Figure 5.

TGF-β1 inhibits proliferation and prolongs the cell cycle of neural progenitor cells. Rat (A, B, D) and mouse (C) neural progenitor cells were cultured in varying amounts of TGF-β1, insulin, FGF-2, and EGF. N2, standard media with N2 supplement. *P ≤ 0.05 compared to no TGF-β1, analysis of variance followed by Dunnett’s posthoc test. Bars are mean ± SEM. Data shown are representative of three to five experiments (rat cells) or two experiments (mouse cells). A: Western blot of lysates from neural progenitor cells grown in either 0 or 1 ng/ml of TGF-β1 and probed for phosphorylated (Smad2-P) and total (Smad2) Smad2. B: MTT assay of rat neural progenitor cells grown in varying amounts of TGF-β1, insulin, and FGF-2. The box labeled N2 on the x axis highlights the concentrations of insulin and FGF-2 present in commercially available N2 neuronal culture supplement. C: MTT assay of mouse neural progenitor cells grown in varying amounts of TGF-β1, EGF, and FGF-2. D: Cell cycle analysis of propidium iodide-stained cells showing the proportion of cells in G₁/G₀, S phase, or G₂/metaphase.