Increased afterload results in 'pathological'
cardiac hypertrophy, the most important risk factor for the development of
heart failure. Current in vitro models fall short in deciphering the mechanisms of
hypertrophy induced by afterload enhancement. The aim of this study was to develop an experimental model that allows investigating the impact of afterload enhancement (AE) on work-performing heart muscles in vitro.
Fibrin-based engineered heart tissue (EHT) was cast between two hollow elastic
silicone posts in a 24-well cell culture format. After 2 weeks, the posts were reinforced with
metal braces, which markedly increased afterload of the spontaneously beating EHTs. Serum-free,
triiodothyronine-, and
hydrocortisone-supplemented medium conditions were established to prevent undefined serum effects. Control EHTs were handled identically without reinforcement.
Endothelin-1 (ET-1)- or
phenylephrine (PE)-stimulated EHTs served as positive control for
hypertrophy. Cardiomyocytes in EHTs enlarged by 28.4 % under AE and to a similar extent by ET-1- or PE-stimulation (40.6 or 23.6 %), as determined by
dystrophin staining. Cardiomyocyte
hypertrophy was accompanied by activation of the fetal gene program, increased
glucose consumption, and increased
mRNA levels and extracellular deposition of collagen-1. Importantly, afterload-enhanced EHTs exhibited reduced contractile force and impaired diastolic relaxation directly after release of the
metal braces. These deleterious effects of afterload enhancement were preventable by
endothelin-A, but not
endothelin-B receptor blockade. Sustained afterload enhancement of EHTs alone is sufficient to induce pathological cardiac remodeling with reduced contractile function and increased
glucose consumption. The model will be useful to investigate novel therapeutic approaches in a simple and fast manner.