Generation and culture of osteoclasts

Osteoclasts are highly specialized cells of haematopoietic lineage that are uniquely responsible for bone resorption. In the past, osteoclasts were isolated as mature cells from chicken long bones, or were generated using osteoblasts or stromal cells to induce osteoclast formation in total bone marrow from mice or rabbits. The Copernican revolution in osteoclast biology began with the identification of macrophage-colony stimulating factor (M-CSF) and receptor activator NFκB-ligand (RANKL ) as the key regulators of osteoclast formation, fusion and function. The availability of recombinant human and mouse M-CSF and RANKL has enabled researchers to reliably generate osteoclasts from primary monocyte/macrophage cells as well as from cell lines such as RAW 264.7. This article summarizes the most commonly used procedures for the isolation, generation and characterization of human, rodent and chicken osteoclasts in vitro. Lists of further reading and recommendations are included to facilitate a successful application by the reader.