Selective and uncoupled role of substrate elasticity in the regulation of replication and transcription in epithelial cells

Abstract

SummaryActin cytoskeleton forms a physical connection between the extracellular matrix, adhesion complexes and nuclear architecture. Because tissue stiffness plays key roles in adhesion and cytoskeletal organization, an important open question concerns the influence of substrate elasticity on replication and transcription. To answer this major question, polyelectrolyte multilayer films were used as substrate models with apparent elastic moduli ranging from 0 to 500 kPa. The sequential relationship between Rac1, vinculin adhesion assembly, and replication becomes efficient at above 200 kPa because activation of Rac1 leads to vinculin assembly, actin fiber formation and, subsequently, to initiation of replication. An optimal window of elasticity (200 kPa) is required for activation of focal adhesion kinase through auto-phosphorylation of tyrosine 397. Transcription, including nuclear recruitment of heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1), occurred above 50 kPa. Actin fiber and focal adhesion signaling are not required for transcription. Above 50 kPa, transcription was correlated with v-integrin engagement together with histone H3 hyperacetylation and chromatin decondensation, allowing little cell spreading. By contrast, soft substrate (below 50 kPa) promoted morphological changes characteristic of apoptosis, including cell rounding, nucleus condensation, loss of focal adhesions and exposure of phosphatidylserine at the outer cell surface. On the basis of our data, we propose a selective and uncoupled contribution from the substrate elasticity to the regulation of replication and transcription activities for an epithelial cell model.

Adhesion, proliferation, and gene expression profile of human umbilical vein endothelial cells cultured on bilayered polyelectrolyte coatings composed of glycosaminoglycans

“…Indeed, apoptosis ͑programed cell death͒ has been reported to manifest in cells cultured on soft nonrigid substrates. 56 It is precisely because of this reason that there is a preference to utilize polymers that form a stiffer, less gel-like coating on stents, such as polystyrene-sulfonate/poly-allylamine hydrochloride ͑PSS/PAH͒, 46,57-59 which does not exhibit the water-retaining and absorbing properties of glycosaminoglycans.…”

Liver bioengineering

“…42 By contrast, soft substrates promote morphological changes characteristic of apoptosis, including cell rounding, nucleus condensation, and loss of focal adhesions. 43 Integrin movement is related to downstream signaling pathways, with Rho guanosine triphosphatases (Rho GTPase) and the contraction of the actin-myosin cytoskeleton being the main mediators of this process. 40 While less understood than cellmatrix interactions, cell-cell junctions are equally important in cell mechanosensitivity.…”

Deposition Mechanisms in Layer-by-Layer or Step-by-Step Deposition Methods: From Elastic and Impermeable Films to Soft Membranes with Ion Exchange Properties

“…Many bioapplications of PEM films are reported and have been reviewed [79,80]. Of particular interest is the finding that a change in the mechanical properties allows to fine tune not only the cellular adhesion [81], but also the level of nuclear expression of the adherent cells [82].…”