Real-world validation of the minimal disease activity index in psoriatic arthritis: an analysis from a prospective, observational, biological treatment registry

OBJECTIVE

To describe the minimal disease activity (MDA) rate over time in patients with psoriatic arthritis (PsA) receiving antitumour necrosis factor agents, evaluate prognostic factors of MDA achievement and identify the most common unmet criteria among MDA achievers.

DESIGN

Biologic Treatment Registry Across Canada (BioTRAC): ongoing, prospective registry of patients initiating treatment for rheumatoid arthritis, ankylosing spondylitis or PsA with infliximab (IFX), golimumab (GLM) or ustekinumab.

SETTING

46 primary-care Canadian rheumatology practices.

PARTICIPANTS

223 patients with PsA receiving IFX (enrolled since 2005) and GLM (enrolled since 2010) with available MDA information at baseline, 6 months and/or 12 months.

PRIMARY AND SECONDARY OUTCOME MEASURES

MDA was defined as ≥5 of the following criteria: 28-item tender joint count (TJC28) ≤1, 28-item swollen joint count (SJC28) ≤1, Psoriasis Area and Severity Index (PASI) ≤1 or body surface area≤3, Pain Visual Analogue Scale (VAS) ≤15 mm, patient's global assessment (PtGA) (VAS) ≤20 mm, Health Assessment Questionnaire (HAQ) ≤0.5, tender entheseal points ≤1. Independent prognostic factors of MDA achievement were assessed with multivariate logistic regression.

RESULTS

MDA was achieved by 11.7% of patients at baseline, 43.5% at 6 months, 44.8% at 12 months and 48.8% at either 6 or 12 months. Among MDA achievers at 6 months, 75.7% had sustained MDA at 12 months. Lower baseline HAQ (OR=0.210; 95% CI: 0.099 to 0.447) and lower TJC28 (OR=0.880; 95% CI: 0.804 to 0.964), were significant prognostic factors of MDA achievement over 12 months of treatment. The most commonly unmet MDA criteria among MDA achievers was patient reported pain (25%), PtGA (15%) and PASI (12%).

CONCLUSIONS

Almost 50% of patients treated with IFX or GLM in routine clinical care achieved MDA within the first year of treatment. Lower baseline HAQ and lower TJC28, were identified as significant prognostic factors of MDA achievement. The most commonly unmet criteria in patients who achieved MDA were pain, PtGA and PASI.

TRIAL REGISTRATION NUMBER

BioTRAC (NCT00741793).

Ixekizumab for the treatment of patients with active psoriatic arthritis and an inadequate response to tumour necrosis factor inhibitors: results from the 24-week randomised, double-blind, placebo-controlled period of the SPIRIT-P2 phase 3 trial

BACKGROUND

Patients who have had inadequate response to tumour necrosis factor inhibitors have fewer treatment options and are generally more treatment refractory to subsequent therapeutic interventions than previously untreated patients. We report the efficacy and safety of ixekizumab, a monoclonal antibody that selectively targets interleukin-17A, in patients with active psoriatic arthritis and previous inadequate response to tumour necrosis factor inhibitors.

METHODS

In this double-blind, multicentre, randomised, placebo-controlled, phase 3 study (SPIRIT-P2), patients were recruited from 109 centres across ten countries in Asia, Australia, Europe, and North America. Patients were aged 18 years or older, had a confirmed diagnosis of psoriatic arthritis for at least 6 months, and had a previous inadequate response, distinguished by being refractory to therapy or had loss of efficacy, or were intolerant to tumour necrosis factor inhibitors. Patients were randomly assigned (1:1:1) by a computer-generated random sequence to receive a subcutaneous injection of 80 mg ixekizumab every 4 weeks or every 2 weeks after a 160 mg starting dose or placebo. The primary endpoint was the proportion of patients who attained at least 20% improvement in the American College of Rheumatology response criteria (ACR-20) at week 24. This study is registered with ClinicalTrials.gov, number NCT02349295.

FINDINGS

Between March 3, 2015, to March 22, 2016, 363 patients were randomly assigned to placebo (n=118), ixekizumab every 4 weeks (n=122), or ixekizumab every 2 weeks (n=123). At week 24, a higher proportion of patients attained ACR-20 with ixekizumab every 4 weeks (65 [53%] patients; effect size vs placebo 33·8% [95% CI 22·4-45·2]; p<0·0001) and ixekizumab every 2 weeks (59 [48%] patients; 28.5% [17·1-39.8]; p<0·0001) than did patients with placebo (23 [20%] patients). Up to week 24, serious adverse events were reported in three (3%) patients with ixekizumab every 4 weeks, eight (7%) with ixekizumab every 2 weeks, and four (3%) with placebo; no deaths were reported. Infections were reported in 47 (39%) patients with ixekizumab every 4 weeks, 47 (38%) with ixekizumab every 2 weeks, and 35 (30%) with placebo. Three (2%) serious infections, all in patients in the ixekizumab every 2 weeks group, were reported.

INTERPRETATION

Both the 2-week and 4-week ixekizumab dosing regimens improved the signs and symptoms of patients with active psoriatic arthritis and who had previously inadequate response to tumour necrosis factor inhibitors, with a safety profile consistent with previous studies investigating ixekizumab.

FUNDING

Eli Lilly and Company.

Large scale meta-analysis characterizes genetic architecture for common psoriasis associated variants

Psoriasis is a complex disease of skin with a prevalence of about 2%. We conducted the largest meta-analysis of genome-wide association studies (GWAS) for psoriasis to date, including data from eight different Caucasian cohorts, with a combined effective sample size >39,000 individuals. We identified 16 additional psoriasis susceptibility loci achieving genome-wide significance, increasing the number of identified loci to 63 for European-origin individuals. Functional analysis highlighted the roles of interferon signalling and the NFκB cascade, and we showed that the psoriasis signals are enriched in regulatory elements from different T cells (CD8⁺ T-cells and CD4⁺ T-cells including T_H0, T_H1 and T_H17). The identified loci explain ∼28% of the genetic heritability and generate a discriminatory genetic risk score (AUC=0.76 in our sample) that is significantly correlated with age at onset (p=2 × 10^-89). This study provides a comprehensive layout for the genetic architecture of common variants for psoriasis.

Treating Psoriasis and Psoriatic Arthritis: Position Paper on Applying the Treat-to-target Concept to Canadian Daily Practice

Objective.

To develop preliminary treat-to-target (T2T) recommendations for psoriasis and psoriatic arthritis (PsA) for Canadian daily practice.

Methods.

A task force composed of expert Canadian dermatologists and rheumatologists performed a needs assessment among Canadian clinicians treating these diseases as well as an extensive literature search on the outcome measures used in clinical trials and practice.

Results.

Based on results from the needs assessment and literature search, the task force established 5 overarching principles and developed 8 preliminary T2T recommendations.

Conclusion.

The proposed recommendations should improve management of psoriasis and PsA in Canadian daily practice. However, these recommendations must be further validated in a real-world observational study to ensure that their use leads to better longterm outcomes.

Ustekinumab Treatment and Improvement of Physical Function and Health-Related Quality of Life in Patients With Psoriatic Arthritis

Objective

To examine the effects of ustekinumab on patient‐reported outcomes (PROs) in PSUMMIT 1 and PSUMMIT 2 patients with active psoriatic arthritis (PsA) who were methotrexate (MTX) naive, MTX experienced, or anti–tumor necrosis factor (TNF) experienced.

Methods

Patients in the phase 3, PSUMMIT 1 (n = 615) and PSUMMIT 2 (n = 312) studies randomly (1:1:1) received placebo, ustekinumab 45‐mg, or ustekinumab 90‐mg subcutaneous injections at weeks 0, 4, 16, 28, 40, and 52. The PROs (Health Assessment Questionnaire [HAQ] disability index [DI], Dermatology Life Quality Index [DLQI], 36‐Item Short Form [SF‐36] health survey physical (PCS) and mental component summary scores, patient assessments of pain and disease activity, and impact of disease on productivity) were assessed at weeks 0, 24, and 52. In these post hoc analyses, outcomes were compared between the ustekinumab and placebo groups for 3 mutually exclusive antecedent‐exposure populations from the combined studies: MTX/anti‐TNF naive (placebo, n = 56; 45 mg, n = 58; and 90 mg, n = 66), MTX experienced, biologic agent naive (placebo, n = 192; 45 mg, n = 190; and 90 mg, n = 185), and anti‐TNF experienced with or without MTX (placebo, n = 62; 45 mg, n = 60; and 90 mg, n = 58).

Results

At week 24, mean improvements from baseline in HAQ DI, DLQI, and SF‐36 PCS scores were significantly greater in both ustekinumab groups versus placebo across antecedent‐exposure groups. Greater proportions of ustekinumab‐treated than placebo‐treated patients (all P < 0.05) had clinically meaningful improvements in HAQ DI (≥0.3), DLQI (≥5), and SF‐36 (≥5) scores at week 24, irrespective of drug exposure. Improvements in pain, disease activity, and impact of disease on productivity were similar, and benefits were maintained through week 52.

Conclusion

Significant improvements in PROs with ustekinumab versus placebo were observed in 3 antecedent‐exposure populations of PsA patients, including those with prior MTX and anti‐TNF use.

Lysophosphatidylcholines to phosphatidylcholines ratio predicts advanced knee osteoarthritis

OBJECTIVE

To identify novel biomarker(s) for predicting advanced knee OA.

METHODS

Study participants were derived from the Newfoundland Osteoarthritis Study and the Tasmania Older Adult Cohort Study. All knee OA cases were patients who underwent total knee replacement (TKR) due to primary OA. Metabolic profiling was performed on fasting plasma. Four thousand and eighteen plasma metabolite ratios that were highly correlated with that in SF in our previous study were generated as surrogates for joint metabolism.

RESULTS

The discovery cohort included 64 TKR cases and 45 controls and the replication cohorts included a cross-sectional cohort of 72 TKR cases and 76 controls and a longitudinal cohort of 158 subjects, of whom 36 underwent TKR during the 10-year follow-up period. We confirmed the previously reported association of the branched chain amino acids to histidine ratio with advanced knee OA (P = 9.3 × 10(-7)) and identified a novel metabolic marker-the lysophosphatidylcholines (lysoPCs) to phosphatidylcholines (PCs) ratio-that was associated with advanced knee OA (P = 1.5 × 10(-7)) after adjustment for age, sex and BMI. When the subjects of the longitudinal cohort were categorized into two groups based on the optimal cut-off of the ratio of 0.09, we found the subjects with the ratio ⩾0.09 were 2.3 times more likely to undergo TKR than those with the ratio <0.09 during the 10-year follow-up (95% CI: 1.2, 4.3, P = 0.02).

CONCLUSION

We identified the ratio of lysoPCs to PCs as a novel metabolic marker for predicting advanced knee OA. Further studies are required to examine whether this ratio can predict early OA change.

Pharmacogenetics and pharmacogenomics in psoriasis treatment: current challenges and future prospects

INTRODUCTION

Topical, systemic, oral disease modifying, and biologic agents are part of the armamentarium to manage psoriatic disease. The choice of therapy depends upon disease severity, relevant co-morbidities and patient preference. There is great variability in patient response with these agents, and there is still no clear method of selecting the preferred therapeutic agent for efficacy or lack of adverse events.

AREAS COVERED

This article will review the pharmacogenetic and pharmacogenomic targets that are currently known with respect to psoriasis vulgaris, and the most frequent co-morbidity of psoriasis, psoriatic arthritis.

EXPERT OPINION

Presently, no clinically actionable biomarker exists for any therapeutic agent used to treat psoriasis or psoriatic arthritis. The lack of validated outcome measures and conflicting results of open-label studies conducted may be attributed to a multitude of issues that confound discovery. Consequently, studies have been underpowered to identify genes or genetic variants worth translating to clinical practice. In order to achieve a pharmacogenetic/pharmacogenomic signature, improvements in study design of future investigations are required, including carefully designed prospective studies. It is imperative to combine known clinical, serological, and molecular markers with consistent outcomes and an adequate health economic evaluation before they can be adopted widely in clinical practice.

Maintenance of Clinical Efficacy and Radiographic Benefit Through Two Years of Ustekinumab Therapy in Patients With Active Psoriatic Arthritis: Results From a Randomized, Placebo-Controlled Phase III Trial

Objective

To evaluate the efficacy and safety of ustekinumab through 2 years in adult patients with active psoriatic arthritis (PsA).

Methods

A total of 615 adult patients with active PsA were randomized to placebo, ustekinumab 45 mg, or ustekinumab 90 mg, at weeks 0, 4, and every 12 weeks through week 88 (last dose). At week 16, patients with <5% improvement in both tender and swollen joint counts entered blinded early escape (placebo to 45 mg, 45 mg to 90 mg, and 90 mg to 90 mg). All remaining placebo patients crossed over to ustekinumab 45 mg at week 24. Clinical efficacy measures included American College of Rheumatology criteria for 20% improvement (ACR20), Disease Activity Score in 28 joints using the C‐reactive protein level (DAS28‐CRP), and ≥75% improvement in the Psoriasis Area and Severity Index (PASI75). Radiographic progression was evaluated using the modified Sharp/van der Heijde score (SHS).

Results

At week 100, ACR20, DAS28‐CRP moderate/good response, and PASI75 rates ranged from 56.7–63.6%, 71.9–76.7%, and 63.9–72.5%, respectively, across the 3 treatment groups. In both ustekinumab groups, the median percent improvement in dactylitis and enthesitis was 100% at week 100. The mean changes in SHS score from week 52 to week 100 were similar to those observed from week 0 to week 52 in the ustekinumab groups. Through week 108, 70.7% and 9.7% of patients had an adverse event (AE) or serious AE, respectively. The rates and type of AEs were similar between the dose groups.

Conclusion

Clinical and radiographic benefits from ustekinumab treatment were maintained through week 100 in the PSUMMIT 1 study. No unexpected safety events were observed; the safety profile of ustekinumab in this population was similar to that previously observed in psoriasis patients treated with ustekinumab.

Metabolomic analysis of human plasma reveals that arginine is depleted in knee osteoarthritis patients

OBJECTIVE

To identify novel biomarker(s) for knee osteoarthritis (OA) using a metabolomics approach.

METHOD

We utilized a two-stage case-control study design. Plasma samples were collected from knee OA patients and healthy controls after 8-h fasting and metabolically profiled using a targeted metabolomics assay kit. Linear regression was used to identify novel metabolic markers for OA. Receiver operating characteristic (ROC) analysis was used to examine diagnostic values. Gene expression analysis was performed on human cartilage to explore the potential mechanism for the novel OA marker(s).

RESULTS

Sixty-four knee OA patients and 45 controls were included in the discovery stage and 72 knee OA patients and 76 age and sex matched controls were included in the validation stage. We identified and confirmed six metabolites that were significantly associated with knee OA, of which arginine was the most significant metabolite (P < 3.5 × 10(-13)) with knee OA patients having on average 69 μM lower than that in controls. ROC analysis showed that arginine had the greatest diagnostic value with area under the curve (AUC) of 0.984. The optimal cutoff of arginine concentration was 57 μM with 98.3% sensitivity and 89% specificity. The depletion of arginine in OA patients was most likely due to the over activity of arginine to ornithine pathway, leading to imbalance between cartilage repair and degradation.

CONCLUSION

Arginine is significantly depleted in refractory knee OA patients. Further studies within a longitudinal setting are required to examine whether arginine can predict early OA changes.

Efficacy and safety of ustekinumab in psoriatic arthritis patients with peripheral arthritis and physician-reported spondylitis: post-hoc analyses from two phase III, multicentre, double-blind, placebo-controlled studies (PSUMMIT-1/PSUMMIT-2)

Objective

To evaluate ustekinumab efficacy and safety in psoriatic arthritis (PsA) patients with peripheral arthritis and physician-reported spondylitis (termed the ‘spondylitis subset’).

Methods

Adults with active PsA (PSUMMIT-1/PSUMMIT-2, n=615/312) were randomised to ustekinumab 45 mg, 90 mg or placebo at week 0/week 4/q12 week. At week 16, patients with <5% improvement in tender and swollen joints entered blinded early escape. A subset of patients with physician-identified spondylitis was evaluated with spondylitis-specific assessments, including Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) and Ankylosing Spondylitis Disease Activity Score employing C reactive protein (ASDAS-CRP), through week 24.

Results

256/927 (27.6%) PSUMMIT-1/PSUMMIT-2 patients (placebo/ustekinumab, n=92/164) comprised the evaluable spondylitis subset. At week 24, in this analysis subset, significantly more patients achieved BASDAI20/50/70 responses (54.8%/29.3%/15.3% vs 32.9%/11.4%/0%; p≤0.002), improvement in BASDAI question 2 concerning axial pain (1.85 vs 0.24; p<0.001) and mean per cent ASDAS-CRP improvements (27.8% vs 3.9%; p<0.001) for ustekinumab versus placebo recipients, respectively. Comparable to the overall study population, significant improvements were also achieved in psoriasis, peripheral arthritis, enthesitis, dactylitis, physical function and peripheral joint radiographs in the spondylitis subset.

Conclusions

In this post-hoc analysis of PsA patients with baseline peripheral arthritis and physician-reported spondylitis, ustekinumab-treated patients demonstrated significant improvements in axial signs and symptoms through week 24.

Trial registration number

PSUMMIT-1 (NCT01009086, EudraCT 2009-012264-14) and PSUMMIT-2 (NCT01077362, EudraCT 2009-012265-60); post-study results.

Biologic Treatment Registry Across Canada (BioTRAC): a multicentre, prospective, observational study of patients treated with infliximab for ankylosing spondylitis

OBJECTIVES

To describe the profile of patients with ankylosing spondylitis (AS) treated with infliximab in Canadian routine care and to assess the effectiveness and safety of infliximab in real world.

SETTING

46 primary care rheumatology practices across Canada.

PARTICIPANTS

303 biological-naïve patients with AS or patients previously treated with a biological for <6 months and who were eligible for infliximab treatment as per routine care within the Biologic Treatment Registry Across Canada (BioTRAC).

INTERVENTION

Not applicable (non-interventional study).

PRIMARY AND SECONDARY OUTCOMES

Effectiveness was assessed with changes in disease parameters (AS Disease Activity Score (ASDAS), Bath AS Disease Activity Index (BASDAI), Bath AS Functional Index (BASFI), Health Assessment Questionnaire Disease Index (HAQ-DI), physician global assessment of disease activity (MDGA), patient global disease activity (PtGA), back pain, C-reactive protein, erythrocyte sedimentation rate (ESR), morning stiffness). Safety was assessed with the incidence of adverse events (AEs).

RESULTS

Of the 303 patients included, 44.6% were enrolled in 2005-2007 and 55.4% in 2008-2013. Patients enrolled in 2005-2007 had significantly higher MDGA and ESR at baseline while all other disease parameters examined were numerically higher with the exception of PtGA. Treatment with infliximab significantly (p<0.001) improved all disease parameters over time in both groups. At 6 months, 56% and 31% of patients achieved clinically important (change≥1.1) and major (change≥2.0) improvement in ASDAS, respectively; at 48 months, these proportions increased to 75% and 50%, respectively. Among patients unemployed due to disability at baseline, 12.1% returned to work (mean Kaplan-Meier (KM)-based time=38.8 months). The estimated retention rate at 12 and 24 months was 78.3% and 60.1%, respectively. The profile and incidence of AEs were comparable to data previously reported for tumour necrosis factor-α inhibitors.

CONCLUSIONS

Characteristics of patients with AS at infliximab initiation changed over time towards lower disease activity and shorter disease duration. Infliximab treatment significantly reduced disease activity independent of treatment initiation year, although patients enrolled in recent years achieved lower disease activity over 48 months.

TRIAL REGISTRATION NUMBER

NCT00741793.

Efficacy and Safety of Subcutaneous and Intravenous Loading Dose Regimens of Secukinumab in Patients with Active Rheumatoid Arthritis: Results from a Randomized Phase II Study

OBJECTIVE

To evaluate the efficacy and safety of secukinumab, a fully human antiinterleukin-17A monoclonal antibody, administered with an intravenous (IV) or subcutaneous (SC) loading regimen versus placebo, in patients with active rheumatoid arthritis (RA).

METHODS

In this phase II, double-blind, double-dummy, 52-week study (ClinicalTrials.gov NCT01359943), 221 patients with inadequate response to methotrexate were randomized (2:2:1) to secukinumab, IV loading 10 mg/kg at baseline, Weeks 2 and 4, then SC 150 mg every 4 weeks (n = 88); secukinumab SC loading 150 mg once weekly for 5 weeks, then every 4 weeks (n = 89); or a matching placebo (followed by secukinumab 150 mg every 4 weeks starting Week 16; n = 44). The primary endpoint was superior efficacy of pooled secukinumab versus placebo using American College of Rheumatology 20% response (ACR20) at Week 12.

RESULTS

The primary efficacy endpoint was not met: ACR20 response at Week 12 was 49.2% for pooled secukinumab versus 40.9% for placebo (p = 0.3559). These variables improved significantly with pooled secukinumab versus placebo at Week 12 (all p < 0.05): the 28-joint Disease Activity Score (DAS28), patient's and physician's global assessment of disease activity, patient's assessment of RA pain, and high-sensitivity C-reactive protein levels. Results of continuous efficacy outcomes were similar between the IV and SC loading regimens. The most frequent adverse events were infections, with similar rates across secukinumab and placebo.

CONCLUSION

Although the primary endpoint (ACR20) was not met, secukinumab demonstrated improved efficacy in reducing disease activity over placebo as measured by DAS28 and other secondary endpoints.

Genetic structure of the Newfoundland and Labrador population: founder effects modulate variability

The population of the province of Newfoundland and Labrador (NL) has been a resource for genetic studies because of its historical isolation and increased prevalence of several monogenic disorders. Controversy remains regarding the genetic substructure and the extent of genetic homogeneity, which have implications for disease gene mapping. Population substructure has been reported from other isolated populations such as Iceland, Finland and Sardinia. We undertook this study to further our understanding of the genetic architecture of the NL population. We enrolled 494 individuals randomly selected from NL. Genome-wide SNP data were analyzed together with that from 14 other populations including HapMap3, Ireland, Britain and Native American samples from the Human Genome Diversity Project. Using multidimensional scaling and admixture analysis, we observed that the genetic structure of the NL population resembles that of the British population but can be divided into three clusters that correspond to religious/ethnic origins: Protestant English, Roman Catholic Irish and North American aboriginals. We observed reduced heterozygosity and an increased inbreeding coefficient (mean=0.005), which corresponds to that expected in the offspring of third-cousin marriages. We also found that the NL population has a significantly higher number of runs of homozygosity (ROH) and longer lengths of ROH segments. These results are consistent with our understanding of the population history and indicate that the NL population may be ideal for identifying recessive variants for complex diseases that affect populations of European origin.

SMAD3 Is Upregulated in Human Osteoarthritic Cartilage Independent of the Promoter DNA Methylation

Objective.

To compare SMAD3 gene expression between human osteoarthritic and healthy cartilage and to examine whether expression is regulated by the promoter DNA methylation of the gene.

Methods.

Human cartilage samples were collected from patients undergoing total hip/knee joint replacement surgery due to primary osteoarthritis (OA), and from patients with hip fractures as controls. DNA/RNA was extracted from the cartilage tissues. Real-time quantitative PCR was performed to measure gene expression, and Sequenom EpiTyper was used to assay DNA methylation. Mann-Whitney test was used to compare the methylation and expression levels between OA cases and controls. Spearman rank correlation coefficient was calculated to examine the association between the methylation and gene expression.

Results.

A total of 58 patients with OA (36 women, 22 men; mean age 64 ± 9 yrs) and 55 controls (43 women, 12 men; mean age 79 ± 10 yrs) were studied. SMAD3 expression was on average 83% higher in OA cartilage than in controls (p = 0.0005). No difference was observed for DNA methylation levels in the SMAD3 promoter region between OA cases and controls. No correlation was found between SMAD3 expression and promoter DNA methylation.

Conclusion.

Our study demonstrates that SMAD3 is significantly overexpressed in OA. This overexpression cannot be explained by DNA methylation in the promoter region. The results suggest that the transforming growth factor-β/SMAD3 pathway may be overactivated in OA cartilage and has potential in developing targeted therapies for OA.

Genome-wide Association Analysis of Psoriatic Arthritis and Cutaneous Psoriasis Reveals Differences in Their Genetic Architecture

Psoriasis vulgaris (PsV) is a common inflammatory and hyperproliferative skin disease. Up to 30% of people with PsV eventually develop psoriatic arthritis (PsA), an inflammatory musculoskeletal condition. To discern differences in genetic risk factors for PsA and cutaneous-only psoriasis (PsC), we carried out a genome-wide association study (GWAS) of 1,430 PsA case subjects and 1,417 unaffected control subjects. Meta-analysis of this study with three other GWASs and two targeted genotyping studies, encompassing a total of 9,293 PsV case subjects, 3,061 PsA case subjects, 3,110 PsC case subjects, and 13,670 unaffected control subjects of European descent, detected 10 regions associated with PsA and 11 with PsC at genome-wide (GW) significance. Several of these association signals (IFNLR1, IFIH1, NFKBIA for PsA; TNFRSF9, LCE3C/B, TRAF3IP2, IL23A, NFKBIA for PsC) have not previously achieved GW significance. After replication, we also identified a PsV-associated SNP near CDKAL1 (rs4712528, odds ratio [OR] = 1.16, p = 8.4 × 10(-11)). Among identified psoriasis risk variants, three were more strongly associated with PsC than PsA (rs12189871 near HLA-C, p = 5.0 × 10(-19); rs4908742 near TNFRSF9, p = 0.00020; rs10888503 near LCE3A, p = 0.0014), and two were more strongly associated with PsA than PsC (rs12044149 near IL23R, p = 0.00018; rs9321623 near TNFAIP3, p = 0.00022). The PsA-specific variants were independent of previously identified psoriasis variants near IL23R and TNFAIP3. We also found multiple independent susceptibility variants in the IL12B, NOS2, and IFIH1 regions. These results provide insights into the pathogenetic similarities and differences between PsC and PsA.

Genome-wide DNA methylation study of hip and knee cartilage reveals embryonic organ and skeletal system morphogenesis as major pathways involved in osteoarthritis

Background

Evidence suggests that epigenetics plays a role in osteoarthrits (OA). The aim of the study was to describethe genome wide DNA methylation changes in hip and knee OA and identify novel genes and pathwaysinvolved in OA by comparing the DNA methylome of the hip and knee osteoarthritic cartilage tissues withthose of OA-free individuals.

Methods

Cartilage samples were collected from hip or knee joint replacement patients either due to primary OA or hip fractures as controls. DNA was extracted from the collected cartilage and assayed by Illumina Infinium HumanMethylation450 BeadChip array, which allows for the analysis of >480,000 CpG sites. Student T-test was conducted for each CpG site and those sites with at least 10 % methylation difference and a p value <0.0005 were defined as differentially methylated regions (DMRs) for OA. A sub-analysis was also done for hip and knee OA separately. DAVID v6.7 was used for the functional annotation clustering of the DMR genes. Clustering analysis was done using multiple dimensional scaling and hierarchical clustering methods.

Results

The study included 5 patients with hip OA, 6 patients with knee OA and 7 hip cartilage samples from OA-free individuals. The comparisons of hip, knee and combined hip/knee OA patients with controls resulted in 26, 72, and 103 DMRs, respectively. The comparison between hip and knee OA revealed 67 DMRs. The overall number of the sites after considering the overlaps was 239, among which 151 sites were annotated to 145 genes. One-fifth of these genes were reported in previous studies. The functional annotation clustering of the identified genes revealed clusters significantly enriched in skeletal system morphogenesis and development. The analysis revealed significant difference among OA and OA-free cartilage, but less different between hip OA and knee OA.

Conclusions

We found that a number of CpG sites and genes across the genome were differentially methylated in OA patients, a remarkable portion of which seem to be involved in potential etiologic mechanisms of OA. Genes involved in skeletal developmental pathways and embryonic organ morphogenesis may be a potential area for further OA studies.

Electronic supplementary material

The online version of this article (doi:10.1186/s12891-015-0745-5) contains supplementary material, which is available to authorized users.