Abstract 516: Intermittent Stretch-Induced Formation of Gap Junction Between Fibrocytes and Cardiomyocytes Improves Dyssynchronous Contraction in Circular Engineered Heart Tissue
Background: Three-dimensional engineered heart tissue (EHT) is a potential source for cardiomyoplasty. However, EHT often exhibits dyssynchronous contraction because of a lack of electrical coupling between cardiomyocytes and fibrocytes. Here we report that intermittent stretching helps electrical coupling between cardiomyocytes and fibrocytes through gap junction formation.
Methods: Circular 3-D EHTs were constructed by mixing neonatal rat cardiomyocytes (3x106 cells/EHT) including fibrocytes, Matrigel, and serum containing culture medium. EHTs were trained by a custom-made stretch device for 7 days (2 Hz). Structure and function of EHTs were analyzed by immunohistochemistry, electron microscopy, and optical action potential mapping.
Results: Although unstretched or statically stretched EHTs exhibited asynchrony, dynamically stretched EHTs showed highly synchronous contractions and regular cycles of action potential (Fig. 1⇓). We also confirmed more than 2-fold increase in Cx43 after stretching. A histological analysis revealed only sparsely arranged cardiomyocytes in contrast to a number of proliferating fibrocytes within EHTs. Electron microscopy demonstrated formation of gap junctions between cardiomyocytes and fibrocytes (Fig. 2⇓).
Conclusions: These results provide direct evidence that intermittent stretching helps electrical coupling between cardiomyocytes and fibrocytes through gap junction formation in 3-D EHTs.