# Development of a Three-Dimensional Pathology-Simulating Model of Neurotrauma Using a Polymer-Encapsulated Neural Cell Network

## TL;DR

A 3D brain injury model using a soft collagen hydrogel simulates neurotrauma pathology and allows testing of biomaterials for neural repair.

## Contribution

A reproducible 3D neural tissue model with immune cells is developed to simulate neurotrauma and test biomaterials.

## Key findings

- A 3D neural cell network in collagen hydrogel mimics brain injury pathology, including astrocyte scarring and microglial activation.
- The model allows implantation of biomaterials into injury sites to study neural cell responses.
- The model replicates key features of traumatic brain injury and supports advanced neural modeling for therapeutic screening.

## Abstract

Penetrating traumatic injuries of the brain have a poor clinical prognosis necessitating development of new therapies to improve neurological outcomes. Laboratory research is hampered by reliance on highly invasive experimental approaches in living animals to simulate penetrating injuries e.g., by cutting/crushing the brain tissue, with a range of associated ethical, technical and logistical challenges. Accordingly, there is a critical need to develop neuromimetic in vitro alternative neural models to reduce harm to animals. However, most in vitro, reductionist simulations of brain injury are too simplistic to simulate the complex environment of the injured nervous system. We recently reported a complex, two-dimensional in vitro mouse model of neurotrauma containing five major brain cell types to replicate neural architecture, grown on a “hard” glass substrate in a brain cell sheet. We now demonstrate the translation of this approach into a three-dimensional tissue injury model, by propagating the entire cellular network in a “soft” compliant collagen hydrogel, similar to native brain tissue stiffness (an important determinant of cell fate). A multicellular network of neural cells was observed to form in the polymer matrix containing all major brain cell populations, including the immune cells (microglia). We demonstrate that it is feasible to create a reproducible, focal traumatic injury in the synthesised neural tissue construct. Importantly, key pathological features of neurological injury, such as astrocyte scarring, immune cell (microglial) activation, impeded axonal outgrowth and stem/progenitor cell migration, can be successfully induced. We also prove that it is feasible to implant a biomaterial into the lesion gap to study neural cell responses for screening applications. The findings support the concept that the model can be used in a versatile manner for advanced neural modelling.