Arthritis Research & Therapy - Latest Articles

A novel in vitro bovine cartilage punch model for assessing the regeneration of focal cartilage defects with biocompatible bacterial nanocellulose

David Pretzel — 2013-05-14T00:00:00Z

IntroductionCurrent therapies for articular cartilage defects fail to achieve qualitatively sufficient tissue regeneration, possibly because of a mismatch between the speed of cartilage rebuilding and the resorption of degradable implant polymers. The present study focused on the self-healing capacity of resident cartilage cells in conjunction with cell-free and biocompatible (but non-resorbable) bacterial nanocellulose (BNC). This was tested in a novel in vitro bovine cartilage punch model. Methods: Standardized bovine cartilage discs with a central defect filled with BNC were cultured for up to 8 weeks with/without stimulation with TGF-beta1. Cartilage formation and integrity were analyzed by histology, immunohistochemistry, and electron microscopy. Content, release, and neosynthesis of the matrix molecules proteoglycan/aggrecan, collagen II, and collagen I were also quantified. Finally, gene expression of these molecules was profiled in resident chondrocytes and chondrocytes migrated onto the cartilage surface or the implant material. Results: Non-stimulated and especially TGF-beta1-stimulated cartilage discs displayed a preserved structural and functional integrity of the chondrocytes and surrounding matrix, remained vital in long-term culture (8 weeks) without signs of degeneration, and showed substantial synthesis of cartilage-specific molecules at the protein and mRNA level. Whereas mobilization of chondrocytes from the matrix onto the surface of cartilage and implant was pivotal for successful seeding of cell-free BNC, chondrocytes did not immigrate into the central BNC area, possibly due to the relatively small diameter of its pores (2-5 um). Chondrocytes on the BNC surface showed signs of successful redifferentiation over time, including increase of aggrecan/collagen type II mRNA, decrease of collagen type I mRNA, and initial deposition of proteoglycan and collagen type II in long-term high-density pellet cultures. Although TGF-beta1 stimulation showed protective effects on matrix integrity, effects on other parameters were limited. Conclusions: The present bovine cartilage punch model represents a robust, reproducible, and highly suitable tool for the long-term culture of cartilage, maintaining matrix integrity and homoeostasis. As an alternative to animal studies, this model may closely reflect early stages of cartilage regeneration, allowing the evaluation of promising biomaterials with/without chondrogenic factors.

Adenosine A2A receptors promote collagen production by a Fli1- and CTGF-mediated mechanism

Edwin Chan — 2013-05-11T00:00:00Z

IntroductionAdenosine, acting through the A2A receptor, promotes tissue matrix production in the skin and the liver and induces the development of dermal fibrosis and cirrhosis in murine models. Since expression of A2A receptors is increased in scleroderma fibroblasts, we examined the mechanisms by which the A2A receptor produces its fibrogenic effects. Methods: The effects of A2A receptor ligation on the expression of the transcription factor, Fli1, a constitutive repressor for the synthesis of matrix proteins, such as collagen, is studied in dermal fibroblasts. Fli1 is also known to repress the transcription of CTGF/CCN2, and the effects of A2A receptor stimulation on CTGF and TGF-beta1 expression are also examined. Results: A2A receptor occupancy suppresses the expression of Fli1 by dermal fibroblasts. A2A receptor activation induces the secretion of CTGF by dermal fibroblasts, and neutralization of CTGF abrogates the A2A receptor-mediated enhancement of collagen type I production. A2AR activation, however, resulted in a decrease in TGF-beta1 protein release. Conclusions: Our results suggest that Fli1 and CTGF are important mediators of the fibrogenic actions of adenosine and the use of small molecules such as adenosine A2A receptor antagonists may be useful in the therapy of dermal fibrosis in diseases such as scleroderma.

Correction: TNF/TNFR signal transduction pathway-mediated anti-apoptosis and anti-inflammatory effects of sodium ferulate on IL-1beta-induced rat osteoarthritis chondrocytes in vitro

Abigail Jones — 2013-05-10T00:00:00Z

N/A

A complicated liaison: IL-33 and IL-33R in arthritis pathogenesis

Thomas Kamradt — 2013-05-02T00:00:00Z

Interruption of cytokine signaling, by targeting either the cytokine itself or its cellular receptor, is a mainstay in the therapy for patients with rheumatic diseases. Interleukin (IL)-33, a member of the IL-1 cytokine family, has emerged as an important mediator of inflammatory responses. In a side-by-side examination of IL-33-deficient and IL-33 receptor (IL-33R)-deficient mice in the K/BxN serum transfer model, arthritis was ameliorated in the IL-33R knockout (KO) mice but not in the IL-33 KO mice. These findings complement previous knowledge on IL-33R signaling, demonstrating that the IL-33R cross-activates other signaling pathways in addition to IL-33-mediated signals. The results reported by Martin and colleagues in a previous issue of Arthritis Research & Therapy underline the clinical relevance of IL-33R cross-signaling and further illustrate that targeting a cytokine receptor (IL-33R) can have completely different clinical outcomes than targeting the respective cytokine.

What can rheumatologists learn from translational cancer therapy?

Jonathan Sherlock — 2013-05-01T00:00:00Z

It is well established that an intimate connection exists between inflammation and neoplasia. Indeed, particular chronic infections and autoimmune processes giving rise to prolonged site-specific inflammation are known to increase the probability of the development of specific cancers. Molecular characterisation of these processes has revealed profound similarities in the specific molecules involved in persistence of inflammation and in both the primary induction of neoplastic processes and in specification of the preferred anatomic sites of metastatic spread. The therapeutic importance of these findings is underscored by the remarkable success in the treatment of autoimmune pathology using medications initially developed for use in oncology and this arena is one of considerable therapeutic promise for rheumatologists.

MMP-2 mediates local degradation and remodeling of collagen by annulus fibrosus cells of the intervertebral disc

Anshu Rastogi — 2013-04-27T00:00:00Z

IntroductionDegeneration of the intervertebral disc (IVD) is characterized by marked degradation and re-structuring of the annulus fibrosus (AF). While several matrix metalloproteinases (MMPs) have been found to be more prevalent in degenerate discs, their coordination and function within the context of the disease process are still not well understood. In this study, we sought to determine whether MMP-2 is associated with degenerative changes in the AF, and to identify the manner by which AF cells utilize MMP-2. Methods: Two established animal models of disc degeneration, static compression and trans-annular needle puncture of rodent caudal discs, were examined for MMP-2 immunopositivity. Using lentiviral transduction of an shRNA expression cassette we screened and identified an effective shRNA sequence for generating stable RNA interference to silence MMP-2 expression in primary rat AF cells. Gelatin films were used to compare gelatinase activity and spatial patterns of degradation between transduced cells, and both non-infected and nonsense shRNA controls. The functional significance of MMP-2 was determined by assessing the ability for cells to remodel collagen gels. Results: Both static compression and 18g annular puncture of rodent caudal discs stimulated an increase in MMP-2 activity with concurrent lamellar disorganization in the AF, while 22g and 26g needle injuries did not. To investigate the functional role of MMP-2, we established lentivirus-mediated RNAi to induce stable knock down of transcript levels by as much as 88%, and protein levels by as much as 95% over 10 days. Culturing transduced cells on gelatin films confirmed that MMP-2 is the primary functional gelatinase in AF cells, and that MMP-2 is utilized locally in regions immediately around AF cells. In collagen gels, transduced cells demonstrated an inability to remodel collagen matrices. Conclusions: Our study indicates that increases in MMP-2 observed in human degenerate discs are mirrored in experimentally-induced degenerative changes in rodent animal models. AF cells appear to utilize MMP-2 in a very directed fashion for local matrix degradation and collagen remodeling. This suggests that MMP-2 may have a functionally significant role in the etiology of degenerative disc disease, and could be a potential therapeutic target.

Cigarette smoking and smoking cessation in relation to risk of rheumatoid arthritis in women

Daniela Di Giuseppe — 2013-04-22T00:00:00Z

IntroductionWhereas the overall association between smoking and rheumatoid arthritis (RA) must be regarded as established, considerably less is known about how much smoking is needed to increase the risk of RA, that is, the effect of smoking intensity, duration and cessation. Methods: The Swedish Mammography Cohort, including 34,101 women aged 54 to 89 years, was followed up from January 1, 2003 through December 31, 2010 (219 RA cases identified). Relative risks (RR) and their 95% confidence intervals (CI) were estimated as rate ratios using Cox proportional hazards model. Results: There was a statistically significant association between smoking intensity (RR comparing 1 to 7 cigarettes/day vs never smoking 2.31 (95% CI: 1.59, 3.36)) as well as duration of smoking (comparing 1 to 25 years vs never smoking RR = 1.60 (95% CI: 1.07, 2.38)) and risk of RA. Compared to never smokers, the risk was still significantly elevated 15 years after smoking cessation (RR = 1.99 (95% CI: 1.23, 3.20)). However, among former smokers, the risk of RA seemed to be decreasing over time since stopping smoking: women who stopped smoking 15 years before the start of the follow-up had 30% lower risk of RA compared to those who stopped only a year before start of the follow-up (RR = 0.70 (95% CI: 0.24,2.02)). Conclusions: This prospective study highlights that even light cigarette smoking is associated with increased risk of RA in women and that smoking cessation may reduce, though not remove, this risk.

Correlations between angiogenic factors and capillaroscopic patterns in systemic sclerosis

Jerome Avouac — 2013-04-19T00:00:00Z

IntroductionTo assess whether nailfold videocapillaroscopy (NVC) patterns are associated with levels of angiogenic factors in systemic sclerosis (SSc). Methods: Circulating endothelial progenitor cells (EPCs) and circulating endothelial cells (CECs) were measured in the peripheral blood of 60 consecutive SSc patients. Serum levels of eight endothelial markers were first measured in these 60 patients, and then in an independent replication cohort of 43 SSc patients in case of association with NVC patterns. NVC patterns were determined by four independent investigators blinded to vascular markers. Results: Patients with the late NVC pattern exhibited lower EPC levels (p<0.0001) and higher VEGF levels (p=0.03). Higher VEGF levels were confirmed to be associated with the late NVC pattern in the replication cohort (p=0.01). By multivariate analysis focused on biomarkers, lower EPC (p=0.03) and higher VEGF levels (p=0.001) were independently associated with the late NVC pattern. In an alternate multivariate model including these 2 factors and SSc-related disease characteristics, lower EPC counts (p=0.005), higher VEGF levels (p=0.01), history of digital ulcers (p=0.04) and a modified Rodnan skin score >14 (p<0.0001), were independently associated with the late NVC pattern. Conclusion: Our data revealed decreased EPC counts and increased VEGF levels in patients with the late NVC pattern. Further studies are now needed to determine the role of VEGF and EPCs in endothelial injury and repair in SSc.

Open label study of escalating doses of oral treprostinil diethanolamine in patients with systemic sclerosis and digital ischemia: pharmacokinetics and correlation with digital perfusion

Ami Shah — 2013-04-18T00:00:00Z

IntroductionTreprostinil diethanolamine is an innovative salt form of the prostacyclin analogue, treprostinil sodium, developed as an oral sustained release (SR) osmotic tablet. The availability of a formulation permitting convenient systemic delivery might have applicability to scleroderma vascular complications. We evaluated pharmacokinetics and perfusion in scleroderma patients with digital ischemia following escalating twice-daily doses of treprostinil diethanolamine SR. Methods: In this dual-center, open-label, phase I pharmacokinetic study, scleroderma patients with digital ulcers were enrolled. Drug concentrations and perfusion, quantified by laser Doppler imaging, were measured over 12 hours at the 2mg and 4mg (or maximally tolerated) doses. Pharmacokinetic parameters were determined from individual plasma concentration versus time profiles using non-compartmental analysis methods. Digital perfusion and skin temperature were modeled as a function of log-transformed drug concentration and other covariates by performing repeated measures analyses using random effects models. Results: Nineteen scleroderma patients (84% female, 53% limited scleroderma) received treprostinil diethanolamine SR with dose titration up to 4mg twice daily as tolerated. Peak concentrations (mean maximum plasma concentration [Cmax] = 1176 and 2107 pg/mL) occurred approximately 3.6 hours after dose administration, and overall exposure (under the plasma concentration-time curve from time 0 to 12 hours post dose [AUC0-12] = 7187 and 12992 hr*pg/mL) was linear between the 2mg and 4mg doses. Perfusion and digital skin temperature were positively associated with log-transformed plasma concentration at the 4mg dose (p=0.015 and p=0.013, respectively). The most frequent adverse events were similar to those seen with prostacyclin analogues. Conclusions: Oral treprostinil diethanolamine was effectively absorbed in patients with scleroderma. Drug administration was temporally associated with improved cutaneous perfusion and temperature. Treprostinil diethanolamine may provide a new therapeutic option for Raynaud's phenomenon and the peripheral vascular disease of scleroderma.Trial Registration: ClinicalTrials.gov NCT00848939.

Gene-environment interaction between body mass index and transforming growth factor beta 1 (TGFbeta1) gene in knee and hip osteoarthritis

Stella Muthuri — 2013-04-18T00:00:00Z

IntroductionThe objective was to investigate potential gene-environment interaction between body mass index (BMI) and each of eight TGFbeta1 polymorphisms in knee and hip osteoarthritis (OA). Methods: We conducted a case-control study of Caucasian men and women aged 45-86 years from Nottingham, United Kingdom (Genetics of OA and Lifestyle [GOAL] study). Cases had clinically severe symptoms and radiographic knee or hip OA; controls had no symptoms and no radiographic knee/hip OA. We used logistic regression to investigate the association of TGFbeta1 polymorphisms and OA when stratifying by BMI. Knee and hip OA were analyzed separately with adjustment for potential confounders. Additive and multiplicative interactions were examined. Results: 2048 cases (1042 knee OA, 1006 hip OA) and 967 controls were studied. For hip OA, the highest risk was in overweight (BMI[greater than or equal to]25kg/m2) individuals with the variant allele of single-nucleotide polymorphism (SNP) rs1800468 (odds ratio [OR] 2.21, 95% confidence interval [CI] 1.55-3.15). Evaluation of gene-environment interaction indicated significant synergetic interaction (relative excess risk due to interaction [RERI]=0.93, synergy index [SI]=4.33) with an attributable proportion due to interaction (AP) of 42% (AP=0.42; 95%CI 0.16-0.68). Multiplicative interaction was also significant (OR for interaction [ORINT]=2.27, p=0.015). For knee OA, the highest risk was in overweight individuals with homozygous genotype 11 of SNP rs2278422 (OR=6.95, p<0.001). In contrast, the variant allele indicated slightly lower risks (OR= 4.72, p<0.001), a significant antagonistic interaction (RERI= -2.66, SI=0.59), AP= -0.56 (95%CI -0.94- -0.17) and a significant multiplicative interaction (ORINT=0.47, p=0.013). Conclusion: TGFbeta1 gene polymorphisms interact with being overweight to influence the risk of large joint OA.