Cells grown on coverslips were collected on culture day 0, 3, 6, 9, and 15; and their morphological characteristics were analyzed. The cells were fixed with 4% paraformaldehyde dissolved in phosphate based saline (PBS, pH 7.4) for 30 minutes. Cells were imaged with a microscope (Imager Z2, Zeiss) and the images were acquired with Zeiss camera (Axiocam 506 mono, Zeiss). The soma area, neurite length, and branches were analyzed with ImageJ 1.4.3.67 and NeuronJ 1.4.3. Statistic figure of T test was output by GraphPad Prism5.01.
