3 research outputs found
Architecture and Composition Dictate Viscoelastic Properties of Organ-Derived Extracellular Matrix Hydrogels
Full text linkThe 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.</p
Human lung extracellular matrix hydrogels resemble the stiffness and viscoelasticity of native lung tissue
Full text linkChronic lung diseases such as idiopathic pulmonary fibrosis (IPF) and chronic obstructive pulmonary disease (COPD) are associated with changes in extracellular matrix (ECM) composition and abundance affecting the mechanical properties of the lung. This study aimed to generate ECM hydrogels from control, severe COPD [Global Initiative for Chronic Obstructive Lung Disease (GOLD) IV], and fibrotic human lung tissue and evaluate whether their stiffness and viscoelastic properties were reflective of native tissue. For hydrogel generation, control, COPD GOLD IV, and fibrotic human lung tissues were decellularized, lyophilized, ground into powder, porcine pepsin solubilized, buffered with PBS, and gelled at 37°C. Rheological properties from tissues and hydrogels were assessed with a low-load compression tester measuring the stiffness and viscoelastic properties in terms of a generalized Maxwell model representing phases of viscoelastic relaxation. The ECM hydrogels had a greater stress relaxation than tissues. ECM hydrogels required three Maxwell elements with slightly faster relaxation times (τ) than that of native tissue, which required four elements. The relative importance (Ri) of the first Maxwell element contributed the most in ECM hydrogels, whereas for tissue the contribution was spread over all four elements. IPF tissue had a longer-lasting fourth element with a higher Ri than the other tissues, and IPF ECM hydrogels did require a fourth Maxwell element, in contrast to all other ECM hydrogels. This study shows that hydrogels composed of native human lung ECM can be generated. Stiffness of ECM hydrogels resembled that of whole tissue, while viscoelasticity differed.</p
3D Culture of human lung fibroblasts decreases proliferative and increases extracellular matrix remodeling genes
Full text linkFibroblasts are the main producers of extracellular matrix (ECM) responsible for ECM maintenance and repair, a process often disrupted in chronic lung diseases. The accompanying mechanical changes adversely affect resident cells and overall lung function. Numerous models have been used to elucidate fibroblast behavior which are now evolving towards complex 3D models incorporating ECM, aiming to replicate the cells' native environment. Little is known about the cellular changes that occur when moving from 2D to 3D cell culture. This study compared gene expression profiles of primary human lung fibroblasts from 7 subjects with normal lung function, cultured for 24 hours on 2D collagen I-coated tissue culture plastic and in 3D collagen I hydrogels, which are commonly used to mimic ECM in various models, from contraction assays to organ-on-a-chip models. Comparing 3D to 2D cell culture, 6,771 differentially expressed genes (2,896 up, 3,875 down) were found; enriched gene sets within the downregulated genes, identified through Gene Set Enrichment Analysis and Ingenuity pathway analysis, were involved in the initiation of DNA replication which implied downregulation of fibroblast proliferation in 3D. Observation of cells for 72 hours in 2D and 3D environments confirmed the reduced progression through the cell cycle in 3D. A focused analysis examining the Hippo pathway and ECM-associated genes, showed differential patterns of gene expression in the 3D versus 2D culture. Altogether, the transcriptional response of fibroblasts cultured in 3D indicated inhibition of proliferation, and alterations in Hippo and ECM pathways indicating a complete switch from proliferation to ECM remodeling.</p
