Alginate-Laminin Hydrogel Supports Long-Term Neuronal Activity in 3D Human Induced Pluripotent Stem Cell Derived Neuronal Networks

Since the human brain is a three-dimensional structure, 3D culturing techniques can help researchers to create more accurate and realistic neural models, thus improving our understanding of the brain’s structure and function. Moreover, many neurological diseases are characterized by changes in the structure and connectivity of neurons. Creating a 3D neuronal network can be used to model a range of neurological disorders, including autism, epilepsy, and schizophrenia. This allows researchers to study disease mechanisms in a more physiologically relevant cellular context and improve the development of new treatments. Furthermore, a 3D neuronal network can be used to screen drug candidates for their efficacy and simultaneously identify neurotoxicity. This allows researchers to identify promising drug candidates early in the drug development process and avoid costly clinical trial failures.

However, developing a 3D neuronal network can be challenging, and there are several factors to consider. Some of the challenges include the choice of biomaterial since its properties highly influence the developing 3D neuronal network. To support neuronal growth and connectivity,  the materials should be biocompatible, must not elicit an immune response and must exhibit suitable mechanical properties such as stiffness and elasticity. The material should be porous, allowing for the diffusion of nutrients and waste products. Moreover, the material should be conductive to support the electrical activity of neurons.

Alginate is a natural polymer derived from seaweed that can form soft and porous gels when mixed with water and calcium ions. Laminin is a component of the extracellular matrix, which forms the scaffold that surrounds and supports cells in tissues. Laminin can bind to receptors on the surface of cells including human induced pluripotent stem cells (hiPSCs) and influence their behavior. In a new study published in the peer-reviewed Journal Advanced Materials Interfaces by PhD candidate Julia Hartmann, Dr. Ines Lauria, Ms Farina Bendt, Mr. Stephan Rütten, Dr. Katharina Koch and led by Professor Ellen Fritsche from Leibniz-Research Institute for Environmental Medicine in collaboration with Professor Andreas Blaeser at the Technical University of Darmstadt, the authors employed hiPSCs to generate human neural progenitor cells (NPCs) and subsequently let them differentiate into neural 3D models in both pure alginate hydrogels and hydrogels functionalized with the extracellular matrix protein laminin 111 (L111). The authors evaluated various properties of the tested biomaterials, such as their porosity, distribution of L111, shear viscosity, and biocompatibility. Additionally, the influence of the hydrogels on neural cell functions was studied by observing cell migration, differentiation, and the formation and activity of neural networks on multielectrode arrays (MEAs).

The research team used a 3D model of human NPCs derived from hiPSCs to study how the progenitors differentiate into functional neural networks. They found that L111 improved the survival, migration, and differentiation of NPCs into neurons and astrocytes, two key effector cell types in the brain that support each other. L111 also increased the formation of synapses, which are connections between neurons that allow them to transmit signals. They measured the electrical activity of these networks using MEAs and found that they were more mature, stable, and synchronized than those grown in alginate without L111. They also recovered faster from a drug that blocked their activity. The new 3D model established in the study provided a more physiological representation of human brain function than traditional 2D models and can be used for long-term disease models or studies of drug or chemical effects. Their work follows the 3R principles of reducing, refining, and replacing animal experiments with human-based methods.

In conclusion, Julia Hartmann and colleagues established a 3D model of hiPSC-derived neural networks embedded in alginate or alginate-laminin 111 (L111) hydrogels. They fully characterized the hydrogel’s material properties, cell compatibility, and effect on NPC differentiation and neural network formation over a long-term period of more than six months. Interestingly, L111 supplementation enhanced NPC-derived cell migration, differentiation, synaptogenesis, and electrical activity in alginate hydrogels. Moreover, neural networks in alginate-L111 hydrogel blends recovered faster from sodium channel blockage than neural networks in pure alginate hydrogels. In conclusion, alginate-L111 hydrogel is a suitable matrix for long-term cultivation and maturation of human neural networks. The new 3D neural cell model can be a powerful tool for medical research, allowing researchers to model diseases, study disease mechanisms, and develop new treatments.