Hyaluronic acid matrices show matrix stiffness in 2D and 3D dictates cytoskeletal order and myosin-II phosphorylation within stem cells

Abstract

Physical features of microenvironments such as matrix elasticity E can clearly influence cell morphology and cell phenotype, but many differences between model matrices raise questions as to whether a standard biological scale for E exists, especially in 3D as well as in 2D. An E-series of two distinct types of hydrogels are ligand-functionalized here with non-fibrous collagen and used to elucidate wide-ranging cell and cytoskeletal responses to E in both 2D and 3D matrix geometries. Cross-linked hyaluronic acid (HA) based matrices as well as standard polyacrylamide (PA) hydrogels show that, within hours of initial plating, the adhesion, asymmetric shape, and cytoskeletal order within mesenchymal stem cells generally depend on E nonmonotonically over a broad range of physiologically relevant E. In particular, with overlays of a second matrix the stiffer of the upper or lower matrix dominates key cell responses to 3D: the cell invariably takes an elongated shape that couples to E in driving cytoplasmic stress fiber assembly. In contrast, embedding cells in homogeneous HA matrices constrains cells to spherically symmetric shapes in which E drives the assembly of a predominantly cortical cytoskeleton. Non-muscle myosin II generates the forces required for key cell responses and is a target of a phospho-Tyrosine signaling pathway that likely regulates contractile assemblies and also depends nonmonotonically on E. The results can be understood in part from a theory for stress fiber polarization that couples to matrix elasticity as well as cell shape and accurately predicts cytoskeletal order in 2D and 3D, regardless of polymer system.

Traction force microscopy on soft elastic substrates: A guide to recent computational advances

“…If these assumptions are not justified anymore, then finite element methods (FEM) can be used. This might be the case for soft substrates or strong cells, and usually is the case if cells are embedded in a 3D elastic matrix [63,[72][73][74]. Moreover FEM-TFM can also be used in the linear case [62,63].…”

Poly (hydroxyethyl methacrylate-glycidyl methacrylate) films modified with different functional groups: In vitro interactions with platelets and rat stem cells

“…Therefore, preparation of acrylate based hydrogels using various acrylic monomers is of great importance in biomedical applications as it paves the way for the preparation of novel biomaterials with improved mechanical properties [26]. As reported earlier, physical features of microenvironments such as matrix elasticity can clearly influence cell morphology and cell phenotype [27][28][29]. Cells grown on gels that mimic the elasticity of tissue reveal a significant influence of matrix elasticity on adhesion, cytoskeletal organization, and even the differentiation of human adult derived stem cells.…”

Stem cell mechanobiology: diverse lessons from bone marrow

“…Access to soluble factors and impact on secreted matrix deposition remain to be understood in such systems. However, when symmetry is forcibly broken by using thin, non-degradable HA gels that are layered on top of MSCs pre-cultured on a soft or stiff gel, the cells appear to exhibit cytoskeletal characteristics and polarization similar of cells cultured on a stiffer gel [80]. …”