Obesity defined molecular endotypes in the synovium of patients with osteoarthritis provides a rationale for therapeutic targeting of fibroblast subsets.

BACKGROUND: Osteoarthritis (OA), a multifaceted condition, poses a significant challenge for the successful clinical development of therapeutics due to heterogeneity. However, classifying molecular endotypes of OA pathogenesis could provide invaluable phenotype-directed routes for stratifying subgroups of patients for targeted therapeutics, leading to greater chances of success in trials. This study establishes endotypes in OA soft joint tissue driven by obesity in both load-bearing and non-load bearing joints. METHODS: Hand, hip, knee and foot joint synovial tissue was obtained from OA patients (n = 32) classified as obese (BMI > 30) or normal weight (BMI 18.5-24.9). Isolated fibroblasts (OA SF) were assayed by Olink proteomic panel, seahorse metabolic flux assay, Illumina's NextSeq 500 bulk and Chromium 10X single cell RNA-sequencing, validated by Luminex and immunofluorescence. RESULTS: Targeted proteomic, metabolic and transcriptomic analysis found the inflammatory landscape of OA SFs are independently impacted by obesity, joint loading and anatomical site with significant heterogeneity between obese and normal weight patients, confirmed by bulk RNAseq. Further investigation by single cell RNAseq identified four functional molecular endotypes including obesity specific subsets defined by an inflammatory endotype related to immune cell regulation, fibroblast activation and inflammatory signaling, with up-regulated CXCL12, CFD and CHI3L1 expression. Luminex confirmed elevated chitase3-like-1(229.5 vs. 49.5 ng/ml, p < .05) and inhibin (20.6 vs. 63.8 pg/ml, p < .05) in obese and normal weight OA SFs, respectively. Lastly, we find SF subsets in obese patients spatially localise in sublining and lining layers of OA synovium and can be distinguished by differential expression of the transcriptional regulators MYC and FOS. CONCLUSION: These findings demonstrate the significance of obesity in changing the inflammatory landscape of synovial fibroblasts in both load bearing and non-load bearing joints. Describing multiple heterogeneous OA SF populations characterised by specific molecular endotypes, which drive heterogeneity in OA disease pathogenesis. These molecular endotypes may provide a route for the stratification of patients in clinical trials, providing a rational for the therapeutic targeting of specific SF subsets in specific patient populations with arthritic conditions.

The role of extracellular vesicle miRNAs and tRNAs in synovial fibroblast senescence.

Extracellular vesicles are mediators of intercellular communication with critical roles in cellular senescence and ageing. In arthritis, senescence is linked to the activation of a pro-inflammatory phenotype contributing to chronic arthritis pathogenesis. We hypothesised that senescent osteoarthritic synovial fibroblasts induce senescence and a pro-inflammatory phenotype in non-senescent osteoarthritic fibroblasts, mediated through extracellular vesicle cargo. Small RNA-sequencing and mass spectrometry proteomics were performed on extracellular vesicles isolated from the secretome of non-senescent and irradiation-induced senescent synovial fibroblasts. ß-galactosidase staining confirmed senescence in SFs. RNA sequencing identified 17 differentially expressed miRNAs, 11 lncRNAs, 14 tRNAs and one snoRNA and, 21 differentially abundant proteins were identified by mass spectrometry. Bioinformatics analysis of miRNAs identified fibrosis, cell proliferation, autophagy, and cell cycle as significant pathways, tRNA analysis was enriched for signaling pathways including FGF, PI3K/AKT and MAPK, whilst protein analysis identified PAX3-FOXO1, MYC and TFGB1 as enriched upstream regulators involved in senescence and cell cycle arrest. Finally, treatment of non-senescent synovial fibroblasts with senescent extracellular vesicles confirmed the bystander effect, inducing senescence in non-senescent cells potentially through down regulation of NF-κß and cAMP response element signaling pathways thus supporting our hypothesis. Understanding the exact composition of EV-derived small RNAs of senescent cells in this way will inform our understanding of their roles in inflammation, intercellular communication, and as active molecules in the senescence bystander effect.

Synovial tissue from sites of joint pain in knee osteoarthritis patients exhibits a differential phenotype with distinct fibroblast subsets.

BACKGROUND: Synovial inflammation is associated with pain severity in patients with knee osteoarthritis (OA). The aim here was to determine in a population with knee OA, whether synovial tissue from areas associated with pain exhibited different synovial fibroblast subsets, compared to synovial tissue from sites not associated with pain. A further aim was to compare differences between early and end-stage disease synovial fibroblast subsets. METHODS: Patients with early knee OA (n = 29) and end-stage knee OA (n = 22) were recruited. Patient reported pain was recorded by questionnaire and using an anatomical knee pain map. Proton density fat suppressed MRI axial and sagittal sequences were analysed and scored for synovitis. Synovial tissue was obtained from the medial and lateral parapatellar and suprapatellar sites. Fibroblast single cell RNA sequencing was performed using Chromium 10X and analysed using Seurat. Transcriptomes were functionally characterised using Ingenuity Pathway Analysis and the effect of fibroblast secretome on neuronal growth assessed using rat DRGN. FINDINGS: Parapatellar synovitis was significantly associated with the pattern of patient-reported pain in knee OA patients. Synovial tissue from sites of patient-reported pain exhibited a differential transcriptomic phenotype, with distinct synovial fibroblast subsets in early OA and end-stage OA. Functional pathway analysis revealed that synovial tissue and fibroblast subsets from painful sites promoted fibrosis, inflammation and the growth and activity of neurons. The secretome of fibroblasts from early OA painful sites induced greater survival and neurite outgrowth in dissociated adult rodent dorsal root ganglion neurons. INTERPRETATION: Sites of patient-reported pain in knee OA exhibit a different synovial tissue phenotype and distinct synovial fibroblast subsets. Further interrogation of these fibroblast pathotypes will increase our understanding of the role of synovitis in OA joint pain and provide a rationale for the therapeutic targeting of fibroblast subsets to alleviate pain in patients. FUNDING: This study was funded by Versus Arthritis, UK (21530; 21812).

Polygenic basis and biomedical consequences of telomere length variation.

Telomeres, the end fragments of chromosomes, play key roles in cellular proliferation and senescence. Here we characterize the genetic architecture of naturally occurring variation in leukocyte telomere length (LTL) and identify causal links between LTL and biomedical phenotypes in 472,174 well-characterized UK Biobank participants. We identified 197 independent sentinel variants associated with LTL at 138 genomic loci (108 new). Genetically determined differences in LTL were associated with multiple biological traits, ranging from height to bone marrow function, as well as several diseases spanning neoplastic, vascular and inflammatory pathologies. Finally, we estimated that, at the age of 40 years, people with an LTL >1 s.d. shorter than the population mean had a 2.5-year-lower life expectancy compared with the group with ≥1 s.d. longer LDL. Overall, we furnish new insights into the genetic regulation of LTL, reveal wide-ranging influences of LTL on physiological traits, diseases and longevity, and provide a powerful resource available to the global research community.

The Expression and Function of Metastases Associated Lung Adenocarcinoma Transcript-1 Long Non-Coding RNA in Subchondral Bone and Osteoblasts from Patients with Osteoarthritis.

Metastasis Associated Lung Adenocarcinoma Transcript-1 (MALAT1) is implicated in regulating the inflammatory response and in the pathology of several chronic inflammatory diseases, including osteoarthritis (OA). The purpose of this study was to examine the relationship between OA subchondral bone expression of MALAT1 with parameters of joint health and biomarkers of joint inflammation, and to determine its functional role in human OA osteoblasts. Subchondral bone and blood were collected from hip and knee OA patients (n = 17) and bone only from neck of femur fracture patients (n = 6) undergoing joint replacement surgery. Cytokines were determined by multiplex assays and ELISA, and gene expression by qPCR. MALAT1 loss of function was performed in OA patient osteoblasts using locked nucleic acids. The osteoblast transcriptome was analysed by RNASeq and pathway analysis. Bone expression of MALAT1 positively correlated to serum DKK1 and galectin-1 concentrations, and in OA patient osteoblasts was induced in response to IL-1ß stimulation. Osteoblasts depleted of MALAT1 exhibited differential expression (>1.5 fold change) of 155 genes, including PTGS2. Both basal and IL-1ß-mediated PGE2 secretion was greater in MALAT1 depleted osteoblasts. The induction of MALAT1 in human OA osteoblasts upon inflammatory challenge and its modulation of PGE2 production suggests that MALAT1 may play a role in regulating inflammation in OA subchondral bone.

Regulation of the Inflammatory Synovial Fibroblast Phenotype by Metastasis-Associated Lung Adenocarcinoma Transcript 1 Long Noncoding RNA in Obese Patients With Osteoarthritis.

OBJECTIVE: To identify long noncoding RNAs (lncRNAs) associated with the inflammatory phenotype of synovial fibroblasts from obese patients with osteoarthritis (OA), and to explore the expression and function of these lncRNAs. METHODS: Synovium was collected from normal-weight patients with hip fracture (non-OA; n = 6) and from normal-weight (n = 8) and obese (n = 8) patients with hip OA. Expression of RNA was determined by RNA-sequencing and quantitative reverse transcription-polymerase chain reaction. Knockdown of lncRNA was performed using LNA-based GapmeRs. Synovial fibroblast cytokine production was measured by enzyme-linked immunosorbent assay. RESULTS: Synovial fibroblasts from obese patients with OA secreted greater levels of interleukin-6 (IL-6) (mean ± SEM 162 ± 21 pg/ml; P < 0.001) and CXCL8 (262 ± 67 pg/ml; P < 0.05) compared to fibroblasts from normal-weight patients with OA (IL-6, 51 ± 4 pg/ml; CXCL8, 78 ± 11 pg/ml) or non-OA patients (IL-6, 35 ± 3 pg/ml; CXCL8, 56 ± 6 pg/ml) (n = 6 patients per group). RNA-sequencing revealed that fibroblasts from obese OA patients exhibited an inflammatory transcriptome, with increased expression of proinflammatory messenger RNAs (mRNAs) as compared to that in fibroblasts from normal-weight OA or non-OA patients (>2-fold change, P < 0.05; n = 4 patients per group). A total of 19 lncRNAs were differentially expressed between normal-weight OA and non-OA patient fibroblasts, and a further 19 lncRNAs were differentially expressed in fibroblasts from obese OA patients compared to normal-weight OA patients (>2-fold change, P < 0.05 for each), which included the lncRNA for metastasis-associated lung adenocarcinoma transcript 1 (MALAT1). MALAT1 was rapidly induced upon stimulation of OA synovial fibroblasts with proinflammatory cytokines, and was up-regulated in the synovium from obese OA patients as compared to normal-weight OA patients (1.6-fold change, P < 0.001) or non-OA patients (6-fold change, P < 0.001). MALAT1 knockdown in OA synovial fibroblasts (n = 4 patients) decreased the levels of mRNA expression and protein secretion of CXCL8 (>1.5-fold change, P < 0.01), whereas it increased expression of mRNAs for TRIM6 (>2-fold change, P < 0.01), IL7R (<2-fold change, P < 0.01), HIST1H1C (>1.5-fold change, P < 0.001), and MAML3 (>1.5-fold change, P < 0.001). In addition, MALAT1 knockdown inhibited the proliferation of synovial fibroblasts from obese patients with OA. CONCLUSION: Synovial fibroblasts from obese patients with hip OA exhibit an inflammatory phenotype. MALAT1 lncRNA may mediate joint inflammation in obese OA patients.

The combination of local infiltration analgesia reagents increases their detrimental effect on human hip OA patient osteoblast viability and function.

The purpose was to evaluate the effect of Local infiltration analgesia (LIA) reagents in monotherapy and in combinations at clinical doses, on the viability and function of osteoblasts isolated from hip OA patients undergoing orthopaedic surgery. Human hip OA osteoblasts were exposed to LIA reagents including Bupivacaine, Lidocaine, Ropivacaine, Ketorolac and combinations with Adrenaline for 30 min. Osteoblast cellular viability and function was determined at 24 h and 7 days post-exposure. In conclusion, our data shows that LIA reagents, most notably Bupivacaine and its use in combination, are detrimental to human hip OA osteoblasts at concentrations advocated for clinical use.

Differential glucocorticoid metabolism in patients with persistent versus resolving inflammatory arthritis.

INTRODUCTION: Impairment in the ability of the inflamed synovium to generate cortisol has been proposed to be a factor in the persistence and severity of inflammatory arthritis. In the inflamed synovium, cortisol is generated from cortisone by the 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) enzyme. The objective of this study was to determine the role of endogenous glucocorticoid metabolism in the development of persistent inflammatory arthritis. METHODS: Urine samples were collected from patients with early arthritis (symptoms ≤12 weeks duration) whose final diagnostic outcomes were established after clinical follow-up and from patients with established rheumatoid arthritis (RA). All patients were free of disease-modifying anti-rheumatic drugs at the time of sample collection. Systemic measures of glucocorticoid metabolism were assessed in the urine samples by gas chromatography/mass spectrometry. Clinical data including CRP and ESR were also collected at baseline. RESULTS: Systemic measures of 11ß-HSD1 activity were significantly higher in patients with early arthritis whose disease went on to persist, and also in the subgroup of patients with persistent disease who developed RA, when compared with patients whose synovitis resolved over time. We observed a significant positive correlation between systemic 11ß-HSD1 activity and ESR/CRP in patients with established RA but not in any of the early arthritis patients group. CONCLUSIONS: The present study demonstrates that patients with a new onset of synovitis whose disease subsequently resolved had significantly lower levels of systemic 11ß-HSD1 activity when compared with patients whose synovitis developed into RA or other forms of persistent arthritis. Low absolute levels of 11ß-HSD1 activity do not therefore appear to be a major contributor to the development of RA and it is possible that a high total body 11ß-HSD1 activity during early arthritis may reduce the probability of disease resolution.

TNFα regulates cortisol metabolism in vivo in patients with inflammatory arthritis.

OBJECTIVE: To determine the relationship between inflammation and glucocorticoid metabolism in vivo, in a clinical study of patients with inflammatory arthritis treated with anti-TNFα therapy. METHODS: Urine samples were collected from patients with rheumatoid arthritis (RA) and psoriatic arthritis (PsA) as part of a multicentre study assessing responses to infliximab and etanercept. Systemic measures of glucocorticoid metabolism were assessed by gas chromatography/mass spectrometry at weeks 0 (baseline), 4 and 12 after anti-TNFα therapy. Clinical data including DAS28 and C-reactive protein were also collected. RESULTS: Systemic measures of 11ß-HSD1 activity in patients with inflammatory arthritis decreased significantly following anti-TNFα therapy in patients with RA and PsA. Additionally, the activity of the glucocorticoid inactivating enzyme 5α-reductase appeared to increase significantly. CONCLUSIONS: This study demonstrates, for the first time, that the increased 11ß-HSD1 activity seen in patients with inflammatory arthritis is mediated through TNFα. Furthermore, the changes in related glucocorticoid metabolising enzymes suggest that there is a coordinated change in glucocorticoid metabolism which promotes higher tissue glucocorticoid levels.

Inflammatory regulation of glucocorticoid metabolism in mesenchymal stromal cells.

OBJECTIVE: Tissue glucocorticoid (GC) levels are regulated by the GC-activating enzyme 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1). This enzyme is expressed in cells and tissues arising from mesenchymal stromal cells. Proinflammatory cytokines dramatically increase expression of 11ß-HSD1 in stromal cells, an effect that has been implicated in inflammatory arthritis, osteoporosis, obesity, and myopathy. Additionally, GCs act synergistically with proinflammatory cytokines to further increase enzyme expression. The present study was undertaken to investigate the mechanisms underlying this regulation. METHODS: Gene reporter analysis, rapid amplification of complementary DNA ends (RACE), chemical inhibition experiments, and genetic disruption of intracellular signaling pathways in mouse embryonic fibroblasts (MEFs) were used to define the molecular mechanisms underlying the regulation of 11ß-HSD1 expression. RESULTS: Gene reporter, RACE, and chemical inhibitor studies demonstrated that the increase in 11ß-HSD1 expression with tumor necrosis factor α (TNFα)/interleukin-1ß (IL-1ß) occurred via the proximal HSD11B1 gene promoter and depended on NF-κB signaling. These findings were confirmed using MEFs with targeted disruption of NF-κB signaling, in which RelA (p65) deletion prevented TNFα/IL-1ß induction of 11ß-HSD1. GC treatment did not prevent TNFα-induced NF-κB nuclear translocation. The synergistic enhancement of TNFα-induced 11ß-HSD1 expression with GCs was reproduced by specific inhibitors of p38 MAPK. Inhibitor and gene deletion studies indicated that the effects of GCs on p38 MAPK activity occurred primarily through induction of dual-specificity phosphatase 1 expression. CONCLUSION: The mechanism by which stromal cell expression of 11ß-HSD1 is regulated is novel and distinct from that in other tissues. These findings open new opportunities for development of therapeutic interventions aimed at inhibiting or stimulating local GC levels in cells of mesenchymal stromal lineage during inflammation.