Possible strategies for treatment of SMA patients: a neurobiologist's view

This paper discusses possible strategies that might prevent or alleviate muscle weakness of SMA patients and hence improve their condition. The strategies discussed are as follows. (1) Prevention of motoneurone death. To achieve this two main approaches have been applied. Firstly, trophic factors have been used to prevent motoneurone death after nerve injury and clinically in diseases such as motoneurone disease. The results of these attempts will be described. Secondly, the possibility that injured motoneurones die as a result of the excitotoxic effects of the excitatory transmitter glutamate will be explored. Evidence will be presented which indicates that blocking glutamate receptors can rescue injured motoneurones from death. (2) Replacement of lost motoneurones by embryonic grafts. Motoneurones from grafts of embryonic spinal cord have been shown to survive in the adult spinal cord and are able to reinnervate skeletal muscles. The potential and practical problems of this approach will be discussed. (3) Expansion or motor unit territory of surviving motoneurones. Such an expansion of the territory occupied by individual motor units can be achieved by encouraging sprouting and ensuring that the newly formed connections between the motoneurone and muscle fibres are maintained, so that individual motor units are capable of developing more force. Strategies to achieve such an expansion of motor unit territory will be described. Finally, combinations of some of these approaches are considered.