Activated Cardiac Fibroblasts Control Contraction of Human Fibrotic Cardiac Microtissues by a β-Adrenoreceptor-Dependent Mechanism

Abstract

Cardiac fibrosis represents a serious clinical problem. Development of novel treatment strategies is currently restricted by the lack of the relevant experimental models in a human genetic context. In this study, we fabricated self-aggregating, scaffold-free, 3D cardiac microtissues using human inducible pluripotent stem cell (iPSC)-derived cardiomyocytes and human cardiac fibroblasts. Fibrotic condition was obtained by treatment of cardiac microtissues with profibrotic cytokine transforming growth factor β1 (TGF-β1), preactivation of foetal cardiac fibroblasts with TGF-β1, or by the use of cardiac fibroblasts obtained from heart failure patients. In our model, TGF-β1 effectively induced profibrotic changes in cardiac fibroblasts and in cardiac microtissues. Fibrotic phenotype of cardiac microtissues was inhibited by treatment with TGF-β-receptor type 1 inhibitor SD208 in a dose-dependent manner. We observed that fibrotic cardiac microtissues substantially increased the spontaneous beating rate by shortening the relaxation phase and showed a lower contraction amplitude. Instead, no changes in action potential profile were detected. Furthermore, we demonstrated that contraction of human cardiac microtissues could be modulated by direct electrical stimulation or treatment with the β-adrenergic receptor agonist isoproterenol. However, in the absence of exogenous agonists, the β-adrenoreceptor blocker nadolol decreased beating rate of fibrotic cardiac microtissues by prolonging relaxation time. Thus, our data suggest that in fibrosis, activated cardiac fibroblasts could promote cardiac contraction rate by a direct stimulation of β-adrenoreceptor signalling. In conclusion, a model of fibrotic cardiac microtissues can be used as a high-throughput model for drug testing and to study cellular and molecular mechanisms of cardiac fibrosis.

Fibroblast‐mediated intercellular crosstalk in the healthy and diseased heart

“…However, after TGFβ1 stimulation and differentiation of fibroblasts toward myofibroblasts, fibroblast‐specific depolarization or hyperpolarization directly modulated cardiomyocyte membrane potential and accelerated or blocked spontaneous beating, respectively. Together, multiple studies have demonstrated the role of electrical coupling of activated myofibroblasts and cardiomyocyte in aging and disease [98], but the extent of cardiac fibroblast–cardiomyocyte interactions in the healthy heart and the role they play in the maintenance of electrophysiological conduction remains to be elucidated.…”

3D Stem Cell Culture

“…This Special Issue includes articles highlighting the effective use of induced pluripotent stem cells (iPSCs) to develop cardiac microtissue [ 1 ], neurospheres [ 2 ], and cortical progenitors [ 3 ]. In addition, this Special Issue contains work on scaffolds with mesenchymal stem cells (MSCs) [ 4 ] and embryonic stem cells (ESCs) [ 5 ].…”

“…A very relevant problem in cardiology is cardiac fibrosis. In the work by Blyszczuk et al, a model of fibrotic cardiac microtissue was generated using iPSC-derived cardiomyocytes and cardiac fibroblasts by treatment with transforming growth factor β1 (TGF- β1) or by use of cardiac fibroblasts from heart failure patients [ 1 ]. The authors demonstrated that activated cardiac fibroblasts could, via direct stimulation of β-adrenoreceptor signaling, promote cardiac contraction rate.…”

“…The authors demonstrated that activated cardiac fibroblasts could, via direct stimulation of β-adrenoreceptor signaling, promote cardiac contraction rate. Furthermore, the generated model could be used as a high-throughput model for drug testing or general studies of cardiac fibrosis [ 1 ].…”

“…This Special Issue includes articles highlighting recent discoveries in 3D stem cell cultures using MSCs [ 4 ], ESCs [ 5 , 8 ], iPSCs [ 1 , 2 , 3 ], and intestinal stem cells [ 6 , 7 ]. This Special Issue also includes a review article by Ribeiro-Filho et al that discusses the 2D and 3D culture of hematopoietic stem cells (HSCs) as a relevant model to study both normal and abnormal hematopoiesis [ 9 ].…”