心臟細胞在週期性拉伸過後，我們發現細胞的跳動週期會接近拉伸的週期。 在持續性拉伸下，細胞的跳動週期變長。加入釓之後我們發現，拉伸對細胞跳動週期的影響小很多。除此之外，本實驗抑制了纖維母細胞的增長，發現在低密度纖維母細胞的情況下，跳動週期以及心律變異度明顯的高於高密度纖維母細胞的心臟細胞。 ;Traditionally, it is believed that cardiac dynamics is controlled only by electrical activities. However, it is known that mechanical forces can also activate mechanical sensitive channels in the cell which can bring changes in electrical activity. The purpose of our experiment is to understand whether mechanical forces affect the cardiac beating dynamics. We also want to understand whether the number of fibroblasts which is mechanical sensitive affect the beating dynamics. Cardiomyocytes were dissected from rat embryos and seeded on a deformable silicon chamber in which stretching can be realized by elongation. Two kinds of stretching were used: (1) Periodic stretching at 1 Hz for 2 to 4 hours and the dynamics are observed by calcium imaging, (2) Sustained stretching for 5 minutes and the dynamics are observed by bright field microscopy. The stretch-activated ion channels (SACs) blocker, Gadolinium (Gd3+), was used in our experiment to investigate its effect on the beating dynamics. Under periodic stretching, we found that the frequency of cardiomyocytes can almost be synchronized by the stretching frequency. As for sustained stretching, we found that the heart rate decreases during stretching. After treating with $Gd^{3+}$, the difference of inter-beat interval (IBI) between stretched and non-stretched samples significantly decreases. In addition, we also investigated the beating of cardiac culture in the presence of high and low density fibroblasts. As for low density of fibroblasts, the IBI and heart rate variability is higher than those in the high density one.
