Effects of coadministration of PTH and ALN on hematopoiesis. PTH + ALN-treated mice have increased HPC frequency in the BM (A) but unchanged absolute number per tibia (B) as measured by the CFU-C assay. Data are mean ± SEM; n = 8. *P < .05. PTH-treated mice have increased proportion (C) and absolute numbers (D) of LKSFlk2⁻ cells in the BM, whereas PTH + ALN-treated mice have a comparable number of HSCs with the untreated age-matched controls as defined by FACS analysis. Data are mean ± SEM; n = 8. ***P < .001. (E) The cell-cycle kinetics of the lineage-negative cells are comparable between untreated, PTH-treated, and PTH + ALN treated mice. (F) Representative graphs of the cell cycle analysis by FACS. (G) BM cells from PTH-treated mice have increased ability to reconstitute irradiated recipients as shown by FACS analysis for CD45.2 at 4, 8, and 20 weeks after transplantation; after coadministration of ALN, this effect is abolished. Columns represent mean ± SEM; n = 6 in each group. **P < .01. ***P < .001. ns indicates not significant.