Adherent bone marrow stromal cells were cultured to 70% confluency. Cells were then harvested and then seeded at a density of 30,000 cells per cm2. WT cells were maintained in maintenance media (α-MEM supplemented with 10% Fetal bovine serum (FBS), 1% Penicillin-streptomycin, 1% L-glutamine, 1% Non-essential amino acids), osteogenic media (maintenance media + 10 mM β-glycerol phosphate + 50 μM ascorbate-2-phosphate + 100 nM Dexamethasone), osteogenic media in combination with conditioned media collected form either WT or dnMMAL osteoclasts (here condition media was first concentrated using 3 KDa cut off concentration filters (Amicon, Millipore) and then mixed in a ratio of 1:10 with osteogenic media), or osteogenic media in combination with 30 ng/mL Bone Morphogenetic Protein 6 (BMP-6) (R & D Systems). Media were refreshed every 3rd days. Alkaline phosphatase (ALP) activity was measured by SensoLyte pNPP Alkaline Phosphatase Assay Kit (AnaSpec, Inc)39 (link) as per the manufacturer’s instructions. Mineralized nodules were stained with alizarin red as per the protocol described earlier40 (link).