Modelling of Traumatic Spinal Cord Injury In Vitro

Traumatic spinal cord injury arises from varied primary mechanisms, leaving individuals with significant long-term disability. Mechanically distinct secondary damage patterns have been observed in vivo; however, there remains a lack of consensus on how biomechanical parameters, such as displacement and velocity, influences secondary pathology. Astrocytes are key responders to mechanical insult, thus the aim of this project was to evaluate the effects of varied displacement and velocity parameters of contusion and distraction injury on primary astrocyte reactivity in vitro. A 3D culture model with astrocytes embedded in a collagen hydrogel (5 x 10^5 cells.ml−1) was used to simulate the CNS environment. Using the BOSE Electroforce BioDynamic 5110, contusion was modelled at 100 and 1000 mm.s−1 to depths of 25, 50, and 75% gel thickness. Distraction was simulated at 100 mm.s−1 to 10, 20, and 30% of the gauge length. Increasing displacement and velocity resulted in an increase in energy applied, resulting in astrogliotic alterations: hypertrophy, ramification, loss of individual domains, increased glial fibrillary acidic protein volume, and increased chondroitin sulfate proteoglycan deposition. Increased astrocyte reactivity was observed with increasing contusion depth at 100, but not 1000 mm.s−1. Distraction injury also induced astrogliotic changes, but with temporal differences in GFAP volume and CSPG expression. Further, distraction length had no effect on injury severity from Day 7 onwards, suggesting injury mechanism influences astrocyte reactivity in different ways. In vitro models of contusion and distraction injury were developed, but with scope for adapting them to use different neural cell types and increase cellular complexity in a controlled manner. This may enable the user to evaluate the biomechanical thresholds of different cell populations and the influence of cell-cell interactions on secondary pathophysiology. These preclinical models may also be useful for early stage testing of therapeutic interventions and refinement of animal experiments.