Effect of clodronate-loaded liposomes on endosteal niches. (A) Time course of clo-lipo treatment on mRNA expression of osteocalcin, CXCL12, KL, and Ang-1 in endosteal cells relative to β2-microglobulin. Each symbol represents 1 mouse, and bars are average for each group. ***P < .001, **P < .01, and *P < .05 between PSB-lip– (time 0) and clo-lip–treated mice. (B) Immunohistochemical staining of femoral sections from C57BL/6 mice treated with clo-lip (24 or 48 hours) or PBS-lip (48 hours). Brown positive staining for F4/80 and osteocalcin is shown in near serial sections of metaphysal bone. Clo-lip treatment resulted in the depletion of F4/80⁺ cells at 24 and 48 hours after clo-lip treatment. Subsequent reduction in osteocalcin⁺ osteoblasts occurred at 48 hours. All sections were counterstained with hematoxylin. Original magnification ×20. (C) Histomorphometry for osteoid surface per bone surface (OS/BS), osteoblast surface per bone surface (ObS/BS), and number of osteoblasts per bone perimeter (NOb/BPm) in the trabeculae of the proximal tibial secondary spongiosa from mice treated with clo-lip or PBS-lip. Data are means ± SEM of both tibias from 4-8 mice per group. *P < .05, **P < .01; and ***P < .001.