N-cadherin-mediated cell adhesion determines the plasticity for cell alignment in response to mechanical stretch in cultured cardiomyocytes.

Mechanical stretch has been implicated as the growth stimuli in the heart. Physiologically, mechanical stretch is reported to contribute to the orientation of cardiomyocytes, though the molecular mechanism remains to be elucidated. This study was designed to make clear functional significances of N-cadherin in plasticity of cell alignment in response to mechanical stretch. Neonatal rat cardiomyocytes, cultured on silicone dishes, were subjected to artificial uniaxial cyclic stretch. Mechanical stretch was started at certain times (3-75h) after seeding and continued for 24h. Stretch stimulation in 3h after cultivation promoted cell orientation running parallel to tension direction. In contrast, cardiac myocytes fail to align when exposed to stretch 24-75h after cultivation. To address the importance of N-cadherin in the responsiveness to stretch, the expression and distribution of N-cadherin were analyzed. Immediately after seeding, N-cadherin showed dispersed distributions. During cultivation, N-cadherin localized to cell-cell contacts accompanied by the upregulation of its protein. Next, to investigate influence of cell-cell adhesion, cardiomyocytes cultured for 72h were replated by trypsin treatment and exposed to stretch 3h after replating. The cardiomyocytes replated by trypsinization were oriented in parallel to tension direction by mechanical stretch. Finally, adenoviral transfection of dominant-negative N-cadherin recovered the ability to exhibit cell orientation in response to stretch. Our results suggested that N-cadherin was involved in the oriented responses of cardiomyocytes induced by mechanical stretch.