Amyotrophic lateral sclerosis (ALS) is a rare disease that affects motor neurons that control muscles for movement and breathing, causing total paralysis and death on average within 2-5 years of diagnosis.
Through the study of mouse models of some genetic forms of the pathology, in particular mice carrying the mutated form of SOD1, the laboratory aims to understand what are the mechanisms responsible for the onset and progression of the disease in order to modulate them to block or at least slow down the evolution of the disease in early stages.
ALS: study of the mechanisms governing the course of disease
ALS, is a heterogeneous disease in terms of progression rate and survival. This is probably one of the reasons for the failure of many clinical trials and the lack of effective therapies. We found that two ALS mouse models carrying the same SOD1G93A mutation showed marked difference in the onset and progression of disease due to their different genetic background. This project aims to investigate the mechanisms underlying the difference in the disease for providing new prognostic stratification and new disease-modifying therapeutic options to be translated to patients. We undertook a comparative analysis of the two mouse models using a broad spectrum of analytical techniques including molecular biology, immunohistochemistry, confocal microscopy, MRI, transcriptomic, proteomic and metabolomic analysis. By means of the metabolomic analysis of the spinal cord of the two SOD1G93A mouse models, we observed important differences in the basal metabolic rate between the two strains of mice in relation to the different disease progression. Next step is to examine the differentially expressed metabolites at the peripheral level (blood and muscles) to identify potential diagnostic and prognostic markers of disease to be translated in ALS patients. We have also found that the levels of some tRNA fragments generated by the enzymatic action of angiogenin, a protective factor in ALS, are associated with a slower disease progression in both SOD1G93A mice and ALS patients. The prognostic value of this biomarkers needs be validated on a larger number of patients while in mice we are trying to understand the potential therapeutic action and mechanism of angiogenin. As part of the study of the mechanisms responsible for the variability of onset and progression of the disease in the two mouse models SOD1G93A, we also focused attention on the study of the muscles of these mice. Preliminary results show that slow progressing mice are able to activate compensatory mechanisms for muscle function that allow the disease to slow down. We have recently identified one such mechanism which consists in the activation of the P2X7 receptor, belonging to the ionotropic family of purinergic receptors for extracellular ATP, which is abundantly expressed in healthy skeletal muscles, where it controls cell duplication, differentiation, regeneration or death.
ALS: role of neuroinflammation and immune response
Among the mechanisms responsible for the different progression of the disease in mouse models of ALS we have shown an important role of the immune response, especially at the peripheral level of the neuromuscular system. For example, we have shown that the early recruitment of macrophages and lymphocytes at the level of the nerve and neuromuscular plaque is essential for delaying the onset of symptoms. On the contrary, in the spinal cord a prolonged neuroinflammation is detrimental to the motor neurons causing a rapid progression of the disease in the long term. This opposite role of inflammation could explain why anti-inflammatory and immunosuppressive drugs have not shown efficacy in ALS patients. We are examining new strategies that can potentially interfere with the immune response in different compartments of the neuromuscular system using viral vector technology. For example, inducing a predominant expression of the chemokine CCL2 in the skeletal muscles, we observed an increased macrophage recruitment in this compartment associated to a partial slowing of the disease in SOD1G93A mice. The study is still underway to identify the molecular mechanisms underlying this protective response and to compare the transcriptomic profile of macrophages at the level of skeletal muscle in mice with slow and rapid disease progression.
Genetic SLA: development of a new platform of ALS mouse models for preclinical trials
We have a long-standing expertise in undertaking preclinical trials of potential therapeutic agents in SOD1G93A mouse models of ALS. However, although studies carried out on mice with SOD1 mutations gave very important information on the development and evolution of the disease, they have not yet led to the development of effective therapies for patients. This is partially due to the fact that only 3% of patients carry SOD1 gene mutation. To date the C9orf72 gene mutation is the one most represented in familial and sporadic ALS patients while the accumulation of TDP43 aggregates in the central nervous system is the typical hallmark of all patients with ALS. Thus, we decided to implement our animal facility with two other murine models of the disease, the C9orf72 mutated mice and the transgenic mice overexpressing wild type human TDP43. We are deeply studying these mice by using a broad spectrum of analytical technique such as behavioral testing, in vivo muscle electrophysiology recording, immunohistochemistry, biochemistry and molecular biology. A combination of these mouse models allows to undertake and validate preclinical trials of potential therapeutic agents. We also contributed to the development of a porcine model carrying the SOD1G93A mutation, which, like the mouse, shows progressive paralysis of the limbs. Thanks to its anatomical and physiological characteristics, this model effectively integrates the preclinical study of ALS by bridging the gap between rodents and humans.
International Consensus on Cardiopulmonary Resuscitation.