Cardiac fibrosis is the pathological excess of deposition of extracellular matrix inside the cardiac muscle, which may lead to heart failure. In heart disease, myocardial viscoelasticity is often increased, and this can reduce heart compliance. Indeed, it is essential to find new therapeutic approaches to reduce cardiac fibrosis and the resulting elevated viscoelasticity. Yet, our understanding of the myocardial rheology is insufficient, partially because we lack the appropriate techniques to model it. In this study, 3D microtissues of the heart are created by mixing neonatal rat cardiomyocytes and fibroblasts (post-natal day 3-5) in definite ratios to form cardiac spheroids (CSs) of healthy and fibrotic tissues. We study the mechanobiology of such models using Atomic Force Spectroscopy, outlining their viscoelastic behavior. To overcome the size limitations dictated by commercial cantilevers, “macro-cantilevers” are fabricated via UV photolithography and allow us to compress the whole spheroid during stress-relaxation (SR) experiments. After sudden stress, a rapid, elastic relaxation is observed right before a viscous dissipation. Both regimens are described by distinct relaxation times (𝜏;1 and 𝜏;2) as extracted from least-square fitting to a two-component Maxwell model. Different viscoelastic behaviors are observed for each cellular composition, possibly relating to the viscous contribution of the extracellular matrix. We note that CSs do not spontaneously contract at the beginning of SR experiments. However, the P3 CSs start to, after a few SR cycles. Then, we have a quantitative description of the beating frequency and force, within a micronewton range, down to a nanonewton sensitivity. Moreover, the translation of a mechanical stimulus to a mechanical beating indicates the presence of a mechano-electric feedback within the spheroid. This aspect could be further explored by stimulating over a wide range of forces, enabling to perform a “micro-CPR” at the single organoid level.
Cardiac fibrosis rheology elucidated by afm whole-spheroid stress-relaxation
Andolfi, Laura;Lazzarino, Marco
2022-01-01
Abstract
Cardiac fibrosis is the pathological excess of deposition of extracellular matrix inside the cardiac muscle, which may lead to heart failure. In heart disease, myocardial viscoelasticity is often increased, and this can reduce heart compliance. Indeed, it is essential to find new therapeutic approaches to reduce cardiac fibrosis and the resulting elevated viscoelasticity. Yet, our understanding of the myocardial rheology is insufficient, partially because we lack the appropriate techniques to model it. In this study, 3D microtissues of the heart are created by mixing neonatal rat cardiomyocytes and fibroblasts (post-natal day 3-5) in definite ratios to form cardiac spheroids (CSs) of healthy and fibrotic tissues. We study the mechanobiology of such models using Atomic Force Spectroscopy, outlining their viscoelastic behavior. To overcome the size limitations dictated by commercial cantilevers, “macro-cantilevers” are fabricated via UV photolithography and allow us to compress the whole spheroid during stress-relaxation (SR) experiments. After sudden stress, a rapid, elastic relaxation is observed right before a viscous dissipation. Both regimens are described by distinct relaxation times (𝜏;1 and 𝜏;2) as extracted from least-square fitting to a two-component Maxwell model. Different viscoelastic behaviors are observed for each cellular composition, possibly relating to the viscous contribution of the extracellular matrix. We note that CSs do not spontaneously contract at the beginning of SR experiments. However, the P3 CSs start to, after a few SR cycles. Then, we have a quantitative description of the beating frequency and force, within a micronewton range, down to a nanonewton sensitivity. Moreover, the translation of a mechanical stimulus to a mechanical beating indicates the presence of a mechano-electric feedback within the spheroid. This aspect could be further explored by stimulating over a wide range of forces, enabling to perform a “micro-CPR” at the single organoid level.Pubblicazioni consigliate
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