Recent progresses in novel in vitro models of primary neurons: A biomaterial perspective

Abstract

Central nervous system (CNS) diseases have been a growing threat to the health of humanity, emphasizing the urgent need of exploring the pathogenesis and therapeutic approaches of various CNS diseases. Primary neurons are directly obtained from animals or humans, which have wide applications including disease modeling, mechanism exploration and drug development. However, traditional two-dimensional (2D) monoculture cannot resemble the native microenvironment of CNS. With the increasing understanding of the complexity of the CNS and the remarkable development of novel biomaterials, in vitro models have experienced great innovation from 2D monoculture toward three-dimensional (3D) multicellular culture. The scope of this review includes the progress of various in vitro models of primary neurons in recent years to provide a holistic view of the modalities and applications of primary neuron models and how they have been connected with the revolution of biofabrication techniques. Special attention has been paid to the interaction between primary neurons and biomaterials. First, a brief introduction on the history of CNS modeling and primary neuron culture was conducted. Next, detailed progress in novel in vitro models were discussed ranging from 2D culture, ex vivo model, spheroid, scaffold-based model, 3D bioprinting model, and microfluidic chip. Modalities, applications, advantages, and limitations of the aforementioned models were described separately. Finally, we explored future prospects, providing new insights into how basic science research methodologies have advanced our understanding of the CNS, and highlighted some future directions of primary neuron culture in the next few decades.

Developing hippocampal spheroids model ictogenesis and epileptogenesis

“…The robust network activity displayed by hippocampal spheroids manifests the importance of using primary cells over embryonic stem cells, neural progenitors, or induced pluripotent stem cells, as these hardly achieve spontaneous electrophysiological function, despite the expression of synaptic components, ion channels and neurotransmitters demonstrated by transcriptomic analysis. For these reasons, primary brain cells are re-gaining attention for producing spheroids thanks to the faster maturation, high reproducibility and moderate costs 28 . These features support reliable high-throughput platforms to address neuronal function in health and disease as well as to study novel treatments for brain disorders.…”

Electroactive Materials Surface Charge Impacts Neuron Viability and Maturation in 2D Cultures

“…Among the methods available to analyze neuron behavior in vitro, 2D cultures represent a simple approach with several advantages over more complex methods. 3 Primary neurons can be isolated from animals or humans using already established methods. 3 Nevertheless, after extraction, in vitro maintenance can be quite challenging.…”

“…Primary neurons can be isolated from animals or humans using already established methods . Nevertheless, after extraction, in vitro maintenance can be quite challenging.…”

“…In this context, in vitro studies are very suitable for the initial analysis of the response of neural cells to external stimulation under controlled conditions. Among the methods available to analyze neuron behavior in vitro , 2D cultures represent a simple approach with several advantages over more complex methods …”

“…3 Primary neurons can be isolated from animals or humans using already established methods. 3 Nevertheless, after extraction, in vitro maintenance can be quite challenging. For instance, it is difficult to culture primary neurons with morphology and behavior similar to their basic nature or even to maintain the cultures for extended periods of time in most cases due to adherence issues that are particularly prominent in case of glass coverslips and hinder imaging and electrophysiological assays.…”