Three-Dimensional Collagen Gel Networks for Neural Stem Cell-Based Neural Tissue Engineering

Stem and progenitor cells isolated from the embryonic rat cerebral cortex were immobilized by matrix entrapment in three‐dimensional (3D) Type I collagen gels, and cultured in serum‐free medium containing basic fibroblast growth factor. The cells trapped within the collagen networks actively proliferated and formed clone‐like aggregates. Neurons were the first differentiated cells to appear within the aggregates, followed by generation of astrocytes and oligodendrocytes. In addition, necrotic cores were developed as the aggregate diameter increased and cell viability declined significantly after 3 weeks in culture. To overcome these problems, the cell‐collagen constructs were transferred to Rotary Wall Vessel bioreactors for up to 10 weeks. In the rotary culture, the collagen gels compacted 3‐4 folds and a long‐term growth and differentiation of neural stem and progenitor cells was dynamically maintained. Remarkably, the cell‐collagen constructs formed a complex two‐layered structure that superficially emulated to a certain extent the cerebral cortex of the embryonic brain in architecture and functionality. The engineered 3D tissue‐like constructs displaying characteristic properties of neuronal circuits may have potential use in tissue replacement therapy for injured brain and spinal cord.