MiR-219a-5p Enriched Extracellular Vesicles Induce OPC Differentiation and EAE Improvement More Efficiently Than Liposomes and Polymeric Nanoparticles.

Remyelination is a key aspect in multiple sclerosis pathology and a special effort is being made to promote it. However, there is still no available treatment to regenerate myelin and several strategies are being scrutinized. Myelination is naturally performed by oligodendrocytes and microRNAs have been postulated as a promising tool to induce oligodendrocyte precursor cell differentiation and therefore remyelination. Herein, DSPC liposomes and PLGA nanoparticles were studied for miR-219a-5p encapsulation, release and remyelination promotion. In parallel, they were compared with biologically engineered extracellular vesicles overexpressing miR-219a-5p. Interestingly, extracellular vesicles showed the highest oligodendrocyte precursor cell differentiation levels and were more effective than liposomes and polymeric nanoparticles crossing the blood-brain barrier. Finally, extracellular vesicles were able to improve EAE animal model clinical evolution. Our results indicate that the use of extracellular vesicles as miR-219a-5p delivery system can be a feasible and promising strategy to induce remyelination in multiple sclerosis patients.

Human recombinant glutamate oxaloacetate transaminase 1 (GOT1) supplemented with oxaloacetate induces a protective effect after cerebral ischemia.

Blood glutamate scavenging is a novel and attractive protecting strategy to reduce the excitotoxic effect of extracellular glutamate released during ischemic brain injury. Glutamate oxaloacetate transaminase 1 (GOT1) activation by means of oxaloacetate administration has been used to reduce the glutamate concentration in the blood. However, the protective effect of the administration of the recombinant GOT1 (rGOT1) enzyme has not been yet addressed in cerebral ischemia. The aim of this study was to analyze the protective effect of an effective dose of oxaloacetate and the human rGOT1 alone and in combination with a non-effective dose of oxaloacetate in an animal model of ischemic stroke. Sixty rats were subjected to a transient middle cerebral artery occlusion (MCAO). Infarct volumes were assessed by magnetic resonance imaging (MRI) before treatment administration, and 24 h and 7 days after MCAO. Brain glutamate levels were determined by in vivo MR spectroscopy (MRS) during artery occlusion (80 min) and reperfusion (180 min). GOT activity and serum glutamate concentration were analyzed during the occlusion and reperfusion period. Somatosensory test was performed at baseline and 7 days after MCAO. The three treatments tested induced a reduction in serum and brain glutamate levels, resulting in a reduction in infarct volume and sensorimotor deficit. Protective effect of rGOT1 supplemented with oxaloacetate at 7 days persists even when treatment was delayed until at least 2 h after onset of ischemia. In conclusion, our findings indicate that the combination of human rGOT1 with low doses of oxaloacetate seems to be a successful approach for stroke treatment.

Comparación de la lesión producida en tres modelos animales de isquemia cerebral focal permanente mediante resonancia magnética / Comparison of the lesion produced by permanent focal cerebral ischaemia in three animal models using magnetic resonance imaging

Introducción. Los modelos animales de isquemia cerebral son indispensables en la investigación de la patología cerebrovascular. Actualmente, no existe un modelo experimental que refleje perfectamente la fisiopatología del ictus, por lo que la selección de éste es fundamental para una interpretación correcta de los resultados obtenidos. Objetivo. Caracterizar la evolución temporal de tres modelos comunes de isquemia cerebral focal permanente mediante resonancia magnética. Materiales y métodos. Treinta ratas macho Sprague-Dawley se dividieron en tres grupos, cada uno sometido a los siguientes modelos quirúrgicos: sutura intracraneal de la arteria cerebral media (ACM), electrocoagulación de la ACM y oclusión intraluminal de la ACM. Cada animal se sometió a una exploración por resonancia magnética los días 1, 2, 3, 4, 7 y 14 tras la cirugía. A partir de imágenes adquiridas con secuencias potenciadas en T2 se calcularon tanto el volumen de lesión como el grado de edema. Resultados. El modelo intraluminal presentó mayor volumen de infarto (media: 297 ± 163 mm3 de volumen máximo) y mayor edema (media: 17 ± 9% de edema máximo) frente al modelo de sutura intracraneal (178 ± 62 mm3 y 9 ± 6%, respectivamente) y electrocoagulación (181 ± 45 mm3 y 9 ± 6%, respectivamente). Discusión. Pese a presentar una mayor mortalidad (28%), el modelo de oclusión intraluminal de la ACM es el más adecuado para estudios a largo plazo al no precisar craneotomía, al contrario que los modelos transcraneales. El modelo de oclusión por electrocoagulación muestra una región cerebral de lesión no isquémica y una evolución de la lesión diferente a los otros dos modelos (AU)

Introduction. Animal models of brain ischemia are essential to reveal the full aspects of cerebrovascular pathologies. The perfect animal model that reflects every aspect of stroke pathophysiology does not exist, hence there is a need for a proper selection of the animal model in order to interpret properly the results from experimental research. Aim. To characterize and compare the temporal evolution of three common models of focal brain ischemia using magnetic resonance imaging (MRI) techniques. Materials and methods. Thirty Sprague-Dawley rats were distributed into three groups, each of them submitted to one of the following surgery procedures: middle cerebral artery (MCA) intracranial suture, MCA electrocoagulation, and MCA intraluminal suture. Each rat was subjected to an MRI study at days 1, 2, 3, 4, 7 and 14 post-surgery. T2 weighted images were obtained in order to calculate both lesion volumes and edema. Results. Infarct volume and edema were maximal for the intraluminal model (peaks of mean 297 ± 163 mm3 and mean 17 ± 9%, respectively) compared to intracranial suture (178 ± 62 mm3 and 9 ± 6%, respectively) and electrocoagulation (181 ± 45 mm3 and 9 ± 6%, respectively) models. Discussion. The intraluminal occlusion of the MCA model, although yields in the highest mortality rate (28%), it is the more suitable for long term studies, mainly because of the absence of craniotomy. In the electrocoagulation model a non ischemic lesion region is observed which leads to an abnormal lesion evolution as compared with the other two models (AU)

[Comparison of the lesion produced by permanent focal cerebral ischaemia in three animal models using magnetic resonance imaging]. / Comparacion de la lesion producida en tres modelos animales de isquemia cerebral focal permanente mediante resonancia magnetica.

INTRODUCTION: Animal models of brain ischemia are essential to reveal the full aspects of cerebrovascular pathologies. The perfect animal model that reflects every aspect of stroke pathophysiology does not exist, hence there is a need for a proper selection of the animal model in order to interpret properly the results from experimental research. AIM: To characterize and compare the temporal evolution of three common models of focal brain ischemia using magnetic resonance imaging (MRI) techniques. MATERIALS AND METHODS: Thirty Sprague-Dawley rats were distributed into three groups, each of them submitted to one of the following surgery procedures: middle cerebral artery (MCA) intracranial suture, MCA electrocoagulation, and MCA intraluminal suture. Each rat was subjected to an MRI study at days 1, 2, 3, 4, 7 and 14 post-surgery. T2 weighted images were obtained in order to calculate both lesion volumes and edema. RESULTS: Infarct volume and edema were maximal for the intraluminal model (peaks of mean 297 ± 163 mm3 and mean 17 ± 9%, respectively) compared to intracranial suture (178 ± 62 mm3 and 9 ± 6%, respectively) and electrocoagulation (181 ± 45 mm3 and 9 ± 6%, respectively) models. DISCUSSION: The intraluminal occlusion of the MCA model, although yields in the highest mortality rate (28%), it is the more suitable for long term studies, mainly because of the absence of craniotomy. In the electrocoagulation model a non ischemic lesion region is observed which leads to an abnormal lesion evolution as compared with the other two models.

Técnicas de imagen para el estudio de la recuperación funcional tras el ictus: II. Técnicas complementarias / Imaging techniques for studying functional recovery following a stroke: II. Complementary techniques

Resumen. Muchos pacientes que sobreviven a un ictus se enfrentan a serias discapacidades funcionales durante el resto de sus vidas, lo que supone un drama personal para sí mismos y sus allegados, y un elevado coste para la sociedad. Por ello, la recuperación funcional del sujeto tras un ictus debe ser un objetivo esencial que habría que considerar en el desarrollo de nuevas aproximaciones terapéuticas. Éste es el segundo de una serie de dos trabajos en los que revisamos las estrategias y herramientas disponibles hoy en día para la evaluación de múltiples aspectos relacionados con la función cerebral (tanto en humanos como en animales de experimentación), y que están ayudando a los neurocientíficos a entender mejor los procesos de restauración y reorganización de la función cerebral que se inician tras un ictus, partiendo de la premisa de que una aproximación multidisciplinar proporciona una perspectiva más completa de los mecanismos que subyacen bajo los procesos de reparación tisular, de reorganización plástica del cerebro y de los compensatorios que se desencadenan tras un ictus. En el segundo de los trabajos de esta serie nos centramos en una serie de técnicas complementarias basadas en la imagen por resonancia magnética y que no se engloban dentro de los grupos de técnicas discutidos en el primer trabajo de esta serie, bien por abordar aspectos no relacionados directamente con la función cerebral, aunque sí lo hacen de forma indirecta, bien por estar basados en principios fisicoquímicos o fisiológicos diferentes a los ya discutidos (AU)

Summary. Many patients that survive stroke have to face serious functional disabilities for the rest of their lives, which is a personal drama for themselves and their relatives, and an elevated charge for society. Thus, functional recovery after stroke must be a key aspect of the development of new therapeutic approaches. This is the second of a series of two works on which we review the strategies and tools available nowadays for the assessment of multiple aspects related to brain function (both in humans and research animals) and that are helping neuroscientist to better understand the processes of functional restoration and reorganization of the brain, that are triggered following stroke. We have assumed that a multidisciplinary approach is able to provide us with a wider perspective of the underlying mechanisms behind tissue repair, plastic reorganization of the brain and compensatory mechanisms, that can be triggered after stroke. In the second of the works of this series we are focusing in a series of techniques, complementary to the already discussed in the first work, and that are based on MR. These techniques are discussed separately from those ones, because they tackle with aspects not directly related to brain function, although they somehow do in indirect ways, or because they are based on physicochemical or physiological principles different from those discussed on the first work of this series (AU)

[Imaging techniques for studying functional recovery following a stroke: I. Methodological aspects]. / Tecnicas de imagen para el estudio de la recuperacion funcional tras el ictus: I. Aspectos metodologicos.

Many patients that survive stroke have to face serious functional disabilities for the rest of their lives, which is a personal drama for themselves and their relatives, and an elevated charge for society. Thus functional recovery following stroke should be a key objective for the development of new therapeutic approaches. In this series of two works we review the strategies and tools available nowadays for the evaluation of multiple aspects related to brain function (both in humans and research animals), and how they are helping neuroscientist to better understand the processes of restoration and reorganization of brain function that are triggered following stroke. We have mainly focused on magnetic resonance applications, probably the most versatile neuroimaging technique available nowadays, and that everyday surprises us with new and exciting applications. But we tackle other alternative and complementary techniques, since a multidisciplinary approach allows a wider perspective over the underlying mechanisms behind tissue repair, plastic reorganization of the brain and compensatory mechanisms that are triggered after stroke. The first of the works of this series is focused on methodological aspects that will help us to understand how it is possible to assess brain function based on different physical and physiological principles. In the second work we will focus on different practical issues related to the application of the techniques here discussed.

Recommendations guide for experimental animal models in stroke research.

INTRODUCTION: The progress of effective therapies for stroke has become a challenging task for both researchers and clinicians. Some pitfalls in clinical trials might have their origins in the pre-clinical experimental ischaemic models for the evaluation of potential neuro-protective agents. METHODS: We aim to standardise the methods for the development of stroke animal models throughout Spain, to produce document with appropriate recommendations and best practice in order to improve experimental methods in the field of stroke research. RESULTS: Members of several experienced stroke research groups prepared a guide with recommendations in the application of focal cerebral ischaemic models. The main features of this guide are based on the selection of the most appropriate animal model, taking in account the objective of the study, the species, strain, age, sex of animals, as well as risk factors. The experimental design must include a sham control group and the sample size calculation. Animal randomisation and blind analysis, masked assessment of outcomes, monitoring of body temperature and cerebral blood flow, and the reporting of reasons for excluding animals from the study, as well as the mortality rate, are other main points to fulfil in the application of stroke models. CONCLUSIONS: Standardised methods are essential to increase the success of the pre-clinical findings in the stroke neuroprotection field to be able to translate to the clinical practice.

[Reorganisation of the cerebral vasculature following ischaemia]. / Reorganización de la vascularización cerebral tras la isquemia.

INTRODUCTION AND DEVELOPMENT: Cerebral function needs a constant oxygen and glucose supply. This is why the regulation of cerebral blood flow is critical for the maintenance of neuronal function. Therefore, vascular system in adult brain is extremely stable and does not withstand big changes under physiological conditions. However, when blood flow is interrupted due to a focal cerebral ischemia the collateral tissue is partially affected, this is known as ischemic penumbra. Although its functionality is affected, this tissue is viable thanks to the collateral blood flow, and it releases angiogenic factors that induce proliferation of endothelial cells and migration of endothelial progenitor cells for the formation of new blood vessels. Angiogenesis induction and new vessel generation allow neurorepair processes, including neurogenesis and synaptogenesis. These two processes should be coupled with angiogenesis in order to contribute to functional recovery of patients who suffered a cerebral infarct. Therefore, angiogenesis could be one of the therapeutic options in ischemic stroke treatment. Nevertheless, some angiogenic factors such as vascular endothelial growth factor, platelet derived growth factor and angiopoyetin also increase vascular permeability which can produce hemorrhagic transformation. CONCLUSIONS: Hence, the knowledge of molecular mechanisms that regulate angiogenesis after an ischemic stroke could contribute to the development of a new therapeutic option based on angiogenesis as a vehicle to promote neurorepair and functional recovery.

Reorganización de la vascularización cerebral tras la isquemia / Reorganization of the cerebral vasculature following ischaemia

Resumen. Introducción y desarrollo. La regulación del flujo sanguíneo cerebral es crítica para el mantenimiento de la función neuronal, que necesita un aporte de oxígeno y glucosa constante. Por ello, el sistema vascular del cerebro adulto es extremadamente estable y, en situaciones fisiológicas, no sufre grandes modificaciones. Sin embargo, cuando se interrumpe el flujo sanguíneo en un área del cerebro debido a una isquemia cerebral, el tejido circundante parcialmente afectado, conocido como área de penumbra isquémica, es viable fundamentalmente gracias al flujo sanguíneo colateral, y libera factores angiogénicos que inducen la proliferación de células endoteliales y la migración de células progenitoras endoteliales para formar nuevos vasos sanguíneos. La inducción de la angiogénesis y la generación de nuevos vasos facilitan procesos de neurorreparación, que incluyen fenómenos de neurogénesis y sinaptogénesis. Estos dos procesos deben estar perfectamente acoplados a la angiogénesis para contribuir a la recuperación funcional de los pacientes que sufren un infarto cerebral. Por todo ello, la angiogénesis podría ser una de las opciones terapéuticas en el tratamiento del ictus isquémico. Sin embargo, determinados factores angiogénicos, como el factor de crecimiento del endotelio vascular, el factor de crecimiento derivado de plaquetas o la angiopoyetina, incrementan la permeabilidad vascular y pueden generar complicaciones, como la transformación hemorrágica. Conclusiones. Por todo ello, el conocimiento de los mecanismos moleculares que regulan la angiogénesis tras el ictus isquémico podría contribuir al desarrollo de una nueva vía terapéutica basada en la angiogénesis como vehículo para la neurorreparación y la recuperación funcional (AU)

Summary. Introduction and development. Cerebral function needs a constant oxygen and glucose supply. This is why the regulation of cerebral blood flow is critical for the maintenance of neuronal function. Therefore, vascular system in adult brain is extremely stable and does not withstand big changes under physiological conditions. However, when blood flow is interrupted due to a focal cerebral ischemia the collateral tissue is partially affected, this is known as ischemic penumbra. Although its functionality is affected, this tissue is viable thanks to the collateral blood flow, and it releases angiogenic factors that induce proliferation of endothelial cells and migration of endothelial progenitor cells for the formation of new blood vessels. Angiogenesis induction and new vessel generation allow neurorepair processes, including neurogenesis and synaptogenesis. These two processes should be coupled with angiogenesis in order to contribute to functional recovery of patients who suffered a cerebral infarct. Therefore, angiogenesis could be one of the therapeutic options in ischemic stroke treatment. Nevertheless, some angiogenic factors such as vascular endothelial growth factor, platelet derived growth factor and angiopoyetin also increase vascular permeability which can produce hemorrhagic transformation. Conclusions. Hence, the knowledge of molecular mechanisms that regulate angiogenesis after an ischemic stroke could contribute to the development of a new therapeutic option based on angiogenesis as a vehicle to promote neurorepair and functional recovery (AU)

MRI of hip prostheses using single-point methods: in vitro studies towards the artifact-free imaging of individuals with metal implants.

Use of magnetic resonance imaging (MRI) in individuals with orthopedic implants is limited because of the large distortions caused by metallic components. As a possible solution for this problem, we suggest the use of single-point imaging (SPI) methods, which are immune to the susceptibility artifacts observed with conventional MRI methods. A further advantage of SPI, based on the fact that signal encoding is achieved in ultra-short times (as short as tens of microseconds), is that they enable the direct visualization of the polymeric elements of the implants, allowing the detection of possible implant failures. We present in vitro SPI images of polymeric sockets of two hip prostheses together with artifact-free images of gelatin phantoms containing their respective metallic stems. These data underscore the great potential of the SPI technique for obtaining artifact-free images of individuals with large metal implants.