Spinal cord repair: releasing the neuron-intrinsic brake on axon regeneration

Lead Research Organisation: University of Cambridge
Department Name: Cambridge Centre for Brain Repair

Abstract

After Spinal Cord Injury, 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 fibers (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 to the tip of the nerve fibre, which may be quite far as the axon can extend a long way from the cell body. Many CNS nerve cells fail to transport growth proteins into their axons after injury. These proteins are essential for nerve fiber regeneration through the hostile terrain of a spinal lesion. In AxonRepair we aim to promote axon regeneration in the spinal cord by 1. Activating the gene program required for nerve fiber extension, and by 2. Overcoming the transport block of growth-promoting proteins into injured axons.
To achieve aim 1 our approach takes advantage of know-how collected by our consortium on the powerful regenerative abilities of peripheral nerve cells. Peripheral nerve cells do regenerate successfully because they have a kind of 'switch' which turns on a robust regenerative machinery, and because they do not exclude growth-related molecules from their axons. We have identified key molecular components of this switch and aim to use these to activate the regeneration program in neurons after a spinal cord lesion. Previous attempts to do this have focused on individual molecules, which can be considered individual parts of the switch. In AxonRepair we are attempting a novel strategy where we target multiple collaborating elements of the switch at the same time.
Many mature CNS neurons have a specialized structure at the transition zone between their cell body and their axon that acts as a molecular barrier for transport of pro-regenerative proteins. It has recently been recognized that this molecular barrier plays a major role in the failure of axon regeneration: following an injury certain proteins (e.g. integrins) required for axon regeneration are excluded from the nerve fibers. Aim 2 of AxonRepair is therefore to "dissolve" the transport barrier allowing transport of essential pro-regenerative proteins into injured axons.
At the completion of AxonRepair we expect to have developed an intervention strategy to promote robust axon regeneration and functional recovery after injury to long spinal cord axon tracts. The results obtained in the context of AxonRepair will provide the basis for a potential therapeutic strategy for SCI.

Technical Summary

Problem: Spinal cord injury (SCI) leads to permanent disability and is a significant clinical problem with 130.000 new cases/year worldwide. Following SCI long axon tracts fail to regenerate. This is the primary reason for the sustained loss of bodily functions.
Objective and added value: AxonRepair aims to develop a strategy to promote long-distance axon regeneration and functional recovery after SCI by reprogramming neurons into a regenerative state and by overcoming the axon transport block that is a barrier to axon regeneration. The added value of AxonRepair is that we bring together world-class experts on the transcriptional control of axon regeneration, axon transport and therapeutic gene delivery. Individually, we have identified factors that promote CNS axon regeneration and modest sensorimotor recovery in animal models of SCI. Collectively, we now seek to combine these factors to deliver greater axon regeneration and clinically significant functional recovery. We will use clinically translatable adeno-associated vector-based gene delivery, novel techniques to quantify axon trajectories in cleared spinal tissue and innovative, automated methods for assessing dexterity in rats.
Workplan: Work package (WP) 1 aims to reprogram neurons into a regenerative state by testing the effect of combinatorial delivery of key transcription factors identified in our collective's discovery pipelines. WP 2 aims to restore axonal transport of growth-related receptors (integrins) to injured spinal axons. WP 3 aims to provide novel mechanistic insight into how interventions at the transcriptional and axon transport level work and whether these interventions act synergistically in rat models of SCI. WP4 defines the management structure, including a data management and sharing plan. A research steering group will direct, coordinate and monitor progress of AxonRepair.

Planned Impact

AxonRepair will advance knowledge relating to axon regeneration following spinal cord injury. This is relevant from a clinical standpoint because the interruption of axonal pathways and their failure to grow back is the reason for paralysis in patients that suffer from a spinal cord injury. There is no therapy that restores function following spinal cord injury. A new treatment would therefore have a huge impact on the health of patients and society. Our ultimate goal is to contribute to the development of a therapy that would promote axon regeneration and functional recovery in patients. The research performed in AxonRepair is preclinical, however, the participation of the world-leading gene therapy company UniQure in an advisory role ensures that know-how generated by us can be rapidly exploited by entering in a co-development agreement and/or intellectual property strategy. UniQure has clinical programs for major CNS-diseases, including AAV-based gene therapy for Parkinson's disease, and conducts early-stage discovery and preclinical research with a R&D focus on gene therapy for CNS-diseases. In this context UniQure has a keen interest in preclinical AAV-based gene therapy for spinal cord injury as developed by AxonRepair.
 
Title Protrudin functions from the endoplasmic reticulum to support axon regeneration in the adult CNS 
Description In this study, we describe the use of a scaffolding protein, Protrudin to boost axon regeneration and neuroprotection in the adult central nervous system. Our work reveals a novel mechanism of axon regeneration where Protrudin-induced axon regeneration is dependent on its interaction with the endoplasmic reticulum and other axon transport molecules. This data opens up new avenues to explore novel therapeutic targets for conditions of the central nervous system such as glaucoma, spinal cord injury and brain injury. 
Type Of Art Image 
Year Produced 2020 
URL https://axonrepair2020.figshare.com/articles/poster/Protrudin_functions_from_the_endoplasmic_reticul...
 
Title Protrudin functions from the endoplasmic reticulum to support axon regeneration in the adult CNS 
Description In this study, we describe the use of a scaffolding protein, Protrudin to boost axon regeneration and neuroprotection in the adult central nervous system. Our work reveals a novel mechanism of axon regeneration where Protrudin-induced axon regeneration is dependent on its interaction with the endoplasmic reticulum and other axon transport molecules. This data opens up new avenues to explore novel therapeutic targets for conditions of the central nervous system such as glaucoma, spinal cord injury and brain injury. 
Type Of Art Image 
Year Produced 2020 
URL https://axonrepair2020.figshare.com/articles/poster/Protrudin_functions_from_the_endoplasmic_reticul...
 
Title Simple RGC: ImageJ plugins for counting retinal ganglion cells and determining the transduction efficiency of viral vectors in retinal wholemounts 
Description 'Simple RGC' consists of a collection of ImageJ plugins to assist researchers investigating retinal ganglion cell (RGC) injury models in addition to helping assess the effectiveness of treatments. The first plugin named 'RGC Counter' accurately calculates the total number of RGCs from retinal wholemount images. The second plugin named 'RGC Transduction' measures the co-localisation between two channels making it possible to determine the transduction efficiencies of viral vectors and transgene expression levels. The third plugin named 'RGC Batch' is a batch image processor to deliver fast analysis of large groups of microscope images. These ImageJ plugins make analysis of RGCs in retinal wholemounts easy, quick, consistent, and less prone to unconscious bias by the investigator. The plugins are freely available from the ImageJ update site https://sites.imagej.net/Sonjoonho/. 
Type Of Art Film/Video/Animation 
Year Produced 2020 
URL https://axonrepair2020.figshare.com/articles/poster/Simple_RGC_ImageJ_plugins_for_counting_retinal_g...
 
Title Simple RGC: ImageJ plugins for counting retinal ganglion cells and determining the transduction efficiency of viral vectors in retinal wholemounts 
Description 'Simple RGC' consists of a collection of ImageJ plugins to assist researchers investigating retinal ganglion cell (RGC) injury models in addition to helping assess the effectiveness of treatments. The first plugin named 'RGC Counter' accurately calculates the total number of RGCs from retinal wholemount images. The second plugin named 'RGC Transduction' measures the co-localisation between two channels making it possible to determine the transduction efficiencies of viral vectors and transgene expression levels. The third plugin named 'RGC Batch' is a batch image processor to deliver fast analysis of large groups of microscope images. These ImageJ plugins make analysis of RGCs in retinal wholemounts easy, quick, consistent, and less prone to unconscious bias by the investigator. The plugins are freely available from the ImageJ update site https://sites.imagej.net/Sonjoonho/. 
Type Of Art Film/Video/Animation 
Year Produced 2020 
URL https://axonrepair2020.figshare.com/articles/poster/Simple_RGC_ImageJ_plugins_for_counting_retinal_g...
 
Description ABBVIE advisory
Geographic Reach Multiple continents/international 
Policy Influence Type Participation in a guidance/advisory committee
Impact ABBVIE decided on the basis of the meeting to proceed to clinical trials
 
Description Vertex advisory board
Geographic Reach Multiple continents/international 
Policy Influence Type Participation in a guidance/advisory committee
Impact Design of clinical trial protocol leading to phase 2/3 trial
 
Description Project grant
Amount SFr. 150,000 (CHF)
Organisation International Foundation for Research in Paraplegia (IRP) 
Sector Charity/Non Profit
Country Switzerland
Start 08/2017 
End 09/2019
 
Description Repair of the corticospinal tract
Amount £638,866 (GBP)
Funding ID MR/R004463/1 
Organisation Medical Research Council (MRC) 
Sector Public
Country United Kingdom
Start 01/2018 
End 12/2020
 
Title New model for measuring intrinsic axon regeneration ability 
Description A new method for culturing mature neurons and measuring regeneration following laser axotomy 
Type Of Material Technology assay or reagent 
Year Produced 2018 
Provided To Others? Yes  
Impact Used in other labs 
 
Description Chet Moritz 
Organisation University of Washington
Country United States 
Sector Academic/University 
PI Contribution Model of bladder stimulation and recording
Collaborator Contribution Electophysiology methods
Impact Grant from GSK
Start Year 2016
 
Description Pavla Jendelova 
Organisation Institute of Experimental Medicine AS CR
Country Czech Republic 
Sector Academic/University 
PI Contribution Axon regeneration through integrin engineering
Collaborator Contribution Spinal injury model
Impact Grant awarded
Start Year 2016
 
Description Simone di Giovanni 
Organisation Imperial College London
Department Imperial College Trust
Country United Kingdom 
Sector Charity/Non Profit 
PI Contribution Axon growth and signalling
Collaborator Contribution Growth cone signalling with PI3Kinase
Impact ERA-NET application
Start Year 2016
 
Description Verhaagen 
Organisation Royal Netherlands Academy of Arts and Sciences
Country Netherlands 
Sector Public 
PI Contribution Investigation into role of Semaphorin 3A in plasticity Integrin engineering for regeneration
Collaborator Contribution Production of AAV vectors Semaphorin staining
Impact Papers on axon regeneration, semaphorin in perineuronal nets
Start Year 2007
 
Description Chrisopher Reeve symposium 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Patients, carers and/or patient groups
Results and Impact Symposium for patients, carers, donors, researchers
Year(s) Of Engagement Activity 2018
 
Description Home Office Inspectors meeting 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Policymakers/politicians
Results and Impact Updating Home Office inspectors on new developments
Year(s) Of Engagement Activity 2016
 
Description Ittingen future of spinal cord research 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Ittingen meeting to plan translation of spinal cord treatments
Year(s) Of Engagement Activity 2016
 
Description New York State Spinal Injury symposium 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact New York meeting for patients, carers, medical staff, researchers
Year(s) Of Engagement Activity 2018
 
Description Utrecht Mind the Brain 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Postgraduate students
Results and Impact Utrecht outreach meeting
Year(s) Of Engagement Activity 2016