The Effects Of In Vitro Exercise Of Engineered Heart Tissues On Cardiac Injury And Function

PURPOSE: Vigorous exercise produces cardiac troponin release, a validated marker of cardiac injury, but the release mechanisms are challenging to study in vivo. This study aims to establish a novel and versatile platform to mimic exercise in vitro through prolonged electrical stimulation of Engineered Heart Tissues (EHTs). METHODS: EHTs were created using human-induced pluripotent stem cell-derived cardiomyocyte and fibroblast. The EHTs were subjected to electrical stimulation with carbon electrodes at a frequency of 2.5 Hz for either 2 or 4 hours and compared to a non-stimulated control group. Concentrations of high-sensitive cardiac troponin T (cTnT; measure of cardiac injury) and lactate dehydrogenase (LDH; measure of cellular injury) were assessed in EHT medium at baseline, immediately post-stimulation and after a recovery phase of 20 hours in fresh medium, whereas contractile performance, including the contractile force of EHTs, was determined at the same timepoints. RESULTS: EHTs stimulated for 2 and 4 hours showed significant elevations in cTnT concentrations 20 hours post-stimulation compared to controls (p = 0.021 and p < 0.001, respectively), with no immediate changes post-stimulation. LDH concentrations immediately increased after 2 and 4 hours of stimulation compared to controls (p = 0.004 and p < 0.001), which was sustained 20 hours post-stimulation (p = 0.044 and p < 0.001). Finally, significant reductions in EHTs contractile force were observed following 2 and 4 hours of stimulation compared to controls (p < 0.001 and p < 0.001), which was sustained 20 hours post-stimulation (p = 0.038 and p < 0.001). CONCLUSIONS: Exercise-like stimulation of EHTs triggered cTnT and LDH release in conjunction with signs of cardiac fatigue (i.e. attenuated contractile force). These findings align with observations in human studies that show that vigorous exercise results in post-exercise cTnT-release and impaired cardiac function. This suggests that our novel platform has the potential to better study the mechanisms for the release of cardiac troponin due to exercise. This work is funded by a Netherlands Organization for Scientific Research (NWO) ENW-XS grant (#OCENW.XS22.2.093) and the Twente University RadBoudumc Opportunities (TURBO) grant.