Adult fibroblasts are more contractile than fetal fibroblasts.

<p>(a) Fetal fibroblasts are less contractile than adult fibroblasts as determined by traction force microscopy. Each bar represents mean ± SEM of more than 20 cells from two independent experiments. Statistical analyses were performed using Student's <i>t</i> test. (b) PDGF treatment of adult fibroblasts results in an increase in the observed cumulative traction force; EGF treatment results in a similar although smaller increase. Each bar represents mean ± SEM of more than 25 cells from two different experiments. Statistical analyses were performed using Student's <i>t</i> test.