Refinement of therapeutic intervention in a mouse model of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS), also known as motor neuron disease, is a neurological disease in which muscles waste away leading to loss of movement and basic functions like breathing, resulting in death within three years of diagnosis. There is no effective treatment. Some patients have inherited forms of ALS, and carry a mutation in a gene called SOD1. Scientists have made laboratory mice with inherited mutations in SOD1, and we use these to understand the cellular and molecular basis of ALS. One very important use of these mice is to test new therapies, prior to their use in patients. Since mice develop ALS in a predictable way, we can follow the progression of their disease symptoms very carefully, and detect small changes in muscle function even before visible signs of disease. However it has become standard practice to determine the effect of a drug on extending the lifespan of a group of mice. We aim to refine this process in order to limit the suffering of the mice used in this research, by studying the effects of drugs at an earlier stage, before they lose a substantial number of motor neurons and become paralysed.
A particular problem in treating ALS is to deliver therapeutic drugs to the motor neurons, which are buried deep within the spinal cord. We will also use these mice to measure at the molecular level how effective treatments are in motor neurons. This is important because most drugs are developed in the laboratory using cells grown in culture, and often have different or reduced effects in a living animal. We can measure the effects of therapeutic drugs using fluorescent probes. We will inject mice so that these probes are taken up by their motor neurons. This will enable us to directly measure how well the drug is working in motor neurons in the spinal cord of the mice. An obvious benefit of this is that we can identify the best drugs and doses to use in our experiments, without having to let the mice develop paralysis. Equally important in terms of animal welfare, is the ability to exclude therapies that are ineffective at an early stage in the drug development process, without excessive animal testing.
In summary we will refine the use of mouse models of ALS, to help develop more effective therapeutic approaches, and to limit the suffering of the mice used in these experiments.

The objective of this project is to minimise the number of mice undergoing procedures of substantial severity when testing therapeutic strategies in mouse models of amyotrophic lateral sclerosis (ALS). We will use two complimentary approaches to achieve this:
(i) Application of new in vivo molecular assays. Using in vitro models we have identified novel therapeutic agents that can reduce oxidative damage or restore axonal transport in the presence of mutant SOD1. These are two of the key pathogenic processes in ALS. We have designed an in vivo molecular approach to test the efficacy of these drugs in motor neurons in G93A mice. This has the potential to identify the drugs that should be taken forwards into formal clinical testing in G93A mice at an early stage and in a small number of animals. Importantly, it also identifies drugs that are ineffective in vivo, and so leads to an overall reduction in the number of mice used for research.
(ii) Determining clinical benefit in ALS mouse models prior to the onset of substantial severity. One widely used measure of therapeutic effect in ALS mouse studies is lifespan extension. However this requires cohorts of mice to undergo scientific procedures of substantial severity. We believe that robust and disease-relevant behavioural and pathological markers of early motor neuron dysfunction can be used to refine this approach. We will test this hypothesis by comparing the effects of therapeutic agents in our short model with historical published data on lifespan extension. We will also investigate the effects of antioxidants and axonal transport drugs identified in the first part of this study.
One application of this work is the development of novel methods for screening for efficacy of drugs in vivo prior to testing their clinical benefits. We hope that the overall reduction in numbers of animals, as well as laboratory time and expense, will demonstrate to our scientific peers the added value of this approach. We will also demonstrate the use of a refined mouse model of ALS, which will potentially be taken up across many international laboratories. We also hope that the results obtained in this project will lead to the identification of novel therapeutic approaches in ALS targeting oxidative damage and axonal transport.