(A and B) Epiphyseal chondrocytes or BMSCs (osteoblasts) were isolated from the femurs of 3–4 week-old 5′ Bmp2 BAC, 5′ Bmp4 BAC, or Nog-LacZ mice, cultured with ascorbate and inorganic phosphate for up to 3 weeks, and stained with X-gal. (A) Time course showing a week-by-week progression of staining, beginning at the point when mineralization-supporting media was first added to the cultures (Day 0). (B) Day 21 cultures counter-stained with Alizarin Red to highlight mineralized nodules (shown at low magnification in insets).