facilitated efficient nuclear translocation of osteoclastogenic transcription factors NF-κB and NFATc1, which are favorable for osteoclast formation.

CONCLUSION

Our findings suggest a possibility that feedforward signaling of osteoclastogenic SELENOW by TNFα derived from multiple myeloma induces overactive osteoclast differentiation, leading to bone loss during multiple myeloma.

Osteocytes and Paget's Disease of Bone

PURPOSE OF REVIEW

To describe the contributions of osteocytes to the lesions in Paget's disease, which are characterized by locally overactive bone resorption and formation.

RECENT FINDINGS

Osteocytes, the most abundant cells in bone, are altered in Paget's disease lesions, displaying increased size, decreased canalicular length, incomplete differentiation, and less sclerostin expression compared to controls in both patients and mouse models. Pagetic lesions show increased senescent osteocytes that express RANK ligand, which drives osteoclastic bone resorption. Abnormal osteoclasts in Paget's disease secrete abundant IGF1, which enhances osteocyte senescence, contributing to lesion formation. Recent data suggest that osteocytes contribute to lesion formation in Paget's disease by responding to high local IGF1 released from abnormal osteoclasts. Here we describe the characteristics of osteocytes in Paget's disease and their role in bone lesion formation based on recent results with mouse models and supported by patient data.

Paget's Disease or Densifying Metastasis: How to Sort It Out

Although the prevalence of Paget's disease has decreased over the past 20 years, incidental discovery on imaging is not unusual. The challenge is to establish the diagnosis, especially in unusual forms that may be mistaken for metastases. This review describes the typical imaging features of Paget's disease and some rare presentations that may be more difficult to recognize.

Unnatural helical peptidic foldamers as protein segment mimics

Unnatural helical peptidic foldamers have attracted considerable attention owing to their unique folding behaviours, diverse artificial protein binding mechanisms, and promising applications in chemical, biological, medical, and material fields. Unlike the conventional α-helix consisting of molecular entities of native α-amino acids, unnatural helical peptidic foldamers are generally comprised of well-defined backbone conformers with unique and unnatural structural parameters. Their folded structures usually arise from unnatural amino acids such as N-substituted glycine, N-substituted-β-alanine, β-amino acid, urea, thiourea, α-aminoxy acid, α-aminoisobutyric acid, aza-amino acid, aromatic amide, γ-amino acid, as well as sulfono-γ-AA amino acid. They can exhibit intriguing and predictable three-dimensional helical structures, generally featuring superior resistance to proteolytic degradation, enhanced bioavailability, and improved chemodiversity, and are promising in mimicking helical segments of various proteins. Although it is impossible to include every piece of research work, we attempt to highlight the research progress in the past 10 years in exploring unnatural peptidic foldamers as protein helical segment mimics, by giving some representative examples and discussing the current challenges and future perspectives. We expect that this review will help elucidate the principles of structural design and applications of existing unnatural helical peptidic foldamers in protein segment mimicry, thereby attracting more researchers to explore and generate novel unnatural peptidic foldamers with unique structural and functional properties, leading to more unprecedented and practical applications.

Paget's Disease of the Bone and Lynch Syndrome: An Exceptional Finding

Our objective is to present an exceptional case of a patient diagnosed with Paget's disease of the bone (PDB) while being confirmed with Lynch syndrome (LS). A 44-year-old woman was admitted for progressive pain in the left forearm 2 years ago, and was partially relieved since admission by non-steroidal anti-inflammatory drugs. Suggestive imaging findings and increased blood bone turnover markers helped the diagnosis of PDB. She was offered zoledronate 5 mg. She had two more episodes of relapse, and a decision of new medication was taken within the following years (a second dose of zoledronate, as well as denosumab 60 mg). Her family history showed PDB (mother) and colorectal cancer (father). Whole exome sequencing was performed according to the manufacturer's standard procedure (Ion AmpliSeq™ Exome RDY S5 Kit). A heterozygous pathogenic variant in the SQSTM1 gene (c.1175C>T, p.Pro392Leu) was confirmed, consistent with the diagnosis of PDB. Additionally, a heterozygous pathogenic variant of MSH2 gene (c.2634+1G>T) was associated with LS. The patient's first-degree relatives (her brother, one of her two sisters, and her only daughter) underwent specific genetic screening and found negative results, except for her daughter, who tested positive for both pathogenic variants while being clinically asymptomatic. The phenotype influence of either mutation is still an open issue. To our current knowledge, no similar case has been published before. Both genetic defects that led to the two conditions appeared highly transmissible in the patient's family. The patient might have an increased risk of osteosarcoma and chondrosarcoma, both due to PDB and LS, and a review of the literature was introduced in this particular matter. The phenotypic expression of the daughter remains uncertain and is yet to be a lifelong follow-up as the second patient harbouring this unique combination of gene anomalies.

Molecular test of Paget's disease of bone in families not linked to SQSTM1 gene mutations

Purpose

Paget's disease of bone (PDB) is a focal metabolic bone disorder characterized by an increased bone remodeling. Fifteen to 40 % of PDB patients have a familial form with an autosomal dominant inheritance. Disease-causing mutations of the SQSTM1 gene have been linked to PDB in about 40 % of families whereas genes linked to the remaining families are unknown. Several single nucleotide polymorphisms (SNPs) have been associated with PDB in unrelated patient non-carriers of a SQSTM1 mutation. The current clinical practice guidelines still recommend the measure of serum total alkaline phosphatase (sALP) for PDB screening. In unrelated individual non-carriers of SQSTM1 mutations, we previously developed a genetic test combining male sex with five genetic markers (rs499345, rs5742915, rs2458413, rs3018362, rs2234968), giving rise to an area under the curve (AUC) for PDB phenotype of 0.73 (0.69; 0.77). A combination of male sex with total calcium corrected for albumin and Procollagen type I N-terminal propeptide (P1NP), had an AUC of 0.82 (0.73; 0.92). Combining both genetic and biochemical tests increased the AUC to 0.89 (0.83; 0.95).

Objective

This study aimed at estimating the performance of our previous test of PDB, in families not linked to SQSTM1 mutations with disease-causing genes yet unknown, and at developing a new algorithm if the performance is not satisfactory.

Methods

We genotyped the five SNPs cited above, and measured calcium corrected for albumin and P1NP in 181 relatives, with PDB or not, from 19 PDB families not linked to SQSTM1 mutations. Bivariate and multivariate logistic regression models including male sex were fitted to search for a molecular test that could best detect PDB in these families. A receiving operating characteristics analysis was done to establish a cut-off point for continuous variables.

Results

Logistic regression estimates of our previous molecular test gave rise to a high sensitivity of 78 %, 97 % and 88 % for the genetic, biochemical, and combined test but the specificity was very low, 35 %, 11 % and 21 %, respectively. This poor specificity persisted even when the cut-off point was changed. We then generated in these families, new logistic regression estimates but on the same parameters as mentioned above, giving rise to an AUC of 0.65 (0.55; 0.75) for the genetic test, of 0.84 (0.74; 0.94) for the biochemical test, and 0.89 (0.82; 0.96) for the combination test, the latter having a sensitivity of 96 % and specificity of 57 %. By comparison serum P1NP alone gave rise to an AUC of 0.84 (0.73; 0.94), with a sensitivity of 71 % and a specificity of 79 %.

Conclusion

In PDB families not linked to SQSTM1 mutations, the estimates of our previous molecular test gave rise to a poor specificity. Using new estimates, the biochemical and combined tests have similar predictive abilities than our former test. Serum P1NP is a bone marker of interest for the screening for PDB in families not linked to SQSTM1 mutations.

An inducible explant model of osteoclast-osteoprogenitor coordination in exacerbated osteoclastogenesis

Elucidating a basic blueprint of osteoclast-osteoblast coordination in skeletal remodeling and understanding how this coordination breaks down with age and disease is essential for addressing the growing skeletal health problem in our aging population. The paucity of simple, activatable, biologically relevant models of osteoclast-osteoblast coordination has hindered our understanding of how skeletal remolding is regulated. Here, we describe an inducible ex vivo model of osteoclast-osteoblast progenitor coordination. Induction activates the release of osteoclastogenic factors from osteoprogenitors, which elicits the differentiation and fusion of neighboring preosteoclasts. In turn, multinucleated osteoclasts release soluble coupling factors, RANK⁺ extracellular vesicles and promote osteoprogenitor proliferation, recapitulating aspects of perturbed coordination in diseases underpinned by excessive osteoclast formation. We expect this model to expedite the investigation of cell-cell fusion, osteoclast-osteoblast progenitor coordination, and extracellular vesicle signaling during bone remodeling and offer a powerful tool for evaluating signaling cascades and novel therapeutic interventions in osteoclast-linked skeletal disease.

The Ying and Yang of Sphingosine-1-Phosphate Signalling within the Bone

Bone remodelling is a highly active and dynamic process that involves the tight regulation of osteoblasts, osteoclasts, and their progenitors to allow for a balance of bone resorption and formation to be maintained. Ageing and inflammation are risk factors for the dysregulation of bone remodelling. Once the balance between bone formation and resorption is lost, bone mass becomes compromised, resulting in disorders such as osteoporosis and Paget's disease. Key molecules in the sphingosine-1-phosphate signalling pathway have been identified for their role in regulating bone remodelling, in addition to its more recognised role in inflammatory responses. This review discusses the accumulating evidence for the different, and, in certain circumstances, opposing, roles of S1P in bone homeostasis and disease, including osteoporosis, Paget's disease, and inflammatory bone loss. Specifically, we describe the current, often conflicting, evidence surrounding S1P function in osteoblasts, osteoclasts, and their precursors in health and disease, concluding that S1P may be an effective biomarker of bone disease and also an attractive therapeutic target for disease.

Prevalence of Paget's disease of bone: review of consecutive abdominopelvic CT scans and literature

BACKGROUND

Previous studies suggest an overall decrease of Paget's disease of bone (PDB) prevalence. However, a large number of asymptomatic patients make previously reported prevalence likely underrepresented.

PURPOSE

To evaluate the prevalence of PDB in our patient population.

MATERIAL AND METHODS

We retrospectively identified 1295 (mean age = 59 years; age range = 18-98 years) consecutive abdominopelvic computed tomography (CT) scans over a 15-day period in 2014. Abdominopelvic CT images were reviewed to assess for the presence of PDB in the lower thoracic spine, lumbar spine, pelvis, or proximal femora. This prevalence was compared with prevalence reported in earlier literature using Fisher's exact test.

RESULTS

Of the included patients, 5/1295 (0.39%) patients had imaging findings of PDB on abdominopelvic CT. Those five patients were all aged ≥55 years and had pelvic bone involvement, with one patient having additional involvement of multiple lower thoracic vertebral bodies. In our studied cohort, 812/1295 (62.7%) patients were aged ≥55 years, which corresponds to a prevalence of 0.62% (5/812) of PDB in patients aged ≥55 years. When accounting for fact that bones of the pelvis are involved in 40%-91% of patients with PDB, the prevalence is estimated at 0.43%-0.98% in the total adult population and estimated at 0.68%-1.55% in older adults. The prevalence was greater than two studies before 1960, and less than some studies during 1960-2019.

CONCLUSION

We found that the prevalence of PDB on abdominopelvic CTs was 0.39% of all adult patients with an increase after the age of 55 years.

Oligoarginine-Conjugated Peptide Foldamers Inhibiting Vitamin D Receptor-Mediated Transcription

The vitamin D receptor (VDR) is a nuclear receptor, which is involved in several physiological processes, including differentiation and bone homeostasis. The VDR is a promising target for the development of drugs against cancer and bone-related diseases. To date, several VDR antagonists, which bind to the ligand binding domain of the VDR and compete with the endogenous agonist 1α,25(OH)D3, have been reported. However, these ligands contain a secosteroidal skeleton, which is chemically unstable and complicated to synthesize. A few VDR antagonists with a nonsecosteroidal skeleton have been reported. Alternative inhibitors against VDR transactivation that act via different mechanisms are desirable. Here, we developed peptide-based VDR inhibitors capable of disrupting the VDR-coactivator interaction. It was reported that helical SRC2-3 peptides strongly bound to the VDR and competed with the coactivator in vitro. Therefore, we designed and synthesized a series of SRC2-3 derivatives by the introduction of nonproteinogenic amino acids, such as β-amino acids, and by side-chain stapling to stabilize helical structures and provide resistance against digestive enzymes. In addition, conjugation with a cell-penetrating peptide increased the cell membrane permeability and was a promising strategy for intracellular VDR inhibition. The nona-arginine-conjugated peptides 24 with side-chain stapling and 25 with cyclic β-amino acids showed strong intracellular VDR inhibitory activity, resulting in suppression of the target gene expression and inhibition of the cell differentiation of HL-60 cells. Herein, the peptide design, structure-activity relationship (SAR) study, and biological evaluation of the peptides are described.

Update on the pathogenesis and genetics of Paget’s disease of bone

Studies over the past two decades have led to major advances in the pathogenesis of Paget’s disease of bone (PDB) and particularly on the role of genetic factors. Germline mutations of different genes have been identified, as a possible cause of this disorder, and most of the underlying pathways are implicated in the regulation of osteoclast differentiation and function, whereas other are involved in cell autophagy mechanisms. In particular, about 30 different germline mutations of the Sequestosome 1 gene (SQSTM1) have been described in a significant proportion of familial and sporadic PDB cases. The majority of SQSTM1 mutations affect the ubiquitin-binding domain of the protein and are associated to a more severe clinical expression of the disease. Also, germline mutations in the ZNF687 and PFN1 genes have been associated to severe, early onset, polyostotic PDB with increased susceptibly to neoplastic degeneration, particularly giant cell tumor. Mutations in the VCP (Valosin Containing Protein) gene cause the autosomal dominant syndrome “Inclusion Body Myopathy, PDB, Fronto-temporal Dementia,” characterized by pagetic manifestations, associated with myopathy, amyotrophic lateral sclerosis and fronto-temporal dementia. Moreover, germline mutations in the TNFRSF11A gene, which encodes for RANK, were associated with rare syndromes showing some histopathological, radiological, and clinical overlap with PDB and in two cases of early onset PDB-like disease. Likewise, genome wide association studies performed in unrelated PDB cases identified other potential predisposition genes and/or susceptibility loci. Thus, it is likely that polygenic factors are involved in the PDB pathogenesis in many individuals and that modifying genes may contribute in refining the clinical phenotype. Moreover, the contribution of somatic mutations of SQSTM1 gene and/or epigenetic mechanisms in the pathogenesis of skeletal pagetic abnormalities and eventually neoplastic degeneration, cannot be excluded. Indeed, clinical and experimental observations indicate that genetic susceptibility might not be a sufficient condition for the clinical development of PDB without the concomitant intervention of viral infection, in primis paramixoviruses, and/or other environmental factors (e.g., pesticides, heavy metals or tobacco exposure), at least in a subset of cases. This review summarizes the most important advances that have been made in the field of cellular and molecular biology PDB over the past decades.

Klippel-Feil Syndrome: morphological findings in a 19th-century musealized skull from Viana del Bollo (Orense, Spain)

The aim of this study is to show the cranial alterations that Klippel-Feil syndrome produced in a case older than 200 years. Few paleopathological case studies diagnosed as Klippel-Feil Syndrome are focused on cranial abnormalities. A skull numbered 778, belonging to the Federico Olóriz Aguilera collection (Spain, 19th century AD), Universidad Complutense de Madrid, belonging to a young man born in a town in the North of Spain, was investigated. This cranium was visually inspected, hence macroscopically and paleoradiologically studied, using the images obtained through conventional radiology and CT scan imaging. In addition to the vertebral fusion between the atlas (C1) and the axis (C2), atlanto-occipital fusion, basilar impression, obliteration of the sagittal suture, enlarged parietal foramina and significant craniofacial asymmetry affecting maxillary bones, sphenoid, orbits, nasal bones and both palatines were observed. Morphological findings make it possible to diagnose a Klippel-Feil syndrome, possibly type-II, although the lack of the rest of the spinal column renders it impossible to verify other spinal anomalies. As a limitation, only the cranium and two cervical vertebrae were preserved, hence the possible involvement of the rest of the skeleton cannot be verified.

Suppression of osteoclast multinucleation via a posttranscriptional regulation-based spatiotemporally selective delivery system

Redundancy of multinucleated mature osteoclasts, which results from the excessive fusion of mononucleated preosteoclasts (pOCs), leads to osteolytic diseases such as osteoporosis. Unfortunately, the currently available clinical drugs completely inhibit osteoclasts, thus interfering with normal physiological bone turnover. pOC-specific regulation may be more suitable for maintaining bone homeostasis. Here, circBBS9, a previously unidentified circular RNA, was found to exert regulatory effects via the circBBS9/miR-423-3p/Traf6 axis in pOCs. To overcome the long-standing challenge of spatiotemporal RNA delivery to cells, we constructed biomimetic nanoparticles to achieve the pOC-specific targeted delivery of circBBS9. pOC membranes (POCMs) were extracted to camouflage cationic polymer for RNA interference with circBBS9 (POCM-NPs@siRNA/shRNA^circBBS9). POCM-NPs endowed the nanocarriers with improved stability, accurate pOC targeting, fusogenic uptake, and reactive oxygen species-responsive release. In summary, our findings may provide an alternative strategy for multinucleated cell-related diseases that involves restriction of mononucleated cell multinucleation through a spatiotemporally selective delivery system.

Helical Foldamers and Stapled Peptides as New Modalities in Drug Discovery: Modulators of Protein-Protein Interactions

A “foldamer” is an artificial oligomeric molecule with a regular secondary or tertiary structure consisting of various building blocks. A “stapled peptide” is a peptide with stabilized secondary structures, in particular, helical structures by intramolecular covalent side-chain cross-linking. Helical foldamers and stapled peptides are potential drug candidates that can target protein-protein interactions because they enable multipoint molecular recognition, which is difficult to achieve with low-molecular-weight compounds. This mini-review describes a variety of peptide-based foldamers and stapled peptides with a view to their applications in drug discovery, including our recent progress.

Impact of the Endocannabinoid System on Bone Formation and Remodeling in p62 KO Mice

Several studies have shown that the G-protein coupled cannabinoid receptor CB2 and its interaction partner p62 are molecularly involved in bone remodeling processes. Pharmacological activation of the CB2 receptor enhanced bone volume in postmenopausal osteoporosis and arthritis models in rodents, whereas knockout or mutation of the p62 protein in aged mice led to Paget’s disease of bone-like conditions. Studies of pharmacological CB2 agonist effects on bone metabolism in p62 KO mice have not been performed to date. Here, we assessed the effect of the CB2-specific agonist JWH133 after a short-term (5 days in 3-month-old mice) or long-term (4 weeks in 6-month-old mice) treatment on structural, dynamic, and cellular bone morphometry obtained by μCT of the femur and histomorphometry of the vertebral bodies in p62 KO mice and their WT littermates in vivo. A genotype-independent stimulatory effect of CB2 on bone formation, trabecular number, and trabecular thickness after short-term treatment and on tissue mineral density after long-term treatment was detected, indicating a weak osteoanabolic function of this CB2 agonist. Moreover, after short-term systemic CB2 receptor activation, we found significant differences at the cellular level in the number of osteoblasts and osteoclasts only in p62 KO mice, together with a weak increase in trabecular number and a decrease in trabecular separation. Long-term treatment showed an opposite JWH133 effect on osteoclasts in WT versus p62 KO animals and decreased cortical thickness only in treated p62 KO mice. Our results provide new insights into CB2 receptor signaling in vivo and suggest that CB2 agonist activity may be regulated by the presence of its macromolecular binding partner p62.

Clinical, Biochemical, Radiological, and Genetic Analyses of a Patient with VCP Gene Variant-Induced Paget's Disease of Bone

Paget's disease of bone (PDB) is a rare metabolic bone disorder, which is extremely rare in Asian population. This study aimed to investigate the phenotypes and the pathogenic mutations of woman with early-onset PDB. The clinical features, bone mineral density, x-ray, radionuclide bone scan, and serum levels of alkaline phosphatase (ALP), procollagen type 1 N-terminal propeptide (P1NP), and β-carboxy-terminal cross-linked telopeptide of type 1 collagen (β-CTX) were measured in detail. The pathogenic mutations were identified by whole-exon sequencing and confirmed by Sanger sequencing. We also evaluated the effects of intravenous infusion of zoledronic acid on the bones of the patient and summarized the phenotypic characteristics of reported patients with mutation at position 155 of the valosin-containing protein (VCP). The patient only exhibited bone pain as the initial manifestation with vertebral compression fracture and extremely elevated ALP, P1NP, and β-CTX levels; she had no inclusion body myopathy and frontotemporal dementia. The missense mutation in exon 5 of the VCP gene (p.Arg155His) was identified by whole-exome sequencing and further confirmed by Sanger sequencing. No mutation in candidate genes of PDB, such as SQSTM1, CSF1, TM7SF4, OPTN, PFN1, and TNFRSF11A, were identified in the patient by Sanger sequencing. Rapid relief of bone pain and a marked decline in ALP, P1NP, and β-CTX levels were observed after zoledronic acid treatment. Previously reported patients with VCP missense mutation at position 155 (R155H) always had myopathy, frontotemporal dementia, and PDB, but the patient in this study exhibited only PDB. This was the first report of R155H mutation-induced early-onset in the VCP gene in Asian population. PDB was the only manifestation having a favorable response to zoledronic acid treatment. We broadened the genetic and clinical phenotype spectra of the VCP mutation.

Ras and Rab Interactor 3: From Cellular Mechanisms to Human Diseases

Ras and Rab interactor 3 (RIN3) functions as a Guanine nucleotide Exchange Factor (GEF) for some members of the Rab family of small GTPase. By promoting the activation of Rab5, RIN3 plays an important role in regulating endocytosis and endocytic trafficking. In addition, RIN3 activates Ras, another small GTPase, that controls multiple signaling pathways to regulate cellular function. Increasing evidence suggests that dysregulation of RIN3 activity may contribute to the pathogenesis of several disease conditions ranging from Paget’s Disease of the Bone (PDB), Alzheimer’s Disease (AD), Chronic Obstructive Pulmonary Disease (COPD) and to obesity. Recent genome-wide association studies (GWAS) identified variants in the RIN3 gene to be linked with these disease conditions. Interestingly, some variants appear to be missense mutations in the functional domains of the RIN3 protein while most variants are located in the noncoding regions of the RIN3 gene, potentially altering its gene expression. However, neither the protein structure of RIN3 nor its exact function(s) (except for its GEF activity) has been fully defined. Furthermore, how the polymorphisms/variants contribute to disease pathogenesis remain to be understood. Herein, we examine, and review published studies in an attempt to provide a better understanding of the physiological function of RIN3; More importantly, we construct a framework linking the polymorphisms/variants of RIN3 to altered cell signaling and endocytic traffic, and to potential disease mechanism(s).

Paget's disease of bone and megaloblastic anemia in a 72‑year‑old patient: A case report and systematic literature review

Paget's disease of bone (PDB) is characterized by abnormal osteoclastic bone resorption with disorganized bone neo-formation, primarily affecting elderly (>55 years) patients. Although the majority of patients are asymptomatic, some patients may experience bone pain due to local periosteal involvement or osteoarthritic lesions in the spine; in addition, limb deformities may lead to secondary gait problems or degenerative joint changes. Anemia has an overall prevalence of 12-17% in elderly adults (>65 years old), with macrocytic anemia being the less common type. Megaloblastic anemia is a macrocytic anemia characterized by the presence of large, immature, nucleated cells (megaloblasts) in the blood, with the most common cause being a deficiency of folate and/or vitamin B12. We herein report the rare case of a 72-year-old male patient exhibiting both these conditions, with the aim of discussing the possible association between the two and, most importantly, the clinical management of the patient in a real-life setting over a period of 10 years. The patient was diagnosed based on clinical symptoms (bone pain), radiological imaging and specific laboratory tests, and received discontinuous courses of bisphosphonates and cyanocobalamin supplementation therapy, based mainly on aggravated symptomatology. A systematic literature review was also performed and revealed not only the scarcity of reports on similar cases, but also the mechanisms that may underlie the possible association of PDB with macrocytic anemia due to vitamin B12 deficiency in elderly patients.

Flavonoids: Classification, Function, and Molecular Mechanisms Involved in Bone Remodelling

Flavonoids are polyphenolic compounds spotted in various fruits, vegetables, barks, tea plants, and stems and many more natural commodities. They have a multitude of applications through their anti-inflammatory, anti-oxidative, anti-carcinogenic properties, along with the ability to assist in the stimulation of bone formation. Bone, a rigid connective body tissue made up of cells embedded in a mineralised matrix is maintained by an assemblage of pathways assisting osteoblastogenesis and osteoclastogenesis. These have a significant impact on a plethora of bone diseases. The homeostasis between osteoblast and osteoclast formation decides the integrity and structure of the bone. The flavonoids discussed here are quercetin, kaempferol, icariin, myricetin, naringin, daidzein, luteolin, genistein, hesperidin, apigenin and several other flavonoids. The effects these flavonoids have on the mitogen activated protein kinase (MAPK), nuclear factor kappa β (NF-kβ), Wnt/β-catenin and bone morphogenetic protein 2/SMAD (BMP2/SMAD) signalling pathways, and apoptotic pathways lead to impacts on bone remodelling. In addition, these polyphenols regulate angiogenesis, decrease the levels of inflammatory cytokines and play a crucial role in scavenging reactive oxygen species (ROS). Considering these important effects of flavonoids, they may be regarded as a promising agent in treating bone-related ailments in the future.

Shoulder Arthroplasty for Patients With Proximal Humeral Paget's Disease

Poorly controlled Paget's disease leads to excessive blood loss following total hip arthroplasty. The effect in shoulder arthroplasty is unknown. The authors reviewed 3 patients with Paget's disease involving the proximal humerus, comparing them with 17 patients with Paget's disease but no humeral involvement. The 3 patients had an estimated blood loss of 1400 mL, 1100 mL, and 350 mL, compared with an average of 280 mL in the control group. The first 2 cases required 4 units of packed red blood cells intraoperatively, and both were not managed with bisphosphonates. Paget's disease of the humerus leads to more intraoperative blood loss and higher blood transfusion requirements, particularly in cases not managed with bisphosphonates. [Orthopedics. 2021;44(4):e614-e619.].

Bilateral Cemented Custom-Made Total Hip Arthroplasty in Paget's Disease with Femoral Cortical Thickening and Canal Narrowing

In this report, we present a case of a 57-year-old man complaining of pain in both his hips. Clinically, the patient reported lameness and reduction in the range of motion of the hips. Radiographic imaging showed a very narrow medullary femoral canal, confirmed by a computed tomography scan. In consideration of the narrowness of the femoral canal and cortex thickening, and due to the rarity of the clinical case, we opted to use a custom-made prosthesis. We performed total hip arthroplasty, initially on the right side. One year later, we repeated the procedure on the left side. One year after the last surgery, the patient reported well-being and continuous improvement in walking, with no complications. This case report highlights the features and the critical issues related to this kind of surgery in patients affected by Paget's disease of the bone and the importance of custom-made implants in challenging cases.

CD13 is a critical regulator of cell-cell fusion in osteoclastogenesis

The transmembrane aminopeptidase CD13 is highly expressed in cells of the myeloid lineage, regulates dynamin-dependent receptor endocytosis and recycling and is a necessary component of actin cytoskeletal organization. Here, we show that CD13-deficient mice present a low bone density phenotype with increased numbers of osteoclasts per bone surface, but display a normal distribution of osteoclast progenitor populations in the bone marrow and periphery. In addition, the bone formation and mineral apposition rates are similar between genotypes, indicating a defect in osteoclast-specific function in vivo. Lack of CD13 led to exaggerated in vitro osteoclastogenesis as indicated by significantly enhanced fusion of bone marrow-derived multinucleated osteoclasts in the presence of M-CSF and RANKL, resulting in abnormally large cells containing remarkably high numbers of nuclei. Mechanistically, while expression levels of the fusion-regulatory proteins dynamin and DC-STAMP1 must be downregulated for fusion to proceed, these are aberrantly sustained at high levels even in CD13-deficient mature multi-nucleated osteoclasts. Further, the stability of fusion-promoting proteins is maintained in the absence of CD13, implicating CD13 in protein turnover mechanisms. Together, we conclude that CD13 may regulate cell–cell fusion by controlling the expression and localization of key fusion regulatory proteins that are critical for osteoclast fusion.

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.

Inhibiting Monoacylglycerol Lipase Suppresses RANKL-Induced Osteoclastogenesis and Alleviates Ovariectomy-Induced Bone Loss

Osteoporosis is a common chronic metabolic bone disease characterized by reduced trabecular bone and increased bone fragility. Monoacylglycerol lipase (MAGL) is a lipolytic enzyme to catalyze the hydrolysis of monoglycerides and specifically degrades the 2-arachidonoyl glycerol (2-AG). Previous studies have identified that 2-AG is the mainly source for arachidonic acid and the most abundant endogenous agonist of cannabinoid receptors. Considering the close relationship between inflammatory mediators/cannabinoid receptors and bone metabolism, we speculated that MAGL may play a role in the osteoclast differentiation. In the present study, we found that MAGL protein expression increased during osteoclast differentiation. MAGL knockdown by adenovirus-mediated shRNA in bone marrow-derived macrophages demonstrated the suppressive effects of MAGL on osteoclast formation and bone resorption. In addition, pharmacological inhibition of MAGL by JZL184 suppressed osteoclast differentiation, bone resorption, and osteoclast-specific gene expression. Activation of the Mitogen-activated protein kinase (MAPK) and nuclear factor κB (NF-κB) pathways was inhibited by JZL184 and deletion of MAGL. Our in vivo study indicated that JZL184 ameliorated bone loss in an ovariectomized mouse model. Furthermore, overexpressing H1 calponin partially alleviated the inhibition caused by JZL184 or MAGL deletion on osteoclastogenesis. Therefore, we conclude that targeting MAGL may be a novel therapeutic strategy for osteoporosis.

Fracture of tibial tuberosity in an adult with Paget's disease of the bone - An interesting case and review of literature

Introduction

Paget's disease of the bone is a non-malignant skeletal disorder characterized by focal abnormalities in bone remodelling at one or more skeletal sites. Pathological fractures occurring from trivial injuries are a well-known clinical presentation in patients with Paget's disease. An avulsion fracture of the tibial tuberosity is an infrequent injury and has an extremely low occurrence in adults, with only a few cases reported in literature. We describe a case of a patient with undiagnosed Paget's Disease of the bone, sustaining a pathological avulsion fracture of the tibial tuberosity.

Case report

A 54-year-old male presented with right knee pain after his knee gave way whilst standing in the goal area during a game of football, twisting his right ankle and falling. Plain radiographs of the knee revealed an avulsion fracture of the tibial tuberosity with abnormal modelling of the proximal half of the tibia. An MRI confirmed a diagnosis of Paget's disease of the bone. The patient underwent open reduction internal fixation. At 3 months follow up, the patient had good knee range of motion from 0 to 100 degrees and by 6 months he had returned to his usual activities.

Conclusion

We describe a unique case of tibial tuberosity avulsion fracture in an adult with PDB. Treatment was successful with cannulated screws and tension band wiring. Patients with PDB who fracture present with diagnostic and operative challenges, it is vital to progress with caution in the postoperative rehabilitation phase.

Pristimerin Suppresses RANKL-Induced Osteoclastogenesis and Ameliorates Ovariectomy-Induced Bone Loss

Osteoporosis is characterized by bone loss and destruction of trabecular architecture, which greatly increases the burden on the healthcare system. Excessive activation of osteoclasts is an important cause of osteoporosis, and suppression of osteoclastogenesis is helpful for the treatment of osteoporosis. Pristimerin, a natural compound, possesses numerous pharmacological effects via inactivating the NF-κB and MAPK pathways, which are closely related to osteoclastogenesis process. However, the relationship between Pristimerin and osteoclastogenesis requires further investigation. In this research, we examined the effect of Pristimerin on osteoclastogenesis and investigated the related mechanisms. Our results showed Pristimerin inhibited RANKL-induced osteoclast differentiation and osteoclastic bone resorption in vitro, with decreased expression of osteoclastogenesis-related markers including c-Fos, NFATc1, TRAP, Cathepsin K, and MMP-9 at both mRNA and protein levels. Furthermore, Pristimerin suppressed NF-κB and MAPK signaling pathways, reduced reactive oxygen species (ROS) production and activated the nuclear factor erythroid 2-related factor 2/heme oxygenase 1 (Nrf2/HO-1) signaling during osteoclastogenesis. Our in vivo experiments showed that Pristimerin remarkably ameliorated ovariectomy-induced bone loss, reduced serum levels of TNF-α, IL-1β, IL-6, and RANKL, and increased serum level of osteoprotegerin (OPG). Therefore, our research indicated that Pristimerin is a potential chemical for the treatment of osteoporosis.

Increased S1P expression in osteoclasts enhances bone formation in an animal model of Paget's disease

Paget's disease (PD) is characterized by increased numbers of abnormal osteoclasts (OCLs) that drive exuberant bone formation, but the mechanisms responsible for the increased bone formation remain unclear. We previously reported that OCLs from 70% of PD patients express measles virus nucleocapsid protein (MVNP), and that transgenic mice with targeted expression of MVNP in OCLs (MVNP mice) develop bone lesions and abnormal OCLs characteristic of PD. In this report, we examined if OCL-derived sphingosine-1-phosphate (S1P) contributed to the abnormal bone formation in PD, since OCL-derived S1P can act as a coupling factor to increase normal bone formation via binding S1P-receptor-3 (S1PR3) on osteoblasts (OBs). We report that OCLs from MVNP mice and PD patients expressed high levels of sphingosine kinase-1 (SphK-1) compared with wild-type (WT) mouse and normal donor OCLs. SphK-1 production by MVNP-OCLs was interleukin-6 (IL-6)-dependent since OCLs from MVNP/IL-6^-/- mice expressed lower levels of SphK-1. Immunohistochemistry of bone biopsies from a normal donor, a PD patient, WT and MVNP mice confirmed increased expression levels of SphK-1 in OCLs and S1PR3 in OBs of the PD patient and MVNP mice compared with normal donor and WT mice. Further, MVNP-OCLs cocultured with OBs from MVNP or WT mice increased OB-S1PR3 expression and enhanced expression of OB differentiation markers in MVNP-OBs precursors compared with WT-OBs, which was mediated by IL-6 and insulin-like growth factor 1 secreted by MVNP-OCLs. Finally, the addition of an S1PR3 antagonist (VPC23019) to WT or MVNP-OBs treated with WT and MVNP-OCL-conditioned media (CM) blocked enhanced OB differentiation of MVNP-OBs treated with MVNP-OCL-CM. In contrast, the addition of the SIPR3 agonist, VPC24191, to the cultures enhanced osterix and Col-1A expression in MVNP-OBs treated with MVNP-OCL-CM compared with WT-OBs treated with WT-OCL-CM. These results suggest that IL-6 produced by PD-OCLs increases S1P in OCLs and S1PR3 on OBs, to increase bone formation in PD.

[The regulatory role of microRNA in osteogenic differentiation of mesenchymal stem cells and its application as a therapeutic target and diagnostic tool in orthopedic diseases]

Objective

To summarize the research progress of the regulatory role of microRNA (miRNA) in osteogenic differentiation of mesenchymal stem cells (MSCs) and its application as a therapeutic target and diagnostic tool in orthopedic diseases.

Methods

The recent literature on the regulation of MSCs osteogenic differentiation by miRNAs was extensively reviewed, and its regulatory mechanism and its application as a therapeutic target and diagnostic tool in orthopedic diseases were reviewed.

Results

miRNAs are small endogenous non-coding RNAs with a length of 20-22 nucleotides, which play an important role in the osteogenic differentiation of MSCs. Osteogenesis begins with the differentiation of MSCs into mature osteoblasts, and each stage of dynamic homeostasis of bone metabolism is associated with the regulation of different miRNAs. miRNAs are regulated from the post-transcriptional level by mRNAs cleavage, degradation, translational repression, or methylation. In addition, current studies suggest that miRNAs can be used as a new diagnostic tool and therapeutic target for orthopedic diseases.

Conclusion

Further study on the regulation mechanism of miRNAs will provide more ideas for finding new therapeutic targets and diagnostic tools for orthopedic disease.

Rab GTPases in Osteoclastic Bone Resorption and Autophagy

Small guanosine triphosphate hydrolases (GTPases) of the Rab family are involved in plasma membrane delivery, fusion events, and lysosomal and autophagic degradation pathways, thereby regulating signaling pathways and cell differentiation and function. Osteoclasts are bone-resorbing cells that maintain bone homeostasis. Polarized vesicular trafficking pathways result in the formation of the ruffled border, the osteoclast’s resorptive organelle, which also assists in transcytosis. Here, we reviewed the different roles of Rab GTPases in the endomembrane machinery of osteoclasts and in bone diseases caused by the dysfunction of these proteins, with a particular focus on autophagy and bone resorption. Understanding the molecular mechanisms underlying osteoclast-related bone disease development is critical for developing and improving therapies.

Mutation of PFN1 Gene in an Early Onset, Polyostotic Paget-like Disease

CONTEXT

Paget disease of bone (PDB) is a metabolic bone disease whose genetic cause remains unknown in up to 50% of familial patients.

OBJECTIVE

Our aim was to investigate the underlying genetic defect in a large pedigree with a severe, early onset, autosomal dominant form of PDB across 3 generations.

METHODS

Whole exome sequencing was performed in affected and unaffected family members, and then mutation screening was replicated in a sample of PDB patients with early-onset, polyostotic PDB.

RESULTS

We identified a frameshift D107Rfs*3 mutation in PFN1 (encoding for profilin 1, a highly conserved regulator of actin-polymerization and cell motility) causing the truncation of the C-terminal part of the protein. The mutation was also detected in a 17-year-old asymptomatic family member who upon biochemical and radiological analyses was indeed found to be affected. Sequencing of the entire PFN1 coding region in unrelated PDB patients identified the same mutation in 1 patient. All mutation carriers had a reduced response to bisphosphonates, requiring multiple zoledronate infusions to control bone pain and achieve biochemical remission over a long term. In vitro osteoclastogenesis in peripheral blood mononuclear cells (PBMCs) from mutation carriers showed a higher number of osteoclasts with PDB-like features. A similar phenotype was observed upon PFN1 silencing in murine bone marrow-derived monocytes, suggesting that the frameshift PFN1 mutation confers a loss of function in profilin 1 activity that induces PDB-like features in the osteoclasts, likely due to enhanced cell motility and actin ring formation.

CONCLUSIONS

Our findings indicate that PFN1 mutation causes an early onset, polyostotic PDB-like disorder.

Osteoclast-derived IGF1 is required for pagetic lesion formation in vivo

We report that transgenic mice expressing measles virus nucleocapsid protein (MVNP) in osteoclasts (OCLs) (MVNP mice) are Paget's disease (PD) models and that OCLs from patients with PD and MVNP mice express high levels of OCL-derived IGF1 (OCL-IGF1). To determine OCL-IGF1's role in PD and normal bone remodeling, we generated WT and MVNP mice with targeted deletion of Igf1 in OCLs (Igf1-cKO) and MVNP/Igf1-cKO mice, and we assessed OCL-IGF1's effects on bone mass, bone formation rate, EphB2/EphB4 expression on OCLs and osteoblasts (OBs), and pagetic bone lesions (PDLs). A total of 40% of MVNP mice, but no MVNP/Igf1-cKO mice, had PDLs. Bone volume/tissue volume (BV/TV) was decreased by 60% in lumbar vertebrae and femurs of MVNP/Igf1-cKO versus MVNP mice with PDLs and by 45% versus all MVNP mice tested. Bone formation rates were decreased 50% in Igf1-cKO and MVNP/Igf1-cKO mice versus WT and MVNP mice. MVNP mice had increased EphB2 and EphB4 levels in OCLs/OBs versus WT and MVNP/Igf1-cKO, with none detectable in OCLs/OBs of Igf1-cKO mice. Mechanistically, IL-6 induced the increased OCL-IGF1 in MVNP mice. These results suggest that high OCL-IGF1 levels increase bone formation and PDLs in PD by enhancing EphB2/EphB4 expression in vivo and suggest OCL-IGF1 may contribute to normal bone remodeling.

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.

Zinc supplements and bone health: The role of the RANKL-RANK axis as a therapeutic target

BACKGROUND

To this day, empirical data suggests that zinc has important roles in matrix synthesis, bone turnover, and mineralization and its beneficial effects on bone could be mediated through different mechanisms. The influence of zinc on bone turnover could be facilitated via regulating RANKL/RANK/OPG pathway in bone tissue. Therefore, the aim of the study was to conduct a review to investigate the possible effect of the zinc mediated bone remodeling via RANKL/RANK/OPG pathway.

METHODS

A comprehensive systematic search was performed in MEDLINE/PubMed, Cochrane Library, SCOPUS, and Google Scholar to explore the studies investigating the effect of zinc as a bone remodeling factor via RANKL/RANK/OPG pathway regulation. Subsequently, the details of the pathway and the impact of zinc supplements on RANKL/RANK/OPG pathway regulation were discussed.

RESULTS

The pathway could play an important role in bone remodeling and any imbalance between RANKL/RANK/OPG components could lead to extreme bone resorption. Although the outcomes of some studies are equivocal, it is evident that zinc possesses protective properties against bone loss by regulating the RANKL/RANK/OPG pathway. There are several experiments where zinc supplementation resulted in upregulation of OPG expression or decreases RANKL level. However, the results of some studies oppose this.

CONCLUSION

It is likely that sufficient zinc intake will elicit positive effects on bone health by RANKL/RANK/OPG regulation. Although the outcomes of a few studies are equivocal, it seems that zinc can exert the protective properties against bone loss by suppressing osteoclastogenesis via downregulation of RANKL/RANK. Additionally, there are several experiments where zinc supplementation resulted in upregulation of OPG expression. However, the results of limited studies oppose this. Therefore, aside from the positive role zinc possesses in preserving bone mass, further effects of zinc in RANKL/RANK/OPG system requires further animal/human studies.

Evidence of Skeletal Fluorosis at the Ray Site, Illinois, USA: a pathological assessment and discussion of environmental factors

OBJECTIVE

To carefully assess skeletal lesions in close environment context in order to evaluate whether skeletal fluorosis was present in individuals living in the prehistoric Midwest, USA.

MATERIALS

Skeletal remains from minimally 117 individuals recovered from the Ray Site, located in western Illinois (USA) and dated to the Middle/early Late Woodland periods (50 BC-AD 400).

METHODS

Macroscopic evaluation of all recovered skeletal elements.

RESULTS

Eight individuals display a constellation of abnormal bony changes, including osteosclerosis, a high frequency of fractures, and dental abnormalities.

CONCLUSIONS

The osteosclerotic changes along with the naturally high fluoride content of west central Illinois soil and water suggests the presence of skeletal fluorosis.

SIGNIFICANCE

This is the first report of skeletal fluorosis from archaeologically recovered human remains from North America.

LIMITATIONS

The ambiguous nature of the skeletal changes associated with fluorosis, especially in the less severe stages of the disease, renders determination of the etiology difficult.

SUGGESTIONS FOR FURTHER RESEARCH

The continuation of paleopathological investigations of fluoride toxicity within archaeological communities recovered from this region with emphasis on the incorporation of biomedical and environmental data. Furthermore, complementary analyses of the chemical composition and the histological presentation of the skeletons could provide support for this diagnosis.

Global deletion of Optineurin results in altered type I IFN signaling and abnormal bone remodeling in a model of Paget's disease

Genome-wide association studies (GWAS) have identified Optineurin (OPTN) as genetically linked to Paget's disease of the bone (PDB), a chronic debilitating bone remodeling disorder characterized by localized areas of increased bone resorption and abnormal bone remodeling. However, only ~10% of mouse models with a mutation in Optn develop PDB, thus hindering the mechanistic understanding of the OPTN-PDB axis. Here, we reveal that 100% of aged Optn global knockout (Optn^-/-) mice recapitulate the key clinical features observed in PDB patients, including polyostotic osteolytic lesions, mixed-phase lesions, and increased serum levels of alkaline phosphatase (ALP). Differentiation of primary osteoclasts ex vivo revealed that the absence of Optn resulted in an increased osteoclastogenesis. Mechanistically, Optn-deficient osteoclasts displayed a significantly decreased type I interferon (IFN) signature, resulting from both defective production of IFNβ and impaired signaling via the IFNα/βR, which acts as a negative feedback loop for osteoclastogenesis and survival. These data highlight the dual roles of OPTN in the type I IFN response to restrain osteoclast activation and bone resorption, offering a novel therapeutic target for PDB. Therefore, our study describes a novel and essential mouse model for PDB and define a key role for OPTN in osteoclast differentiation.

Internal Acoustic Canal Stenosis Due to Hyperostosis

Background  Exostoses and osteomas are benign, insidious lesions of the bone involving the internal acoustic canal (IAC). We present two cases of IAC exostoses managed with surgical decompression and review the clinical outcomes of previously reported cases in the literature. Methods  A comprehensive search was conducted using PubMed Central, Web of Science Core Collection, and Google Scholar databases to identify previous reports of IAC exostoses and osteomas. A total of 26 reported cases were identified, and patient presenting symptoms, management strategies, and response to surgery was obtained when available. Results  Of the 13 patients who underwent surgical decompression, 8 patients had resolution of vertigo symptoms, 10 patients had improvement of tinnitus symptoms, and all patients maintained some level of serviceable hearing. Conclusion  IAC exostoses and osteomas are rare lesions that lead to insidious onset of debilitating symptoms from vestibulocochlear nerve dysfunction. Although the role of surgical decompression remains unclear, it appears that patients presenting with vertigo have more favorable response to surgical decompression as compared with those presenting with tinnitus and sensorineural hearing loss.

Fusion and hemagglutinin proteins of canine distemper virus promote osteoclast formation through NF-κB dependent and independent mechanisms

Paget's disease (PD) features abnormal osteoclasts (OC) which sharply increase in number and size and then intensely induce bone resorption. The purpose of this study was to determine the direct effects of canine distemper virus (CDV) and its fusion protein and hemagglutinin protein (F + H) on receptor activator of nuclear factor kappa-B ligand (RANKL) induced OC formation in vitro. Immunofluorescence assay, OC morphological and functional detection, intracellular signaling pathway detection, Real-time PCR analysis and ELISA were applied in this study. Immunofluorescence assay provided the conclusive proof that CDV can infect and replicate in RAW264.7 mouse monocyte cell line, primary human peripheral blood mononuclear cells (PBMC) and their further fused OC. Both CDV and F + H significantly promoted OC formation and bone resorption ability induced by RANKL. Meanwhile, intracellular signaling transduction analysis revealed CDV and F + H specifically upregulated the phosphorylation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and mitogen-activated protein kinase (MAPK) induced by RANKL, respectively. Furthermore, without RANKL stimulation, both CDV and F + H slightly induced OC-like cells formation in RAW264.7 cell line even in the presence of NF-κB inhibitor. F + H upregulate OC differentiation and activity through modulation of NF-κB signaling pathway, and induce OC precursor cells merging dependent on the function of glycoproteins themselves. These results meant that F and H proteins play a pivotal role in CDV supporting OC formation. Moreover, this work further provide a new research direction that F and H proteins in CDV should be considered as a trigger during the pathogenesis of PD.

VCP/p97 increases BMP signaling by accelerating ubiquitin ligase Smurf1 degradation

The bone morphogenetic protein (BMP)-Smad signaling pathway plays a crucial role in the control of bone homeostasis by regulating osteoblast activity. It is known that the ubiquitin ligase Smad ubiquitination regulatory factor (Smurf)1 is a master negative regulator of BMP signaling, but how its stability and activity are regulated remains poorly understood. Our study showed that valosin-containing protein/p97, the mutations of which lead to rare forms of Paget's disease of bone (PDB)-like syndrome-such as inclusion body myopathy (IBM) associated with Paget's disease of bone and frontotemporal dementia (IBM-PFD)-together with its adaptor nuclear protein localization (NPL)4, specifically interact with Smurf1 and deliver the ubiquitinated Smurf1 for degradation. Depletion of either p97 or NPL4 resulted in the elevation of Smurf1 protein level and decreased BMP signaling accordingly. Mechanically, a typical proline, glutamic acid, serine, and threonine motif specifically existing in Smurf1 is necessary for its recognition and degradation by p97, and this process is dependent on p97 ATPase activity. More importantly, compared with p97 WT, PDB-associated mutation of p97 (mainly A232E) harboring the higher ATPase activity of p97 further promoted Smurf1 degradation, thus increasing BMP signaling activity. Our findings first establish a link between p97 and Smurf1, providing an in-depth understanding of how Smurf1 is regulated, as well as the mechanism of p97-related bone diseases.-Li, H., Cui, Y., Wei, J., Liu, C., Chen, Y., Cui, C.-P., Li, L., Zhang, X., Zhang, L. VCP/p97 increases BMP signaling by accelerating ubiquitin ligase Smurf1 degradation.

Radiological review of skull lesions

Abstract

Calvarial lesions are often asymptomatic and are usually discovered incidentally during computed tomography or magnetic resonance imaging of the brain. Calvarial lesions can be benign or malignant. Although the majority of skull lesions are benign, it is important to be familiar with their imaging characteristics and to recognise those with malignant features where more aggressive management is needed. Clinical information such as the age of the patient, as well as the patient’s history is fundamental in making the correct diagnosis. In this article, we will review the imaging features of both common and uncommon calvarial lesions, as well as mimics of these lesions found in clinical practice.

Teaching Points

• Skull lesions are usually discovered incidentally; they can be benign or malignant.

• Metastases are the most frequent cause of skull lesions.

• Metastatic lesions are most commonly due to breast cancer in adults and neuroblastoma in children.

• Multiple myeloma presents as the classic “punched out” lytic lesions on radiographs.

• Eosinophilic granuloma is an osteolytic lesion with bevelled edges.

Rab GTPases in Osteoclastic Endomembrane Systems

Osteoclasts (OCs) are bone-resorbing cells that maintain bone homeostasis. OC differentiation, survival, and activity are regulated by numerous small GTPases, including those of the Rab family, which are involved in plasma membrane delivery and lysosomal and autophagic degradation pathways. In resorbing OCs, polarized vesicular trafficking pathways also result in formation of the ruffled membrane, the resorbing organelle, and in transcytosis.

Monostotic Paget Disease of the Lumbar Vertebrae: A Pathological Mimicker

Paget disease is a metabolic disorder involving abnormal bone turnover that consists of 3 phases: the initial lytic phase, the intermediate mixed phase, and the chronic sclerotic phase. Paget disease mostly presents as polyostotic or monostotic lesions of the spine, and is rare on the Indian subcontinent. We present a case of isolated Paget disease of the lumbar third vertebra, which was confirmed only at biopsy. The patient presented with chronic low backache with a developing neurological deficit. We managed the patient with posterior spinal stabilisation, using pedicular screws and vertebroplasty of the collapsed vertebrae to regain the height. Upon the diagnosis of Paget disease, the patient was treated with calcitonin and bisphosphonates for 3 months, along with regular monitoring of alkaline phosphatase levels. Through this case, we hope to emphasize that Paget disease should be considered in the differential diagnosis of lytic lesions. Additionally, the alkaline phosphatase level in this patient was high-normal, which was an aspect of the role of Paget disease as a mimicker. Confirmatory biopsy is mandatory in all lesions.

ZNF687 mutations are frequently found in pagetic patients from South Italy: implication in the pathogenesis of Paget's disease of bone

Paget's disease of bone (PDB) is a skeletal disorder whose molecular basis is not fully elucidated. However, 10% of patients show a familial PDB and 35% of them carry mutations in the SQSTM1 gene. We recently reported a founder mutation (p.Pro937Arg) in the ZNF687 gene, underlying PDB complicated by giant cell tumor (GCT/PDB) and rarely occurring in PDB patients without neoplastic degeneration. Since 80% of Italian GCT/PDB patients derive from Avellino, we hypothesized that ZNF687 mutation rate was higher in this region than elsewhere. Interestingly, our molecular analysis on 30 PDB patients showed that 33% hosted ZNF687 mutations, with the p.Pro937Arg identified in 8 familial cases. Two novel ZNF687 mutations (p.Pro665Leu and p.Gln784Glu) were detected in 2 sporadic patients. Only 2 subjects were positive for the p.Pro392Leu mutation in SQSTM1. ZNF687-mutated patients showed a severe PDB, with a remarkable number of affected sites. in vitro studies revealed that the ZNF687-mutant osteoclasts appeared as giant sized with up to 150 nuclei, never described in PDB. Finally, we also confirmed the causality of the p.Pro937Arg mutation in 4 additional GCT/PDB cases deriving from the same geographic area, indicating that PDB and GCT/PDB represent 2 sides of the same coin.

XRK3F2 Inhibition of p62-ZZ Domain Signaling Rescues Myeloma-Induced GFI1-Driven Epigenetic Repression of the Runx2 Gene in Pre-osteoblasts to Overcome Differentiation Suppression

Multiple myeloma bone disease (MMBD) is characterized by non-healing lytic bone lesions that persist even after a patient has achieved a hematologic remission. We previously reported that p62 (sequestosome-1) in bone marrow stromal cells (BMSC) is critical for the formation of MM-induced signaling complexes that mediate OB suppression. Importantly, XRK3F2, an inhibitor of the p62-ZZ domain, blunted MM-induced Runx2 suppression in vitro, and induced new bone formation and remodeling in the presence of tumor in vivo. Additionally, we reported that MM cells induce the formation of repressive chromatin on the Runx2 gene in BMSC via direct binding of the transcriptional repressor GFI1, which recruits the histone modifiers, histone deacetylase 1 (HDAC1) and Enhancer of zeste homolog 2 (EZH2). In this study we investigated the mechanism by which blocking p62-ZZ domain-dependent signaling prevents MM-induced suppression of Runx2 in BMSC. XRK3F2 prevented MM-induced upregulation of Gfi1 and repression of the Runx2 gene when present in MM-preOB co-cultures. We also show that p62-ZZ-domain blocking by XRK3F2 also prevented MM conditioned media and TNF plus IL7-mediated Gfi1 mRNA upregulation and the concomitant Runx2 repression, indicating that XRK3F2's prevention of p62-ZZ domain signaling within preOB is involved in the response. Chromatin immunoprecipitation (ChIP) analyses revealed that XRK3F2 decreased MM-induced GFI1 occupancy at the Runx2-P1 promoter and prevented recruitment of HDAC1, thus preserving the transcriptionally permissive chromatin mark H3K9ac on Runx2 and allowing osteogenic differentiation. Furthermore, treatment of MM-exposed preOB with XRK3F2 after MM removal decreased GFI1 enrichment at Runx2-P1 and rescued MM-induced suppression of Runx2 mRNA and its downstream osteogenic gene targets together with increased osteogenic differentiation. Further, primary BMSC (hBMSC) from MM patients (MM-hBMSC) had little ability to increase H3K9ac on the Runx2 promoter in osteogenic conditions when compared to hBMSC from healthy donors (HD). XRK3F2 treatment enriched Runx2 gene H3K9ac levels in MM-hBMSC to the level observed in HD-hBMSC, but did not alter HD-hBMSC H3K9ac. Importantly, XRK3F2 treatment of long-term MM-hBMSC cultures rescued osteogenic differentiation and mineralization. Our data show that blocking p62-ZZ domain-dependent signaling with XRK3F2 can reverse epigenetic-based mechanisms of MM-induced Runx2 suppression and promote osteogenic differentiation.