US is a feasible imaging modality for measurement of the response of RA small-joint synovitis to therapy.

Increased MMP-3 levels in SF are found in inflammatory arthropathies and are not specific for erosive joint diseases. MMP-3 in SF is therefore a potential candidate for the assessment of the inflammatory process in joints. However, the exclusive determination of the active form could indicate the degree of joint destruction.

Synovial fluid (SF) levels of soluble CD23 (sCD23) were determined in 96 patients presenting with an inflammatory knee effusion (73 with RA and 23 with reactive arthritis (ReA) serving as a control inflammatory non‐erosive group) and were correlated with the degree of joint destruction, with local immune parameters (IL‐1β, IL‐3, IL‐4, IL‐6, IL‐8, IL‐10, IL‐12 and sCD25) and with serum markers of inflammation, C‐reactive protein and erythrocyte sedimentation rate. RA patients, classified as erosive or not according to Larsen’s grade, were separated as follows: (i) 13 patients with non‐erosive RA; (ii) 16 RA patients with erosions in hands but not in knees, matched for disease duration with the first group; (iii) 44 RA patients with hand and knee erosions, matched with the second group for rheumatoid factor positivity but of longer disease duration. SF sCD23 levels were significantly increased in both erosive RA groups compared with non‐erosive diseases, whether RA or ReA (P < 0·05), whose SF levels were not different. SF IL‐10 showed a similar profile to that of SF sCD23 and was the only other parameter characteristic of erosive RA, but no direct correlation was found between the two. SF sCD23 was significantly correlated with IL‐12 (r = 0·65, P = 0·0001) and sCD25 (r = 0·39, P = 0·0019) exclusively in the two erosive RA populations. In conclusion, these data showing that increased levels of sCD23 are not only found in the SF of erosive joints but also in knee SF of patients with erosive RA but without knee x‐ray‐diagnosed erosions suggest that this parameter might be of predictive value for joint destruction. Longitudinal studies are however needed to confirm its potential clinical interest.

The functional capacity of skeletal muscle sarcoplasmic reticulum was explored in slow rat soleus muscle after 21 days of hindlimb suspension. The sarcoplasmic reticulum function was assessed in intact and saponin-skinned fibers by using cyclopiazonic acid, a specific Ca(2+)-adenosinetriphosphatase inhibitor. After hindlimb unweighting, the sensitivity to cyclopiazonic acid of intact and skinned soleus fibers becomes similar to that found in fast-twitch muscles. This change could be related to the expression of fast Ca2(+)-adenosinetriphosphatase-pump protein in unloaded soleus muscles and agrees with a transformation of soleus muscle from slow- to fast-twitch type. These results also indicate that specific pharmacological tools, like cyclopiazonic acid, could be used to analyze subcellular functional changes due to hindlimb unweighting.

No abstract