A New Technique for Reproducible Measurement of Contractile Force of Single Adult Cardiomyocytes in Mammalian Cells

Background: Cardiovascular diseases are still the leading cause of death in industrialized countries. Increasing cardiac failure leads to an insufficient blood supply of organs and ultimately to death. Causes of reduced cardiac function can be very different. The role of changes in contraction force of single cardiomyocytes is still unknown. This is because earlier methods of force analysis of single cardiomyocytes were previously very laborious and not suitable for use in routine diagnostics. Based on a work on force measurement of skeletal muscle cells, we investigated the applicability of a gel-based method for the valid determination of the force of single cardiomyocytes from rat hearts.

Method: Adult cardiomyocytes were obtained from rat hearts by enzymatic digestion via coronary perfusion. Purified cardiomyocytes were then embedded into Matrigel and covered with an oxygen-enriched medium and stimulated with a pacemaker. Recordings were made on microscope using a high-speed camera. The measurement of changes in length and thickness of single cardiomyocytes was performed using a MATLAB program specially created for this purpose. The reaction to catecholamines was tested by adding dopamine in two concentrations: 0.5 and 1 μM. The evaluation of 10 to 15 cardiomyocytes was performed for each test batch. A t-test was used to analyze statistically relevant changes (p < 0.05).

Results: A total of 19 samples from rat hearts were analyzed. The rate of contractile cardiomyocytes after inclusion in gel was 90.12% (±4.9). Without drug additives, cardiomyocytes from different heart samples showed a comparable contraction force (p = 0.08). Increasing pacer voltage had no effect on force (12 vs. 19 V, p = 0.13). However, there was a clear dependence of stimulability on the alignment of the cells in the gel. Similar to a dipole in an electric field, pacer voltage must be increased by the factor U if angle is steeper than 0 degrees. A significant, concentration-dependent increase in force was measured after addition of dopamine; 1 µM dopamine induced an increase in force of 78.3% (±5.4) (p < 0.01).

Conclusion: It is the first experimental setup that allows a simple and quick analysis of contraction force of single cardiomyocytes. We were able to demonstrate the valid reproducibility of this new method in various experimental approaches. In future, this arrangement will offer a broad application in examination of a wide variety of myocardial diseases.

Publication History

Article published online:
03 February 2022