MRI for the assessment and monitoring of RA--what can it tell us?

Magnetic resonance imaging in individuals at risk of rheumatoid arthritis

Individuals with rheumatoid arthritis (RA) benefit from early diagnosis and initiation of therapy. There can be delays in both due to diagnostic uncertainties. Imaging modalities, including magnetic resonance imaging (MRI), can detect inflammation earlier than clinical examination alone in early RA patients. Furthermore, the predictive role of MRI for the future development of RA has recently been explored in 'at-risk' individuals. This review details the use of MRI in early and undifferentiated arthritis and summarises the studies to date in individuals at risk of RA.

The role of the lymphatic system in inflammatory-erosive arthritis

Rheumatoid arthritis (RA) is a prevalent inflammatory joint disease with enigmatic flares, which causes swelling, pain, and irreversible connective tissue damage. Recently, it has been demonstrated in murine models of RA that the popliteal lymph node (PLN) is a biomarker of arthritic flare, as it "expands" in size and contrast enhancement during a prolonged asymptomatic phase, prior to when it "collapses" with accelerated synovitis and joint erosion. This PLN collapse is associated with adjacent knee flare, decreases in PLN volume and contrast enhancement, lymphatic pulse and pumping pressure, and an increase in PLN pressure. Currently, it is known that PLN collapse is accompanied by a translocation of B cells from the follicles to the sinuses, effectively clogging the lymphatic sinuses of the PLN, and that B cell depletion therapy ameliorates arthritic flare by eliminating these B cells and restoring passive lymphatic flow from inflamed joints. Here we review the technological advances that have launched this area of research, describe future directions to help elucidate the potential mechanism of PLN collapse, and speculate on clinical translation towards new diagnostics and therapies for RA.

The microanatomic basis of finger clubbing - a high-resolution magnetic resonance imaging study

OBJECTIVE

Hypervascularization in finger clubbing is recognized, but its microanatomical basis remains unclear. This pilot descriptive study used magnetic resonance imaging (MRI) to explore this further.

METHODS

High-resolution MRI acquired with contrast agent was carried out in 4 patients with finger clubbing and 4 healthy volunteers. The anatomy of the nail bed, capsular structures, and bony changes were described.

RESULTS

Marked nail bed thickening and contrast enhancement was noted in all clubbed fingers, with bone edema in 3 of the 4 patients. None of the healthy subjects had similar abnormalities.

CONCLUSION

This confirms that hypervascularization of the nail bed observed in the microanatomy on high-resolution MRI is associated with clubbed appearances of the nails.

MRI-assessed therapeutic effects of locally administered PLGA nanoparticles loaded with anti-inflammatory siRNA in a murine arthritis model

Rheumatoid arthritis is characterized by systemic inflammation of synovial joints leading to erosion and cartilage destruction. Although efficacious anti-tumor necrosis factor α (TNF-α) biologic therapies exist, there is an unmet medical need for safe and more efficient treatment regimens for disease remission. We evaluated the anti-inflammatory effects of poly(dl-lactide-co-glycolide acid) (PLGA) nanoparticles loaded with small interfering RNA (siRNA) directed against TNF-α in vitro and in vivo. The siRNA-loaded PLGA nanoparticles mediated a dose-dependent TNF-α silencing in lipopolysaccharide-activated RAW 264.7 cells in vitro. The severity of collagen antibody-induced arthritis in DBA/1J mice was assessed by paw scoring and compared to the degree of magnetic resonance imaging (MRI)-quantified joint effusion and bone marrow edema. Two intra-articular treatments per joint with nanoparticles loaded with TNF-α siRNA (1 μg) resulted in a reduction in disease activity, evident by a significant decrease of the paw scores and joint effusions, as compared to treatment with PLGA nanoparticles loaded with non-specific control siRNA, whereas the degree of bone marrow edema in the tibial and femoral head remained unchanged. When the siRNA dose was 5 or 10 μg, there was no difference between the specific and the non-specific siRNA treatment groups. These findings suggest that MRI is a promising method for evaluation of early disease progression and treatment in murine arthritis models. In addition, proper siRNA dosing seems to be important for a positive therapeutic outcome in vivo. However, further studies are needed to fully clarify the mechanism(s) underlying the observed anti-inflammatory effects of the siRNA-loaded nanoparticles.