Guiding Oligodendrocyte Progenitor Cell Maturation Using Electrospun Fiber Cues in a 3D Hyaluronic Acid Hydrogel Culture System

The current lack of therapeutic approaches to demyelinating disorders and injuries stems from a lack of knowledge surrounding the underlying mechanisms of myelination. This knowledge gap motivates the development of effective models to study the role of environmental cues in oligodendrocyte progenitor cell (OPC) maturation. Such models should focus on determining, which factors influence OPCs to proliferate and differentiate into mature myelinating oligodendrocytes (OLs). Here, we introduce a hyaluronic acid (HA) hydrogel system composed of cross-linked HA containing encapsulated HA fibers with swollen diameters similar to mature axons (2.7 ± 0.2 μm). We tuned hydrogel storage moduli to simulate native brain tissue (200-2000 Pa) and studied the effects of fiber presence on OPC proliferation, metabolic activity, protein deposition, and morphological changes in gels of intermediate storage modulus (800 ± 0.3 Pa). OPCs in fiber-containing gels at culture days 4 and 7 exhibited a significantly greater number of process extensions, a morphological change associated with differentiation. By contrast, OPCs in fiber-free control gels maintained more proliferative phenotypes with 2.2-fold higher proliferation at culture day 7 and 1.8-fold higher metabolic activity at culture days 4 and 7. Fibers were also found to influence extracellular matrix (ECM) deposition and distribution, with more, and more distributed, nascent ECM deposition occurring in the fiber-containing gels. Overall, these data indicate that inclusion of appropriately sized HA fibers provides topographical cues, which guide OPCs toward differentiation. This HA hydrogel/fiber system is a promising <i>in vitro</i> scheme, providing valuable insight into the underlying mechanisms of differentiation and myelination.