Biology subjects

Gerum, R. C.

Publications and source records attributed to Gerum, R. C..

3 recordsLinked to original sources

bioRxiv2024

Contractility of cardiac and skeletal muscle tissue increases with environmental stiffness

The mechanical interplay between contractility and mechanosensing in striated muscles is of fundamental importance for tissue morphogenesis, load adaptation, and disease progression, but remains poorly understood. In this study, we investigate the dependence of contractile force generation of cardiac and skeletal muscle on environmental stiffness. Using in vitro engineered muscle micro-tissues that are attached to flexible elastic pillars, we vary the stiffness of the microenvironment over three orders of magnitude and study its effect on contractility. We find that the active contractile force upon electrical stimulation of both cardiac and skeletal micro-tissues increases with environmental stiffness according to a strong power-law relationship. To explore the role of adhesion-mediated mechanotransduction processes, we deplete the focal adhesion protein {beta}-parvin in skeletal micro-tissues. This reduces the absolute contractile force but leaves the mechanoresponsiveness unaffected. Our findings highlight the influence of external stiffness on the adaptive behavior of muscle tissue and shed light on the complex mechanoadaptation processes in striated muscle.

biophysics↗

bioRxiv2022

Viscoelastic properties of suspended cells measured with shear flow deformation cytometry

Numerous cell functions are accompanied by phenotypic changes in viscoelastic properties, and measuring them can help elucidate higher-level cellular functions in health and disease. We present a high-throughput, simple and low-cost microfluidic method for quantitatively measuring the elastic (storage) and viscous (loss) modulus of individual cells. Cells are suspended in a high-viscosity fluid and are pumped with high pressure through a 5.8 cm long and 200 {micro}m wide microfluidic channel. The fluid shear stress induces large, near ellipsoidal cell deformations. In addition, the flow profile in the channel causes the cells to rotate in a tank-treading manner. From the cell deformation and tank treading frequency, we extract the frequency-dependent viscoelastic cell properties based on a theoretical framework developed by R. Roscoe1 that describes the deformation of a viscoelastic sphere in a viscous fluid under steady laminar flow. We confirm the accuracy of the method using atomic force microscopy-calibrated polyacrylamide beads and cells. Our measurements demonstrate that suspended cells exhibit power-law, soft glassy rheological behavior that is cell cycle-dependent and mediated by the physical interplay between the actin filament and intermediate filament networks.

biophysics↗

bioRxiv2021

The desmin mutation R349P increases contractility and fragility of stem cell-generated muscle micro-tissues

Desminopathies comprise hereditary myopathies and cardiomyopathies caused by mutations in the intermediate filament protein desmin that lead to severe and often lethal degeneration of striated muscle tissue. Animal and single cell studies hinted that this degeneration process is associated with massive ultrastructural defects correlating with increased susceptibility of the muscle to acute mechanical stress. The underlying mechanism of mechanical susceptibility, and how muscle degeneration develops over time, however, has remained elusive. Here, we investigated the effect of a desmin mutation on the formation, differentiation, and contractile function of in vitro-engineered three-dimensional micro-tissues grown from muscle stem cells (satellite cells) isolated from heterozygous R349P desmin knock-in mice. Micro-tissues grown from desmin-mutated cells exhibited spontaneous unsynchronized contractions, higher contractile forces in response to electrical stimulation, and faster force recovery compared to tissues grown from wild-type cells. Within one week of culture, the majority of R349P desmin-mutated tissues disintegrated, whereas wild-type tissues remained intact over at least three weeks. Moreover, under tetanic stimulation lasting less than five seconds, desmin-mutated tissues partially or completely ruptured, whereas wild-type tissues did not display signs of damage. Our results demonstrate that the progressive degeneration of desmin-mutated micro-tissues is closely linked to extracellular matrix fiber breakage associated with increased contractile forces and unevenly distributed tensile stress. This suggests that the age-related degeneration of skeletal and cardiac muscle in patients suffering from desminopathies may be similarly exacerbated by mechanical damage from high-intensity muscle contractions. We conclude that micro-tissues may provide a valuable tool for studying the organization of myocytes and the pathogenic mechanisms of myopathies.

biophysics↗