The course of cytokine and chemokine gene expression in clinically suspect arthralgia patients during progression to inflammatory arthritis.

OBJECTIVES: Autoantibody responses increase years before the onset of inflammatory arthritis (IA) and are stable during transitioning from clinically suspect arthralgia (CSA) to IA. Cytokine and chemokine levels also increase years before IA onset. However, the course in the at-risk stage of CSA during progression to disease or non-progression is unknown. To increase the understanding of processes mediating disease development, we studied the course of cytokine, chemokine and related receptors gene expression in CSA patients during progression to IA and in CSA patients who ultimately did not develop IA. METHODS: Whole-blood RNA expression of 37 inflammatory cytokines, chemokines and related receptors was determined by dual-colour reverse transcription multiplex ligation-dependent probe amplification in paired samples of CSA patients at CSA onset and either at IA development or after 24 months without IA development. ACPA-positive and ACPA-negative CSA patients developing IA were compared at CSA onset and during progression to IA. Generalised estimating equations tested changes over time. A false discovery rate approach was applied. RESULTS: None of the cytokine/chemokine genes significantly changed in expression between CSA onset and IA development. In CSA patients without IA development, G-CSF expression decreased (P = 0.001), whereas CCR6 and TNIP1 expression increased (P < 0.001 and P = 0.002, respectively) over a 2 year period. Expression levels in ACPA-positive and ACPA-negative CSA patients who developed IA were similar. CONCLUSION: Whole-blood gene expression of assessed cytokines, chemokines and related receptors did not change significantly from CSA to IA development. This suggests that changes in expression of these molecules may not be related to the final process of developing chronicity and may have occurred preceding CSA onset. Changes in gene expression in CSA patients without IA development may provide clues for processes related to resolution.

Exertional leg pain represents a severe disease phenotype in childhood familial Mediterranean fever.

OBJECTIVES: Familial Mediterranean fever (FMF) is the most common monogenic autoinflammatory disease. Recurrent fever, serositis, and arthritis are common findings of the disease. In addition, musculoskeletal complaints such as exertional leg pain can be overlooked, although they are common and affect patients' quality of life. The aim of this study was to evaluate the frequency of exertional leg pain in pediatric FMF patients and to analyze the association of this finding with other characteristics of FMF. METHODS: The files of FMF patients were retrospectively evaluated. The clinical characteristics and disease severity of the patients with exertional leg pain were compared with the patients without exertional leg pain. International severity scoring system for FMF (ISSF) and Mor severity score were used for assessment. RESULTS: The study included 541 FMF patients (287 females), 149 (27.5%) with exertional leg pain. The median colchicine dosage was significantly higher in patients with exertional leg pain (p = 0.02), arthritis (p = 0.001) and arthralgia (p˂0.001) were encountered more frequently in the attacks of these patients. The median disease severity scores calculated by both Mor severity scale and ISSF were significantly higher in patients with exertional leg pain compared to those without (p˂0.001). In the group of patients with exertional leg pain, the M694V mutation, either in one allele or in two alleles, was found to be significantly more common (p = 0.006 and p˂0.001, respectively). CONCLUSIONS: Exertional leg pain in pediatric FMF patients is the component of moderate-to-severe disease course, and this may be considerably associated with the presence of M694V mutation.

The Role of Genetics in Clinically Suspect Arthralgia and Rheumatoid Arthritis Development: A Large Cross-Sectional Study.

OBJECTIVE: To investigate whether established genetic predictors for rheumatoid arthritis (RA) differentiate healthy controls, patients with clinically suspect arthralgia (CSA), and RA patients. METHODS: Using analyses of variance, chi-square tests, and mean risk difference analyses, we investigated the association of an RA polygenic risk score (PRS) and HLA shared epitope (HLA-SE) with all participant groups, both unstratified and stratified for anti-citrullinated protein antibody (ACPA) status. We used 3 separate data sets sampled from the same Dutch population (1,015 healthy controls, 479 CSA patients, and 1,146 early classified RA patients). CSA patients were assessed for conversion to inflammatory arthritis over a period of 2 years, after which they were classified as either CSA converters (n = 84) or CSA nonconverters (n = 395). RESULTS: The PRS was increased in RA patients (mean ± SD PRS 1.31 ± 0.96) compared to the complete CSA group (1.07 ± 0.94) and compared to CSA converters (1.12 ± 0.94). In ACPA- strata, PRS distributions differed strongly when comparing the complete CSA group (mean ± SD PRS 1.05 ± 0.94) and CSA converters (0.97 ± 0.87) to RA patients (1.20 ± 0.94), while in the ACPA+ strata, the complete CSA group (1.25 ± 0.99) differed clearly from healthy controls (1.05 ± 0.94) and RA patients (1.41 ± 0.96). HLA-SE was more prevalent in the RA group (prevalence 0.64) than the complete CSA group (0.45), with small differences between RA patients and CSA converters (0.64 versus 0.60) and larger differences between CSA converters and CSA nonconverters (0.60 versus 0.42). HLA-SE prevalence differed more strongly within the ACPA+ strata as follows: healthy controls (prevalence 0.43), CSA nonconverters (0.48), complete CSA group (0.59), CSA converters (0.66), and RA patients (0.79). CONCLUSION: We observed that genetic predisposition increased across pre-RA participant groups. The RA PRS differed in early classified RA and inflammatory pre-disease stages, regardless of ACPA stratification. HLA-SE prevalence differed between arthritis patients, particularly ACPA+ patients, and healthy controls. Genetics seem to fulfill different etiologic roles.

Central Role of Semaphorin 3B in a Serum-Induced Arthritis Model and Reduced Levels in Patients With Rheumatoid Arthritis.

OBJECTIVE: Semaphorin 3B (Sema3B) decreases the migratory and invasive capacities of fibroblast-like synoviocytes (FLS) in rheumatoid arthritis (RA) and suppresses expression of matrix metalloproteinases. We undertook this study to examine the role of Sema3B in a mouse model of arthritis and its expression in RA patients. METHODS: Clinical responses, histologic features, and FLS function were examined in wild-type (WT) and Sema3B-/- mice in a K/BxN serum transfer model of arthritis. Protein and messenger RNA expression of Sema3B in mouse joints and murine FLS, as well as in serum and synovial tissue from patients with arthralgia and patients with RA, was determined using enzyme-linked immunosorbent assay, immunoblotting, quantitative polymerase chain reaction, and RNA sequencing. FLS migration was determined using a wound closure assay. RESULTS: The clinical severity of serum-induced arthritis was significantly higher in Sema3B-/- mice compared to WT mice. This was associated with increased expression of inflammatory mediators and increased migratory capacity of murine FLS. Administration of recombinant mouse Sema3B reduced the clinical severity of serum-induced arthritis and the expression of inflammatory mediators. Sema3B expression was significantly lower in the synovial tissue and serum of patients with established RA compared to patients with arthralgia. Serum Sema3B levels were elevated in patients with arthralgia that later progressed to RA, but not in those who did not develop RA; however, these levels drastically decreased 1 and 2 years after RA development. CONCLUSION: Sema3B expression plays a protective role in a mouse model of arthritis. In RA patients, expression levels of Sema3B in the serum depend on the disease stage, suggesting different regulatory roles in disease onset and progression.

Single-cell analysis of arthritogenic alphavirus-infected human synovial fibroblasts links low abundance of viral RNA to induction of innate immunity and arthralgia-associated gene expression.

Infection by (re-)emerging RNA arboviruses including Chikungunya virus (CHIKV) and Mayaro virus primarily cause acute febrile disease and transient polyarthralgia. However, in a significant subset of infected individuals, debilitating arthralgia persists for weeks over months up to years. The underlying immunopathogenesis of chronification of arthralgia upon primary RNA-viral infection remains unclear. Here, we analysed cell-intrinsic responses to ex vivo arthritogenic alphaviral infection of primary human synovial fibroblasts isolated from knee joints, one the most affected joint types during acute and chronic CHIKV disease. Synovial fibroblasts were susceptible and permissive to alphaviral infection. Base-line and exogenously added type I interferon (IFN) partially and potently restricted infection, respectively. RNA-seq revealed a CHIKV infection-induced transcriptional profile that comprised upregulation of expression of several hundred IFN-stimulated and arthralgia-mediating genes. Single-cell virus-inclusive RNA-seq uncovered a fine-tuned switch from induction to repression of cell-intrinsic immune responses depending on the abundance of viral RNA in an individual cell. Specifically, responses were most pronounced in cells displaying low-to-intermediate amounts of viral RNA and absence of virus-encoded, fluorescent reporter protein expression, arguing for efficient counteraction of innate immunity in cells expressing viral antagonists at sufficient quantities. In summary, cell-intrinsic sensing of viral RNA that potentially persists or replicates at low levels in synovial fibroblasts and other target cell types in vivo may contribute to the chronic arthralgia induced by alphaviral infections. Our findings might advance our understanding of the immunopathophysiology of long-term pathogenesis of RNA-viral infections.

The Role of the Trabecular Bone Score in the Assessment of Osteoarticular Disorders in Patients with HFE-Hemochromatosis: A Single-Center Study from Poland.

Type 1 hereditary hemochromatosis (HH) is an autosomal, recessive genetic entity with systemic iron overload. Iron homeostasis disorders develop as a result of HFE gene mutations, which are associated with hepcidin arthropathy or osteoporosis and may cause permanent disability in HH patients despite a properly conducted treatment with phlebotomies. In this study, selected parameters of calcium and phosphate metabolism were analyzed in combination with the assessment of bone mineral density (BMD) disorders in patients from northern Poland with clinically overt HFE-HH. BMD was determined by a dual-energy X-ray absorptiometry (DXA) test with the use of the trabecular bone score (TBS) function. The study included 29 HH patients (mean age = 53.14 years) who were compared with 20 healthy volunteers. A significantly lower TBS parameter and serum 25-OH-D3 concentration, a higher concentration of intact parathormone and more a frequent occurrence of joint pain were found in HH patients compared with the control group. In HH patients, the diagnosis of liver cirrhosis was associated with lower serum 25-OH-D3 and osteocalcin concentrations. In HH, DXA with the TBS option is a valuable tool in the early assessment of the bone microarchitecture and fracture risk. A supplementation of vitamin D, monitoring its concentration, should be considered especially in HH patients with liver damage and liver cirrhosis.

NF-κB inducible miR-30b-5p aggravates joint pain and loss of articular cartilage via targeting SIRT1-FoxO3a-mediated NLRP3 inflammasome.

MicroRNAs (miRNAs) contribute to osteoarthritis (OA) development. Nevertheless, the function and mechanism of miR-30b-5p in OA are unclear. In the present article, we gauged the miR-30b-5p level in OA patients and analyzed its correlation with OA stages. Then, we conducted in-vivo and in-vitro gain-of-function assays to determine the function of miR-30b-5p, silent information regulator 2 homolog 1 (SIRT1) and Fox. Cell counting Kit-8 (CCK-8) assay, BrdU assay and flow cytometry were utilized to gauge cell viability and apoptosis of human chondrocyte (HC-A). The targeting association between miR-30b-5p and SIRT1 was validated through the dual-luciferase reporter assay and RNA immunoprecipitation (RIP) experiment. The results signified that miR-30b-5p was up-regulated in OA patients, OA rats and interleukin-1ß (IL-1ß)-induced chondrocytes. The higher miR-30b-5p expression brought about progressive stages of OA patients and enhanced levels of pro-inflammatory mediators in the synovial fluid. Functionally, overexpressing miR-30b-5p hampered cell viability, aggravated chondrocyte apoptosis and NLRP3 inflammasome activation induced by IL-1ß, while down-regulating miR-30b-5p exerted the reverse effects. The in-vivo experiment exhibited that down-regulating miR-30b-5p improved joint pain and loss of articular cartilage in the rats with restrained inflammation and NLRP3 inflammasome activation. Mechanistically, miR-30b-5p targeted the 3'-non-translated region (3'UTR) of SIRT1, and miR-30b-5p was inducible with NF-κB phosphorylation enhancement. Overexpressing SIRT1 or inhibiting NF-κB relieved miR-30b-5p-induced apoptosis and NLRP3 inflammasome activation by promoting FoxO3a, while down-regulating SIRT1 or FoxO3a reversed miR-30b-5p-in-induced anti-inflammatory and apoptosis-suppressive effects. Collectively, NF-κB-induced miR-30b-5p modulates chondrocyte apoptosis and OA progression by regulating the SIRT1-FoxO3a-mediated NLRP3 inflammasome.

A Novel Mutation in the NBD Domain of NLRC4 Causes Mild Autoinflammation With Recurrent Urticaria.

Background: NOD-like receptor family CARD-containing 4 protein (NLRC4) is a cytosolic protein that forms an inflammasome in response to flagellin and type 3 secretion system (T3SS) proteins from invading Gram-negative bacteria. NLRC4 mutations have been recently identified in early-onset severe autoinflammatory disorders. In this study, we reported a novel mutation in NLRC4 in two Chinese patients, who manifested with recurrent urticaria and arthralgia. Methods: We summarized the clinical data of the two patients. Gene mutations were identified by whole-exome sequencing (WES). Swiss-PdbViewer was used to predict the pathogenicity of the identified mutations. Cytokine levels and caspase-1 activation were detected in the patient PBMCs with lipopolysaccharide (LPS) stimulation. All previously published cases with NLRC4 mutations were reviewed. Results: We identified a missense heterozygous mutation (c.514G>A, p.Gly172Ser), which was located in the highly conserved residue of nucleotide-binding domain (NBD) of NLRC4. The mutation did not alter the expression of NLRC4 protein, but induced considerably much higher production of IL-1ß and IL-6 in patient PBMCs than in healthy controls after LPS stimulation. Four NLRC4 inflammasomopathy phenotypes have been described, with severe inflammatory diseases including macrophage activation syndrome, enterocolitis and NOMID in patients with mutations in the NBD and HD1 domains, whereas a mild clinical phenotype was associated with two mutations in the WHD domain of NLRC4. Conclusion: We identified a novel mutation in the NBD domain, and the patients just presented with a mild inflammatory phenotype. Thus, our findings reinforce the diversity of NLRC4 mutations and expand the clinical spectrum of associated diseases.

Novel Insights Into Rheumatoid Arthritis Through Characterization of Concordant Changes in DNA Methylation and Gene Expression in Synovial Biopsies of Patients With Differing Numbers of Swollen Joints.

In this study, we sought to characterize synovial tissue obtained from individuals with arthralgia and disease-specific auto-antibodies and patients with established rheumatoid arthritis (RA), by applying an integrative multi-omics approach where we investigated differences at the level of DNA methylation and gene expression in relation to disease pathogenesis. We performed concurrent whole-genome bisulphite sequencing and RNA-Sequencing on synovial tissue obtained from the knee and ankle from 4 auto-antibody positive arthralgia patients and thirteen RA patients. Through multi-omics factor analysis we observed that the latent factor explaining the variance in gene expression and DNA methylation was associated with Swollen Joint Count 66 (SJC66), with patients with SJC66 of 9 or more displaying separation from the rest. Interrogating these observed differences revealed activation of the immune response as well as dysregulation of cell adhesion pathways at the level of both DNA methylation and gene expression. We observed differences for 59 genes in particular at the level of both transcript expression and DNA methylation. Our results highlight the utility of genome-wide multi-omics profiling of synovial samples for improved understanding of changes associated with disease spread in arthralgia and RA patients, and point to novel candidate targets for the treatment of the disease.

Association of single nucleotide polymorphisms of cytochrome P450 enzymes with experience of vasomotor, vaginal and musculoskeletal symptoms among breast cancer patients: a systematic review.

BACKGROUND: Adjuvant endocrine therapies are known to induce undesirable adverse effects such as vasomotor, vaginal and musculoskeletal symptoms among breast cancer patients. Drugs used in these therapies are often metabolised by cytochrome P450 (CYP) enzymes, in which their metabolising activities can be modified by single nucleotide polymorphisms (SNP) in CYP genes and CYP genotypes. This review aims to explore whether SNPs or genotypes of CYP are associated with the occurrence, frequency and severity of vasomotor, vaginal and musculoskeletal symptoms in breast cancer patients on adjuvant endocrine therapies. METHODS: A literature review was conducted using five electronic databases, resulting in the inclusion of 14 eligible studies, and their findings were presented narratively. Selected items from the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) checklist were used for critical appraisal of the reporting quality of the included studies. RESULTS: Most of the included studies showed that SNPs or genotypes of CYP that modify its metabolising activity have no effect on the occurrence, frequency or severity of vasomotor symptoms, including hot flashes. One study showed no correlation of these genetic variations in CYP with musculoskeletal symptoms, and no data were available on the association between such genetic variations and vaginal symptoms. CONCLUSIONS: Overall, genetic variations in CYP have no effect on the experience of hot flashes among breast cancer patients. We recommend exploration of the link between the active metabolites of chemotherapeutic drugs and the molecules shown to affect the occurrence or severity of hot flashes, and the establishment of the relationship between such genetic variations and patients' experience of musculoskeletal and vaginal symptoms. Subgroup analyses based on patients' duration of adjuvant endocrine therapies in such studies are recommended.

Expression of Piezo mRNA is unaffected in a rat model of knee osteoarthritis.

Osteoarthritis of the knee impairs activities of daily living of those affected. Its irreversible degenerative changes to the knee joint induce functional disturbance and unpleasant arthralgia. The pain has inflammatory components and often is manifested with mechanical allodynia and hyperalgesia. Sustained weight bearing and joint movements increase pain sensitivity in knee osteoarthritis. Understanding the mechanisms underlying the mechanical allodynia and hyperalgesia might provide a therapeutical target for pain relief in patients with such symptoms. Piezo channel is a mechanically activated ion channel that may be involved in mechanical transduction in the articular cartilage. Although it has been shown that inflammation potentiates Piezo channel current induced by mechanical stimulation, whether Piezo expression levels are influenced by knee osteoarthritis has remained unknown. We measured Piezo mRNA in knee joints and dorsal root ganglia after establishing a model of knee osteoarthritis in rats using monosodium iodoacetate and found Piezo mRNA level is not upregulated. This finding raises a question as whether and how Piezo channels may be involved in mechanically induced pain in osteoarthritis.

Regulation of Toll-like receptor-mediated inflammatory response by microRNA-152-3p-mediated demethylation of MyD88 in systemic lupus erythematosus.

OBJECTIVE: microRNAs (miRNAs) play critical roles in embryogenesis, cell differentiation and the pathogenesis of several human diseases, including systemic lupus erythematosus (SLE). Toll-like receptors (TLRs) are also known to exert crucial functions in the immune response activation occurring in the pathogenesis of autoimmune diseases like SLE. Herein, the current study aimed to explore the potential role of miR-152-3p in TLR-mediated inflammatory response in SLE. METHODS: We determined the miR-152-3p expression profiles in CD4+ T cells and peripheral blood mononuclear cells (PBMCs) harvested from patients with SLE and healthy controls, and analyzed the correlation between miR-152-3p expression and clinicopathological parameters. CD70 and CD40L expression patterns in CD4+ T cells were assessed by RT-qPCR and flow cytometry. ChIP was adopted to determine the enrichment of DNA methyltransferase 1 (DNMT1) in the promoter region of myeloid differentiation factor 88 (MyD88). RESULTS: The obtained findings revealed that miR-152-3p was highly-expressed in CD4+ T cells and PBMCs of patients with SLE, and this high expression was associated with facial erythema, joint pain, double-stranded DNA, and IgG antibody. DNMT1 could be enriched in the MyD88 promoter, and miR-152-3p inhibited the methylation of MyD88 by targeting DNMT1. We also found that silencing miR-152-3p inhibited MyD88 expression not only to repress the autoreactivity of CD4+ T cells and but also to restrain their cellular inflammation, which were also validated in vivo. CONCLUSION: Our study suggests that miR-152-3p promotes TLR-mediated inflammatory response in CD4+ T cells by regulating the DNMT1/MyD88 signaling pathway, which highlights novel anti-inflammatory target for SLE treatment.

Fatty acid sensing GPCR (GPR84) signaling safeguards cartilage homeostasis and protects against osteoarthritis.

It is well known that free fatty acids (FFAs) have beneficial effects on the skeletal system, however, which fatty acid sensing GPCR(s) and how the GPCR(s) regulating cartilage development and osteoarthritis (OA) pathogenesis is largely unknown. In this study, we found Gpr84, a receptor for medium-chain FFAs (MCFA), was the only FFA-sensing GPCR in human and mouse chondrocytes that exhibited elevated expression when stimulated by interleukin (IL)-1ß. Gpr84-deficiency upregulated cartilage catabolic regulator expression and downregulated anabolic factor expression in the IL-1ß-induced cell model and the destabilization of the medial meniscus (DMM)-induced OA mouse model. Gpr84-/- mice exhibited an aggravated OA phenotype characterized by severe cartilage degradation, osteophyte formation and subchondral bone sclerosis. Moreover, activating Gpr84 directly enhanced cartilage extracellular matrix (ECM) generation while knockout of Gpr84 suppressed ECM-related gene expression. Especially, the agonists of GPR84 protected human OA cartilage explants against degeneration by inducing cartilage anabolic factor expression. At the molecular level, GPR84 activation inhibited IL-1ß-induced NF-κB signaling pathway. Furthermore, deletion of Gpr84 had little effect on articular and spine cartilaginous tissues during skeletal growth. Together, all of our results demonstrated that fatty acid sensing GPCR (Gpr84) signaling played a critical role in OA pathogenesis, and activation of GPR84 or MCFA supplementation has potential in preventing the pathogenesis and progression of OA without severe cartilaginous side effect.

Primary hypertrophic osteoarthropathy with severe arthralgia identified by gene mutation of SLCO2A1.

Male, 41 years old (yo) had been complaining of severe arthralgia. Past History indicated obstruction of intestinal tract at 12 yo and gastric ulcer at 13 yo. He had been suffered from polyarthralgia especially at PIP and MP joints of both hands from 38 yo. Finally, he complained severe arthralgia at PIP and MP joints with clubbed fingers without swelling. Biochemical finding indicated negative rheumatoid factor and anti-CCP antibody and normal MMP-3 level, but slightly increased CRP and ESR levels. Radiological finding indicated periostosis of　long bone without bone erosion and osteoporosis. His facial appearance was acromegalic with cutaneous manifestation of pachydermia and cutis vertices gyrate without abnormal growth hormone response. Histological findings of skin indicated oedema and hyperplasia of sebaceous glands with infiltration of lymphocytes around small blood vessels compatible with pachydermoperiostosis. In this case mutation of SLCO2A1 gene, which coded prostaglandin transport protein, was identified. The mutation c.940 + 1G > A of SLCO2A1 gene results in deletion of exon 7 and truncation of PG transporter (p.Arg288Glyfs*7). We suggest that severe arthralgia was originated from over production of prostaglandin E2. Further studies will be required.

Gene expression identifies patients who develop inflammatory arthritis in a clinically suspect arthralgia cohort.

BACKGROUND: Established rheumatoid arthritis (RA) patients display differentially expressed genes coding for cytokine/chemokine-mediated immunity compared to healthy controls. It is unclear, however, if in the pre-arthritis phase of clinically suspect arthralgia (CSA) expression of immune genes differ between patients who do or do not develop clinically evident inflammatory arthritis (IA). METHODS: Two hundred thirty-six consecutive patients presenting with arthralgia clinically suspected for progression to RA were followed until IA development or else for median 24 months (IQR 12-26). Baseline whole blood RNA expression was determined for a previously identified set of 133 genes associated with the innate and adaptive immune system by dual-color reverse-transcription multiplex ligation-dependent probe amplification (dcRT-MLPA) profiling. Cox proportional hazard models were used. RESULTS: Twenty percent of CSA patients developed IA. After correction for multiple testing, expression levels of six genes (IFNG, PHEX, IGF-1, IL-7R, CD19, CCR7) at the time of presentation were associated with progression to IA. PHEX and IGF-1 were highly correlated with each other (ρ = 0.97). In multivariable analysis correcting for the different genes, expressions of IL-7R and IGF-1 were independently associated with IA development (p = 0.025, p = 0.046, respectively). Moreover, IL-7R and IGF-1 remained significantly associated even after correction for known predictors (ACPA, CRP, imaging-detected subclinical joint inflammation; p = 0.039, p = 0.005, respectively). These genes are also associated with RA development. CONCLUSIONS: IL-7R and IGF-1 were differentially expressed between CSA patients who did or did not progress to IA, independent from regularly used predictors. These biomarkers may become helpful in prognostication of CSA patients. Furthermore, because both genes are associated with T cell functioning, T cell dysregulation may mediate progression from arthralgia to arthritis.

The neurohypophysial oxytocin and arginine vasopressin system is activated in a knee osteoarthritis rat model.

Osteoarthritis (OA) causes chronic joint pain and significantly impacts daily activities. Hence, developing novel treatment options for OA has become an increasingly important area of research. Recently, studies have reported that exogenous, as well as endogenous, hypothalamic-neurohypophysial hormones, oxytocin (OXT) and arginine-vasopressin (AVP), significantly contribute to nociception modulation. Moreover, the parvocellular OXT neurone (parvOXT) extends its projection to the superficial spinal dorsal horn, where it controls the transmission of nociceptive signals. Meanwhile, AVP produced in the magnocellular AVP neurone (magnAVP) is released into the systemic circulation where it contributes to pain management at peripheral sites. The parvocellular AVP neurone (parvAVP), as well as corticotrophin-releasing hormone (CRH), suppresses inflammation via activation of the hypothalamic-pituitary adrenal (HPA) axis. Previously, we confirmed that the OXT/AVP system is activated in rat models of pain. However, the roles of endogenous hypothalamic-neurohypophysial hormones in OA have not yet been characterised. In the present study, we investigated whether the OXT/AVP system is activated in a knee OA rat model. Our results show that putative parvOXT is activated and the amount of OXT-monomeric red fluorescent protein 1 positive granules in the ipsilateral superficial spinal dorsal horn increases in the knee OA rat. Furthermore, both magnAVP and parvAVP are activated, concurrent with HPA axis activation, predominantly modulated by AVP, and not CRH. The OXT/AVP system in OA rats was similar to that in systemic inflammation models, including adjuvant arthritis; however, magnocellular OXT neurones (magnOXT) were not activated in OA. Hence, localised chronic pain conditions, such as knee OA, activate the OXT/AVP system without impacting magnOXT.

Genetic and clinical predictors of arthralgia during letrozole or anastrozole therapy in breast cancer patients.

PURPOSE: Female patients with breast cancer frequently develop arthralgia when treated with aromatase inhibitors (AI). Although the mechanism of AI-induced arthralgia is unknown, potential biomarkers have been identified. The purpose of this study was to investigate the clinical and genetic predictors of AI-induced arthralgia in a prospective cohort of patients with estrogen receptor-positive breast cancer. METHODS: One hundred and ninety-six patients were enrolled at initiation of AI therapy with either letrozole or anastrozole. Patients completed two validated self-report questionnaires assessing pain, stiffness, and physical function at baseline, and repeated the questionnaires at two and at six months after the initiation of treatment with an AI. Germline DNA of all patients was genotyped for seven single-nucleotide polymorphisms (SNPs) previously identified by genetic screens and genome-wide association studies as associated with AI-induced arthralgia. RESULTS: More than 50% of the study group experienced arthralgia symptoms. Genetic analysis revealed that four SNPs, in CYP19A1 (rs4775936) and ESR1 (rs9322336, rs2234693, rs9340799), were associated with the development of arthralgia (adjusted P = 0.016, 0.018, 0.017, 0.047). High body mass index (BMI) was also associated with the development of arthralgia symptoms (adjusted P = 0.001). Patients prescribed letrozole were significantly more likely to develop arthralgia than patients on anastrozole (P = 0.018), and also more likely to discontinue AI therapy due to arthralgia. The CYP19A1 (rs4775936) SNP was significantly associated with discontinuation of therapy due to intolerable arthralgia. CONCLUSIONS: Our results suggested that BMI and AI drug (letrozole versus anastrozole) were clinical predictors of arthralgia, while genetic variants rs4775936, rs9322336, rs2234693, and rs9340799 were genetic predictors of AI-induced arthralgia. Significantly, rs4775936 was also a predictor of discontinuation of therapy.

High bone mass from mutation of low-density lipoprotein receptor-related protein 6 (LRP6).

Wnt/ß-catenin signaling is important for skeletal development and health. Eleven heterozygous gain-of-function missense mutations within the first ß-propeller of low-density lipoprotein receptor-related protein 5 (LRP5) are known to cause the autosomal dominant disorder called high bone mass (HBM). In 2019, different heterozygous LRP6 missense mutations were identified in two American families with the HBM phenotype but including absent lateral maxillary and mandibular incisors. We report a 19-year-old Argentinian man referred for "osteopetrosis" and nine years of generalized, medium-intensity bone pain and arthralgias of both knees. His jaw and nasal bridge were broad and several teeth were missing. Routine biochemical testing, including of mineral homeostasis, was normal. Urinary deoxypyridinoline and serum CTX were slightly increased. Radiographic skeletal survey showed diffusely increased radiodensity. DXA revealed substantially elevated BMD Z-scores. Digital orthopantomography confirmed agenesis of his maxillary and mandibular lateral incisors and his second left superior premolar. Cranial magnetic resonance imaging showed diffuse thickening of the calvarium and skull base, dilation of the sheath of the optic nerves containing increased fluid and associated with subtle stenosis of the optic canal, and narrow internal auditory canals. Mutation analyses identified a heterozygous indel mutation in exon 4 of LRP6 involving a single nucleotide change and 6-nucleotide deletion (c.678T>Adel679-684, p.His226Gln-del227-228ProPhe) leading to a missense change and 2-amino acid deletion that would compromise the first ß-propeller of LRP6. Experience to date indicates LRP6 HBM is indistinguishable from LRP5 HBM without mutation analysis, although in LRP6 HBM absence of adult lateral incisors may prove to be a unique feature.

Analysis of genetically independent phenotypes identifies shared genetic factors associated with chronic musculoskeletal pain conditions.

Chronic musculoskeletal pain affects all aspects of human life. However, mechanisms of its genetic control remain poorly understood. Genetic studies of pain are complicated by the high complexity and heterogeneity of pain phenotypes. Here, we apply principal component analysis to reduce phenotype heterogeneity of chronic musculoskeletal pain at four locations: the back, neck/shoulder, hip, and knee. Using matrices of genetic covariances, we constructed four genetically independent phenotypes (GIPs) with the leading GIP (GIP1) explaining 78.4% of the genetic variance of the analyzed conditions, and GIP2-4 explain progressively less. We identified and replicated five GIP1-associated loci and one GIP2-associated locus and prioritized the most likely causal genes. For GIP1, we showed enrichment with multiple nervous system-related terms and genetic correlations with anthropometric, sociodemographic, psychiatric/personality traits and osteoarthritis. We suggest that GIP1 represents a biopsychological component of chronic musculoskeletal pain, related to physiological and psychological aspects and reflecting pain perception and processing.