Background: Galectin-3 is expressed in the synovial tissue of patients with rheumatoid arthritis (RA), particularly at sites of joint destruction. Objective: To explore the possibilities that galectin-3 is induced either by proinflammatory cytokines or by adhesion to cartilage components. Methods: Cell culture plates were coated with fibronectin, collagens I-VI, or cartilage oligomeric matrix protein (COMP), and the suspended cells were then added. The medium was changed after 1 hour at 37˚C. Adherent cells were further incubated for 18 hours in the presence or absence of tumour necrosis factor a (TNFa) or interleukin 1b. Cells were pretreated with murine IgG1, anti-CD29, -CD51, -CD61 (integrins), or -CD3 monoclonal antibodies and transferred to culture plates coated with COMP. Adherent cells were counted by light microscopy. The expression of intracellular galectin-3, or cell surface CD29, CD51, and CD61 was determined by flow cytometry before and after adhesion. Results: Four times more RA synovial fibroblasts (SF) than osteoarthritis SF adhered to COMP. RA SF presented more cell surface integrins, and monoclonal antibodies against CD51 inhibited the adhesion to COMP by 80%. TNFa reduced the expression of CD61 and the adhesion to COMP, but did not reverse the adhesion once it had taken place. The adhesion of RA SF to COMP was found to increase the intracellular level of galectin-3. In contrast, intracellular galectin-3 decreased after exposure to TNFa. Conclusion: The increase of galectin-3 occurs after adhesion to COMP, and the aVb3 receptor (CD51/ CD61) has a pivotal role in this process.

We characterized a full length L1 mRNA in a rheumatoid arthritis (RA) synovial tissue and determined the degree of methylation of its 5'-UTR. We asked whether not only intact but also altered L1s can exert biological activities by transfecting RA synovial fibroblasts (SF) with either retrotransposition-competent or incompetent L1s and examined their capacity to induce p38delta. Total RNA was isolated from the synovial tissue of a 35-year-old woman with highly destructive RA. A complete L1 sequence was obtained by 3'/5'-RACE. Methylation of the genomic 5'-UTR was determined by the sodium-disulfide/PCR method. RA-SF were transfected by lipofection with either a functional L1 or an ORF2-mutated L1 element. The expression of p38delta was measured by RT-PCR and Western blot. The full length L1 mRNA included a 5'-UTR, an ORF1 and an ORF2. Three of five CpG islands (60%) of the genomic L1 5'-UTR were hypomethylated and the ORF2 was deactivated by the insertion of stop codons. Both, intact and ORF2-mutated L1 vectors, induced the expression of p38delta. Thus, even an ORF2-mutated L1 element, as expressed in RA, is biologically active and both L1 ORF1 and p38delta transcripts may appear as a consequence of genomic hypomethylation. The induction of p38delta appears to be mediated by an ORF1/p40-dependent process. This is the first indication of a p40 mediated transactivation.