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Fig. 5 Characterization of Flow Forces within the Pericardial Cavity
(A and A′) Measurement of the distance between the myocardium and the pericardial wall during heart contraction.
(A) Ventral view of a 48 hpf heart immersed in Bodipy TR. The continuous and discontinuous lines outline the myocardium at diastole and systole, respectively; ventricle is in green, and atrium is in yellow.
(A′) Average maximum distance over four heartbeats between the pericardial wall and ventricle (green) and pericardial wall and atrium (yellow).
(B) Localization of PE cells within three regions (R1, R2, and R3) of the pericardial cavity. Numbers are the percentages of cells within each region from a total of 30 cells or cell clusters.
(C and D) Tracking of a PE cell (dot) at the periphery of the pericardial cavity (C) and tracking of a PE cell flowing around the ventricle (D) (Movie S8). Speed (μm/s) of advected PE cells is represented by a color code; minimum and maximum speeds are indicated.
(E) Speed of advected cells within the pericardial cavity (means ± SD), varied significantly in different areas, indicated by letters a–d (one-way ANOVA followed by Tukey’s mixed-effect test. p < 0.05 for all pairwise comparisons).
(F) Positions probed with optical tweezers: 1, cell positioned close to the vpPE site; 2, cell close to the avcPE site; 3, cell at a distance from the ventricle; 4, cell close to the ventricle; and 5, cell positioned at the AVC.
(G and H) Vector and force maps obtained by optical tweezing.
(I–K′) In vivo confocal imaging and tracking of fluorescent beads injected into the pericardial cavity; beads recapitulate the pattern of advected PE cells (Movie S9).
(K and K′) Advected PE cell (K) and bead (K′) following the same flow.
(L) Model summarizing the circulatory pattern of PE cells moving with the pericardial flow in conjunction with the observed order of myocardial adhesion.
PEC, proepicardial cells; pN, picoNewton. Scale bars represent 50 μm. See also Movies S8 and S9.