Figure 3. Actin cytoskeleton of murine syncytiotrophoblast (SYN) contributes to its elastic strength.

A. Microrheology with an atomic force microscope was used to measure elastic strength of mouse trophoblast stem cells (TSC) and SYN. Photos depict microscopic cantilever positioned above cultured live cells prior to measurement. B. The elastic modulus (Young's modulus) of SYN is significantly higher than that of TSC (p = 4.7×10⁻⁵ by Student's T-test). Elastic modulus of SYN was measured in the exact same spot prior to and after treatment with Cyto-D for 40–60 min. Disruption of the actin cytoskeleton with Cyto-D significantly decreased the elastic modulus of SYN (p = 0.001 by Student's T-test). Bars represent median values. Graph is based on three independent experiments performed in triplicate. C. Immunofluorescence images of the actin (red) in mSYN show that the characteristic actin meshwork (i–iii) is disrupted by 1 hr treatment with Cyto-D (iv–vi). Nuclei are shown in white. Bars in panels i and iv are 50 um. Panels ii–iii and v–vi are representative close-up images of untreated and Cyto-D treated mSYN, respectively. Panels iii and vi show just the actin channel of ii and v respectively. Aggregation of microfilaments in distinct puncta are observed upon treatment. Bars = 10 um.