Single‐Cell isolation of myocytes: A potential measure of chronological cardiac regularity
Authors: Feldman Jacob R. , Kumar Mohit , Sadayappan Sakthivel 
Published: April 2020

Heart failure is the leading cause of death in the United states and is responsible for over 500,000 deaths a year– in other words, one in every 4 deaths is associated with heart failure or its complications. As such, numerous models of its basis, progression, and symptomology have been conducted. Many of these assays have worked to establish the biophysiological basis of the Frank Starling Law of the Heart, which is a staple of cardiac regularity and establishes the relationship between diastolic/systolic volume and subsequent myocardial contraction(s). As a means of investigating these properties, I designed an experiment in which I extracted individual myocytes from mice hearts, permeabilized these cells in different concentrations of calcium solutions (to emulate contractional activity), and recorded the force of their length‐dependent‐activation, a phenomenon that can be conceptualized as the exertional activity from the muscular tissues that compose a myocyte.

By comparing the exertional activity of control hearts to those of genetically engineered mice to present with hypertrophic cardiomyopathy, the physiological differences in heart activity can be elucidated. Furthermore, by analyzing these physiological differences on a longitudinal time frame, the efficacy of the disease can be better understood. To account for this, cells were extracted from hearts of both the control and experimental group that were 1 month, 2 months, and 3 months old. To ensure that the ages of the mice hearts were maintained, the hearts that were not immediately used were frozen in a laboratory grade freezer at −80 degrees.

I propose that the hearts of the experimental group will display a higher level of length‐dependent‐activation in comparison to the hearts of their control counterparts, indicating a physiological basis of cardiac irregularity. Additionally, I suspect that the control and experimental groups will not show a significant difference in the first month but will have a difference of statistical significance at all other time points. The results from the two groups at different chronological stages will allow for interpretation of the prognosis of cardiac illness, potentially advancing cardiology towards an aggrandized understanding of the biophysiological properties of the heart.

After the data collection was complete it was input into Microsoft Excel so that the active force, absolute force, force rundown, and actual force projections could be calculated. While the data gathered was genuine, it was determined through these calculations that the acquired results were not representative, prompting investigation into procedural/mechanical errors that may have taken place. The data itself was not indicative of any specific result at this time, yet there is confidence that continued analysis and investigation into the experiment are promising. Further trials to account for the aforementioned errors are currently underway with optimism of a new experimental design soon.

Support or Funding Information

This experiment was performed with the support of University of Cincinnati Cardiology and funded by the American Physiology Society Short‐Term Research Education Program to Increase Diversity in Health Related Research (STRIDE) fellowship.

This is a screen capture of an isolated myocyte being moved from a resting, relaxed solution into a an active, calcium based solution. The positive spikes are evidence of the subsequent force contractions. There are two spikes in this photo because the cell was moved in and out of the active solution twice. For reference, the first spike is the myocyte’s reaction to a 20 second exposure and the second spike a 10 second exposure.

Figure 1