Fig 1. TRAcP activity of osteoclasts, FBGCs, and macrophages cultured on bone.

Human CD14⁺ monocytes were cultured on bone slices for 25 days with M-CSF and RANK-L (osteoclasts); M-CSF, IL-4, and IL-13 (FBGCs); M-CSF (macrophages) and without cytokines (control). Osteoclasts were TRAcP-positive (a; black arrow) and most contained < 10 nuclei (e). FBGCs were larger with > 10 nuclei (f), and stained less intensely for TRAcP (b; black arrow). Macrophages were generally mononuclear and stained weakly for TRAcP (c, g), similar as CD14⁺ cells that were cultured without cytokines (d, h). Bar plots represent the mean ± S.D. of multinucleated cells (MNCs) per 0.25 cm² bone surface, from 5 independent donors. Scale bar = 100 μm. Red asterisk = bone. *p<0.05, **p<0.01.