Advances in understanding the genetic basis of rheumatoid arthritis and osteoarthritis: implications for therapy

Genetics, environment, and gene-environment interactions in the development of systemic rheumatic diseases

Rheumatic diseases offer distinct challenges to researchers because of heterogeneity in disease phenotypes, low disease incidence, and geographic variation in genetic and environmental factors. Emerging research areas, including epigenetics, metabolomics, and the microbiome, may provide additional links between genetic and environmental risk factors in the pathogenesis of rheumatic disease. This article reviews the methods used to establish genetic and environmental risk factors and studies gene-environment interactions in rheumatic diseases, and provides specific examples of successes and challenges in identifying gene-environment interactions in rheumatoid arthritis, systemic lupus erythematosus, and ankylosing spondylitis. Emerging research strategies and future challenges are discussed.

Human single-chain variable fragment that specifically targets arthritic cartilage

Objective

To demonstrate that posttranslational modification of type II collagen (CII) by reactive oxygen species (ROS), which are known to be present in inflamed arthritic joints, can give rise to epitopes specific to damaged cartilage in rheumatoid arthritis (RA) and osteoarthritis (OA) and to establish a proof of concept that antibodies specific to ROS-modified CII can be used to target therapeutics specifically to inflamed arthritic joints.

Methods

We used a semisynthetic phage display human antibody library to raise single-chain variable fragments (scFv) specific to ROS-modified CII. The specificity of anti–ROS-modified CII scFv to damaged arthritic cartilage was assessed in vitro by immunostaining articular cartilage from RA and OA patients and from normal controls. The in vivo targeting potential was tested using mice with antigen-induced arthritis, in which localization of anti–ROS-modified CII scFv in the joints was determined. The therapeutic effect of anti–ROS-modified CII scFv fused to soluble murine tumor necrosis factor receptor II–Fc fusion protein (mTNFRII-Fc) was also investigated.

Results

The anti–ROS-modified CII scFv bound to damaged arthritic cartilage from patients with RA and OA but not to normal preserved cartilage. When systemically administered to arthritic mice, the anti–ROS-modified CII accumulated selectively at the inflamed joints. Importantly, when fused to mTNFRII-Fc, it significantly reduced inflammation in arthritic mice, as compared with the effects of mTNFRII-Fc alone or of mTNFRII-Fc fused to an irrelevant scFv.

Conclusion

Our findings indicate that biologic therapeutics can be targeted specifically to arthritic joints and suggest a new approach for the development of novel treatments of arthritis.

How men and women are affected by osteoarthritis of the hand

Factors other than age and genetics may play a role in explaining the onset of osteoarthritis of the hand. Genetic, physiologic, and anatomic differences in men and women cause the variable expressions of osteoarthritis. These different factors affect women's ability to modify osteoarthritis of the hand before and after its onset, although it is genetic. By maintaining normal weight, good health, and nutrition, one can diminish the genetic and multifactorial effects of osteoarthritis of the hand. Future research in genetics, polymorphism, anatomy, hormonal influences, association with other disease processes, and multifactorial issues will clarify these relationships. Additional studies are needed to investigate the outcomes of gender-specific treatments, joint replacement surgery, and other interventions for osteoarthritis of the hand.

Oxidative activation of antioxidant defence

Living cells maintain a delicate balance between oxidizing and reducing species, and many disorders such as rheumatoid arthritis and Alzheimer's disease have been associated with a disturbed intracellular 'redox equilibrium'. The past few years have witnessed accelerated research into how natural redox responses and antioxidant defence systems are activated and how they restore a healthy redox balance. To function properly, many of these processes rely on a powerful sulfur redox chemistry, which is best exemplified by the complex, newly emerging cysteine-based redox regulation of the glutathione and thioredoxin pathways. Other redox systems based on oxidatively activated amino acid side chains in proteins are also becoming increasingly important, but are still barely understood or explored.

Effects of cis-resveratrol on inflammatory murine macrophages: antioxidant activity and down-regulation of inflammatory genes

This study investigated for the first time the effects of the cis isomer of resveratrol (c-RESV) on the responses of inflammatory murine peritoneal macrophages, namely on the production of reactive oxygen species (ROS) and reactive nitrogen species (RNS) during the respiratory burst; on the biosynthesis of other mediators of inflammation such prostaglandins; and on the expression of inflammatory genes such as inducible nitric oxide synthase (NOS)-2 and inducible cyclooxygenase (COX)-2. Treatment with 1-100 microM c-RESV significantly inhibited intracellular and extracellular ROS production, and c-RESV at 10-100 microM significantly reduced RNS production. c-RESV at 1-100 microM was ineffective for scavenging superoxide radicals (O(2)(.-)), generated enzymatically by a hypoxanthine (HX)/xanthine oxidase (XO) system and/or for inhibiting XO activity. However, c-RESV at 10-100 microM decreased nicotinamide adenine dinucleotide/nicotinamide adenine dinucleotide phosphate (NADH/NADPH) oxidase activity in macrophage homogenates. c-RESV at 100 microM decreased NOS-2 and COX-2 mRNA levels in lipopolysaccharide (LPS) interferon gamma (IFN-gamma)-treated macrophages. At 10-100 microM, c-RESV also significantly inhibited NOS-2 and COX-2 protein synthesis and decreased prostaglandin E(2) (PGE(2)) production. These results indicate that c-RESV at micromolar concentrations significantly attenuates several components of the macrophage response to proinflammatory stimuli (notably, production of O(2)(.-)(-) and of the proinflammatory mediators NO(.-) and PGE(2)).

Gene therapy for arthritis

Rheumatoid arthritis is an autoimmune disease with intra-articular inflammation and synovial hyperplasia that results in progressive degradation of cartilage and bone, in severe cases it causes systemic complications. Recently, biological agents that suppress the activities of proinflammatory cytokines have shown efficacy as antiarthritic drugs, but require frequent administration. Thus, gene transfer approaches are being developed as an alternative approach for targeted, more efficient and sustained delivery of inhibitors of inflammatory cytokines as well as other therapeutic agents. Indeed, the efficacy of gene transfer for the treatment of arthritis has been demonstrated in mouse, rat, rabbit, and horse models of disease whereas the feasibility of the approach has been demonstrated in Phase I clinical trials. In this review, the current status of both preclinical and clinical arthritis gene therapy is presented. In addition, the advantages and disadvantages of different types of vectors, target cells and therapeutic genes being developed for the treatment of arthritis are summarized. Finally, the future directions of the rapidly developed field of arthritis gene therapy are outlined.