Vala Sciences

We have used IC200 KIC to study
1) different the properties of cardiac myocytes obtained from different sources (e.g., primary cardiac myocytes vs. cardiac myocytes derived from embryonic or induced pluripotent stem cells),
2) the time course of cardiomyocyte maturation,
3) effect of different chemicals on guiding the differentiation/maturation process; 4) contribution of different elements of intracellular calcium machinery to the cardiac action potential (shape, duration, amplitude) using pharmacological tools and 5) cardiomyocytes in which the intracellular calcium regulatory apparatus has been altered via molecular biology techniques.

A) Diagram representing the analysis of subcellular compartments in cardiomyocytes by CyteSeer.
B) Changes in intracellular calcium concentration in cardiomyocytes during the action potential triggered by electrical stimulation. Note that amplitude and kinetics of Ca responses are very different in distinct subcellular regions, implying different mechanisms involved in Ca flux

Spontaneous activity of iCell(TM) Cardiomyocytes cultured for 2 weeks. The frequency of spontaneous calcium spikes is ~0.4 Hz.

Calcium flux during the action potential triggered by electrical stimulation in iCell(TM) cardiomyocytes cultured for 3 weeks.

A) Electrical stimulation protocol: a 1-Hz train of 6 pulses of 15 V amplitude and 5 ms duration was initiated at t= 2seconds.

B) Changes in intracellular calcium concentration in cardiomyocytes during the action potential triggered by electrical stimulation. Note that these responses are reversible, as intracellular Ca concentration is restored by the intracellular Ca-handling machinery to the resting levels of Ca between each stimulation pulse. The 7th calcium spike at the end of the trace is the result of spontaneous action potential.

Calcium transients triggered by electrical stimulation in iCell(TM) cardiomyocytes cultured for 4 weeks.

A) Electrical stimulation protocol: a 2-Hz train of 12 pulses of 15 V amplitude and 5 ms duration was initiated at t= 2 seconds.

B) Changes in intracellular calcium concentration in cardiomyocytes during the action potential triggered by electrical stimulation. The first and the last calcium spikes are the result of spontaneous electrical activity of cardiomyocytes.

Effect of Diltiazem, a Ca-channel blocker, on calcium transients recorded from different subcellular areas of cardiomyocytes.

Diltiazem is a non-dihydropyridine (DHP) member of the group of drugs known as benzothiazepines, which are a class of calcium channel blockers, used in the treatment of hypertension, angina pectoris, and some types of arrhythmia. It is also an effective preventive medication for migraine. The molecular structure of Diltiazem includes a 1,4-thiazepine ring.

Stem-cell derived cardiomyocytes were incubated with 10 mkM of Diltiazem for 10 minutes prior to experiment.

For this experiment the following electrical stimulation protocol was used:

2-sec delay after start of recording, 2-Hz train of 12 pulses of 15 V amplitude and 5 ms duration.

Changes in intracellular calcium concentration in cardiomyocytes during the electrical stimulation train is large for the 1st stimulation pulse, but is progressively reduced in response to subsequent pulses.

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