Identification and characterization of the precursors committed to osteoclasts induced by TNF-related activation-induced cytokine/receptor activator of NF-kappa B ligand.

Osteoclasts are terminally differentiated from cells of monocyte/macrophage lineage by stimulation with TNF-related activation-induced cytokine (TRANCE) (receptor activator of NF-kappaB ligand/osteoprotegerin ligand/osteoclast differentiation factor/TNFSF11/CD254). In the present study, we attempted to determine when and how the cell fate of precursors becomes committed to osteoclasts following TRANCE stimulation. Although mouse bone marrow-derived macrophages (BMMs) were able to differentiate into either osteoclasts or dendritic cells, the cells no longer differentiated into dendritic cells after treatment with TRANCE for 24 h, indicating that their cell fate was committed to osteoclasts.

Differentiation and function of osteoclasts cultured on bone and cartilage.

We examined the differentiation and resorptive function of osteoclasts (OC) cultured on the slices of calcified bone, decalcified bone and hyaline cartilage, and found that OC differentiation depends on the co-cultured substratum, as well as osteoblast-derived factors. Bone marrow-derived macrophages (BMM) were formed from marrow cells of 5 week old ddY mice and cultured for 3 days on freeze-dried slices of calcified bone, decalcified bone or cartilage, all prepared from rabbit costal bone. BMM cultured on calcified bone slices exhibited tartrate-resistant acid phosphatase (TRAP) activity and were structurally characterized by multinucleation and ruffled border development.