FIGURE 2.

Changes in cardiomyocyte surface topography and dyadic organization in the developing and HFrEF rat heart. (A) Left panels: Scanning electron micrographs show the appearance of Z-spines (arrowheads) from an early time point during development and their re-appearance during post-infarction HFrEF. Z-grooves (dashed lines) and t-tubule openings (arrows) appear gradually during development and are lost in HFrEF. Right panels: temporally matched confocal captures of internal t-tubules (di-8-ANEPPS staining). (B) Quantification of these t-tubule signals illustrates an organizational shift from a predominantly longitudinal to largely transverse orientation during maturation, but reversion to an immature phenotype during HFrEF. (C) Structural parallels between developing and failing myocytes include not only t-tubule structure, but also similarly sparse arrangements of RyRs that exhibit low co-localization with LTCCs. d.o., days old. *P < 0.05 vs. adult in same category, ^†P < 0.05 vs. SHAM in same category. Reproduced from Lipsett et al. (2019) with permission.