Figure 2. Composition and structure of the cardiac rings.

(A) Example brightfield images of cardiomyocytes seeded with or without fibroblasts 1 day after seeding. Scale bar: 200 µm. (B) Number of full cardiac rings per well in time according to the cardiomyocytes derived from human induced pluripotent stem cell (hiPSC-CMs):fibroblasts ratio they contain (4:1, 3:1, or 2:1). Mean ± SD, for n=4 differentiations. (C) Confocal imaging of immunostained tissues at different heights: cardiac ring (top panel), and basal layer (bottom panel) of a tissue at ×40 magnification. Vimentin, stained in green, corresponds to fibroblasts, troponin T, in red, is specific to cardiomyocytes, and DAPI is in blue. Scale bars: 100 µm. (D) Picture of the immunostained contractile fibers at ×63 magnification. Vimentin (green), troponin T (red), and DAPI (blue). Scale bar: 50 µm. (E) 3D reconstruction of a ring. x, y, and z scale bars: 100 µm.

Figure 2—figure supplement 1. Contractile parameters at D14 for the different fibroblasts ratios.

(A) Contraction frequency. (B) Contraction stress. (C) Maximum contraction speed. (D) Maximum relaxation speed. Mean ± SD, for n=23, 52 and 16 tissues respectively for the ratios 4:1, 3:1 and 2:1.

Figure 2—figure supplement 2. Magnified regions of rings displayed in Figure 2C.

Larger scale confocal pictures of immunostained tissues at different heights basal layer (left) and cardiac ring (right) at ×40 magnification: vimentin is stained in green, troponin in red, and DAPI in blue. Scale bars: 50 µm.

Figure 2—figure supplement 3. Immunostaining of rings at D1 and D7.

Top panels: troponin T (red), vimentin (green), and DAPI (blue) staining of a ring at D1, basal layer (left) and cardiac ring (right). Bottom panels: troponin T (red), vimentin (green), and DAPI (blue) staining of a ring at D7, basal layer (left), and cardiac ring (right). Scale bars: 100 µm.

Figure 2—video 1. 3D reconstruction of a ring.

Download video file ^{(2.6MB, mp4)}