Osteoblasts and stromal cells isolated from femora in rheumatoid arthritis(RA) and osteoarthritis (OA) patients express IL-11, leukaemia inhibitory factor and oncostatin M

We investigated both in vitro and ex vivo the role of mature osteoblasts (O B) and bone marrow stromal cells (BMSC) in RA and OA by analysing the expre ssion of the following IL-6-type cytokines: IL-11, leukaemia inhibitory fac tor (LIF), oncostatin M (OSM) and IL-6. OB and BMSC were isolated from femo ra of RA, OA and post-traumatic (PT) patients, cultured in vitro in the pre sence or absence of IL-1 beta and tumour necrosis factor-alpha (TNF-alpha), and assessed for the production and mRNA expression of IL-6-type cytokines . Trabecular bone biopsies were obtained from the inner portions of femoral heads and used for cytokine in situ immunostaining. Cultured OB and BMSC f rom different patients constitutively secreted IL-11 and IL-6 but not OSM. LIF was secreted only by BMSC, at very low levels. Interestingly, IL-11 bas al production was significantly higher in BMSC than in OB in all three grou ps tested. IL-1 beta and TNF-alpha strongly stimulated IL-6-type cytokine r elease (except for OSM) by both OB and BMSC. OSM was expressed only at mRNA levels in all groups studied. Cytokine immunostaining on bone biopsies con firmed the data obtained on cultured cells: IL-11, IL-6 and LIF proteins we re detected both in mesenchymal (BMSC and OB) and mononuclear cells; OSM wa s found only in mononuclear cells. These data demonstrate that IL-6-type cy tokines are constitutively expressed in the bone compartment in RA, OA and PT patients and can be secreted by bone cells at different stages of differ entiation (BMSC and OB). This suggests that these cytokines may be involved in the mechanisms of bone remodelling in OA and RA.