An in vitro spinal cord injury model to screen neuroregenerative materials

Implantable ‘structural bridges’ based on nanofabricated polymer scaffolds have great promise to aid spinal cord regeneration. Their development (optimal formulations, surface functionalizations, safety, topographical influences and degradation profiles) is heavily reliant on live animal injury models. These have several disadvantages including invasive surgical procedures, ethical issues, high animal usage, technical complexity and expense. In vitro 3-D organotypic slice arrays could offer a solution to overcome these challenges, but their utility for nanomaterials testing is undetermined. We have developed an in vitro model of spinal cord injury that replicates stereotypical cellular responses to neurological injury in vivo, viz. reactive gliosis, microglial infiltration and limited nerve fibre outgrowth. We describe a facile method to safely incorporate aligned, poly-lactic acid nanofibre meshes (±poly-lysine + laminin coating) within injury sites using a lightweight construct. Patterns of nanotopography induced outgrowth/alignment of astrocytes and neurons in the in vitro model were strikingly similar to that induced by comparable materials in related studies in vivo. This highlights the value of our model in providing biologically-relevant readouts of the regeneration-promoting capacity of synthetic bridges within the complex environment of spinal cord lesions. Our approach can serve as a prototype to develop versatile bio-screening systems to identify materials/combinatorial strategies for regenerative medicine, whilst reducing live animal experimentation.