Myofibroblast modulation of cardiac myocyte structure and function

Abstract

After myocardial infarction, resident fibroblasts (Fb) differentiate towards myofibroblasts (MyoFb), generating the scar tissue and the interstitial fibrosis seen in the adjacent myocardium. Fb and MyoFb have the potential to interact with cardiac myocytes (CMs) but insight into the phenotype-specific role and mode of interaction is still incomplete. Our objectives are to further define the modulation of CMs by MyoFbs compared to Fbs, as well as the role of direct contact through gap junctions vs. soluble mediators, using Fbs and CMs from pig left ventricle. Fbs were treated to maintain an undifferentiated state (SD-208) or to attain full differentiation to MyoFb (TGF-β1). Fbs and MyoFbs were co-cultured with CMs, with the possibility of direct contact or separated by a Thincert membrane. Only in direct co-culture, both Fbs and MyoFbs were able to decrease CM viability after 2 days. Only MyoFbs induced significant distal spreading of CMs in both direct and indirect co-culture. MyoFbs, but not Fbs, readily made connections with CMs in direct co-culture and connexin 43 expression in MyoFb was higher than in Fb. When coupled to CMs, MyoFbs reduced the CM action potential duration and hyperpolarized the CM resting membrane potential. Uncoupling reversed these effects. In conclusion, MyoFbs, but not Fbs, alter the CM structural phenotype. MyoFbs, but not Fbs, are likely to electrically connect to CMs and thereby modulate the CM membrane potential. These data provide further support for an active role of MyoFbs in the arrhythmogenic substrate after cardiac remodelling.

NOTCH1 is critical for fibroblast-mediated induction of cardiomyocyte specialization into ventricular conduction system-like cells in vitro

“…The absence of CaT alteration in the MSC co-cultures reinforces the hypothesis that cardiac fibroblasts specifically influence cardiomyocytes to specialize into fast-conducting fibers. Other studies have reported similar functional changes related to excitation–contraction coupling when cardiomyocytes are under the influence of cardiac fibroblasts 32 , 45 – 48 . Recently, Nagaraju et al showed that myofibroblasts coupled with cardiomyocytes can also modulate cardiomyocyte action potentials 48 .…”

“…Other studies have reported similar functional changes related to excitation–contraction coupling when cardiomyocytes are under the influence of cardiac fibroblasts 32 , 45 – 48 . Recently, Nagaraju et al showed that myofibroblasts coupled with cardiomyocytes can also modulate cardiomyocyte action potentials 48 . Similarly, they observed hyperpolarization of the resting membrane potential; however, action potential duration was faster in cardiomyocytes coupled with myofibroblasts.…”

Comparison of 10 Control hPSC Lines for Drug Screening in an Engineered Heart Tissue Format

“…Even though mRNAs for some markers of fibrosis and extracellular matrix were more abundant in some cell lines (AT1, NCR, REB), increased fibrosis could not be confirmed histologically and was absent in all investigated slides with the exception of a few collagen fibrils on the surface of ERC-EHT. However, this issue should be taken into consideration when working with multicellular EHT preparations or different matrix protein such as collagen in the future ( Giacomelli et al., 2020 ; Li et al., 2017 ; Mills et al., 2017 ; Nagaraju et al., 2019 ). (7) Predominance of cells with atrial or ventricular-like phenotype could theoretically explain differences in baseline contractility.…”

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

“…Increased compaction and stiffness were expected, as cardiac fibroblasts are a remodeling and ECM-producing cell type; however, the increased MCR was surprising, given the previous reports that cardiac fibroblasts are nonexcitable cells which decrease beating rate with increasing percentage [ 58 ]. A possible explanation is that the higher fibroblast content may have caused cardiac myocyte electromechanical remodeling including shortening of APDs and hyperpolarizing resting membrane potentials [ 59 ], resulting in increased MCR and spontaneous activity of ECTs with 10% and 15% hCFs. Further evidence for this was demonstrated through optical mapping of ectopic activity in 15% hCF ECTs.…”