Figure 7. Mitogen and Adipogenic Stimuli Must Be Simultaneously Regulated in Order to Control the Total Number of Differentiated Cells Produced while Keeping the Number of Progenitor Cells at Similar Levels.

(A) Schematic of how delaying the time to reach the differentiation commitment threshold increases the proliferative window, or time during which progenitor cells can proliferate before differentiating and becoming post-mitotic. Thus, delaying the time to reach the differentiation threshold increases the total number of differentiated cells.

(B) Schematic showing how variable numbers of cell divisions before reaching the differentiation threshold can produce significantly different number of terminally differentiated cells while maintaining similar numbers of progenitor cells. Both scenarios maintain a pool of three progenitor cells (green cells) while producing very different numbers of differentiated cells (three versus nine).

(C) Combinations of fetal bovine serum (FBS) and DMI stimuli were applied to OP9 preadipocyte cells, and differentiation was measured 96 h later as in Figure 1. The black line was drawn in manually and marks a contour line connecting stimulus conditions which maintain similar numbers of progenitor cells. As predicted in the schematics in (A) and (B), manipulating both mitogen and differentiation stimuli synegistically allows for very different numbers of terminally differentiated cells to be produced while keeping similar numbers of progenitor cells in reserve. The red dot marks conditions which produced approximately three times more adipocytes than the blue dot conditions, while still maintaining similar numbers of progenitor cells that remain undifferentiated Data shown are representative of two independent experiments.