The increase in mesenchymal progenitors is independent of the site of inflammation with disease progression. (a) A significant increase in the number of CFU-F, independent of the proximity to an inflamed joint, was found in the bone marrow of Balb/c IL-1ra-/- mice compared to WT controls with disease progression (n = 8). A significant increase in the number of progenitors with osteogenic (b) (n = 8) and adipogenic (c) (n = 8) potential in the bone marrow not adjacent to an inflamed joint in Balb/c IL1 ra-/- mice compared to WT age matched controls. Mice showed signs of RA-like disease for five weeks. All data are presented as means ± SEM and analysed 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.