Purified populations of CR cells. (A) CR cells were cultured for 21 days and 5 clones were isolated; then the cells were replated at 50 cells/cm2 every 14 days. Total doubling number of each clone was shown. (B-D) A mixed population of CR cells was compared with a population of CR clone, CD31+ fraction, and osteoblastic cells for chondrocyte (B), adipocyte (C), and osteoblast differentiation (D). Each population was derived from 3 donors and each assay was triplicated. The data are expressed as mean ± SD.