Osteoarthritis Phenotypes Research Articles

Nuclear magnetic resonance spectroscopy of biofluids for osteoarthritis.

BackgroundOsteoarthritis is a common degenerative musculoskeletal disease of synovial joints. It is characterized by a metabolic imbalance resulting in articular cartilage degradation, reduced elastoviscosity of synovial fluid and an altered chondrocyte phenotype. This is often associated with reduced mobility, pain and poor quality of life. Subsequently, with an ageing world population, osteoarthritis is of increasing concern to public health. Nuclear magnetic resonance (NMR) spectroscopy can be applied to characterize the metabolomes of biofluids, determining changes associated with osteoarthritis pathology, identifying potential biomarkers of disease and alterations to metabolic pathways.Sources of dataA comprehensive search of PubMed and Web of Science databases using combinations of the following keywords: ‘NMR Spectroscopy’, ‘Blood’, ‘Plasma’, ‘Serum’, ‘Urine’, ‘Synovial Fluid’ and ‘Osteoarthritis’ for articles published from 2000 to 2020.Areas of agreementThe number of urine metabolomics studies using NMR spectroscopy to investigate osteoarthritis is low, whereas the use of synovial fluid is significantly higher. Several differential metabolites have previously been identified and mapped to metabolic pathways involved in osteoarthritis pathophysiology.Areas of controversyConclusions are sometimes conservative or overinflated, which may reflect the variation in reporting standards. NMR metabolic experimental design may require further consideration, as do the animal models used for such studies.Growing pointsThere are various aspects which require improvement within the field. These include stricter adherence to the Metabolomics Standards Initiative, inclusive of the standardization of metabolite identifications; increased utilization of integrating NMR metabolomics with other ‘omic’ disciplines; and increased deposition of raw experimental files into open access online repositories, allowing greater transparency and enabling additional future analyses.Areas timely for developing researchOverall, this research area could be improved by the inclusion of more heterogeneous cohorts, reflecting varying osteoarthritis phenotypes, and larger group sizes ensuring studies are not underpowered. To correlate local and systemic environments, the use of blood for diagnostic purposes, over the collection of synovial fluid, requires increased attention. This will ultimately enable biomarkers of disease to be determined that may provide an earlier diagnosis, or provide potential therapeutic targets for osteoarthritis, ultimately improving patient prognosis.

Comparison of two ASC-derived therapeutics in an in vitro OA model: secretome versus extracellular vesicles

BackgroundIn the last years, several clinical trials have proved the safety and efficacy of adipose-derived stem/stromal cells (ASC) in contrasting osteoarthritis (OA). Since ASC act mainly through paracrine mechanisms, their secretome (conditioned medium, CM) represents a promising therapeutic alternative. ASC-CM is a complex cocktail of proteins, nucleic acids, and lipids released as soluble factors and/or conveyed into extracellular vesicles (EV). Here, we investigate its therapeutic potential in an in vitro model of OA.MethodsHuman articular chondrocytes (CH) were induced towards an OA phenotype by 10 ng/ml TNFα in the presence of either ASC-CM or EV, both deriving from 5 × 105 cells, to evaluate the effect on hypertrophic, catabolic, and inflammatory markers.ResultsGiven the same number of donor cells, our data reveal a higher therapeutic potential of ASC-CM compared to EV alone that was confirmed by its enrichment in chondroprotective factors among which TIMP-1 and -2 stand out. In details, only ASC-CM significantly decreased MMP activity (22% and 29% after 3 and 6 days) and PGE2 expression (up to 40% at day 6) boosted by the inflammatory cytokine. Conversely, both treatments down-modulated of ~ 30% the hypertrophic marker COL10A1.ConclusionsThese biological and molecular evidences of ASC-CM beneficial action on CH with an induced OA phenotype may lay the basis for its future clinical translation as a cell-free therapeutic in the management of OA.

EGFR Signaling Is Required for Maintaining Adult Cartilage Homeostasis and Attenuating Osteoarthritis Progression.

The uppermost superficial zone of articular cartilage is the first line of defense against the initiation of osteoarthritis (OA). We previously used Col2-Cre to demonstrate that epidermal growth factor receptor (EGFR), a tyrosine kinase receptor, plays an essential role in maintaining superficial chondrocytes during articular cartilage development. Here, we showed that EGFR activity in the articular cartilage decreased as mice age. In mouse and human OA samples, EGFR activity was initially reduced at the superficial layer and then resurged in cell clusters within the middle and deep zone in late OA. To investigate the role of EGFR signaling in postnatal and adult cartilage, we constructed an inducible mouse model with cartilage-specific EGFR inactivation (Aggrecan-CreER EgfrWa5/flox , Egfr iCKO). EdU incorporation revealed that postnatal Egfr iCKO mice contained fewer slow-cycling cells than controls. EGFR deficiency induced at 3months of age reduced cartilage thickness and diminished superficial chondrocytes, in parallel to alterations in lubricin production, cell proliferation, and survival. Furthermore, male Egfr iCKO mice developed much more severe OA phenotypes, including cartilage erosion, subchondral bone plate thickening, cartilage degeneration at the lateral site, and mechanical allodynia, after receiving destabilization of the medial meniscus (DMM) surgery. Similar OA phenotypes were also observed in female iCKO mice. Moreover, tamoxifen injections of iCKO mice at 1 month post-surgery accelerated OA development 2 months later. In summary, our data demonstrated that chondrogenic EGFR signaling maintains postnatal slow-cycling cells and plays a critical role in adult cartilage homeostasis and OA progression. © 2022 American Society for Bone and Mineral Research (ASBMR).

Igf1 Regulates Fibrocartilage Stem Cells, Cartilage Growth, and Homeostasis in the Temporomandibular Joint of Mice.

Temporomandibular joint (TMJ) growth requires orchestrated interactions between various cell types. Recent studies revealed that fibrocartilage stem cells (FCSCs) in the TMJ cartilage play critical roles as cell resources for joint development and repair. However, the detailed molecular network that influences FCSC fate during TMJ cartilage development remains to be elucidated. Here, we investigate the functional role of Igf1 in FCSCs for TMJ cartilage growth and homeostasis by lineage tracing using Gli1-CreER+ ; Tmflfl mice and conditional Igf1 deletion using Gli1-/Col2-CreER+ ; Igf1fl/fl mice. In Gli1-CreER+ ; Tmflfl mice, red fluorescence+ (RFP+ ) FCSCs show a favorable proliferative capacity. Igf1 deletion in Gli1+ /Col2+ cell lineages leads to distinct pathological changes in TMJ cartilage. More serious cartilage thickness and cell density reductions are found in the superficial layers in Gli1-CreER+ ; Igf1fl/fl mice. After long-term Igf1 deletion, a severe disordered cell arrangement is found in both groups. When Igf1 is conditionally deleted in vivo, the red fluorescent protein-labeled Gli1+ FCSC shows a significant disruption of chondrogenic differentiation, cell proliferation, and apoptosis leading to TMJ cartilage disarrangement and subchondral bone loss. Immunostaining shows that pAkt signaling is blocked in all cartilage layers after the Gli1+ -specific deletion of Igf1. In vitro, Igf1 deletion disrupts FCSC capacities, including proliferation and chondrogenesis. Moreover, the deletion of Igf1 in FCSCs significantly aggravates the joint osteoarthritis phenotype in the unilateral anterior crossbite mouse model, characterized by decreased cartilage thickness and cell numbers as well as a loss of extracellular matrix secretions. These findings uncover Igf1 as a regulator of TMJ cartilage growth and repair. The deletion of Igf1 disrupts the progenitor capacity of FCSCs, leading to a disordered cell distribution and exaggerating TMJ cartilage dysfunction. © 2023 American Society for Bone and Mineral Research (ASBMR).

Transcriptional response of human articular chondrocytes treated with fibronectin fragments: an in vitro model of the osteoarthritis phenotype

Fibronectin is a matrix protein that is fragmented during cartilage degradation in osteoarthritis (OA). Treatment of chondrocytes with fibronectin fragments (FN-f) has been used to model OA in vitro, but the system has not been fully characterized. This study sought to define the transcriptional response of chondrocytes to FN-f, and directly compare it to responses traditionally observed in OA. Normal human femoral chondrocytes isolated from tissue donors were treated with either FN-f or PBS (control) for 3, 6, or 18h. RNA-seq libraries were compared between time-matched FN-f and control samples in order to identify changes in gene expression over time. Differentially expressed genes were compared to a published OA gene set and used for pathway, transcription factor motif, and kinome analysis. FN-f treatment resulted in 3,914 differentially expressed genes over the time course. Genes that are up- or downregulated in OA were significantly up- (P<0.00001) or downregulated (P<0.0004) in response to FN-f. Early response genes were involved in proinflammatory pathways, whereas many late response genes were involved in ferroptosis. The promoters of upregulated genes were enriched for NF-κB, AP-1, and IRF motifs. Highly upregulated kinases included CAMK1G, IRAK2, and the uncharacterized kinase DYRK3, while growth factor receptors TGFBR2 and FGFR2 were downregulated. FN-f treatment of normal human articular chondrocytes recapitulated many key aspects of the OA chondrocyte phenotype. This in vitro model is promising for future OA studies, especially considering its compatibility with genomics and genome-editing techniques.

Widespread regulation of gene expression by glucocorticoids in chondrocytes from patients with osteoarthritis as determined by RNA-Seq

BackgroundIntra-articular glucocorticoid (GC) injections are widely used as a symptomatic treatment for osteoarthritis (OA). However, there are also concerns about their potentially harmful effects, and their detailed effects on chondrocyte phenotype remain poorly understood.MethodsWe studied the effects of dexamethasone on gene expression in OA chondrocytes with RNA-Seq. Chondrocytes were isolated from the cartilage from OA patients undergoing knee replacement surgery and cultured with or without dexamethasone for 24 h. Total RNA was isolated and sequenced, and functional analysis was performed against the Gene Ontology (GO) database. Results for selected genes were confirmed with RT-PCR. We also investigated genes linked to OA in recent genome-wide expression analysis (GWEA) studies.ResultsDexamethasone increased the expression of 480 and reduced that of 755 genes with a fold change (FC) 2.0 or greater. Several genes associated with inflammation and cartilage anabolism/catabolism as well as lipid and carbohydrate metabolism were among the most strongly affected genes. In the GO analysis, genes involved in the extracellular matrix organization, cell proliferation and adhesion, inflammation, and collagen synthesis were enriched among the significantly affected genes. In network analysis, NGF, PI3KR1, and VCAM1 were identified as central genes among those most strongly affected by dexamethasone.ConclusionsThis is the first study investigating the genome-wide effects of GCs on the gene expression in OA chondrocytes. In addition to clear anti-inflammatory and anticatabolic effects, GCs affect lipid and glucose metabolism in chondrocytes, an observation that might be particularly important in the metabolic phenotype of OA.

FoxO1 is a crucial mediator of TGF-β/TAK1 signaling and protects against osteoarthritis by maintaining articular cartilage homeostasis

Transforming growth factor-β (TGF-β) signaling is a critical regulator for articular cartilage tissue maintenance and chondrocyte homeostasis. Nonetheless, the regulatory networks and downstream signaling pathways that govern the chondroprotective function of TGF-β in the context of osteoarthritis (OA) are not fully defined. Recent studies reveal that mice with postnatal deletion of triple forkhead box class Os (FoxOs) (1, 3, and 4) spontaneously develop OA-like pathologies. The OA phenotype largely recapitulates that observed in mice with loss of TGF-βR2. In the present study, we investigated the role of FoxOs as downstream mediators of TGF-β signaling and define their role in articular cartilage homeostasis. Among the three FoxOs (1, 3, and 4), TGF-β signaling exclusively regulates FoxO1 in a TGF-β activated kinase 1 (TAK1)-dependent manner. Furthermore, FoxO1 was genetically ablated in mice in a tissue-specific manner in articular cartilage or overexpressed in adult cartilage immediately followed by meniscal/ligament injury (MLI). Histological and microcomputed tomography (micro-CT) analyses demonstrated that loss of FoxO1 postnatally in articular cartilage leads to OA-like pathologies, and gain of FoxO1 in adult cartilage has both preventative and therapeutic effects on surgically induced OA. Mechanistically, FoxO1 was found to maintain articular chondrocyte homeostasis through induction of anabolic and autophagy-related gene expressions. Importantly, overexpression of FoxO1 markedly rescued the OA phenotypes caused by deficiency in TGF-β signaling in chondrocytes. Our study identifies that TGF-β/TAK1-FoxO1 is a key signaling cascade in regulation of articular cartilage autophagy and homeostasis and is a potentially important therapeutic target for OA-like joint diseases.

An evaluation of the relationship between the degree of entheseal changes and the severity of osteodegenerative processes at fibrocartilaginous entheses.

An enthesis refers to the interface at which a tendon or a ligament integrates into the periosteum. Its morphology can be influenced by intrinsic factors such as sex, age, and extrinsic factors such as levels of activity, which will in turn impact on bone remodeling and lead to morphological changes. In bioarcheology, entheseal changes have had a long tradition of being used for the reconstruction of past activities. The literature has shown that in some cases of osteoarthritis, entheseal changes are associated with osteoarthritic manifestations. This work aims to evaluate the relationship between the degree of entheseal changes and the severity of osteodegenerative processes. The studied materials consisted of 30 humeri and 30 femora from the osteological collection at St George's University of London. Intensities of both entheseal changes and osteodegenerative processes were macroscopically assessed and scored. The difference in scores of entheseal changes between osteoarthritic groups and nonosteoarthritic groups is statistically significant at a confidence level of 95% (α=.05) for both the humeri and femora. Results show a positive correlation between the degree of entheseal changes and the severity of osteodegenerative processes in the femora, suggesting that enthesis may play a role in osteoarthritis. Findings from this work supports the proposed hypothesis that the degree of entheseal changes and the severity of osteoarthritic manifestation are related. This work contributes to current knowledge that osteoarthritis is a disease involving the whole joint; the enthesis could potentially be a target for the diagnosis of osteoarthritis.

Genome-wide association of phenotypes based on clustering patterns of hand osteoarthritis identify WNT9A as novel osteoarthritis gene

BackgroundDespite recent advances in the understanding of the genetic architecture of osteoarthritis (OA), only two genetic loci have been identified for OA of the hand, in part explained by the...

Associations Between Calcaneal Enthesophytes and Osteoarthritis of the Hands and Feet.

To examine associations between calcaneal enthesophytes and osteoarthritis (OA) in the hands and feet, and to provide insights into the role of biomechanical and systemic processes in the development of OA. Adults ages ≥50 years who were registered with 4 general practices were mailed a Health Survey. Responders reporting foot pain within the last 12 months underwent a detailed assessment, including hand and foot radiographs. Calcaneal enthesophytes (plantar and posterior) and OA features (osteophytes and joint space narrowing) were documented. Associations between enthesophytes and hand and foot OA (including OA phenotypes and OA features at individual joints) were explored using generalized estimating equations, adjusting for age, sex, and body mass index. Data were available from 532 participants (298 women, mean ± SD age 64.9 ± 8.4 years). Calcaneal enthesophytes were not associated with hand OA phenotypes or OA at individual hand joints. In contrast, plantar calcaneal enthesophytes were positively associated with polyarticular foot OA (odds ratio [OR] 1.80 [95% confidence interval (95% CI) 1.02-3.17]). When individual foot joints were examined, posterior enthesophytes were associated with talonavicular joint OA (OR 1.58 [95% CI 1.02-2.44]) and plantar enthesophytes were associated with first metatarsophalangeal joint OA (OR 0.67 [95% CI 0.49-0.98]) and navicular-cuneiform joint OA (OR 2.30 [95% CI 1.40-3.79]). Patterns of association were similar for osteophytes and joint space narrowing. Calcaneal enthesophytes are associated with foot OA but not hand OA. The pattern of association is indicative of a local, biomechanical rather than systemic bone-forming process.

Nociceptive mechanisms driving pain in a post-traumatic osteoarthritis mouse model

In osteoarthritis (OA), pain is the dominant clinical symptom, yet the therapeutic approaches remain inadequate. The knowledge of the nociceptive mechanisms in OA, which will allow to develop effective therapies for OA pain, is of utmost need. In this study, we investigated the nociceptive mechanisms involved in post-traumatic OA pain, using the destabilization of the medial meniscus (DMM) mouse model. Our results revealed the development of peripheral pain sensitization, reflected by augmented mechanical allodynia. Along with the development of pain behaviour, we observed an increase in the expression of calcitonin gene-related peptide (CGRP) in both the sensory nerve fibers of the periosteum and the dorsal root ganglia. Interestingly, we also observed that other nociceptive mechanisms commonly described in non-traumatic OA phenotypes, such as infiltration of the synovium by immune cells, neuropathic mechanisms and also central sensitization were not present. Overall, our results suggest that CGRP in the sensory nervous system is underlying the peripheral sensitization observed after traumatic knee injury in the DMM model, highlighting the CGRP as a putative therapeutic target to treat pain in post-traumatic OA. Moreover, our findings suggest that the nociceptive mechanisms involved in driving pain in post-traumatic OA are considerably different from those in non-traumatic OA.

Investigating the Association of Metabolic Biomarkers With Knee Cartilage Composition and Structural Abnormalities Using MRI: A Pilot Study.

The goal of this study was to explore the metabolic syndrome-associated phenotype of osteoarthritis by investigating the cross-sectional associations of glycemic markers and serum lipids with knee cartilage composition and structural abnormalities in middle-aged adults. Twenty participants between 40 to 70 years of age with Kellgren-Lawrence score 0-1 in at least one knee were recruited at a single center. Knee cartilage composition was assessed using 3.0 T cartilage T2 and T1ρ mapping. Evaluation of structural knee abnormalities was performed using the modified Whole-Organ Magnetic Resonance Imaging Score (WORMS). Linear regression was used to assess the associations of standardized fasting glucose (FG), hemoglobin A1c (HbA1c), insulin, total cholesterol, high-density lipoprotein (HDL), low-density lipoprotein (LDL), non-HDL cholesterol, and triglycerides with cartilage T2 and T1ρ as well as WORMS subscores, adjusting for body mass index. Higher FG and higher HbA1c were associated with higher WORMS meniscus sum (beta coefficient 1.31 [95% confidence interval (CI): 0.57, 2.05], P = 0.002 per standard deviation [SD] increase in FG; beta coefficient 0.90 [95% CI: 0.07, 1.73], P = 0.035 per SD increase in HbA1c). Also, higher total cholesterol and higher non-HDL cholesterol were associated with higher WORMS cartilage sum (beta coefficient 0.94 [95% CI: 0.01, 1.86], P = 0.048 per SD increase in total cholesterol; beta coefficient 1.05 [95% CI: 0.14, 1.96], P = 0.03 per SD increase in non-HDL cholesterol). Higher FG and HbA1c were associated with increased meniscal degeneration while higher total and non-HDL cholesterol were associated with increased cartilage degeneration.

Distinct Pattern of Inflammation of Articular Cartilage and the Synovium in Early and Late Hip Femoroacetabular Impingement

Background: The molecular mechanism of how femoroacetabular impingement (FAI) morphology leads to hip osteoarthritis (OA) is yet to be determined. The expression and location of inflammation-related molecules during early- and late-stage FAI have not been previously described. Moreover, the characterization of intra-articular inflammation away from the cam deformity as well as the nature of adjacent synovial tissue have also not been extensively reported. Hypothesis: Early-stage FAI has a similar expression of inflammation-related markers in the head-neck and acetabular cartilage but less synovitis than late-stage FAI. Study Design: Controlled laboratory study. Methods: Head-neck cartilage, acetabular cartilage, and synovial samples were obtained from patients undergoing hip preservation surgery for the treatment of symptomatic cam FAI (early FAI group; n = 15) and advanced OA secondary to cam FAI (late FAI group; n = 15). Samples procured from healthy young adult donors served as the control group (n = 7). Cartilage degeneration was assessed by histology, and the expression of inflammation-related proteins (interleukin–1 beta [IL-1β], matrix metalloproteinase–13 [MMP-13], a disintegrin and metalloproteinase with thrombospondin motifs–4 [ADAMTS-4], type II collagen [COL2], and aggrecan neoepitope [NITEGE]) was measured by immunostaining. Synovial samples in the early and late FAI groups were examined for synovitis and the expression of IL-1β. Results: Head-neck cartilage in the early FAI group showed significantly more degeneration than the control group and an increased expression of inflammation-related proteins (IL-1β: 69.7% ± 18.1% vs 20.2% ± 4.9%, respectively; MMP-13: 79.6% ± 12.6% vs 25.3% ± 9.5%; ADAMTS-4: 83.9% ± 12.2% vs 24.3% ± 11.1%; NITEGE: 89.7% ± 7.7% vs 39.8% ± 20.5%) (P < .001). Head-neck and acetabular cartilage in the early and late FAI groups showed a similar degree of degeneration. Moreover, a similar expression of inflammation-related proteins was observed between the early and late FAI groups for head-neck cartilage (IL-1β: 69.7% ± 18.1% vs 72.5% ± 13.2%; MMP-13: 79.6% ± 12.6% vs 71.4% ± 18.8%; ADAMTS-4: 83.9% ± 12.2% vs 82.6% ± 12.5%; COL2: 93.6% ± 3.9% vs 92.5% ± 5.8%; NITEGE: 89.7% ± 7.7% vs 95.7% ± 4.7%) and acetabular cartilage (IL-1β: 83.3% ± 24.8% vs 80.7% ± 15.6%; MMP-13: 94.3% ± 9.7% vs 85.2% ± 12.3%; ADAMTS-4: 98.5% ± 2.3% vs 98.4% ± 3.4%; COL2: 99.8% ± 0.7% vs 99.7% ± 1.1%; NITEGE: 96.7% ± 6.7% vs 99.2% ± 2.2%). In contrast, synovitis was minimal with a low expression of IL-1β in the early FAI group compared with the late FAI group. Conclusion: Hip cartilage exhibited an OA phenotype in patients with early-stage FAI, similar to what was observed in hip OA secondary to FAI. Severe synovitis was only evident with late-stage FAI. Clinical Relevance: This study supports the concept that early hip impingement is associated with cartilage degeneration and catabolism.

Metabolic Syndrome and Its Effects on Cartilage Degeneration vs Regeneration: A Pilot Study Using Osteoarthritis Biomarkers.

Osteoarthritis (OA) of the knee is one of the leading causes of disability characterized by degeneration of hyaline cartilage combined with reparative processes. Its strong association with metabolic syndrome is postulated to be due to both mechanical and biochemical factors. Our study aims to study differential effect of metabolic risk factors on cartilage degeneration and regeneration at biomarker level. After screening 281 patients presenting with knee pain, 41 patients who met the selection criteria were included and were divided into metabolic (MetS) OA and non-metabolic (Non-MetS) OA phenotypes using National Cholesterol Education Programme-Adult Treatment Panel-III (NCEP-ATP-III) criteria for metabolic syndrome. Serum Cartilage Oligomeric Matrix Protein (COMP) and Procollagen type IIA N terminal Propeptide (PIIANP) levels were used as tools to assess cartilage degeneration and regeneration, respectively. 22 among 41 patients (53.66%) had metabolic syndrome. Covariates like age, gender, Kellgren Lawrence (KL) grades were comparable in both groups. MetS-OA group showed significant increase in serum COMP levels (p = 0.03) with no significant effect on serum PIIANP levels (p = 0.46). Hypertriglyceridemia showed independent association with both cartilage anabolism (p = 0.03) and catabolism (p = 0.03). Metabolic syndrome, though has no effect on cartilage regeneration tends to shift cartilage homeostasis towards degeneration with hypertriglyceridemia showing significant independent effect on cartilage metabolism.

Mediation of Cartilage Matrix Degeneration and Fibrillation by Decorin in Post-traumatic Osteoarthritis.

To elucidate the role of decorin, a small leucine-rich proteoglycan, in the degradation of cartilage matrix during the progression of post-traumatic osteoarthritis (OA). Three-month-old decorin-null (Dcn-/- ) and inducible decorin-knockout (Dcni KO ) mice were subjected to surgical destabilization of the medial meniscus (DMM) to induce post-traumatic OA. The OA phenotype that resulted was evaluated by assessing joint morphology and sulfated glycosaminoglycan (sGAG) staining via histological analysis (n = 6 mice per group), surface collagen fibril nanostructure via scanning electron microscopy (n = 4 mice per group), tissue modulus via atomic force microscopy-nanoindentation (n = 5 or more mice per group) and subchondral bone structure via micro-computed tomography (n = 5 mice per group). Femoral head cartilage explants from wild-type and Dcn-/- mice were stimulated with the inflammatory cytokine interleukin-1β (IL-1β) in vitro (n = 6 mice per group). The resulting chondrocyte response to IL-1β and release of sGAGs were quantified. In both Dcn-/- and Dcni KO mice, the absence of decorin resulted in accelerated sGAG loss and formation of highly aligned collagen fibrils on the cartilage surface relative to the control (P < 0.05). Also, Dcn-/- mice developed more salient osteophytes, illustrating more severe OA. In cartilage explants treated with IL-1β, loss of decorin did not alter the expression of either anabolic or catabolic genes. However, a greater proportion of sGAGs was released to the media from Dcn-/- mouse explants, in both live and devitalized conditions (P < 0.05). In post-traumatic OA, decorin delays the loss of fragmented aggrecan and fibrillation of cartilage surface, and thus, plays a protective role in ameliorating cartilage degeneration.

Cohort profile: The Applied Public-Private Research enabling OsteoArthritis Clinical Headway (IMI-APPROACH) study: a 2-year, European, cohort study to describe, validate and predict phenotypes of osteoarthritis using clinical, imaging and biochemical markers

PurposeThe Applied Public-Private Research enabling OsteoArthritis Clinical Headway (APPROACH) consortium intends to prospectively describe in detail, preselected patients with knee osteoarthritis (OA), using conventional and novel clinical, imaging, and biochemical...

Molecular Fluorescent Probes for Imaging and Evaluation of Hypochlorite Fluctuations during Diagnosis and Therapy of Osteoarthritis in Cells and in a Mouse Model.

The early diagnosis of osteoarthritis (OA) can halt or delay the progression of the disease, and it is essentially beneficial to its treatment. However, biomarkers with sufficient sensitivity for dynamically identifying early OA are still yet to be determined. The overproduced hypochlorous acid (HOCl) has been proposed as an obvious symptom in early OA. Herein, based on the oxidation reaction of the sulfur atom in phenothiazine into sulfoxide, we design and synthesize a phenothiazine-derived coumarin fluorescent probe PDC for the detection of ClO- in cells and in an OA mouse model. The probe PDC exhibits excellent selectivity and sensitivity for ClO- detection with a limit of detection as low as 16.1 nM. Taking advantage of the probe PDC, we visualize and evaluate the level changes of ClO- in macrophage cells, which is stimulated by various inflammatory factors. The anti-inflammatory and therapeutic effects of selenocysteine and methotrexate in inflamed cells are also confirmed. Finally, with in vivo imaging of ClO- concentration changes in OA BALB/c mouse models, we successfully inspected the relationship between OA phenotypes and the burst of ClO-. We suggest that abnormal changes in HOCl concentration may be considered as a new biomarker for the early OA diagnosis.

Therapeutic Delivery of rAAV sox9 via Polymeric Micelles Counteracts the Effects of Osteoarthritis-Associated Inflammatory Cytokines in Human Articular Chondrocytes.

Osteoarthritis (OA) is a prevalent joint disease linked to the irreversible degradation of key extracellular cartilage matrix (ECM) components (proteoglycans, type-II collagen) by proteolytic enzymes due to an impaired tissue homeostasis, with the critical involvement of OA-associated pro-inflammatory cytokines (interleukin 1 beta, i.e., IL-1β, and tumor necrosis factor alpha, i.e., TNF-α). Gene therapy provides effective means to re-establish such degraded ECM compounds by rejuvenating the altered OA phenotype of the articular chondrocytes, the unique cell population ubiquitous in the articular cartilage. In particular, overexpression of the highly specialized SOX9 transcription factor via recombinant adeno-associated viral (rAAV) vectors has been reported for its ability to readjust the metabolic balance in OA, in particular via controlled rAAV delivery using polymeric micelles as carriers to prevent a possible vector neutralization by antibodies present in the joints of patients. As little is known on the challenging effects of such naturally occurring OA-associated pro-inflammatory cytokines on such rAAV/polymeric gene transfer, we explored the capacity of polyethylene oxide (PEO) and polypropylene oxide (PPO)-based polymeric micelles to deliver a candidate rAAV-FLAG-hsox9 construct in human OA chondrocytes in the presence of IL-1β and TNF-α. We report that effective, micelle-guided rAAV sox9 overexpression enhanced the deposition of ECM components and the levels of cell survival, while advantageously reversing the deleterious effects afforded by the OA cytokines on these processes. These findings highlight the potentiality of polymeric micelles as effective rAAV controlled delivery systems to counterbalance the specific contribution of major OA-associated inflammatory cytokines, supporting the concept of using such systems for the treatment for chronic inflammatory diseases like OA.

Pain trajectory defines knee osteoarthritis subgroups: a prospective observational study.

Knee osteoarthritis (OA) is a heterogeneous disease, and identification of its subgroups/phenotypes can improve patient treatment and drug development. We aimed to identify homogeneous OA subgroups/phenotypes using pain development over time; to understand the interplay between pain and functional limitation in time course; and to investigate subgroups' responses to available pharmacological and surgical treatments. We used group-based trajectory modelling to identify pain trajectories in the phase-3 VIDEO trial (n = 474, 3-year follow-up) and also in the Osteoarthritis Initiative cohort study (n = 4796, 9-year follow-up). We extended trajectory models by (1) fitting dual trajectories to investigate the interplay between pain and functional limitation over time, and (2) including analgesic use as a time-varying covariate. Also, we investigated the relationship between trajectory groups and knee replacement in regression models. We identified 4 pain trajectory groups in the trial and 6 in the cohort. These overlapped and led us to define 4 OA phenotypes: low-fluctuating, mild-increasing, moderate-treatment-sensitive, and severe-treatment-insensitive pain. Over time, functional knee limitation followed the same trajectory as pain with almost complete concordance (94.3%) between pain and functional limitation trajectory groups. Notably, we identified a phenotype with severe pain that did not benefit from available treatments, and another one most likely to benefit from knee replacement. Thus, knee OA subgroups/phenotypes can be identified based on patients' pain experiences in studies with long and regular follow-up. We provided a robust approach, reproducible between different study designs, which informs clinicians about symptom development and delivery of treatment options and opens a new avenue toward personalized medicine in OA.

Different Phenotypes of Osteoarthritis in the Lumbar Spine Reflected by Demographic and Clinical Characteristics: The Johnston County Osteoarthritis Project.

To determine if associations between demographic and clinical characteristics and appendicular joint osteoarthritis (OA) reflect different phenotypes of OA in the lumbar spine. Participants were from the Johnston County OA Project. Demographic information consisted of age, sex, and race (white and African American), and clinical characteristics consisted of body mass index (BMI), low back pain and injury, and knee, hip, and hand OA. Participants were categorized as having spine OA, facet joint OA, both spine OA and facet joint OA, or neither spine OA nor facet joint OA (referent group). Multinomial regression models were used to determine odds ratios (ORs) and 95% confidence intervals (95% CIs). Of 1,793 participants, the mean ± SD age was 66.2 ± 10.1 years, and the mean ± SD BMI was 30.7 ± 6.2. The majority of the participants were women (n = 1,144 [63.8%]), and 31.8% of the participants (n = 570) were African American. Eighteen percent of participants had neither spine OA nor facet joint OA, 22.8% had facet joint OA, 13.2% had spine OA, and 46.0% had both spine OA and facet joint OA. In adjusted analyses, African Americans were less likely to have facet joint OA (OR 0.68 [95% CI 0.49-0.95]) or both spine OA and facet joint OA (OR 0.51 [95% CI 0.37-0.70]). Women were more likely to have facet joint OA (OR 1.71 [95% CI 1.24-2.36]). Having a BMI of ≥30 was associated with having facet joint OA (OR 1.76 [95% CI 1.28-2.42]) and both spine OA and facet joint OA (OR 1.85 [95% CI 1.37-2.51]). Knee OA was associated with all 3 OA groups, while lower back injury was associated only with those with spine OA. Participants with hip OA were less likely to have facet joint OA. Race, sex, BMI, hip OA, and lower back injury may help identify different OA phenotypes in the lumbar spine.