Figure 7: Stress-stimulated Ca²⁺ transient and Ca²⁺ sparks.

A: Schematic of a myocyte embedded in 3-D hydrogel matrix containing red fluorescence beads. B: Confocal imaging of the myocyte and beads demonstrating cell contraction and gel deformation as seen in the movement of the cell’s edge. (C) Cell contracting in normal Tyrode solution provides load-free control. (D) Cell contracting in-gel under load. (E) Fractional shortening of cell contraction in-gel (n=17 Cells) compared with load-free control (n=17). (F) Systolic Ca²⁺ transient (CaT) peak in cell-in-gel (n=17) compared with load-free control (n=17). (G) Diastolic Ca2+ spark frequency in the cells for load-free (n=18), in soft gel made of 5% crosslinker (Gel5%, n=9), in gel with 7.5% crosslinker (Gel7.5%, n=18), and after blebbistatin treatment (n=5). One-way ANOVA with Bonferroni post-test was used for pair-wise comparison: P< 0.001***. (Jian et al. 2014)