Progenitor assay: CR cells and BM cells were cultured in complete culture medium for 14 days, and then medium was switched to adipogenic medium or calcification medium for an additional 21 days at primary culture. The ratio of Oil Red-O- or Alizarin Red-positive colonies to the total number of colonies was calculated for each dish and Oil Red-O-positive colony efficiency (A) and Alizarin Red-positive colony efficiency (B) are shown. The data are expressed as mean ± SD (n = 6).