PCI-32765 diminished bone resorption activity. (A) Human OCPs from normal donors were stimulated with RANKL/M-CSF and cultured on glass cover slips for 15 to 17 days, followed by immunofluorescence staining to observe OC morphology using Alexa-568–conjugated phalloidin (red) for actin and 4,6-diamidino-2-phenylindole (blue) for nuclei. (B) Abnormal OCs observed in panel A were further quantitated for extended spreading area per multinucleated OC (> 3 nuclei) and number of nuclei per OC (C). (D) OCPs were cultured on the dentine slice for 2 weeks, in the presence or absence of PCI-32765, alone or with dexamethasone (Dex), and analyzed for pit formation to determine percentage of bone erosion area. Images of representative bone resorption on dentine slices, with or without PCI-32765 treatment, are shown on the right (10× lens).