Architecture and Composition Dictate Viscoelastic Properties of Organ-Derived Extracellular Matrix Hydrogels

Abstract

The proteins and polysaccharides of the extracellular matrix (ECM) provide architectural support as well as biochemical and biophysical instruction to cells. Decellularized, ECM hydrogels replicate in vivo functions. The ECM’s elasticity and water retention renders it viscoelastic. In this study, we compared the viscoelastic properties of ECM hydrogels derived from the skin, lung and (cardiac) left ventricle and mathematically modelled these data with a generalized Maxwell model. ECM hydrogels from the skin, lung and cardiac left ventricle (LV) were subjected to a stress relaxation test under uniaxial low-load compression at a 20%/s strain rate and the viscoelasticity determined. Stress relaxation data were modelled according to Maxwell. Physical data were compared with protein and sulfated GAGs composition and ultrastructure SEM. We show that the skin-ECM relaxed faster and had a lower elastic modulus than the lung-ECM and the LV-ECM. The skin-ECM had two Maxwell elements, the lung-ECM and the LV-ECM had three. The skin-ECM had a higher number of sulfated GAGs, and a highly porous surface, while both the LV-ECM and the lung-ECM had homogenous surfaces with localized porous regions. Our results show that the elasticity of ECM hydrogels, but also their viscoelastic relaxation and gelling behavior, was organ dependent. Part of these physical features correlated with their biochemical composition and ultrastructure.

Matrix Metalloproteases from Adipose Tissue-Derived Stromal Cells Are Spatiotemporally Regulated by Hydrogel Mechanics in a 3D Microenvironment

“…Cell-loaded and cell-free hydrogels of 1 d, 7 d, and 14 d were prepared, as described previously [ 46 ], by fixing with a 1:1 ratio mix of 1% paraformaldehyde and 1% formalin at 4 °C for 24 h. After, all samples were washed with DPBS and Milli-Q ® water, snap-frozen in liquid nitrogen, and freeze-dried for 24 h. The lyophilised hydrogels were mounted on top of 0.5″ pin stubs (Agar Scientific, Stansted, UK), placed inside a Leica EM SCD050 sputter coater device (Leica Microsystems B.V., Amsterdam, Netherlands), and rinsed and coated with Au-Pd one day before scanning electron microscopy (SEM) imaging. Hydrogels were visualised with Zeiss Supra 55 STEM (Carl Zeiss NTS GmbH, Oberkochen, Germany) at 2500× magnification, 3.0 kV, and Z = 40.0 mm ( Figure 1 d).…”

An in vitro model of fibrosis using crosslinked native extracellular matrix-derived hydrogels to modulate biomechanics without changing composition

“…The stress relaxation test was performed with a low-load compression tester (LLCT) at RT as described previously. 26, 28, 29 The LabVIEW 7.1 program was used for the LLCT load cell and linear positioning for control and data acquisition. The resolution in position, load, and time determination was 0.001 mm, 2 mg, and 25 ms, respectively, and the compression speed was controlled in feedback mode.…”

“…TWOMBLI plugin for FIJI ImageJ was used to assess the number of fibres, end points, branching points, total fibre length and alignment, lacunarity, high density matrix (HDM) and curvature of the fibres as previously described ( Supplementary Figure 1 ). 26, 31 Fluorescent images of cell-seeded hydrogels stained for αSMA, wheat germ agglutinin and DAPI were generated with Leica SP8 confocal microscope (Leica, Wetzlar, Germany), using λ ex 627 nm / λ em 650 nm for αSMA, λ ex 555 nm / λ em 580 nm for wheat germ agglutinin and λ ex 359 nm / λ em 457 nm for DAPI at 40X and 63X magnifications. CellProfiler 4.2.1 software was used to analyse the nuclei characteristics on the DAPI-stained images as previously described.…”

“…The lung homogenate was decellularized as previously described. 26, 27 In short, the homogenate was repeatedly washed with Milli-Q ® water and centrifuged at 3,000 x g until the supernatant was completely clear. The sedimented material went through two rounds of sequential treatment with 0.1 % Triton X-100 (Sigma-Aldrich, St. Louis, MO, USA), 2 % sodium deoxycholate (Sigma-Aldrich), 1 M NaCl solution and 30 μg/mL DNase (Sigma-Aldrich) in MgSO 4 (Sigma-Aldrich) 1.3 mM and CaCl 2 (Sigma-Aldrich) 2 mM, 10 mM Tris pH8 (Sigma-Aldrich) solution each for 24 h at 4°C with constant shaking, except for the DNAse treatments, which were at 37°C with shaking.…”

Viscoelasticity Acts as a Marker for Tumor Extracellular Matrix Characteristics

“…Extracellular matrices and entire tissues and cannot be treated as linearly elastic materials because they manifest far more complexity in mechanical response, involving viscoelasticity ( Abidine et al, 2021 ; Martinez-Garcia et al, 2021 ) mechanical plasticity ( Buchmann et al, 2021 ) and nonlinear elasticity ( Elosegui-Artola et al, 2014 ). Hence, matrix viscoelasticity seems to govern essential cellular processes and can foster types of behaviors not evident in cells that are cultured in purely elastic hydrogels in both two- and three-dimensional culture surroundings ( Charbonier et al, 2021 ).…”