Enhanced Characterization of Contractility in Cardiomyocytes During Early Drug Safety Assessment

Abstract

We sought to investigate whether drug-induced changes in contractility were affected by pacing rates that represent the range of heart rates encountered in vivo. Using the cell geometry measurement system (IonOptix), we paced dog cardiomyocytes at different cycle lengths (CLs) of 2000, 1000, 500, and 333.3 ms, before and after exposure to 13 inotropic drugs. Time course data using vehicle control (0.1% dimethyl sulfoxide (DMSO)) demonstrated stability of the system at all CLs tested. Seven positive inotropes (eg isoproterenol) exerted rate-dependent increases in sarcomere shortening (Sarc. short.; maximal effect at a CL of 333.3 ms [0.1 µM isoproterenol increased Sarc. short. by 41.1% and 145.9% at 2000 and 333.3 ms, respectively]). Omecamtiv mecarbil showed an atypical profile (increased Sarc. short. at 2000 ms [106.9%] and decreased at 333.3 ms [IC(50) = 0.64 µM]). Four negative inotropes (eg flecainide) showed rate-independent inhibition of Sarc. short. (IC(50)s: 3.3 µM [2000 ms] versus 2.3 µM [333.3 ms]). The remaining negative inotropes, verapamil, and BTS (N-benzyl-p-toluene sulphonamide) produced an increase (IC(50)s: 3.9 µM [2000 ms] versus 0.043 µM [333.3ms]) and decrease (IC(50)s: 18.3 µM [2000 ms] versus 34.0 µM [333.3 ms]) in potency, respectively. Negative inotropes (eg flecainide, BTS, and verapamil) decreased the area of the Ca(2+) transient versus Sarc. short. hysteresis loop, although rate dependency was seen with verapamil only. Positive inotropes (eg isoproterenol and levosimendan) induced a rate-dependent increase in the area, however Omecamtiv mecarbil increased and decreased the area at CLs of 2000 and 333.3 ms, respectively. Thus, the use of different pacing rates may improve the detection of inotropes in early drug discovery and illustrate the potential for finger-printing different mechanisms of action.

Multi-Imaging Method to Assay the Contractile Mechanical Output of Micropatterned Human iPSC-Derived Cardiac Myocytes

“…23, 24 The consistent increase in single cell mechanical output and beat rate upon incubation in 0.1 μM demonstrated the ability of this system to detect the inotropic effects of isoproterenol (Figure 3 and Online Figure VI). However, the low magnitude of this increase and the drastic decrease in mechanical output after incubation in 1 μM also show that these cells do not fully recapitulate the contractile physiology of a well-matured myocardial tissue.…”

“…23 We tested the ability of our platform to detect variations in mechanical output induced by isoproterenol and omecamtiv mecarbil.…”

“…The contractile effects of omecamtiv mecarbil in CMs have been previously reported to be atypical when compared with the effects of other inotropes. 23 Omecamtiv mecarbil acts specifically on cardiac myosin by increasing the time of its strong actin-bound state 25 ; it also delays the relaxation of myofibris. 46 Consistent with this information, our data showed an increase in the time of contractions at higher drug concentrations (Online Figure VII D) and an increased br at lower drug concentration (Online Figure VII E).…”

3D Micropillars Guide the Mechanobiology of Human Induced Pluripotent Stem Cell‐Derived Cardiomyocytes

“…An abnormal mechanical stretching may lead to cardiomyocyte apoptosis or cardiac fibroblasts proliferation triggering cardiac remodeling . The most common way to monitor cardiomyocyte contraction is to measure globally cell shortening from the displacement of cell extremities . Measuring cardiac cell contractility and stiffness at nanoscale provides clinically relevant data on the fundamental mechanisms leading to heart failure.…”

The cardiac work-loop technique: An in vitro model for identifying and profiling drug-induced changes in inotropy using rat papillary muscles

“…Another class of techniques currently used experimentally to assess contractility are cellular assays such as impedance-or sarcomere shortening-assays [15][16][17][18] . These techniques have the potential to be higher throughput than those mentioned previously.…”