(20a) Matrix Remodeling Modulates Human Neural Maturation

Human induced pluripotent stem cells (hiPSCs) have emerged as a promising in vitro model system for studying neurodevelopment. However, current models remain limited in their ability to efficiently incorporate biochemical and biomechanical signaling cues imparted by the neural extracellular matrix (ECM) and achieve limited degrees of maturation. The native brain ECM is viscoelastic and stress relaxing, exhibiting a time-dependent response to an applied force, yet most conventional biomaterials are formed via static covalent crosslinks and are therefore highly elastic. Here, we develop a family of recombinant materials, consisting of aldehyde-modified hyaluronic acid and hydrazine-modified elastin-like protein (ELP), which are crosslinked with dynamic covalent bonds and exhibit independently tunable stiffness and stress relaxation rate. This platform facilitates the creation of hyaluronan-elastin-like protein (HELP) hydrogels with consistent brain-mimetic stiffnesses, a range of stress relaxation rates, and modular cell-interactive domains. hiPSC-derived neural progenitor cells (NPCs) encapsulated within these gels exhibit high viability and undergo relaxation rate dependent maturation. Specifically, NPCs within faster relaxing, more remodelable HELP matrices extend longer, more complex neuritic projections, adopt decreased metabolic activity, and express higher levels of genes and proteins associated with neural maturation. In addition to relaxation rate, a cell’s ability to remodel its microenvironment is also influenced by degradation of the local biopolymer scaffold. We observe heightened matrix degradation and a concomitant increase in protease and hyaluronidase secretion in faster relaxing gels. To elucidate the cell-matrix interactions underlying these observations, we replace the integrin-binding peptide domain (RGD) within HELP with a scrambled analog and introduce inhibitors of myosin contractility and actin polymerization. In these gels, we observe that both the loss of integrin ligands and the inability to polymerize actin preclude NPCs from extending neurites. Taken together, these results suggest that cell-mediated strain and enzyme secretion within remodelable matrices drive neural maturation and that tuning biomechanical signaling cues within engineered microenvironments may advance current models of human neurodevelopment.