Morphology of MPCs.
CD45−GlyA− cells were plated on FN in expansion medium with 2% FCS, 10 ng/mL EGF, and 10 ng/mL PDGF-BB and passaged for 15 cell doublings (A) and 53 cell doublings (B) to maintain a cell density between 2 and 8 × 103/cm2. Alternatively, MPCs were maintained for 15 cell doublings in MPC medium containing 10% FCS (C) or at a density greater than 104/cm2 (D). MPCs cultured at low density and with 2% or less FCS are small (10 to 15 μm diameter) and have scant cytoplasm with few vacuoles or granules. In contrast, MPCs cultured either with 10% FCS or at higher density are significantly larger (greater than 20 μm diameter) and often contain vacuoles or granules. Shown are phase-contrast pictures at 80 × magnification. A representative example of more than 5 experiments is shown.
