Following Spinal Cord Injury, the connections between nerve cells in the brain and in the spinal cord are lost and fail to grow back, which results in permanent disability. In the framework of project AxonRepair the Bradke-group in Bonn developed methodologies to perform high resolution 3D imaging of axon regeneration in unsectioned adult mouse spinal cord. This work, by Hilton et al. published in the journal Nature Protocols, allows the other consortium partners to test the effects of various regeneration-related factors that they are studying.
Following Spinal Cord Injury (SCI), the connections between nerve cells in the brain and in the spinal cord are lost and fail to grow back. In patients with SCI this results in permanent disability, including paralysis below the level of the injury, and loss of sensory, bladder and sexual function. There are two major obstacles to the regeneration of nerve fibres (referred to as axons) of central nervous system (CNS) neurons. First, CNS nerve cells do not switch on the necessary machinery for vigorous regrowth of axons. Second, a nerve cell has to deliver the necessary components for growth and regeneration from the cell body to the tip of the nerve fibre, which may be quite a large distance. Project AxonRepair, which is funded under NEURON’s JTC2016 co-funded call, aims to promote axon regeneration in the spinal cord.
Project AxonRepair is a worldwide multinational collaboration between the groups of Prof. Joost Verhaagen from the Netherlands, Prof. James Fawcett and Prof. Lawrence Moon from the UK, Prof. Frank Bradke from Germany, Prof. Alyson Fournier from Canada and Prof. Dasa Ciszkova from Slovakia. These specialists joined together and complement each other to study key aspects of axon regeneration in order to advance the knowledge and provide a base on which potential therapeutic strategies for SCI can be envisaged.
When designing and carrying out any kind of research project, one of the most important aspects is developing and using the right tools and technologies to answer the research questions. In the framework of project AxonRepair, several technical advances occurred, amongst them the Bradke-group in Bonn developed methodologies to perform high resolution 3D imaging of axon regeneration in unsectioned adult mouse spinal cord. This work, by Hilton et al., which was published in the journal Nature Protocols, included state-of-the-art techniques to trace dorsal column sensory and corticospinal motor axons in the adult mouse spinal cord expressing adeno-associated viruses encoding GFP.
The axons are then injured, the unsectioned spinal cord is immune-stained and tissue is cleared, and 2-photon microscopy is carried out to determine the 3- dimensional anatomy of spinal pathways before and after spinal cord injury. This innovative protocol can be used to elucidate the molecular and cellular mechanisms, which underlie nervous system degeneration and regeneration and to help determine the therapeutic efficacy of potential neuroregenerative treatments. Due to the fact that tissue sectioning is not required, this protocol enables explicit evaluation of regeneration and significantly increases the speed at which analyses can be carried out. This major technical advancement positively impacts the in vivo work of other groups in the consortium, as it allows them to test the effects of the various regeneration-related factors that they are studying.
“There have been ‘false positives’ in the axon regeneration field before, in part due to technical limitations of previous techniques making it difficult to tell if axons truly regenerated or were simply spared after injury. This technique enabled us, our colleagues in the AxonRepair project and the field more generally to overcome these problems and to quickly and unambiguously analyze axon regeneration following spinal cord injury.”
Brett Hilton (headed the development of this technique)
Read more about 3D imaging and axon regeneration
“High-resolution 3D imaging and analysis of axon regeneration in unsectioned spinal cord with or without tissue clearing” (nature.com, published: 22 March 2019; Brett J. Hilton, Oriane Blanqui, Andreas Tedeschi, Frank Bradke)
Article on nature.com