Sculpting Rupture‐Free Nuclear Shapes in Fibrous Environments

Abstract

Cytoskeleton-mediated force transmission regulates nucleus morphology. How nuclei shaping occurs in fibrous in vivo environments remains poorly understood. Here suspended nanofiber networks of precisely tunable (nm-μm) diameters are used to quantify nucleus plasticity in fibrous environments mimicking the natural extracellular matrix. Contrary to the apical cap over the nucleus in cells on 2-dimensional surfaces, the cytoskeleton of cells on fibers displays a uniform actin network caging the nucleus. The role of contractility-driven caging in sculpting nuclear shapes is investigated as cells spread on aligned single fibers, doublets, and multiple fibers of varying diameters. Cell contractility increases with fiber diameter due to increased focal adhesion clustering and density of actin stress fibers, which correlates with increased mechanosensitive transcription factor Yes-associated protein (YAP) translocation to the nucleus. Unexpectedly, large-and small-diameter fiber combinations lead to teardrop-shaped nuclei due to stress fiber anisotropy across the cell. As cells spread on fibers, diameter-dependent nuclear envelope invaginations that run the nucleus's length are formed at fiber contact sites. The sharpest invaginations enriched with heterochromatin clustering and sites of DNA repair are insufficient to trigger nucleus rupture. Overall, the authors quantitate the previously unknown sculpting and adaptability of nuclei to fibrous environments with pathophysiological implications.

Chiral Cell Nanomechanics Originated in Clockwise/Counterclockwise Biofunctional Microarrays to Govern the Nuclear Mechanotransduction of Mesenchymal Stem Cells

“…In particular, transcription cofactor YAP will give a response to biomechanical tension along with the stretched direction . YAP nuclear translocation may be related to cytoskeleton parallel stretch, FA kinase activation, and zyxin relocation by anisotropic cell nanomechanics. , Cell nanomechanics has been reported to suppress cell senescence and aging by the inhibition of cGAS-STING signaling due to YAP/TAZ mechanotransduction. , In addition, the nuclear shape is changed by cytoskeleton force to regulate chromatin remodeling and phenotype alternation. − Therefore, in this study, the nuclear DNA synthesis level could be regulated by the mechanotransduction from anisotropic YAP signaling and biased cell nanomechanics due to chiral FA formation and heterogeneous cytoskeleton assembly (Figure ).…”

“…52 YAP nuclear translocation may be related to cytoskeleton parallel stretch, FA kinase activation, and zyxin relocation by anisotropic cell nanomechanics. 53,54 Cell nanomechanics has been reported to suppress cell senescence and aging by the inhibition of cGAS-STING signaling due to YAP/TAZ mechanotransduction. 55,56 In addition, the nuclear shape is changed by cytoskeleton force to regulate chromatin remodeling and phenotype alternation.…”

Dynamic Heterochromatin States in Anisotropic Nuclei of Cells on Aligned Nanofibers

“…We used suspended nanofibers that mimic the loose interstitial network found in vivo with large and small pore sizes to the extent that cells make contact with only single fibers. 52 We have recently shown that nuclei may lack apicobasal polarity, which causes a uniform distribution of proteins, including lamins, actin, and cytoskeleton, 53 which causes compression of the nuclei from all sides of the nanofiber. Thus, the nuclei of the cells attached to suspended nanofibers show considerable differences from the other in vitro systems with constrained apicobasal polarity, potential reason for the difference in heterochromatin organization and dynamics.…”

Ultra-thin and ultra-porous nanofiber networks as a basement-membrane mimic

“…Unlike conventional tracked-etched membranes which are flat, the fibrous nature of our nanofiber membrane allows for a 3D environment for cell attachment. 63,64 The interface between the monolayers and the track-etched membrane is clearly visible in the confocal Z-stack image.…”