Fig. 4.

Increased levels of mitochondrial proteins in working culture engineered heart tissues (EHTs) are attenuated by a myosin ATPase inhibitor. A: representative force twitches plotted against tissue length. Twitches were collected during acute testing and represent the shortening protocol that each tissue was cultured under. B–F: peroxisome proliferator-activated receptor γ coactivator 1 α (PGC1α), ATP synthase (ATP5H), mitochondrial calcium uniporter (MCU), voltage-dependent anion channel (VDAC), and mitochondrial import receptor subunit 20 (TOM20) protein levels were significantly increased in EHTs cultured under working conditions compared with EHTs cultured isometrically. Blebbistatin treatment significantly reduced protein levels in working culture EHTs. G: phosphatase and tensin homolog-induced putative kinase 1 (PINK1) protein levels showed significant interaction between blebbistatin treatment and culture conditions. Fold change (F.C.) normalized to untreated isometric culture (IC); n = 3, 3, 4, and 4 tissues for IC, IC+blebbistatin, working culture (WC), and WC+blebbistatin, respectively, 2-way ANOVA with Tukey multiple comparisons test; *P < 0.05, **P < 0.01, ***P < 0.001.