Human Cardiac Fibroblast Number and Activation State Modulate Electromechanical Function of hiPSC-Cardiomyocytes in Engineered Myocardium

Abstract

Cardiac tissue engineering using hiPSC-derived cardiomyocytes is a promising avenue for cardiovascular regeneration, pharmaceutical drug development, cardiotoxicity evaluation, and disease modeling. Limitations to these applications still exist due in part to the need for more robust structural support, organization, and electromechanical function of engineered cardiac tissues. It is well accepted that heterotypic cellular interactions impact the phenotype of cardiomyocytes. The current study evaluates the functional effects of coculturing adult human cardiac fibroblasts (hCFs) in 3D engineered tissues on excitation and contraction with the goal of recapitulating healthy, nonarrhythmogenic myocardium in vitro. A small population (5% of total cell number) of hCFs in tissues improves tissue formation, material properties, and contractile function. However, two perturbations to the hCF population create disease-like phenotypes in engineered cardiac tissues. First, increasing the percentage of hCFs to 15% resulted in tissues with increased ectopic activity and spontaneous excitation rate. Second, hCFs undergo myofibroblast activation in traditional two-dimensional culture, and this altered phenotype ablated the functional benefits of hCFs when incorporated into engineered cardiac tissues. Taken together, the results of this study demonstrate that human cardiac fibroblast number and activation state modulate electromechanical function of hiPSC-cardiomyocytes and that a low percentage of quiescent hCFs are a valuable cell source to advance a healthy electromechanical response of engineered cardiac tissue for regenerative medicine applications.

Human pluripotent stem cell-derived cardiomyocytes align under cyclic strain when guided by cardiac fibroblasts

“…This strongly suggests a crosstalk between cFBs and hiPSC-CMs where the presence of cFBs influences the mechanoresponsiveness of hiPSC-CMs. This is in line with previous studies that showed that the number and activation state of cFBs modulated the electromechanical functioning of hiPSC-CMs [48][49][50][51]. Further studies should be directed to investigating the mechanisms that trigger the strain-induced reorientation response in the CM-cFB co-culture.…”

Engineered Human Cardiac Microtissues: The State-of-the-(He)art

“…20 Another recent study compared the effects of including human cardiac fibroblasts vs dermal fibroblasts in engineered cardiac tissues and found that incorporating dermal fibroblasts disrupted the electrical function of tissues causing them to display beating and nonbeating regions. 21 These studies indicate that hPSC-CFs may be better suited to cardiac tissue engineering in general than fibroblasts from other organ sources.…”

“…A later study demonstrated that hiPSC‐CFs form connexin 43 gap junctions with hiPSC‐CMs in engineered spheroids and that dermal fibroblasts do not have this capacity, even when connexin 43 was overexpressed in the dermal fibroblasts 20 . Another recent study compared the effects of including human cardiac fibroblasts vs dermal fibroblasts in engineered cardiac tissues and found that incorporating dermal fibroblasts disrupted the electrical function of tissues causing them to display beating and nonbeating regions 21 . These studies indicate that hPSC‐CFs may be better suited to cardiac tissue engineering in general than fibroblasts from other organ sources.…”

A Predictive in Vitro Risk Assessment Platform for Pro-Arrhythmic Toxicity Using Human 3D Cardiac Microtissues

“…73 Incorporation of human cardiac broblasts (hCFs) enables heterotypic cell-cell interactions characteristic of the intact myocardium. 36,74,75 While 5% primary adult normal hCF content is used for stable, healthy cardiac electromechanical function based on our previous 76 and current work, the platform allows for alterations in cell composition (such as other cell types, including endothelial cells) and ratios to mimic physiological and pathophysiological conditions that may be important for toxicity evaluation. While our platform can produce hundreds of microtissues in standard cell culture plates, the low variability beat-to-beat, microtissue-to-microtissue, mold-to-mold, and notably hiPSC-CM differentiation batch-to-batch ( Fig.…”