Effects of coadministration of PTH and ALN on bone and bone cells. (A) Schematic representation of the experimental procedure to analyze the effects of PTH + ALN coadministration on the HSC niche. (B) Experimental mice that were continuously treated with PTH (1-34) with the use of Alzet osmotic pumps had increased levels of PTH in the serum blood as determined by immunoradiometric assay. Data are mean ± SEM; n = 8. ***P < .001. (C) PTH + ALN-treated mice, but not PTH-treated mice, had reduced concentration of TRAPCP-5b in the PB as defined by ELISA. Columns represent mean plus or minus SEM; n = 8. *P < .05. (D) Tibias from PTH-, PTH + ALN-treated, or untreated mice were subjected to micro-CT scanning, reconstructed with the use of Nrecon and CTAn software programs, and visualized by the use of CTVol program (SkyScan). Representative transaxial views of tibias indicating that in vivo coadministration of PTH and ALN produces greater changes in the bone morphometric parameters than PTH alone. (E) Osteoblast number (Ob.N) and (F) osteoclast number (Oc.N) were defined by histomorphometry in methyl methacrylate-embedded tibial sections stained with toluidine blue. Data are mean ± SEM; n = 6. *P < .05. **P < .01. ns indicates not significant.