Modelos experimentales murinos en la esclerosis lateral amiotrófica. Puesta al día / Murine experimental models of amyotrophic lateral sclerosis: An update

Introducción: La esclerosis lateral amiotrófica (ELA) es una enfermedad neurodegenerativa, progresiva y de etiología desconocida caracterizada por la degeneración de motoneuronas superiores e inferiores. Aproximadamente el 90% de los casos de ELA son esporádicos, mientras que el 10% restante se consideran familiares. Independientemente de si son familiares o esporádicas, los pacientes desarrollan una debilidad progresiva, atrofia muscular con espasticidad y contracturas. Por lo general, la esperanza de vida en los pacientes de ELA es de 2 a 5 años. Desarrollo: Los modelos in vivo han ayudado a explicar la etiología y la patogénesis, así como los mecanismos de la ELA. Sin embargo, estos mecanismos no están del todo esclarecidos aún, por lo que los modelos experimentales son fundamentales para continuar con el estudio de los mismos, así como para la búsqueda de posibles dianas terapéuticas. A pesar de que el 90% de los casos son esporádicos, la mayoría de los modelos utilizados hasta la actualidad para estudiar la patogénesis están basados en las mutaciones genéticas asociadas a la enfermedad familiar, lo que provoca que la patogénesis de la ELA esporádica no sea aún conocida. Por tanto, sería fundamental el estudio de la enfermedad en modelos basados en la enfermedad esporádica. Conclusión: En el presente artículo se han revisado los principales modelos experimentales, tanto genéticos como esporádicos, utilizados en el estudio de esta enfermedad, enfocándonos en los que se han desarrollado utilizando el roedor como plataforma experimental.(AU)

Introduction: Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease whose aetiology is unknown. It is characterised by upper and lower motor neuron degeneration. Approximately 90% of cases of ALS are sporadic, whereas the other 10% are familial. Regardless of whether the case is familial or sporadic, patients will develop progressive weakness, muscle atrophy with spasticity, and muscle contractures. Life expectancy of these patients is generally 2–5 years after diagnosis. Development: In vivo models have helped to clarify the aetiology and pathogenesis of ALS, as well as the mechanisms of the disease. However, as these mechanisms are not yet fully understood, experimental models are essential to the continued study of the pathogenesis of ALS, as well as in the search for possible therapeutic targets. Although 90% of cases are sporadic, most of the models used to study ALS pathogenesis are based on genetic mutations associated with the familial form of the disease; the pathogenesis of sporadic ALS remains unknown. Therefore, it would be critical to establish models based on the sporadic form. Conclusion: This article reviews the main genetic and sporadic experimental models used in the study of this disease, focusing on those that have been developed using rodents.(AU)

Murine experimental models of amyotrophic lateral sclerosis: an update.

INTRODUCTION: Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease whose aetiology is unknown. It is characterised by upper and lower motor neuron degeneration. Approximately 90% of cases of ALS are sporadic, whereas the other 10% are familial. Regardless of whether the case is familial o sporadic, patients will develop progressive weakness, muscle atrophy with spasticity, and muscle contractures. Life expectancy of these patients is generally 2 to 5 years after diagnosis. DEVELOPMENT: In vivo models have helped to clarify the aetiology and pathogenesis of ALS, as well as the mechanisms of the disease. However, as these mechanisms are not yet fully understood, experimental models are essential to the continued study of the pathogenesis of ALS, as well as in the search for possible therapeutic targets. Although 90% of cases are sporadic, most of the models used to study ALS pathogenesis are based on genetic mutations associated with the familial form of the disease; the pathogenesis of sporadic ALS remains unknown. Therefore, it would be critical to establish models based on the sporadic form. CONCLUSIONS: This article reviews the main genetic and sporadic experimental models used in the study of this disease, focusing on those that have been developed using rodents.

Exonic variants of the P2RX7 gene in familial multiple sclerosis.

INTRODUCTION: Several studies have analysed the presence of P2RX7 variants in patients with MS, reporting diverging results. METHODS: Our study analyses P2RX7 variants detected through whole-exome sequencing (WES). RESULTS: We analysed P2RX7, P2RX4, and CAMKK2 gene variants detected by whole-exome sequencing in all living members (n = 127) of 21 families including at least 2 individuals with multiple sclerosis. P2RX7 gene polymorphisms previously associated with autoimmune disease. Although no differences were observed between individuals with and without multiple sclerosis, we found greater polymorphism of gain-of-function variants of P2RX7 in families with individuals with multiple sclerosis than in the general population. Copresence of gain-of-function and loss-of-function variants was not observed to reduce the risk of presenting the disease. Three families displayed heterozygous gain-of-function SNPs in patients with multiple sclerosis but not in healthy individuals. We were unable to determine the impact of copresence of P2RX4 and CAMKK2 variants with P2RX7 variants, or the potential effect of the different haplotypes described in the gene. No clinical correlations with other autoimmune diseases were observed in our cohort. CONCLUSIONS: Our results support the hypothesis that the disease is polygenic and point to a previously unknown mechanism of genetic predisposition to familial forms of multiple sclerosis. P2RX7 gene activity can be modified, which suggests the possibility of preventive pharmacological treatments for families including patients with familial multiple sclerosis.

Variant rs4149584 (R92Q) of the TNFRSF1A gene in patients with familial multiple sclerosis.

INTRODUCTION: Genomic studies have identified numerous genetic variants associated with susceptibility to multiple sclerosis (MS); however, each one explains only a small percentage of the risk of developing the disease. These variants are located in genes involved in specific pathways, which supports the hypothesis that the risk of developing MS may be linked to alterations in these pathways, rather than in specific genes. We analyzed the role of the TNFRSF1A gene, which encodes one of the TNF-α receptors involved in a signaling pathway previously linked to autoimmune disease. METHODS: We included 138 individuals from 23 families including at least 2 members with MS, and analyzed the presence of exonic variants of TNFRSF1A through whole-exome sequencing. We also conducted a functional study to analyze the pathogenic mechanism of variant rs4149584 (-g.6442643C > G, NM_001065.4:c.362 G > A, R92Q) by plasmid transfection into human oligodendroglioma (HOG) cells, which behave like oligodendrocyte lineage cells; protein labeling was used to locate the protein within cells. We also analyzed the ability of transfected HOG cells to proliferate and differentiate into oligodendrocytes. RESULTS: Variant rs4149584 was found in 2 patients with MS (3.85%), one patient with another autoimmune disease (7.6%), and in 5 unaffected individuals (7.46%). The 2 patients with MS and variant rs4149584 were homozygous carriers and belonged to the same family, whereas the remaining individuals presented the variant in heterozygosis. The study of HOG cells transfected with the mutation showed that the protein does not reach the cell membrane, but rather accumulates in the cytoplasm, particularly in the endoplasmic reticulum and near the nucleus; this suggests that, in the cells presenting the mutation, TNFRSF1 does not act as a transmembrane protein, which may alter its signaling pathway. The study of cell proliferation and differentiation found that transfected cells continue to be able to differentiate into oligodendrocytes and are probably still capable of producing myelin, although they present a lower rate of proliferation than wild-type cells. CONCLUSIONS: Variant rs4149584 is associated with risk of developing MS. We analyzed its functional role in oligodendrocyte lineage cells and found an association with MS in homozygous carriers. However, the associated molecular alterations do not influence the differentiation into oligodendrocytes; we were therefore unable to confirm whether this variant alone is pathogenic in MS, at least in heterozygosis.

Will neurological care change over the next 5 years due to the COVID-19 pandemic? Key informant consensus survey. / ¿Va a cambiar la neurología tras la pandemia de COVID-19 en los próximos 5 años? Estudio de enfoque mediante informadores clave.

INTRODUCTION: The COVID-19 pandemic will give rise to long-term changes in neurological care, which are not easily predictable. MATERIAL AND METHODS: A key informant survey was used to enquire about the changes expected in the specialty over the next 5 years. The survey was completed by heads of neurology departments with broad knowledge of the situation, having been active during the pandemic. RESULTS: Despite a low level of consensus between participants, there was strong (85%) and moderate consensus (70%) about certain subjects, mainly the increase in precautions to be taken, the use of telemedicine and teleconsultations, the reduction of care provided in in-person consultations to avoid the presence of large numbers of people in waiting rooms, the development of remote training solutions, and the changes in monitoring visits during clinical trials. There was consensus that there would be no changes to the indication of complementary testing or neurological examination. CONCLUSION: The key informant survey identified the foreseeable changes in neurological care after the pandemic.

Should we expect neurological symptoms in the SARS-CoV-2 epidemic? / ¿Es esperable que haya cuadros neurológicos por la pandemia por SARS-CoV-2?

INTRODUCTION: There is growing evidence that SARS-CoV-2 can gain access to the central nervous system (CNS). We revise the literature on coronavirus infection of the CNS associated with neurological diseases. DEVELOPMENT: Neurological symptoms were rarely reported in the SARS-CoV and MERS-CoV epidemics, although isolated cases were described. There are also reports of cases of neurological symptoms associated with CoV-OC43 and CoV-229E infection. The presence of neurological lesions, especially demyelinating lesions in the mouse hepatitis virus model, may explain the mechanisms by which coronaviruses enter the CNS, particularly those related with the immune response. This may explain the presence of coronavirus in patients with multiple sclerosis. We review the specific characteristics of SARS-CoV-2 and address the question of whether the high number of cases may be associated with greater CNS involvement. CONCLUSION: Although neurological symptoms are not frequent in coronavirus epidemics, the high number of patients with SARS-CoV-2 infection may explain the presence of the virus in the CNS and increase the likelihood of early- or delayed-onset neurological symptoms. Follow-up of patients affected by the SARS-CoV-2 epidemic should include careful assessment of the CNS.

Management of neurological care during the COVID-19 pandemic. / La gestión de la asistencia neurológica en tiempos de la pandemia de Covid-19.

INTRODUCTION: The COVID-19 epidemic has led to the need for unprecedented decisions to be made to maintain the provision of neurological care. This article addresses operational decision-making during the epidemic. DEVELOPMENT: We report the measures taken, including the preparation of a functional reorganisation plan, strategies for hospitalisation and emergency management, the use of telephone consultations to maintain neurological care, provision of care at a unit outside the hospital for priority patients, decisions about complementary testing and periodic in-hospital treatments, and the use of a specific telephone service to prioritise patients with epileptic seizures. CONCLUSION: Despite the situation of confinement, neurology departments must continue to provide patient care through different means of operation. Like all elements of management, these must be evaluated.

Experimental models of demyelination and remyelination. / Modelos experimentales de desmielinización-remielinización.

INTRODUCTION: Experimental animal models constitute a useful tool to deepen our knowledge of central nervous system disorders. In the case of multiple sclerosis, however, there is no such specific model able to provide an overview of the disease; multiple models covering the different pathophysiological features of the disease are therefore necessary. DEVELOPMENT: We reviewed the different in vitro and in vivo experimental models used in multiple sclerosis research. Concerning in vitro models, we analysed cell cultures and slice models. As for in vivo models, we examined such models of autoimmunity and inflammation as experimental allergic encephalitis in different animals and virus-induced demyelinating diseases. Furthermore, we analysed models of demyelination and remyelination, including chemical lesions caused by cuprizone, lysolecithin, and ethidium bromide; zebrafish; and transgenic models. CONCLUSIONS: Experimental models provide a deeper understanding of the different pathogenic mechanisms involved in multiple sclerosis. Choosing one model or another depends on the specific aims of the study.

NG2 and GFAP co-expression after differentiation in cells transfected with mutant GFAP and in undifferentiated glioma cells. / Coexpresión de NG2/GFAP tras la diferenciación en células transfectadas con las mutaciones de GFAP y en células procedentes de gliomas indiferenciados.

INTRODUCTION: Alexander disease is a rare disorder caused by mutations in the gene coding for glial fibrillary acidic protein (GFAP). In a previous study, differentiation of neurospheres transfected with these mutations resulted in a cell type that expresses both GFAP and NG2. OBJECTIVE: To determine the effect of molecular marker mutations in comparison to undifferentiated glioma cells simultaneously expressing GFAP and NG2. METHODS: We used samples of human glioblastoma (GBM) and rat neurospheres transfected with GFAP mutations to analyse GFAP and NG2 expression after differentiation. We also performed an immunocytochemical analysis of neuronal differentiation for both cell types and detection of GFAP, NG2, vimentin, Olig2, and caspase-3 at 3 and 7 days from differentiation. RESULTS: Both the cells transfected with GFAP mutations and GBM cells showed increased NG2 and GFAP expression. However, expression of caspase-3-positive cells was found to be considerably higher in transfected cells than in GBM cells. CONCLUSIONS: Our results suggest that GFAP expression is not the only factor associated with cell death in Alexander disease. Caspase-3 expression and the potential role of NG2 in increasing resistance to apoptosis in cells co-expressing GFAP and NG2 should be considered in the search for new therapeutic strategies for the disease.

Vitamin D and remyelination in multiple sclerosis. / Vitamina D y remielinización en la esclerosis múltiple.

INTRODUCTION: Several studies have found an association between multiple sclerosis and vitamin D (VD) deficiency, which suggests that VD may play a role in the immune response. However, few studies have addressed its role in remyelination. DEVELOPMENT: The VD receptor and the enzymes transforming VD into metabolites which activate the VD receptor are expressed in central nervous system (CNS) cells, which suggests a potential effect of VD on the CNS. Both in vitro and animal model studies have shown that VD may play a role in myelination by acting on factors that influence the microenvironment which promotes both proliferation and differentiation of neural stem cells into oligodendrocyte progenitor cells and oligodendrocytes. It remains unknown whether the mechanisms of internalisation of VD in the CNS are synergistic with or antagonistic to the mechanisms that facilitate the entry of VD metabolites into immune cells. CONCLUSIONS: VD seems to play a role in the CNS and our hypothesis is that VD is involved in remyelination. Understanding the basic mechanisms of VD in myelination is necessary to manage multiple sclerosis patients with VD deficiency.

Histological changes in the rat brain and spinal cord following prolonged intracerebroventricular infusion of cerebrospinal fluid from amyotrophic lateral sclerosis patients are similar to those caused by the disease. / La infusión intracerebroventricular prolongada de líquido cefalorraquídeo procedente de pacientes con esclerosis lateral amiotrófica provoca cambios histológicos en el cerebro y la médula espinal de la rata similares a los hallados en la enfermedad.

INTRODUCTION: Cerebrospinal fluid (CSF) from amyotrophic lateral sclerosis (ALS) patients induces cytotoxic effects in in vitro cultured motor neurons. MATERIAL AND METHODS: We selected CSF with previously reported cytotoxic effects from 32 ALS patients. Twenty-eight adult male rats were intracerebroventricularly implanted with osmotic mini-pumps and divided into 3 groups: 9 rats injected with CSF from non-ALS patients, 15 rats injected with cytotoxic ALS-CSF, and 4 rats injected with a physiological saline solution. CSF was intracerebroventricularly and continuously infused for periods of 20 or 43days after implantation. We conducted clinical assessments and electromyographic examinations, and histological analyses were conducted in rats euthanised 20, 45, and 82days after surgery. RESULTS: Immunohistochemical studies revealed tissue damage with similar characteristics to those found in the sporadic forms of ALS, such as overexpression of cystatinC, transferrin, and TDP-43 protein in the cytoplasm. The earliest changes observed seemed to play a protective role due to the overexpression of peripherin, AKTpan, AKTphospho, and metallothioneins; this expression had diminished by the time we analysed rats euthanised on day 82, when an increase in apoptosis was observed. The first cellular changes identified were activated microglia followed by astrogliosis and overexpression of GFAP and S100B proteins. CONCLUSION: Our data suggest that ALS could spread through CSF and that intracerebroventricular administration of cytotoxic ALS-CSF provokes changes similar to those found in sporadic forms of the disease.

Cerebrospinal fluid cytotoxicity does not affect survival in amyotrophic lateral sclerosis.

OBJECTIVES: Cerebrospinal fluid (CSF) from some patients with amyotrophic lateral sclerosis (ALS) has been demonstrated to significantly reduce the neuronal viability of primary cell cultures of motor neurons. We aimed to study the potential clinical consequences associated with the cytotoxicity of CSF in a cohort of patients with ALS. METHODS: We collected CSF from thirty-one patients with ALS. We analysed cytotoxicity by incubating it into the primary cultures of motor cortex neurons. Neural viability was quantified after 24 hours using the colorimetric MTT reduction assay. All patients were followed up from the moment of diagnosis to death, and a complete evaluation during disease progression and survival was performed, including gastrostomy and respiratory assistance. RESULTS: Twenty-one patients (67.7%) presented a cytotoxic CSF. There were no significant differences between patients with and without cytotoxicity regarding mean time from symptom onset to the diagnosis, from the diagnosis to death, from the diagnosis to respiratory assistance with BIPAP, from diagnosis to gastrostomy and from the onset of symptoms to death. In Cox regression analysis, bulbar onset, but not cytotoxicity, gender or age at onset, was associated with a lower risk of survival. CONCLUSIONS: Cerebrospinal fluid cytotoxicity was not associated with differential survival rates. This suggests that the presence of cytotoxicity in CSF, measured through neuronal viability in primary cultures of motor cortex neurons, could reflect different mechanisms of the disease, but it does not predict disease outcome.

18F-FDG PET/CT and functional MRI in a case of crossed logopenic primary progressive aphasia. / 18F-FDG PET/TC y RM funcional en un caso de afasia progresiva primaria logopénica cruzada.

Primary progressive aphasia is a clinical syndrome caused by a neurodegeneration of areas and neural networks involved in language, usually in the left hemisphere. The term "crossed aphasia" denotes an acquired language dysfunction caused by a lesion in the hemisphere ipsilateral to the dominant hand. A case is presented on a 75-year-old right-handed woman with a logopenic variant of primary progressive aphasia with word-finding difficulties of 2 years onset. The 18F-FDG PET/CT showed right temporoparietal hypometabolism. A functional MRI scan was performed during a verb naming task in order to characterise language lateralisation patterns. A similar activation pattern was observed in both hemispheres, with less activation than expected in bilateral inferior frontal gyrus. These findings support that logopenic variant of primary progressive aphasia should not be considered as a neurodegeneration starting in the left brain hemisphere, but as a syndrome characterised by asymmetric neurodegeneration of brain regions and neural networks involved in language.