Library

Notes: In osteoarthritis (OA), cartilage and bone fragments have been described within the synovial tissue which are surrounded by synovial cells (i.e. detritus synovitis). These cells appear to attach actively to the cartilage and bone fragments. In rheumatoid arthritis (RA), on the other hand, synovial fibroblasts (SF) have also been shown to be localized at sites of invasion into cartilage and bone and to degrade extracellular matrix (ECM) by secreting proteolytic enzymes. One prerequisite for exerting their aggressive properties is the attachment to cartilage and bone ECM. This attachment appears to be mediated by the expression of different adhesion molecules for which corresponding binding sites on ECM components are known. As it has not been addressed to which ECM proteins SF adhere and with which affinity this process takes place, we investigated the adherence of SF from patients with OA and RA to different cartilage and bone matrix proteins. Synovial tissue samples were obtained during synovectomy or arthroplastic surgery and used for isolating and culturing SF. Synovial cells attaching to cartilage/bone fragments were characterized using immunohistochemistry. The adherence of SF to ECM proteins was examined using an adhesion assay with the following proteins coated on 96-well plates: aggrecan (AGG), bone sialoprotein (BSP), cartilage oligomeric matrix protein (COMP), collagen type I, II and VI, proline arginine-rich, end leucine-rich repeat protein (PRELP), osteopontin (OPN) and recombinant chondroadherin (CHAD). Bovine serum albumin was used as negative control. In addition, adhering fibroblasts were photographed using a phase-contrast microscope. As compared with RA-SF, significantly higher numbers of OA-SF adhering to collagen type II, OPN and CHAD could be detected (P 〈 0.05). In contrast, RA-SF showed increased attachment to collagen type II, OPN and BSP. Adhesion to AGG, COMP and PRELP appeared not to be significantly increased and differed widely among the SF samples, and, apart from one exception (BSP), OA-SF adhered in higher numbers to the matrix proteins than did RA-SF. Using immunohistochemistry, synovial cells attached to cartilage/bone fragments could be shown to predominantly express CD68 (≥50%). The CD68-negative population was of the fibroblast phenotype (AS02 positive). The study demonstrates that the binding pattern of OA-SF and RA-SF to ECM proteins differs considerably and therefore provides novel insights into the difficult pathophysiology of OA and RA. In general, it appeared that SF adhere primarily to ECM proteins that contain known binding sites for adhesion molecules (e.g. integrins: collagen/integrin α2β1) and that higher numbers of OA-SF adhered to the cartilage and bone matrix proteins than did RA-SF.

Notes: Background : 6-Thioguanine-nucleotides seem to be the active metabolites of thiopurine therapy, and their monitoring has been considered a useful tool for optimizing response in inflammatory bowel diseases. Tioguanine (thioguanine) therapy results in much higher levels of 6-thioguanine-nucleotide levels when compared with azathioprine or mercaptopurine.Aim : To elucidate the influence of 6-thioguanine-nucleotide and methylated 6-thioguanine-nucleotide levels under tioguanine on efficacy and toxicity in Crohn's disease.Methods : 6-Thioguanine-nucleotide and methylated 6-tioguanine-nucleotide levels were measured regularly in 26 Crohn's disease patients treated with tioguanine. Nucleotide levels were related to efficacy and toxicity.Results : 6-Thioguanine-nucleotide levels rose very high [median 1241 pmol/8 × 108 red blood cells (range 313–1853)]. Methylated 6-thioguanine-nucleotide levels were detected in all patients [491 pmol/8 × 108 red blood cells (154–1775)]. 6-Thioguanine-nucleotide and methylated 6-thioguanine-nucleotide concentrations correlated significantly (r = 0.7, P 〈 0.0001). Nucleotide levels from patients achieving remission (n = 14) did not differ significantly from non-remitters (n = 12) [6-thioguanine-nucleotide: 1077 (599–2160) vs. 1210 (534–4665); methylated 6-thioguanine-nucleotide: 510 (214–1222) vs. 421 (145–1284)]. One patient with intermediate thiopurine S-methyltransferase activity experienced bone marrow toxicity upon dose escalation parallel with excessively high thioguanine-nucleotide levels.Conclusions : 6-Thioguanine-nucleotide as well as methylated 6-thioguanine-nucleotide levels under tioguanine therapy were not related to efficacy. This suggests that monitoring of 6-thioguanine-nucleotide levels is not a useful tool to predict response to thiopurines.

Notes: Steroids are still widely used in the treatment of inflammatory bowel diseases. Pharmacological studies have shown that there is no major abnormality in the pharmacokinetics of steroids in these disorders. Foam preparations with rectal application decrease the bioavailability to low levels, eliminating systemic complications. For oral use, ‘nonsystemic’ steroids have been developed. In ulcerative colitis, steroids are rarely needed as 5-aminosalicylates are effective in the majority of patients. This is true for rectal application in distal colitis, as well as in more extensive disease. In Crohn's disease, steroids are more often used; however, in population-based studies, less than 50% of patients have been treated with steroids, as there are alternative treatments available for the large group of patients with mild to moderate activity. For those patients needing steroid treatment, budesonide seems to be a good choice in active disease, but has not shown convincing effects in the maintenance of remission over longer periods of time. There is no place for long-term steroid treatment in ulcerative colitis and very little in Crohn's disease — immunosuppression with azathioprine or related drugs is certainly the better alternative.