Mechanosensitive molecular mechanisms of myocardial fibrosis in living myocardial slices

Abstract

Aims Altered mechanical load in response to injury is a main driver of myocardial interstitial fibrosis. No current in vitro model can precisely modulate mechanical load in a multicellular environment while maintaining physiological behaviour. Living myocardial slices (LMS) are a 300 μm-thick cardiac preparation with preserved physiological structure and function. Here we apply varying degrees of mechanical preload to rat and human LMS to evaluate early cellular, molecular, and functionality changes related to myocardial fibrosis. Methods and resultsLeft ventricular LMS were obtained from Sprague Dawley rat hearts and human cardiac samples from healthy and failing (dilated cardiomyopathy) hearts. LMS were mounted on custom stretchers and two degrees of diastolic load were applied: physiological sarcomere length (SL) (SL = 2.2 μm) and overload (SL = 2.4 μm). LMS were maintained for 48 h under electrical stimulation in circulating, oxygenated media at 37°C. In overloaded conditions, LMS displayed an increase in nucleus translocation of Yes-associated protein (YAP) and an up-regulation of mechanotransduction markers without loss in cell viability. Expression of fibrotic and inflammatory markers, as well as Collagen I deposition were also observed. Functionally, overloaded LMS displayed lower contractility (7.48 ± 3.07 mN mm À2 at 2.2 SL vs. 3.53 ± 1.80 mN mm À2 at 2.4 SL). The addition of the profibrotic protein interleukin-11 (IL-11) showed similar results to the application of overload with enhanced fibrosis (8% more of collagen surface coverage) and reduced LMS contractility at physiological load. Conversely, treatment with the Transforming growth factor β receptor (TGF-βR) blocker SB-431542, showed down-regulation of genes associated with mechanical stress, prevention of fibrotic response and improvement in cardiac function despite overload (from 2.40 ± 0.8 mN mm À2 to 4.60 ± 1.08 mN mm À2 ). Conclusions The LMS have a consistent fibrotic remodelling response to pathological load, which can be modulated by a TGF-βR blocker. The LMS platform allows the study of mechanosensitive molecular mechanisms of myocardial fibrosis and can lead to the development of novel therapeutic strategies.

Biomimetic cultivation of atrial tissue slices as novel platform for in-vitro atrial arrhythmia studies

“…Histology of LMS showed clear unidirectional fibre orientation, indicating good handling of the vibratome during LMS production and preservation of the native preferred fibre orientation of the cardiomyocytes in-vivo. Nuclei of cardiac fibroblasts were observed in between cardiomyocytes, demonstrating a co-culture of multiple cell-types in LMS, in accordance with work on ventricular LMS 18 , 19 . The amount of fibrosis did not seem to increase during culture, suggesting near-physiological cultivation conditions without excessive cardiac injury.…”

A year in heart failure: updates of clinical and preclinical findings

“…Importantly, LMS responded with fibrotic remodelling to pathological load, which could be modulated by a transforming growth factor beta-blocker. 67 Taken together, here, we illuminated papers published in ESC Heart Failure during 2022 in selected themes of HF. We are confident that these studies (and others not referenced in this review article) of ESC Heart Failure faithfully illustrate preclinical and clinical efforts around the globe for an improved HF management.…”

“…A novel approach, where living myocardial slices (LMS) of human and rodent hearts were included, served as experimental preparations to answer this question. Importantly, LMS responded with fibrotic remodelling to pathological load, which could be modulated by a transforming growth factor beta‐blocker 67 …”

Profiling the Biomechanical Responses to Workload on the Human Myocyte to Explore the Concept of Myocardial Fatigue and Reversibility: Rationale and Design of the POWER Heart Failure Study

“…from severe aortic stenosis or hypertension), myocardial recovery may be possible if the pathological load is promptly removed before irreversible damage occurs [15,26,27]. One way to investigate this hypothesis is to examine the in vitro behaviour of cardiomyocytes in response to a range of load, without the confounding influences of autonomic tone in vivo and extracellular tissue and fibrosis in multi-cellular preparations [16,28].…”