The future of MS research

In addition to acute inflammation with or without an associated clinical attack, characterised by the presence of 'active' plaques, it is important to gain a better understanding, measure and map the long-term consequences of the destruction of the myelin sheath, the death of demyelinated nerve fibres and the neurons from which they originate, and the activation of macrophages phagocytosing myelin residues. These macrophages have a dual origin, either derived from blood monocytes that have entered the brain with the self-aggressive lymphocytes, or from permanent residents of the nervous system known as microglia. They can have two opposing functions, either pro-inflammatory or anti-inflammatory and restorative. In the latter case, they could induce the differentiation of oligodendrocyte precursor cells into mature oligodendrocytes capable of synthesising new myelin. These neurochemical processes require the activation of numerous genes, the synthesis of numerous molecules and enzymes, and inter-cellular cooperation, all of which are currently the subject of intense research. Ideally, this could lead to the discovery of new neuroprotective and pro-remyelinating drugs, which could then be combined with anti-inflammatory treatments.

Since the early 1990s, considerable progress has been made in the treatment of MS. In recent years, new drugs have been validated through rigorous clinical trials. Their effectiveness in suppressing relapses is remarkable, but remains limited in terms of the progression of disability in the absence of relapses. What's more, improved efficacy often goes hand in hand with an increase in risk, which requires relatively frequent clinical, biological and radiological checks. Fundamental research into molecules that are better tolerated, can act within the brain itself and specifically correct the pathological mechanisms responsible for the disease, therefore remains a preliminary and essential step in improving the efficacy/risk ratio of our treatments.

Choosing the best treatment for each patient is the principle of "personalised medicine". The neurologist must therefore explain the mode of action of each treatment available, their overall efficacy, their advantages, but also their disadvantages and potential side effects. For each of these treatments, we know that there will be "good responders", "average responders" and "poor responders". Unfortunately, we have no real way of predicting whether a particular patient will be a good responder to the proposed treatment. The important thing is to monitor the effectiveness of a treatment regularly and to replace it with another if it fails. The problem is to assess this therapeutic response and to define the criteria which make it necessary to change treatment.

The aim is to determine the evolutionary profile of the disease in each patient using radiological markers in MRI and immunobiological markers in blood samples.

In terms of brain imaging, research is focusing on markers of progression and worsening in the absence of clinical relapses or the appearance of new lesions. The aim is to detect chronically active plaques which increase in volume very gradually in a centrifugal manner, iron deposits at the periphery of these plaques which may be neurotoxic, abnormal liquid uptake of the myelin sheaths, and the density of these sheaths at a distance from the known plaques. MRI should also make it possible to detect signs of synthesis of new myelin sheaths, and to analyse the deleterious effect on the cerebral cortex of inflammatory nodules located in the meninges. This research can only be carried out with the help of engineers specialising in magnetic resonance.

In terms of biological markers, the aim is to develop ultra-sensitive assays for cerebral proteins released by inflammation in the brain and spinal cord, which ultimately diffuse into the bloodstream. These assays must be reproducible, standardised and accessible wherever MS is present. The two best-known markers are the level of neurofilament light protein (NfL), which is elevated in cases of acute axonal damage, and the level of glial fibrillary acidic protein (GFAP), which is elevated as a function of overall brain atrophy. Other protein markers are being studied, for example from activated brain macrophages.

The search for blood immunological markers of the disease is even more complicated, as our knowledge of the mechanisms by which the immune system is deregulated in MS is incomplete. The most widely used immunological marker, known for over 60 years, is the presence of oligoclonal antibody bands observed only in cerebrospinal fluid.

In the future, molecular markers could be used to identify people at risk of developing MS. We still do not know the pathological mechanisms that come into play long before the first clinical signs appear. Observations have already revealed genome anomalies in the programming of the immune system several years before the onset of the disease. Being able to identify biological markers associated with the risk of developing MS would be a huge step forward, as it could perhaps prevent it. This would be a complex index incorporating genetic susceptibility factors, genetic resistance factors, environmental factors already known, and immune factors involved in the deregulation and hyper-reactivity of the immune system.