The direction of contraction at each location in the heat map before (A)
and after (B) shape transition is indicated by color [coded to the polar
histograms] and the overlaid vector field. Semicircular histograms of
contraction angles indicate the overall directionality of contracting cardiac
cells, of one field of view, on surfaces before and after shape transition. The
black lines in the center of the histogram indicate the mean resultant vector
length. The shift in contraction direction is better visualized in (C). The
distribution of the contraction orientation after shape transition exhibits a
bimodal behavior and does not behave like a Gaussian distribution. (Kurtosis =
2.184, −1.220 before and after, respectively. *p ≤ 0.001, n = 3,
D’Agostino & Pearson omnibus normality test). Representative
images of NRVM alignment on SMPs before (D) and after (E) shape transition
(nuclei staining = blue, f-actin staining = green, vinculin staining= red; scale
bar = 20 µm). Histograms of NRVM nuclei (F) before and after shape
transition.