Increase in bone marrow mesenchymal progenitors at the onset of RA-like disease. A significant increase in BM-MSC (a), progenitors with osteogenic (b-c) and adipogenic (d) potential was found in Balb/c IL-1ra-/- mice compared to WT controls at the onset of disease (n = 5 with disease in adjacent joint, n = 7 with disease in non-adjecent joint). (b) is a representative example of CFU-O cultures from bone marrow cells of Balb/c IL1ra-/- mice affected by RA and age matched WT control. All data are presented as means ± SEM and analysed by one way ANOVA and Bonferroni post-test. *P < 0.05, **P < 0.01, ***P < 0.001. WT, wild type mice; CFU-F, colony forming unit fibroblast; CFU-O, colony forming unit osteoblast; CFU-A, colony forming unit adipocyte; BM, bone marrow.