(A) Murine MSCs are multilineage-potent fibroblastoid cells that can differentiate into osteoblasts and adipocytes; they are hematopoietic lineage negative, CD45^–, and CD105⁺. Ops are Osx positive. Upon differentiation, MSCs lose 105 staining, form von Kossa staining ECM nodules, and express high levels of BSP. (B) Isolated murine MSCs (CD105-selected cells) showed increased alkaline phosphatase activity, blue staining (left panel, control; right panel, 1 nM). Alkaline phosphatase–positive cells per well increased with 1 and 2 nM of Bzb. *P = 0.01; ^†P = 0.01; n = 6 wells each. Original magnification, ×100. (C) CD105-selected cells exposed to osteogenic medium with or without 1.5 nM Bzb were analyzed by qPCR. BSP transcript levels and Runx-2 transcript levels (plotted against the baseline value of untreated MSCs assigned as 1.00) increased significantly in Bzb-treated samples at 30 hours (^‡P = 0.04; ^ΧP = 0.03; n = 2), while preexposure to osteogenic differentiation (MSC→Og) for 8 days followed by Bzb treatment abrogated the response (white bars for 0 and 1.5 nM; P = NS). (D) Von Kossa–positive area increased with 1 and 2 nM Bzb. ^ζP = 0.05; ^#P = 0.01; n = 3 wells. Original magnification, ×100.