Abstract Body (Do not enter title and authors here): Introduction:
Restrictive cardiomyopathy (RCM) is a rare cardiomyopathy characterized by ventricular diastolic dysfunction. There is limited research on RCM due to the lack of an in vitro model for diastolic dysfunction. Recently, engineered heart tissue (EHT) has significantly advanced disease modeling and drug discovery as a model reflecting contractile dynamics in vivo. Here, we evaluate the relaxation impairment of EHTs generated from an RCM patient using the Phase-Only Correlation (POC) method.
Methods:
An iPSC line from a pediatric patient with severe RCM harboring the TNNI3 R170W mutation (R170W-iPSC) was generated. An isogenic iPSC line corrected for the mutation was also established using CRISPR/Cas9 technology. The EHTs were created by casting into pillar system using cardiomyocytes differentiated from iPSCs (Figure 1). Video microscopy was used to track one-dimensional pillar deflection under 1 Hz stimulation. The force generation of EHTs was analyzed with POC method, a template-based image matching technique that estimates displacement between two images with subpixel accuracy by locating the correlation peak. We defined the contractile force and the relaxation force using the force waveform calculated from the pillar deflection (Figure 2a).
Results:
The calculated force at the maximum pillar deflection, showed no difference between R170W-EHT and Isogenic-EHT (Figure 2b). The time for the pillar deflection to decrease from 100% to 20% during relaxation, the time to relaxation, was significantly longer in R170W-EHT than in Isogenic-EHT (Figure 2c). These findings indicated impaired relaxation of R170W-EHT. Furthermore, the ratio of contractile force to total force was lower and the ratio of relaxation force to total force was higher in R170W-EHT than in Isogenic-ETH (Figure 3a and 3b). In addition, the ratio of relaxation force to contractile force was significantly higher in R170W-EHT (Figure 3c). These data showed that R170W-EHT required greater force to dilate.
Conclusions: Our EHT model with POC method reflects the clinical manifestation of RCM with diastolic dysfunction by comparing the contractile and relaxation forces and their ratio in vitro.