Microenvironmental Modulation of Calcium Wave Propagation Velocity in Engineered Cardiac Tissues
In the myocardium, rapid propagation of action potentials and subsequent calcium waves is critical for synchronizing the contraction of cardiac myocytes and maximizing cardiac output. In many pathological settings, diverse remodeling of the tissue microenvironment is correlated with arrhythmias and decreased cardiac output, but the precise impact of tissue remodeling on propagation is not completely understood. Our objective was to delineate how multiple features within the cardiac tissue microenvironment modulate propagation velocity.
To recapitulate diverse myocardial tissue microenvironments, we engineered substrates with tunable elasticity, patterning, composition, and topography using two formulations of polydimethylsiloxane (PDMS) micropatterned with fibronectin and gelatin hydrogels with flat or micromolded features. We cultured neonatal rat ventricular myocytes on these substrates and quantified cell density, tissue alignment, and cell shape. We used a fluorescent calcium indicator, high-speed microscopy, and newly-developed analysis software to record and quantify calcium wave propagation velocity (CPV).
For all substrates, tissue alignment and cell aspect ratio were higher in aligned compared to isotropic tissues. Isotropic CPV and longitudinal CPV were similar across conditions, but transverse CPV was lower on micromolded gelatin hydrogels compared to micropatterned soft and stiff PDMS. In aligned tissues, the anisotropy ratio of CPV (longitudinal CPV/transverse CPV) was lower on micropatterned soft PDMS compared to micropatterned stiff PDMS and micromolded gelatin hydrogels.
Propagation velocity in engineered cardiac tissues is sensitive to features in the tissue microenvironment, such as alignment, matrix elasticity, and matrix topography, which may underlie arrhythmias in conditions with pathological tissue remodeling.
KeywordsCardiac myocytes Microfabrication Micromolding Microcontact printing Extracellular matrix Elastic modulus Calcium imaging
This work was funded by the USC Viterbi School of Engineering, the USC Graduate School (Rose Hills Fellowship to APP, Annenberg Fellowship to DML, and Provost Fellowship to NRA and NC), the American Heart Association Scientist Development Grant 16SDG29950005 to MLM, USC Women in Science and Engineering to MLM and CMG, and the USC Provost Undergraduate Fellowship to JYK. We also thank the W. M. Keck Foundation Photonics Center Cleanroom for access to photolithography equipment.
Conflict of interest
Andrew P. Petersen, Davi M. Lyra-Leite, Nethika R. Ariyasinghe, Nathan Cho, Celeste M. Goodwin, Joon Young Kim, and Megan L. McCain declare that they have no conflict of interest.
No human studies were carried out by the authors for this article. All laboratory animals involved in this research were cared for and used in accordance with all institutional and national guidelines using only protocols approved by the University of Southern California Institutional Animal Care and Use Committee.
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