Figure 5. Changes in alkaline phosphatase based on position on the cell cycle. It has long been recognized that BMSC/ SSC colonies are heterogeneous with respect to alkaline phosphatase activity (left panel, slide given to PGR by Alexander Friedenstein). Later, it was determined that when cultures of osteogenic cells are synchronized using an amphidicolin protocol, cells in S phase have high levels of activity. During G2 + M phase, alkaline phosphatase is cleaved from the cell surface and released into the medium. Cell surface activity is restored during the following G1 and S phases. Adapted in part from Fedarko et al.53 BMSC: bone marrow stromal cells; SSC: skeletal stem cell.
