Microscopy of cultured whole periosteal cells from 3-month-old PdgfracreER;Osxdre;R26ZT1;Col1a1BFP mice revealed that there were significantly fewer Col1a1-BFP+osteoblasts (OBs) among ZsGreen+cells than among tdTomato+cells. Whole periosteal cells were cultured in nutrient media at clonal density for 2 weeks to allow spontaneous osteogenic differentiation (n = 5 mice from 3 independent experiments).
