Expression array of mouse bone marrow-derived macrophages and osteoclasts

In response to the cytokines, macrophage colony-stimulating factor and receptor activator of NF-kB ligand, monocyte precursors differentiate into bone marrow-derived macrophages (BMDMs) that ultimately fuse to form multi-nucleated osteoclasts, following a tightly controlled genetic program where specific sets of genes are differentially expressed. We used microarrays to examine the gene expression profile underlying mouse osteoclast differentiation. Bone marrow-derived macrophages and osteoclasts were lysed at specified stages of differentiation for RNA extraction and hybridization to Affymetrix microarrays for a time-dependent profile of the BMDM-osteoclast transition. We selected BMDM-osteoclasts at five time-points: before differentiation, i.e. BMDMs (day 0), during differentiation (day 1, 2 and 3) and the mature osteoclasts (day 5).