Antibody Response to Paramyxoviruses in Paget's Disease of Bone

Loss of the Ubiquitin-Associated Domain of sqstm1/p62 in Zebrafish Causes a Phenotype Resembling Paget's Disease of Bone

The ubiquitin-binding protein p62, encoded by Sequestosome 1 (SQSTM1), is an essential molecular adaptor for selective autophagy. Heterozygous mutations deleting or disrupting the ubiquitin-associated (UBA) domain of p62 have been reported as the major genetic cause for Paget's disease of bone (PDB), the second most common skeletal disease, characterized by hyperactive osteoclasts and focal increases of bone turnover. In this study, we aimed to determine the impact of a similar sqstm1/p62 mutation on the skeleton of zebrafish. We successfully established a sqstm1tmΔUBA zebrafish line with premature truncation of the UBA domain and performed skeletal phenotyping of heterozygous and homozygous mutant zebrafish. Homozygous sqstm1tmΔUBA zebrafish suffered from early lethality after 6 mpf, possibly related to a dysregulated autophagy process. Nevertheless, we detected skeletal abnormalities that were generally more severe in older animals and in homozygous versus heterozygous sqstm1tmΔUBA zebrafish. MicroCT analysis and histologic staining showed alterations in the vertebral bodies and/or bone density in heterozygous sqstm1tmΔUBA zebrafish. We also detected signs of osteocytic osteolysis in carriers of a mutant sqstm1tmΔUBA allele, shown by a higher percentage of enlarged osteocyte lacunae at 12mpf (36% in heterozygote mutants, 20% in wild types). By performing scale histomorphometry, we also detected a higher degree of scale resorption in homozygous sqstm1tmΔUBA zebrafish at 6 mpf. In conclusion, we have generated a Sqstm1 mutant zebrafish model with features of PDB, characterized by focal bone defects and increased osteoclast activity. This model may be useful to further define PDB disease mechanisms and other p62-related (patho)physiological processes.

Paget's bone disease in a nonendemic region: Exploring novel therapeutic strategies

Paget's disease of bone (PDB) is a chronic condition causing abnormal bone remodeling, leading to pain, fractures, and complications. A 57-year-old female patient, asymptomatic and devoid of pain, incidentally exhibited elevated levels of alkaline phosphatase. Following a thorough consideration of potential differential diagnoses, the eventual diagnosis established was PDB. We recommended Fosamax (70 mg alendronate tablets) at two tablets twice weekly for 3 months to manage PDB due to patient preference and side effects with intravenous zoledronic acid. Subsequent assessments of alkaline phosphatase levels during follow-up examinations post-treatment revealed a reduction in their values.

[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.

Paget's disease: a review of the epidemiology, etiology, genetics, and treatment

Paget's disease of bone (PDB) is the second most prevalent metabolic bone disorder worldwide, with a prevalence rate of 1.5%-8.3%. It is characterized by localized areas of accelerated, disorganized, and excessive bone production and turnover. Typically, PDB develops in the later stages of life, particularly in the late 50s, and affects men more frequently than women. PDB is a complex disease influenced by both genetic and environmental factors. PDB has a complex genetic basis involving multiple genes, with SQSTM1 being the gene most frequently associated with its development. Mutations affecting the UBA domain of SQSTM1 have been detected in both familial and sporadic PDB cases, and these mutations are often associated with severe clinical expression. Germline mutations in other genes such as TNFRSF11A, ZNF687 and PFN1, have also been associated with the development of the disease. Genetic association studies have also uncovered several PDB predisposing risk genes contributing to the disease pathology and severity. Epigenetic modifications of genes involved in bone remodelling and regulation, including RANKL, OPG, HDAC2, DNMT1, and SQSTM1, have been implicated in the development and progression of Paget's disease of bone, providing insight into the molecular basis of the disease and potential targets for therapeutic intervention. Although PDB has a tendency to cluster within families, the variable severity of the disease across family members, coupled with decreasing incidence rates, indicates that environmental factors may also play a role in the pathophysiology of PDB. The precise nature of these environmental triggers and how they interact with genetic determinants remain poorly understood. Fortunately, majority of PDB patients can achieve long-term remission with an intravenous infusion of aminobisphosphonates, such as zoledronic acid. In this review, we discuss aspects like clinical characteristics, genetic foundation, and latest updates in PDB research.

Epigenetic DNA Methylation Signatures Associated With the Severity of Paget's Disease of Bone

Background: Paget's disease of bone (PDB) is characterized by focal areas of dysregulated bone turnover resulting in increased bone loss and abnormal bone formation with variable severity. PDB has a complex etiology and both genetics and environmental factors have been implicated. A recent study has identified many differentially methylated loci in PDB compared to healthy subjects. However, associations between DNA methylation profiles and disease severity of PDB have not been investigated. Objectives: To investigate the association between DNA methylation signals and PDB severity. Methods: Using 232 well-characterized PDB subjects from the PRISM trial, a disease severity score was devised based on the clinical features of PDB. DNA methylation profiling was performed using Illumina Infinium HumanMethylation 450K array. Results: We identified 100 CpG methylation sites significantly associated with PDB severity at FDR <0.05. Additionally, methylation profiles in 11 regions showed Bonferroni-significant association with disease severity including six islands (located in VCL, TBX5, CASZ1, ULBP2, NUDT15 and SQSTM1), two gene bodies (CXCR6 and DENND1A), and 3 promoter regions (RPL27, LINC00301 and VPS29). Moreover, FDR-significant effects from region analysis implicated genes with genetic variants previously associated with PDB severity, including RIN3 and CSF1. A multivariate predictor model featuring the top severity-associated CpG sites revealed a significant correlation (R = 0.71, p = 6.9 × 10-16) between observed and predicted PDB severity scores. On dichotomizing the severity scores into low and high severity, the model featured an area under curve (AUC) of 0.80, a sensitivity of 0.74 and a specificity of 0.68. Conclusion: We identified several CpG methylation markers that are associated with PDB severity in this pioneering study while also highlighting the novel molecular pathways associated with disease progression. Further work is warranted to affirm the suitability of our model to predict the severity of PDB in newly diagnosed patients or patients with family history of PDB.

Fabrication of an Oscillating Thermocycler to Analyze the Canine Distemper Virus by Utilizing Reverse Transcription Polymerase Chain Reaction

The reverse transcription-polymerase chain reaction (RT-PCR) has been utilized as an effective tool to diagnose the infectious diseases of viruses. In the present work, the oscillating thermocycler is fabricated and performed to carry out the one-step RT-PCR process successfully. The ribonucleic acid (RNA) mixture is pipetted into the fixed sample volume inside an aluminum reaction block. The sample oscillates the pathway onto the linear motion control system and through the specific RT-PCR heating zones with individual homemade thermal control modules. The present oscillating thermocycler combines the merits of the chamber type and the CF type systems. Before PCR, the reaction chamber moves to the low-temperature zone to complete the RT stage and synthesize the complementary deoxyribonucleic acid (DNA). Next, the low-temperature zone is regulated to the annealing zone. Furthermore, the reactive sample is moved back and forth among three isothermal zones to complete PCR. No extra heating zone is required for the RT stage. The total length of the moving displacement of the chamber is within 100 mm. The miniaturization of the oscillating thermocycler can be expected. In our oscillatory device, the denaturation zone located between the annealing and extension zones is suggested as the appropriate arrangement of the heating blocks. Heat management without thermal cross-talk is easy. Finally, an improved oscillating device is demonstrated to execute the RT-PCR process directly, utilized to amplify the canine distemper virus templates successfully, which could be well applied to a low-cost DNA analysis system in the future.

Genetic Determinants of Paget's Disease of Bone

PURPOSE OF REVIEW

To provide an overview of the role of genes and loci that predispose to Paget's disease of bone and related disorders.

RECENT FINDINGS

Studies over the past ten years have seen major advances in knowledge on the role of genetic factors in Paget's disease of bone (PDB). Genome wide association studies have identified six loci that predispose to the disease whereas family based studies have identified a further eight genes that cause PDB. This brings the total number of genes and loci implicated in PDB to fourteen. Emerging evidence has shown that a number of these genes also predispose to multisystem proteinopathy syndromes where PDB is accompanied by neurodegeneration and myopathy due to the accumulation of abnormal protein aggregates, emphasising the importance of defects in autophagy in the pathogenesis of PDB. Genetic factors play a key role in the pathogenesis of PDB and the studies in this area have identified several genes previously not suspected to play a role in bone metabolism. Genetic testing coupled to targeted therapeutic intervention is being explored as a way of halting disease progression and improving outcome before irreversible skeletal damage has occurred.

Epigenetic analysis of Paget's disease of bone identifies differentially methylated loci that predict disease status

Paget's disease of bone (PDB) is characterized by focal increases in disorganized bone remodeling. This study aims to characterize PDB-associated changes in DNA methylation profiles in patients' blood. Meta-analysis of data from the discovery and cross-validation set, each comprising 116 PDB cases and 130 controls, revealed significant differences in DNA methylation at 14 CpG sites, 4 CpG islands, and 6 gene-body regions. These loci, including two characterized as functional through expression quantitative trait-methylation analysis, were associated with functions related to osteoclast differentiation, mechanical loading, immune function, and viral infection. A multivariate classifier based on discovery samples was found to discriminate PDB cases and controls from the cross-validation with a sensitivity of 0.84, specificity of 0.81, and an area under curve of 92.8%. In conclusion, this study has shown for the first time that epigenetic factors contribute to the pathogenesis of PDB and may offer diagnostic markers for prediction of the disease.

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.

Bisphosphonates in the management of Paget's disease

The first clinical use of bisphosphonates was in Paget's disease of bone (PDB) when disodium etidronate was found to be effective at suppressing metabolic activity of the disease. Subsequently, PDB became a testing ground for many bisphosphonates using changes in alkaline phosphatase (ALP) as the primary outcome measure in clinical trials. Bisphosphonates are now considered to be the treatment of choice for PDB since they are highly effective at suppressing the elevations in bone turnover that are characteristic of the disease. Short term studies have shown that treatment with alendronate and risedronate can promote formation of lamellar bone in affected sites and improve x-ray appearances in some patients. Bisphosphonates have also been shown to improve bone pain in PDB and within the bisphosphonates, zoledronic acid (ZA) is most likely to give a favourable pain response. Many patients with PDB do not have pain however, even when there is increased metabolic activity and more research is needed to find out why this is the case. The effects of bisphosphonates on complications of PDB such as deformity, pathological fractures and deafness have not been adequately studied since most clinical trials have been short term and have not collected information on these important outcomes. The PRISM and PRISM-EZ studies investigated the long-term effects of bisphosphonates in patients with established PDB using a treat-to-target approach and showed that intensive bisphosphonate therapy aimed at normalising ALP was no more effective than symptom directed treatment with bisphosphonates at preventing complications of PDB. The Zoledronate in the Prevention of Paget's Disease (ZiPP) trial, which is currently in progress, seeks to determine whether early intervention with this potent bisphosphonate might be effective in preventing disease progression. Should the ZiPP study yield positive results, genetic testing coupled to prophylactic bisphosphonate therapy might represent a new indication for these highly effective inhibitors of bone resorption in future years.

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.

Diagnosis and Management of Paget's Disease of Bone in Adults: A Clinical Guideline

An evidence-based clinical guideline for the diagnosis and management of Paget's disease of bone (PDB) was developed using GRADE methodology, by a Guideline Development Group (GDG) led by the Paget's Association (UK). A systematic review of diagnostic tests and pharmacological and nonpharmacological treatment options was conducted that sought to address several key questions of clinical relevance. Twelve recommendations and five conditional recommendations were made, but there was insufficient evidence to address eight of the questions posed. The following recommendations were identified as the most important: 1) Radionuclide bone scans, in addition to targeted radiographs, are recommended as a means of fully and accurately defining the extent of metabolically active disease in patients with PDB. 2) Serum total alkaline phosphatase (ALP) is recommended as a first-line biochemical screening test in combination with liver function tests in screening for the presence of metabolically active PDB. 3) Bisphosphonates are recommended for the treatment of bone pain associated with PDB. Zoledronic acid is recommended as the bisphosphonate most likely to give a favorable pain response. 4) Treatment aimed at improving symptoms is recommended over a treat-to-target strategy aimed at normalizing total ALP in PDB. 5) Total hip or knee replacements are recommended for patients with PDB who develop osteoarthritis in whom medical treatment is inadequate. There is insufficient information to recommend one type of surgical approach over another. The guideline was endorsed by the European Calcified Tissues Society, the International Osteoporosis Foundation, the American Society of Bone and Mineral Research, the Bone Research Society (UK), and the British Geriatric Society. The GDG noted that there had been a lack of research on patient-focused clinical outcomes in PDB and identified several areas where further research was needed. © 2019 The Authors. Journal of Bone and Mineral Research Published by Wiley Periodicals Inc.

Paget's disease of bone

Paget's disease of bone is a focal disorder of bone remodelling that progresses slowly and leads to changes in the shape and size of affected bones and to skeletal, articular and vascular complications. In some parts of the world it is the second most common bone disorder after osteoporosis though in recent years its prevalence and severity appear to decrease. The disease is easily diagnosed and effectively treated but its pathogenesis remains incompletely understood.

Zoledronic acid prevents pagetic-like lesions and accelerated bone loss in the p62P394L mouse model of Paget's disease

Paget's disease of bone (PDB) is an age-related metabolic bone disorder, characterised by focally increased and disorganised bone remodelling initiated by abnormal and hyperactive osteoclasts. The germline P392L mutation of SQSTM1 (encoding p62) is a strong genetic risk factor for PDB in humans, and the equivalent mutation in mice (P394L) causes a PDB-like disorder. However, it is unclear why pagetic lesions become more common with age. Here, we assessed the effect of the p62 P394L mutation on osteoclastogenesis and bone morphometry in relation to ageing, the natural history of lesion progression in p62P394L mice and the effect of zoledronic acid (ZA) on lesion development. p62P394L+/+ osteoclast precursors had increased sensitivity to RANKL (also known as TNFSF11) compared with wild-type (WT) cells, and the sensitivity further increased in both genotypes with ageing. Osteoclastogenesis from 12-month-old p62P394L+/+ mice was twofold greater than that from 3-month-old p62P394L+/+ mice (P<0.001) and three-fold greater than that from age-matched WT littermates. The p62P394L+/+ mice lost 33% more trabecular bone volume in the long bones by 12 months compared with WT mice (P<0.01), and developed pagetic-like lesions in the long bones which progressed with ageing. ZA prevented the development of pagetic-like lesions, and increased trabecular bone volume tenfold compared with vehicle by 12 months of age (P<0.01). This demonstrates that ageing has a pro-osteoclastogenic effect, which is further enhanced by the p62 P394L mutation, providing an explanation for the increased penetrance of bone lesions with age in this model. Lesions are prevented by ZA, providing a rationale for early intervention in humans.