(150s) Viscoelasticity of Hyaluronic Acid Matrix Regulates Spinal Cord Organoid Differentiation and Morphogenesis

Spatial organization of human stem cells with 2D or 3D matrix has been well investigated through substantial studies. Therefore, there are plenty of biomaterials for mimicking extracellular matrix (ECM) to regulate stem cell behaviors. Elasticity (or stiffness), one of the important spatial cues, is a crucial element controlling cell spreading and migration. However, the natural ECM/tissues are all viscoelastic not pure elastic. Hence, viscoelasticity is another puzzle to give full view for the studies of cell-ECM mechano-transduction. It is necessary to study how the viscoelastic matrix regulates cellular behaviors. Neural organoids derived human induced pluripotent stem cells (hiPSCs) have been studied for brain diseases and tissue regeneration. Spinal cord is one of the complex neural organs and has important effects on locomotion. The neurotransmission of sensory input and motor output between the brain and body, the coordination of central pattern creation, and many sensorimotor reflexes are all important functions of the spinal cord. Here, based on methacrylated hyaluronic acid (HA), this study fabricated different HA hydrogels for inducing generation and recapitulating the development of spinal cord organoids from hiPSCs. Four kinds of hydrogels were made including soft-elastic, soft-viscoelastic, stiff-elastic, and stiff-viscoelastic. The biocompatibility of the hydrogel was determined by cell morphology and viability assays. Meanwhile, by adding dopamine in the hydrogel, an iron coordinated hydrogel was fabricated. With different ranges of mechanical properties, the effects of the human stem cell-ECM interactions were investigated. Then, the effect of viscoelasticity of the HA hydrogels on organoid morphogenesis was also investigated. In addition, Yes-associated protein (YAP) nuclear translocation was determined to study the cell-ECM mechano-transduction. This research provides insights on viscoelastic behaviors of the ECM during human organoid differentiation and morphogenesis based on stem cells and the ECM mimicking in vitro microenvironment for applications in regenerative medicines.