Confirmation of two major polyarticular osteoarthritis (POA) phenotypes--differentiation on the basis of joint topography

Iron overload promotes hemochromatosis-associated osteoarthritis via the mTORC1-p70S6K/4E-BP1 pathway

BACKGROUNDS

Joint iron overload in hemochromatosis induces M1 polarization in synovial macrophages, releasing pro-inflammatory factors and leading to osteoarthritis development. However, the mechanism by which iron overload regulates M1 polarization remains unclear. This study aims to elucidate the mechanism by which synovial iron overload promotes macrophage M1 polarization.

METHODS

In vitro, RAW264.7 macrophages were treated with iron and divided into five groups based on the concentration of the iron chelator, desferrioxamine (DFO): Ctrl, Fe, DFO1, DFO2, and DFO3. In vivo, rats were categorized into five groups based on iron overload and intra-articular DFO injection: A-Ctrl, A-Fe, A-DFO1, A-DFO2, and A-DFO3. Osteoarthritis was induced by transecting the left knee anterior cruciate ligament. Macrophage morphology was observed; Prussian Blue staining quantified iron deposition in macrophages, synovium, and liver; serum iron concentration was measured using the ferrozine method; cartilage damage was assessed using H&E and Safranin O-Fast Green staining; qPCR detected iNOS and Arg-1 expression; Western Blot analyzed the protein expression of iNOS, Arg-1, 4E-BP1, phosphorylated 4E-BP1, p70S6K, and phosphorylated p70S6K; ELISA measured TNF-α and IL-6 concentrations in supernatants; and immunohistochemistry examined the protein expression of F4/80, iNOS, Arg-1, 4E-BP1, phosphorylated 4E-BP1, p70S6K, and phosphorylated p70S6K in the synovium.

RESULTS

In vitro, iron-treated macrophages exhibited Prussian Blue staining indicative of iron overload and morphological changes towards M1 polarization. qPCR and Western Blot revealed increased expression of the M1 polarization markers iNOS and its protein. ELISA showed elevated TNF-α and IL-6 levels in supernatants. In vivo, ferrozine assay indicated significantly increased serum iron concentrations in all groups except A-Ctrl; Prussian Blue staining showed increased liver iron deposition in all groups except A-Ctrl. Iron deposition in rat synovium decreased in a DFO concentration-dependent manner; immunohistochemistry showed a corresponding decrease in iNOS and phosphorylated 4E-BP1 expression, and an increase in Arg-1 expression.

CONCLUSION

Intracellular iron overload may exacerbate joint cartilage damage by promoting synovial macrophage M1 polarization through phosphorylation of 4E-BP1 in the mTORC1-p70S6K/4E-BP1 pathway.

Musculoskeletal complications associated with pathological iron toxicity and its molecular mechanisms

Iron is fundamental for several biological functions, but when in excess can lead to the development of toxic events. Some tissues and cells are more susceptible than others, but systemic iron levels can be controlled by treating patients with iron-chelating molecules and phlebotomy. An early diagnostic can be decisive to limit the progression of musculoskeletal complications like osteoarthritis and osteoporosis because of iron toxicity. In iron-related osteoarthritis, aggravation can be associated to a few events that can contribute to joints articular cartilage exposure to high iron concentrations, which can promote articular degeneration with very little chance of tissue regeneration. In contrast, bone metabolism is much more dynamic than cartilage, but progressive iron accumulation and ageing can be decisive factors for bone health. The iron overload associated with hereditary diseases like hemochromatosis, hemophilias, thalassemias and other hereditary anaemias increase the negative impact of iron toxicity in joints and bone, as well as in life quality, even when iron levels can be controlled. The molecular mechanisms by which iron can compromise cartilage and bone have been illusive and only in the last 20 years studies have started to shed some light into the molecular mechanisms associated with iron toxicity. Ferroptosis and the regulation of intracellular iron levels is instrumental in the balance between detoxification and induced cell death. In addition, these complications are accompanied with multiple susceptibility factors that can aggravate iron toxicity and should be identified. Therefore, understanding tissues microenvironment and cell communication is fundamental to contextualize iron toxicity.

Intracellular iron uptake is favored in Hfe-KO mouse primary chondrocytes mimicking an osteoarthritis-related phenotype

HFE-hemochromatosis is a disease characterized by a systemic iron overload phenotype mainly associated with mutations in the HFE protein (HFE) gene. Osteoarthritis (OA) has been reported as one of the most prevalent complications in HFE-hemochromatosis patients, but the mechanisms associated with its onset and progression remain incompletely understood. In this study, we have characterized the response to high iron concentrations of a primary culture of articular chondrocytes isolated from newborn Hfe-KO mice and compared the results with that of a similar experiment developed in cells from C57BL/6 wild-type (wt) mice. Our data provide evidence that both wt- and Hfe-KO-derived chondrocytes, when exposed to 50 μM iron, develop characteristics of an OA-related phenotype, such as an increased expression of metalloproteases, a decreased extracellular matrix production, and a lower expression level of aggrecan. In addition, Hfe-KO cells also showed an increased expression of iron metabolism markers and MMP3, indicating an increased susceptibility to intracellular iron accumulation and higher levels of chondrocyte catabolism. Accordingly, upon treatment with 50 μM iron, these chondrocytes were found to preferentially differentiate toward hypertrophy with increased expression of collagen I and transferrin and downregulation of SRY (sex-determining region Y)-box containing gene 9 (Sox9). In conclusion, high iron exposure can compromise chondrocyte metabolism, which, when simultaneously affected by an Hfe loss of function, appears to be more susceptible to the establishment of an OA-related phenotype.

Defining multiple joint osteoarthritis, its frequency and impact in a community-based cohort

BACKGROUND/PURPOSE

To update definitions of multiple joint osteoarthritis (MJOA), and to determine the frequency and impact of MJOA in a community-based cohort.

METHODS

Following PRISMA guidelines and with the help of a professional research librarian, we performed a systematic review in Medline using the terms osteoarthritis, generalized, polyarticular, multiple joint, and multi-joint among others, to obtain articles related to MJOA. A total of 42 articles were included for data extraction based on multiple criteria including the requirement for a clearly stated definition of OA assessed at more than one body site. We assessed frequency of these definitions in the Johnston County OA Project (JoCo OA) cohort as well as outcomes related to general health and physical function.

RESULTS

A total of 6 clearly stated definitions for MJOA were identified. These definitions were integrated with a list of 24 definitions from our previous systematic review and distilled down to produce 10 literature-derived, operationalized MJOA definitions. Based on these definitions, high frequencies of radiographic (4-74%) and symptomatic (2-52%) MJOA were found in the JoCo OA. Significant detrimental effects were seen on general health and physical function for most definitions.

CONCLUSIONS

We constructed a list of 10 summary MJOA definitions based in the literature that are frequent and associated with important clinical outcomes. These definitions capture some of the variability of MJOA phenotypes and provide a starting point for future analyses of both existing and newly initiated studies.

Do foot & ankle assessments assist the explanation of 1 year knee arthroplasty outcomes?

OBJECTIVE

Whilst a number of risk factors for poor patient reported outcome measures (PROMs) following knee arthroplasty (KA) have been identified, unexplained variability still remains. The role of pre-operative foot and ankle status on such outcomes has not been investigated. The aim of this study was therefore to determine the association of clinical foot and ankle assessments with patient reported outcomes 1 year following KA.

DESIGN

One hundred and fifteen participants from the Clinical Outcomes in Arthroplasty Study (COASt), underwent detailed foot and ankle assessments at baseline, prior to KA (2012-2014) and were followed up for self-reported outcomes 1 year after surgery.

RESULTS

Thirty nine percent of subjects reported foot pain at baseline. Mean pre-operative Oxford Knee Score (OKS; 0 [worst] to 48 [best outcome]) was 21 and post-operative OKS score was 38. In fully adjusted analysis pre-operative foot pain was significantly associated with 1 year outcome (risk ratio [RR] 0.78 95% confidence interval [95% CI] 0.62, 0.98). No significant association was observed between ankle dorsiflexion or foot posture and outcome.

CONCLUSIONS

Patients with pre-operative foot pain are more likely to have poorer clinically important outcomes 1 year following KA than patients without foot pain. Static ankle dorsiflexion and foot posture do not further explain post-operative KA outcomes. Consideration should also be given to address pre-operative foot pain when attempting to achieve a good clinical outcome for KA.

"Generalized osteoarthritis": a systematic review

OBJECTIVES

Given the conflicting definitions of "generalized osteoarthritis" (GOA) in the literature, we performed a systematic review of GOA definitions, risk factors, and outcomes.

METHODS

We searched the MEDLINE literature with the terms osteoarthritis, generalized, polyarticular, multiple joint, and multi-joint to obtain articles related to GOA, following evidence-based guidelines. Titles and abstracts of 948 articles were reviewed, with full-text review of 108. Data were extracted based on pre-specified criteria for 74 articles plus 24 identified through bibliographic review (n = 98).

RESULTS

Twenty-four large cohorts (n ~ 30,000) were represented along with numerous clinical series (n ~ 9000), across 22 countries and 60 years (1952-2012). No less than 15 definitions of GOA were given in 30 studies with a stated GOA definition; at least 6 groups used a summed score of joints or radiographic grades. Prevalence estimates based on these GOA definitions were 1-80%, although most were 5-25%. Increased risk and progression of GOA was associated with age, female sex, and genetic/familial factors. Associations with increased body mass index or bone mineral density were not consistent. A study estimated the heritability of GOA at 42%. Collagen biomarker levels increased with the number of involved joints. Increased OA burden was associated with increased mortality and disability, poorer health, and function.

CONCLUSION

While there remains no standard definition of GOA, this term is commonly used. The impact on health may be greater when OA is in more than one joint. A descriptive term, such as multi-joint or polyarticular OA, designating OA of multiple joints or joint groups is recommended.

Increased risk of arthropathies and joint replacement surgery in patients with genetic hemochromatosis: a study of 3,531 patients and their 11,794 first-degree relatives

OBJECTIVE

Genetic hemochromatosis (GH) is an autosomal recessive disease in individuals of Northern and Western European descent. Heterozygosity for the C282Y mutation is common (6-20%). Arthropathy is one of the few complications of GH suggested not to be associated with iron body stores; synovial iron deposition remains in iron-depleted patients. Previous studies suggest an elevated prevalence of clinical and radiographic signs of arthropathy in patients with GH, and 2 smaller studies suggest a possibly elevated risk of joint replacement surgery, but more mixed results are shown regarding risks with HFE genotype. We therefore assessed the risks of arthropathy and joint replacement surgery in patients with GH and in their first-degree relatives (FDRs).

METHODS

We performed a population-based cohort study of 3,531 patients with GH and of their 11,794 FDRs (assumed to be heterozygous for the C282Y mutation) using nationwide Swedish population-based health and census registers. Hazard ratios (HRs) of arthropathies and joint replacement surgeries among patients and their FDRs (versus the general population) were assessed using Cox regression.

RESULTS

Between 1997 and 2005, 406 of 3,531 patients were reported/hospitalized with any noninfectious arthropathies, including osteoarthritis, corresponding to an HR of 2.38 (95% confidence interval [95% CI] 2.14-2.64). Patients were also at increased risk of hip replacement (HR 2.77, 95% CI 2.27-3.38) and knee replacement (HR 2.14, 95% CI 1.58-2.88) surgery. Among the 11,794 FDRs (patients excluded), we found no increased risk of any of the joint morbidities.

CONCLUSION

Patients with GH, but not their FDRs, are at increased risk of arthropathies, including the need for joint replacement surgery.

Proximal interphalangeal joint arthritis

Proximal interphalangeal joint function is critical for proper finger and hand function and arthritis of this joint can lead to considerable hand impairment. Proximal interphalangeal joint arthritides are broadly categorized into nonerosive and erosive osteoarthritis (OA), posttraumatic arthritis, and inflammatory arthritis. The nonerosive type is considered idiopathic or primary OA, whereas the erosive form exhibits an inflammatory component. Idiopathic or primary OA occurs as a consequence of abnormal mechanical stress that leads to damage of cartilage and subchondral bone, with subsequent cytokine and growth factor activation. Individual genetics then mediate the cellular responses. Although erosive OA is described as a separate entity, this remains controversial, with many suggesting that it is merely a more aggressive form of nonerosive, primary OA. Inflammatory OA occurs when connective tissues are diseased, allowing for normal use to incite arthritic damage. Treatment modalities for proximal interphalangeal joint arthritis are currently limited.

Osteoarthritis of the distal interphalangeal joint

Osteoarthritis occurs with the highest prevalence in the distal interphalangeal joint of the hand and has been divided into an erosive and a nonerosive form. The pathogenesis of the early stages of osteoarthritis is poorly understood, but considerable emphasis has been placed on the role of cartilage and subchondral bone as well as soft tissue structures such as collateral ligaments and tendons. Radiographic evaluation represents the most standardized method to quantify disease progression, with different systems having been developed for defining and grading radiographic features. This current concepts article examines the recent knowledge base regarding the etiology, pathogenesis, and evaluation of osteoarthritis of the distal interphalangeal joint.

Ferritin concentrations in synovial fluid are higher in osteoarthritis patients with HFE gene mutations (C282Y or H63D)

OBJECTIVES

In view of the clinical similarities between polyarticular osteoarthritis (POA) with metacarpophalangeal (MCP) joint involvement and the arthropathy that occurs in hereditary haemochromatosis (HH), it was hypothesized that osteochondral damage in both disorders may be due to localized iron overload. Accordingly, it was predicted that the concentration of ferritin in synovial fluid (SF) would be higher in OA patients with HFE gene mutations than in HFE wild-type (wt) OA patients. The aim of this study was to test this proposition.

METHODS

Sequential patients with physician-diagnosed OA and, for comparison, diverse inflammatory diseases of the joints, who required diagnostic or therapeutic arthrocentesis, were studied. Participants underwent HFE genotyping. SF samples were assayed for ferritin and also for selected cytokines and matrix metalloproteinases (MMPs).

RESULTS

Seventy-three patients with diverse rheumatic disorders were recruited. Of the 29 patients who had knee OA, 15 were wt and 14 were heterozygous for HFE mutations (C282Y or H63D). Mean SF ferritin concentrations in the wt and heterozygous OA groups were 273 and 655 ng/mL, respectively (p = 0.0146).

CONCLUSIONS

A predicted difference in SF ferritin concentrations in patients with knee OA was confirmed. Concentrations of ferritin in the SF were found to be two- to threefold higher in knee OA patients with HFE gene mutations compared to wt patients. This finding is consistent with the possibility that, in OA patients with HFE gene mutations, localized iron overload may contribute either directly or indirectly to osteochondral damage, possibly in a similar way to that which occurs in the arthropathy that complicates HH.

Non-pharmacological care for patients with generalized osteoarthritis: design of a randomized clinical trial

Background

Non-pharmacological treatment (NPT) is a useful treatment option in the management of hip or knee osteoarthritis. To our knowledge however, no studies have investigated the effect of NPT in patients with generalized osteoarthritis (GOA). The primary aim of this study is to compare the effectiveness of two currently existing health care programs with different intensity and mode of delivery on daily functioning in patients with GOA. The secondary objective is to compare the cost-effectiveness of both interventions.

Methods/Design

In this randomized, single blind, clinical trial with active controls, we aim to include 170 patients with GOA. The experimental intervention consist of six self-management group sessions provided by a multi-disciplinary team (occupational therapist, physiotherapist, dietician and specialized nurse). The active control group consists of two group sessions and four sessions by telephone, provided by a specialized nurse and physiotherapist. Both therapies last six weeks. Main study outcome is daily functioning during the first year after the treatment, assessed on the Health Assessment Questionnaire. Secondary outcomes are health related quality of life, specific complaints, fatigue, and costs. Illness cognitions, global perceived effect and self-efficacy, will also be assessed for a responder analysis. Outcome assessments are performed directly after the intervention, after 26 weeks and after 52 weeks.

Discussion

This article describes the design of a randomized, single blind, clinical trial with a one year follow up to compare the costs and effectiveness of two non-pharmacological interventions with different modes of delivery for patients with GOA.

Trial registration

Dutch Trial Register NTR2137

Is osteoarthritis a heterogeneous disease that can be stratified into subsets?

Osteoarthritis is a heterogeneous disease characterized by variable clinical features, biochemical/genetic characteristics, and responses to treatments. To optimize palliative effects of current treatments and develop efficacious disease-modifying interventions, treatments may need to be tailored to the individual or a subset of osteoarthritic joints. The purpose of this review is to explore the current literature on the clinical and physiological variability in osteoarthritis and potential for stratifying patients. Several stratifications have been reported, including mechanism of onset, stage of disease progression, involved joints, inflammatory levels, and effusion. Most of these methods revealed two to three unique subsets of osteoarthritis. Osteoarthritic joints may be stratified by an array of variables, some transient and others consistent throughout the disease process. Future research needs to continue to explore stratification techniques since these may be the key to optimizing palliative interventions and developing disease-modifying interventions for subsets within this heterogeneous disease.