Abstract Introduction Performance of vigorous intensity endurance exercise is known to produce increased concentrations of cardiac troponins, a validated marker of cardiac injury. In vitro models are needed to study the underlying mechanisms of these potential deleterious effects of exercise on the heart. Purpose To develop a novel and versatile platform to mimic exercise-like responses in vitro by applying prolonged electrical stimulation to Engineered Heart Tissues (EHTs). Methods EHTs were created using human-induced pluripotent stem cell-derived cardiomyocytes and fibroblasts. EHTs were subjected to electrical stimulation with carbon electrodes at a frequency of 2.5Hz for either 2 or 4 hours and compared to a non-stimulated control group and a doxorubicin (DOX) exposed group. Concentrations of high-sensitive cardiac troponin T (hs-cTnT) and lactate dehydrogenase (LDH) were assessed in EHT medium at baseline, immediately post-stimulation and after a recovery phase of 20-hours in fresh medium. In addition, contractile performance (e.g. contractile force) was determined at these same timepoints. Results EHTs electrically stimulated for 2h and 4h, and those treated with DOX, showed significant elevations in hs-cTnT at 20h post-stimulation compared to control (291.0±123.1 ng/L vs 496.7±190.8 ng/L vs 1486.2±501.6 ng/L vs 168.4±54.1 ng/L (p0.001), respectively) with no immediate changes post-stimulation. LDH concentrations increased immediately following 4h stimulation compared to control (2.9±1.2 IU/L vs 1.7±0.4 IU/L, (p=0.009)), and were elevated 20h post-stimulation following stimulation of 2h, 4h and DOX treatment compared to control (2.638±1.970 IU/L vs 5.525±2.413 IU/L vs 7.686±2.070 IU/L vs 0.879±0.283 IU/L (p0.001), respectively). Immediate reductions in EHTs contractile force relative to baseline were observed following 2h and 4h stimulation, but not DOX, compared to control (80.2±22.2% vs 70.5±29.0% vs 97.8±16.8% vs 103.1±10.7% (p0.001), respectively). EHTs contractile force partially normalized after 20h recovery for the 2h stimulated EHTs, but remained decreased following 4h stimulation, and reduced for the DOX treated EHTs compared to control (89.7±20.7% vs 71.9±28.3% vs 43.4±13.1% vs 104.1±10.7% (p0.001), respectively). Conclusion Exercise-like stimulation of EHTs increased hs-cTnT and LDH concentrations in conjunction with signs of cardiac fatigue (i.e. attenuated contractile force). These findings align with observations in human studies, indicating that our novel platform mimics the effects of in vivo exercise. Accordingly, our novel model has the potential for future work to better study the underlying mechanisms of exercise-induced cardiac troponin release.
Luiken et al. (Sat,) studied this question.