Do neurons from the primary motor cortex grow in response to signals from the developing spinal cord in vitro?

Abstract

Introduction: Spinal cord injuries (SCIs) are a leading cause of paralysis worldwide, with an estimated 500000 people suffering SCIs each year. No matter what the aetiology of injury, severed axons within the adult central nervous system cannot regenerate axons of sufficient length to re-establish a connection between upper and lower motor neurons following an SCI, even though the upper and lower motor neurons might be completely functional. Objectives: To establish a cell culture system for growing and visualizing axons from primary motor neurons and to examine whether the developing spinal cord may stimulate/direct axonal growth from primary motor neurons. Materials and methods: Primary motor neurons were obtained from the cerebral cortex of E17 Sprague– Dawley rats and cultured in channels on one side of a microfluidic device. The opposite side either contained media alone (controls) or dissociated cells from the developing spinal cord. The channels were connected by microgrooves, which allowed media, molecules and fine cellular processes (but not cells) to move between the two sides. Results: Motor neurons grew axons in ≈ 70% of microgrooves when cultured opposite wells containing spinal cells, with 51% of these extending the full length of the microgroove to the opposite side. In contrast, motor neurons in control conditions extended axons in only ≈ 18% of the microgrooves, with just 7% of these extending the full length to reach the medium-only well on the opposite side. Conclusions: The direction and extent of growth of primary motor neurons is influenced by the presence of cells from the developing spinal cord. Acknowledgements: Dr Monte Gates, Dr Heidi Fuller and Dr Paul Roach for supervision and support.