Variation in Osteoclasts Derived from Mandible and Femur of Mice

Objectives: Previous studies have suggested that osteoclasts derived from the bone marrow of the mandible and femur in mice have different osteoclastogenic potential. We sought to devise an effective protocol for isolating and culturing mandibular osteoclasts to determine if variations in differentiation, gene expression, and resorption capacity exist between these cells and that of their long bone counterparts.
Methods: Osteoclasts precursors from mice mandible and femur bone marrow spaces were extracted and cultured. Osteoclast size, number, gene expression, and function were examined at multiple time points throughout differentiation using tartrate-resistant acid phosphatase (TRAP) staining, 4′,6-diamidino-2-phenylindole (DAPI) staining, qRT-PCR analysis, and bone slice resorption.
Results: Osteoclasts derived from the mandible were larger than osteoclasts derived from the femur at time points later during osteoclast differentiation. The osteoclasts derived from the mandible also showed a significant decrease in cell number before fusion as measured by number of DAPI positive cells. Currently gene expression and resorption capacity are being analyzed to aid in explaining these differences.
Conclusions: Osteoclasts derived from the mandible are larger compared to osteoclasts derived from the femur. This is consistent with previous studies. Furthermore, our research suggests that osteoclasts from the mandible proliferate less after RANKL addition than osteoclasts from the femur as we see fewer cells prior to fusion. A more robust understanding of the regional differences between orofacial and long bone osteoclast formation and function will come from gene expression analysis, M-CSF and RANKL responsiveness, and resorption capability.