טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentDebbi Lior
SubjectCardiac Cell Response to Action-Potential Phase-
Dependent load
DepartmentDepartment of Mechanical Engineering
Supervisor Professor Shelly Tzlil


Abstract

Cardiac cells are subjected to mechanical load during each heart-beat. Cardiac cells are mechanosensitive and are able to adapt to changes in mechanical load. Nevertheless, excessive load can induce pathologies such as cardiac hypertrophy. While the forces working on the heart as an organ are well understood, information regarding the stretch response at the cellular level is limited.

 The cardiac stretch-response depends on the stretch pattern and action potential phase; therefore, timing and directionality of load application must be accurately controlled. Here, we design a new experimental setup, which enables high-resolution fluorescence imaging of cultured cardiac cells under cyclic uniaxial mechanical load and electrical stimulation. Cyclic stretch was applied in different phases relative to the electrical stimulus and the effect on cardiac cell beating was monitored. Our data demonstrate that while after 60 cycles of mechanical loading (1 minute), no change was observed in the beating profile, after 10 minutes of cyclic loading, cell contracts with a phase shift relative to the electrical stimulus. More specifically, contraction occur before the electrical stimulus arrives (‘early beating’). In cases where contraction occurs more than 300msec before the electrical stimulus, a second contraction is generated. The average phase shift increases with the overlap between the applied stretch and the contraction phase of the beating cell. These result may indicate that cyclic loading interfere with spontaneous beating of cardiac cells.