Activin-mediated TGF-β, PDGF, and FGF signaling are also important for MSC growth.Marrow-derived MSCs were cultured for 7 days in the presence of inhibitors of these pathways. Three doses (0.2× IC50 dose, IC50 dose, and 2× IC50 dose) were used for each inhibitor. Panel A shows the morphology of undifferentiated MSCs in the presence of these inhibitors. Panel B shows the fold increase in number of viable cells in these cultures. Fold increase in viable cells was calculated as ratio of viable cells in the culture on day 7 or day 14 compared with the starting number of viable cells that were seeded in these cultures. Micrographs were acquired by imaging with a Zeiss Axiovert 40 C microscope fitted with a 20×/0.3 NA objective and a Canon Powershot A620 camera. Image contrast was adjusted using the Auto Contrast function in Picasa.
