Fig. 6.

Engineered heart tissues (EHTs) subjected to different training regimes with similar work outputs maintain similar levels of ATP synthase. A: position of the spring arm throughout a single culture cycle. High afterload culture (HA) transient is delayed in time and of smaller magnitude compared with low afterload culture (LA), which results in EHTs contracting against higher load. B: representative transients of tissue length during acute HA testing after 7 days of culture under chronic conditions. C: representative force twitches collected during acute testing while EHTs underwent the shortening protocol represented in Fig. 2B (HA). D: representative work loops collected during acute HA testing. E: EHTs generated similar levels of contractile work irrespective of chronic culture conditions during acute HA testing (HA culture, n = 12 tissues; LA culture n = 11 tissues). F: representative transients of tissue length during acute LA testing after 7 days of culture under chronic conditions. G: representative force twitches collected during acute testing while EHTs underwent the shortening protocol represented in Fig. 2F (LA). H: representative work loops collected during acute LA testing. I: EHTs generated similar levels of contractile work irrespective of chronic culture conditions during acute LA testing (HA culture, n = 12 tissues; LA culture, n = 11 tissues). J: EHTs from either culture condition had similar immunoblot levels of ATP synthase (ATP5H) (n = 8 tissues in each condition). F.C., fold change; n.s., not significant.