Three-dimensional in vitro cell culture models are becoming more and more important as the third dimension brings the microenvironment of cells closer to the in vivo situation. The complexity of such model systems to recapitulate the in vivo situation is required especially in central nervous system tissue. In this study, we assess neuronal network formation and dysfunction under disease conditions in multi-week 3D culture.
3D in vitro cultures use hydrogels as a matrix to incorporate cells. This matrix is effectively the microenvironment of the cells and thus should represent mechanical and biological properties similar to the native tissue. The softness of the brain makes 3D in vitro cultures of primary neurons and astrocytes challenging as weak hydrogels are difficult to handle. The mechanical properties of soft hydrogels can be improved by incorporation of thermoplastic fibers created by using additive manufacturing (3D printing) technologies. One of these, melt electrowriting (MEW), allows creation of small-scale, organized structures.
Poly(ɛ-caprolactone) (PCL) fiber scaffolds were fabricated via MEW to reinforce soft hydrogels (i.e. Matrigel, hyaluronic acid, alginate), thus creating 3D matrix composites. Different cell types i.e. cortical neurons, astrocytes, brain tumor cells were seeded into these scaffolds and studied for their viability, gene expression, network formation, electrophysiological properties, maturation, and migration. Cell viability over a time course of three weeks was high using Matrigel but lower in other hydrogels. The survival rates were improved by supplementation of ECM proteins or peptides. Neuronal network formation was demonstrated by an increase in synaptic boutons as well as the detection of functional neuronal network activity.
In summary, we successfully cultured cortical cells in various fiber-reinforced hydrogels. This 3D in vitro model represents a new, powerful tool to optimize the matrix formulation and study cell-cell interactions under normal and disease conditions.