Background The anaemia of chronic disease in patients with rheumatoid arthritis (RA) can be corrected by treatment with recombinant human erythropoietin (rHu-Epo). In addition to an increase of haemoglobin concentration during therapy with rHu-Epo, a significant reduction of disease activity was observed in different RA-studies. Especially the decrease of the number of swollen and tender joints during rhu-Epo treatment suggests a direct anti-inflammatory effect of rHu-Epo.

Objectives As the expression of the erythropoietin-receptor (Epo-R) was recently shown for different non-erythroid cells – as for example endothelial and neuronal cells, we investigated the expression of Epo-R in fibroblast-like synoviocytes to gain a first experimental approach for the observed anti-inflammatory effect of rHu-Epo in RA.

Methods We cultivated fibroblast-like synoviocytes derived from synovial membranes (n = 17) or synovial fluid (n = 13) that were gained from patients with RA (n = 22), osteoarthritis (n = 3) or spondylarthropathy (n = 5). Biopsy material has been minced and digested with collagenase, fluid derived cells have been directly cultured. Cells were passaged two to five times and characterised by FACS analysis. Expression of Epo-R was determined by nested RT-PCR. The chosen primers annealed at Exon III (forward primer 1 and 2), Exon VIII (backward primer 1) and Exon VII (backward primer 2). The obtained PCR-product was sequenced by automated fluorescent DNA sequencing.

Results The cultured cells morphologically represented fibroblast-like cells. It was shown by FACS analysis that they were CD14 and CD86 negative and CD54 and CD90-Thy-1 positive. RT-PCR products representing the human Epo-R could be demonstrated in fibroblast-like synoviocytes from biopsy and arthrocentesis from patients with RA, OA and SpA. The specifity of the PCR products could be proven by sequencing of the product of three different cell-lines. The obtained sequence was completely identical with that of the DNA data base for more than 350 bases (Exon IV to Exon VI).

Conclusion We could demonstrate for the first time the expression of Epo-R in fibroblast-like synoviocytes. This observation gives evidence that rHu-Epo directly afflicts fibroblast-like synoviocytes (via Epo-R) and therefore provides a possible explanation for the anti-inflammatory effect of rHu-Epo in patients with RA.