Phenotypic analysis of OBs from calvariae (C) or long bones (LB) of newborn (2-day) and 6- to 8-week-old mice. OBs were stained as described in “Cell staining and flow cytometry.” Cells were analyzed for Sca1 versus CD45/CD31/Ter119 (top row), and double-negative cells were then analyzed for OPN versus ALCAM (bottom row). Different numbers of events were collected and are displayed for each file. Sort gates defining groups 1 through 11 were established based on fluorescence levels of control samples. Cells in these gates were sorted and used in different assays depending on the number of cells recovered for each fraction. Dot plots are from 1 representative experiment of 3.