Mechanical stimulus with real-time feedback on beating cardiac cells*

Direct excitation of beating of cardiac cells by mechanical stimulus is
of interest to compare with electrical stimulus as a pacemaker.
Deformation resemble to a cycle of contraction and relaxation on a
cardiac cell induces a beat. We have investigated such mechanical
stimulus response of primary cultured cardiac cells forming aggregations
on petri dish or PDMS substrates by using a tungsten probe tip driven by
PZT bimorph. The stimulus was periodic, and the period was set to that
of intrinsic inter beat intervals of cells Continuous observations
showed that the beat intervals were fluctuated initially and then mostly
the beat stopped in 24h. Evidently, the beat rhythms of cell aggregates
under stimuli were sensitive to the phase difference between their
intrinsic beats and the periodic stimuli. To control such phase
differences, we integrated a function to apply mechanical stimulus with
a real-time feedback control using fast image processing using LabVIEW.
This real-time feedback system allows us to apply probe stimuli
synchronized with the intrinsic cardiac beats with variable phase
differences. In this presentation, we will discuss the beat intervals
and the variability of cardiac cell aggregates under phase controlled
mechanical stimulus.