Osteoclasts are dispensable for hematopoietic progenitor mobilization by granulocyte colony-stimulating factor in mice.

The contribution of osteoclasts to hematopoietic stem/progenitor cell (HSPC) retention in the bone marrow is controversial. Studies of HSPC trafficking in osteoclast-deficient mice are limited by osteopetrosis. Here, we employed two non-osteopetrotic mouse models to assess the contribution of osteoclasts to basal and granulocyte colony-stimulating factor (G-CSF)-induced HSPC mobilization. We generated Rank(-/-) fetal liver chimeras using Csf3r(-/-) recipients to produce mice lacking G-CSF receptor expression in osteoclasts. Basal and G-CSF-induced HSPC mobilization was normal in these chimeras. We next acutely depleted osteoclasts in wild-type mice using the RANK ligand inhibitor osteoprotegerin. Marked suppression of osteoclasts was observed after a single injection of osteoprotegerin-Fc. Basal and G-CSF-induced HSPC mobilization in osteoprotegerin-Fc-treated mice was comparable to that in control mice. Together, these data indicate that osteoclasts are not required for the efficient retention of HSPCs in the bone marrow and are dispensable for HSPC mobilization by G-CSF.