Engineering Anisotropic Cardiac Monolayers on Microelectrode Arrays for Non-invasive Analyses of Electrophysiological Properties
Standard culture of cardiac cells as unorganized monolayers on tissue culture plastic or glass does not recapitulate the architectural or the mechanical properties of native myocardium. We investigated physical and protein cues from extracellular matrix to engineer anisotropic cardiac tissues as highly aligned monolayers on top of microelectrode array (MEA). MEA platform allows non-invasive measurement of beating rate and conduction velocity. The effect of different extracellular proteins was tested by using the most common extracellular matrix proteins in the heart; fibronectin and gelatin, which is derived from collagen, after aligning myocytes using microcontact (µC) printing technique. Both proteins showed similar electrophysiological results before the monolayer began to delaminate after the sixth day of culture. Additionally, there were no significant differences on day 4 between the two microcontact printed proteins in terms of sarcomere alignment and gap junction expression. To test the effect of substrate stiffness, micromolded (µM) gelatin hydrogel was fabricated in different concentrations (20% and 2%), corresponding to elastic moduli of approximately 0.7 kPa and 33 kPa, respectively, to cover both spectra of the in vivo range of myocardium. Cardiac monolayers in the micromolded conditions beat in a much more synchronized fashion, and exhibited conduction velocity that was close to the physiological values. Both concentrations of gelatin hydrogel conditions yielded similar sarcomere alignment and gap junction expression on day 4 of culture. Ultimately, 3D micromolded gelatin hydrogel that recapitulated myocardial stiffness improved the synchronicity and conduction velocity of neonatal rat ventricular myocytes (NRVM) without any stimulation. Identifying such microenvironmental factors will inform future efforts to design Heart on a chip platforms that mimic in vivo environments and predict potential cardiotoxicity when testing new drugs.
- This article is part of the themed collection: Bioanalytical tools for enabling precision medicine