PTHrP increases bone angiogenesis in vivo. (A) Stimulation of osteoclast activity by PTHrP increases angiogenesis in mouse calvaria in vivo. Coronal sections of calvaria from mice treated with PTHrP(1-34) every 6 hours for 5 days, labeled for CD31 (brown) and TRAP (red), and lightly counterstained with hematoxylin. indicates prominent CD31⁺ vessel; 2-headed arrow, inner table thickness. Outer surface is at the top of the image. Images of aqueous mounted slides acquired with a Nikon Eclipse TE300 microscope using a 20×/0.45 NA Plan Fluor objective and a Spot Pursuit camera with Spot Advanced 6.4 software. Scale bar represents 100 μm for full field, 25 μm for insets. Auto contrast and auto color adjustment were performed with Adobe Photoshop software. (B) PTHrP increases CD31⁺ vessel density between calvarial bone tables. Total vessel area and vessel density quantified by grid map counting by a blinded observer of the parasagittal areas of CD31-stained calvarial sections. (C) PTHrP increases thickness of inner table. Total tissue area of the inner table was quantified by image analysis by a blinded observer. (D) PTHrP induces osteoclast formation in calvaria. Total TRAP⁺ area as a percentage of tissue area was quantified by image analysis by a blinded observer. Data are mean ± SEM. *P < .05 compared with vehicle. Results are from 1 representative experiment of 2 performed.