Fig. 3. Expansion capacity of long-term cultures of MIAMI cells. More than 50 cell doublings without detectable differentiation could be obtained in cultures grown in medium containing low serum (2%) supplemented with 15% conditioned medium (2% serum). Cells cultured for a few passages or cells expanded in excess of 50 population doublings remained small, with reduced cytoplasm, and differentiated into osteoblastic and neural phenotypes. Cells were counted at each passage with a hemacytometer.