Ex vivo engineering of neural tissue structure and growth using sequential 2D and 3D solid scaffolds

Brain injury disrupts tissue integrity, creating wounds with complex boundaries that hinder effective repair. Regeneration and reconnection require guiding deformed tissue along proper growth pathways. Pre-engineered scaffold implants made from biomaterials offer promise; however, while hydrogel-based scaffolds are common for brain repair, their low mechanical strength and slow cell growth limit effectiveness. This study examined solid scaffolds, which provide superior mechanical support and promote rapid cell growth, to modulate the growth behavior of injured hippocampal tissue. Three scaffold types were used: planar bioactive glass, planar aragonite (promoting neuronal and astrocytic growth), and three-dimensional glass beads. The scaffolds were applied in two steps. First, hippocampal tissue chunks from postnatal rat brains were cultured on the planar substrates; then, glass beads were added. On glass, tissue adopted a round/oval shape with pronounced vertical growth, while on aragonite it flattened and spread irregularly, reaching lengths twice as large and an area 3.8 times greater than on glass. In the second step, adding glass beads led to vertical growth on glass, with tissue encapsulating beads to form a complex 3D structure. In contrast, aragonite-supported tissue formed bump-like structures when encapsulating the beads, remaining largely planar. Also, they showed a tenfold lower bead density and twofold greater inter-bead distances than tissue on glass. In both cases, cellular outgrowth occurred. These findings show that sequential application of solid scaffolds with distinct structural properties can guide diverse tissue growth behaviors and serve as a strategy for fabricating neural implants, with implications for treating brain trauma and disease.