FIG. 1.

Cell stretching alone even without retinoic acid (RA) exposure produced significantly more and longer neurites relative to a non–RA-treated, static control. Human neuroblastoma (SH-SY5Y) cells were stretched (10% equibiaxial strain at 0.25 Hz, 120 min/d for 7 days) using a Flexcell device. Cells were stretched without or with 10 μM RA, a known soluble neurogenic factor. (A) Optical cell images shown with a scale bar of 50 μm. An objective lens with 10× magnification was used (eyepiece with 10×). (B) Neurite length was quantified by the tracing method and neurite number per cell was manually counted. Comparisons with non–RA-treated, static control are shown with **p<0.01. A comparison between no RA and 10 μM RA for stretched samples is shown with ^##p<0.01. A comparison between RA alone and stretch alone is shown with ^ψψp<0.01.