Hydrogel mechanics regulate fibroblast DNA methylation and chromatin condensation

Modular Multiwell Viscoelastic Hydrogel Platform for Two- and Three-Dimensional Cell Culture Applications

Hydrogels have gained significant popularity as model platforms to study reciprocal interactions between cells and their microenvironment. While hydrogel tools to probe many characteristics of the extracellular space have been developed, fabrication approaches remain challenging and time-consuming, limiting multiplexing or widespread adoption. Thus, we have developed a modular fabrication approach to generate distinct hydrogel microenvironments within the same 96-well plate for increased throughput of fabrication as well as integration with existing high-throughput assay technologies. This approach enables in situ hydrogel mechanical characterization and is used to generate both elastic and viscoelastic hydrogels across a range of stiffnesses. Additionally, this fabrication method enabled a 3-fold reduction in polymer and up to an 8-fold reduction in fabrication time required per hydrogel replicate. The feasibility of this platform for two-dimensional (2D) cell culture applications was demonstrated by measuring both population-level and single-cell-level metrics via microplate reader and high-content imaging. Finally, a 96-well hydrogel array was utilized for three-dimensional (3D) cell culture, demonstrating the ability to support high cell viability. Together, this work demonstrates a versatile and easily adaptable fabrication approach that can support the ever-expanding tool kit of hydrogel technologies for cell culture applications.

Modular multiwell viscoelastic hydrogel platform for two- and three-dimensional cell culture applications

Hydrogels have gained significant popularity as model platforms to study the reciprocal interactions between cells and their microenvironment. While hydrogel tools to probe many characteristics of the extracellular space have been developed, fabrication approaches remain challenging and time-consuming, limiting multiplexing or widespread adoption. Thus, we have developed a modular fabrication approach to generate distinct hydrogel microenvironments within 96-well plates for increased throughput of fabrication as well as integration with existing high-throughput assay technologies. This approach enables in situ hydrogel mechanical characterization and was used to generate both elastic and viscoelastic hydrogels across a range of stiffnesses. Additionally, this fabrication method enabled a 3-fold reduction in polymer and up to an 8-fold reduction in fabrication time required per hydrogel replicate. The feasibility of this platform for cell culture applications was demonstrated by measuring both population-level and single cell-level metrics via microplate reader and high-content imaging. Finally, the 96-well hydrogel array was utilized for 3D cell culture, demonstrating the ability to support high cell viability. Together, this work demonstrates a versatile and easily adoptable fabrication approach that can support the ever-expanding tool kit of hydrogel technologies for cell culture applications.

Effects of Cell-Adhesive Ligand Presentation on Pentapeptide Supramolecular Assembly and Gelation: Simulations and Experiments

The extracellular matrix (ECM) is a complex, hierarchical material containing structural and bioactive components. This complexity makes decoupling the effects of biomechanical properties and cell-matrix interactions difficult, especially when studying cellular processes in a 3D environment. Matrix mechanics and cell adhesion are both known regulators of specific cellular processes such as stem cell proliferation and differentiation. However, more information is required about how such variables impact various neural lineages that could, upon transplantation, therapeutically improve neural function after a central nervous system injury or disease. Rapidly Assembling Pentapeptides for Injectable Delivery (RAPID) hydrogels are one biomaterial approach to meet these goals, consisting of a family of peptide sequences that assemble into physical hydrogels in physiological media. In this study, we studied our previously reported supramolecularly-assembling RAPID hydrogels functionalized with the ECM-derived cell-adhesive peptide ligands RGD, IKVAV, and YIGSR. Using molecular dynamics simulations and experimental rheology, we demonstrated that these integrin-binding ligands at physiological concentrations (3-12 mm) did not impact the assembly of the KYFIL peptide system. In simulations, molecular measures of assembly such as hydrogen bonding and pi-pi interactions appeared unaffected by cell-adhesion sequence or concentration. Visualizations of clustering and analysis of solvent-accessible surface area indicated that the integrin-binding domains remained exposed. KYFIL or AYFIL hydrogels containing 3 mm of integrin-binding domains resulted in mechanical properties consistent with their non-functionalized equivalents. This strategy of doping RAPID gels with cell-adhesion sequences allows for the precise tuning of peptide ligand concentration, independent of the rheological properties. The controllability of the RAPID hydrogel system provides an opportunity to investigate the effect of integrin-binding interactions on encapsulated neural cells to discern how hydrogel microenvironment impacts growth, maturation, or differentiation.

Cellular mechanotransduction in health and diseases: from molecular mechanism to therapeutic targets

Cellular mechanotransduction, a critical regulator of numerous biological processes, is the conversion from mechanical signals to biochemical signals regarding cell activities and metabolism. Typical mechanical cues in organisms include hydrostatic pressure, fluid shear stress, tensile force, extracellular matrix stiffness or tissue elasticity, and extracellular fluid viscosity. Mechanotransduction has been expected to trigger multiple biological processes, such as embryonic development, tissue repair and regeneration. However, prolonged excessive mechanical stimulation can result in pathological processes, such as multi-organ fibrosis, tumorigenesis, and cancer immunotherapy resistance. Although the associations between mechanical cues and normal tissue homeostasis or diseases have been identified, the regulatory mechanisms among different mechanical cues are not yet comprehensively illustrated, and no effective therapies are currently available targeting mechanical cue-related signaling. This review systematically summarizes the characteristics and regulatory mechanisms of typical mechanical cues in normal conditions and diseases with the updated evidence. The key effectors responding to mechanical stimulations are listed, such as Piezo channels, integrins, Yes-associated protein (YAP) /transcriptional coactivator with PDZ-binding motif (TAZ), and transient receptor potential vanilloid 4 (TRPV4). We also reviewed the key signaling pathways, therapeutic targets and cutting-edge clinical applications of diseases related to mechanical cues.