Nuclear morphology and deformation in engineered cardiac myocytes and tissues

Abstract

Cardiac tissue engineering requires finely-tuned manipulation of the extracellular matrix (ECM) microenvironment to optimize internal myocardial organization. The myocyte nucleus is mechanically connected to the cell membrane via cytoskeletal elements, making it a target for the cellular response to perturbation of the ECM. However, the role of ECM spatial configuration and myocyte shape on nuclear location and morphology is unknown. In this study, printed ECM proteins were used to configure the geometry of cultured neonatal rat ventricular myocytes. Engineered one- and two-dimensional tissue constructs and single-myocyte islands were assayed using live fluorescence imaging to examine nuclear position, morphology and motion as a function of the imposed ECM geometry during diastolic relaxation and systolic contraction. Image analysis showed that anisotropic tissue constructs cultured on microfabricated ECM lines possessed a high degree of nuclear alignment similar to that found in vivo; nuclei in isotropic tissues were polymorphic in shape with an apparently random orientation. Nuclear eccentricity was also increased for the anisotropic tissues, suggesting that intracellular forces deform the nucleus as the cell is spatially confined. During systole, nuclei experienced increasing spatial confinement in magnitude and direction of displacement as tissue anisotropy increased, yielding anisotropic deformation. Thus, the nature of nuclear displacement and deformation during systole appears to rely on a combination of the passive myofibril spatial organization and the active stress fields induced by contraction. Such findings have implications in understanding the genomic consequences and functional response of cardiac myocytes to their ECM surroundings under conditions of disease.

Selective hydrophilic modification of Parylene C films: a new approach to cell micro-patterning for synthetic biology applications

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Cyclic strain induces dual-mode endothelial-mesenchymal transformation of the cardiac valve

“…Actin OOP, nuclear eccentricity, and cell aspect ratio were based on computational analyses of immunostained images (30,58). The OOP was developed for the study of organization of liquid crystals (29) and adapted for biological applications (59), and was computed from the pixel-based orientation vectors of the actin images.…”

Spatial coordination between cell and nuclear shape within micropatterned endothelial cells

“…Furthermore, perturbations of the intermediate filament network could alter the positioning of the nucleus in both migrating and immobile astrocytes, suggesting that cytoplasmic intermediate filaments are involved in actin-dependent positioning of the nucleus 20 . Concomitant with these recent discoveries, significant advances have been made in terms of identifying the molecular links between the nuclear envelope and the cytoplasmic filaments [21][22][23][24][25] , and new insights have been gained into the mechanistic maintenance of the nucleus 3,23,24,26,27 . Emerging evidence is now accumulating that cytoplasmic filaments are exploited by cells to govern nuclear morphology and finely tune gene expression in response to cell shape changes.…”