Magnetic Resonance Imaging Studies of Angiogenesis and Stem Cell Implantations in Rodent Models of Cerebral Lesions

Molecular biology and stem cell research have had an immense impact on our understanding of neurological diseases, for which little or no therapeutic options exist today. Manipulation of the underlying disease-specific molecular and cellular events promises more efficient therapy. Angiogenesis, i.e. the regrowth of new vessels from an existing vascular network, has been identified as a key contributor for the progression of tumor and, more recently, for regeneration after stroke. Donation of stem cells has proved beneficial to treat cerebral lesions. However, before angiogenesis-targeted and stem cell therapies can safely be used in patients, underlying biological processes need to be better understood in animal models. Noninvasive imaging is essential in order to follow biological processes or stem cell fate in both space and time. We optimized steady state contrast enhanced magnetic resonance imaging (SSCE MRI) to monitor vascular changes in rodent models of tumor and stroke. A modification of mathematical modeling of MR signal from the vascular network allowed for the first time simultaneous measurements of relaxation time T2 and SSCE MRI derived blood volume, vessel size, and vessel density. Limitations of SSCE MRI in tissues with high blood volume and non-cylindrically shaped vessels were explored. SSCE MRI detected angiogenesis and response to anti-angiogenic treatment in two rodent tumor models. In both tumor models, reduction of blood volume in small vessels and a shift towards larger vessels was observed upon treatment. After stroke, decreased vessel density and increased vessel size was found, which was most pronounced one week after the infarct. This is in agreement with two initial, recently published clinical studies. Overall, very little signs of angiogenesis were found. Furthermore, superparamagnetic iron oxide (SPIO) labels were used to study neural stem cells (NSCs) in vivo with MRI. SPIO labeling revealed a decrease in volume of intracerebral grafts over 4 months, assessed by T2* weighted MRI. Since SPIO labels are challenging to quantify and their MR contrast can easily be confounded, we explored the potential of in vivo 19F MRI of 19F labeled NSCs. Hardware was developed for in vitro and in vivo 19F MRI. NSCs were labeled with little effect on cell function and in vivo detection limits were determined at ~10,000 cells within 1 h imaging time. A correction for the inhomogeneous magnetic field profile of surface coils was validated in vitro and applied for both sensitive and quantitative in vivo cell imaging. As external MRI labels do not provide information on NSC function we combined 19F MRI with bioluminescence imaging (BLI). The BLI signal allowed quantification of viable cells whereas 19F MRI provided graft location and density in 3D over 4 weeks both in the healthy and stroke brain. A massive decrease in number of viable cells was detected independent of the microenvironment. This indicates that functional recovery reported in many studies of NSC implantation after stroke, is rather due to release of factors by NSCs than direct tissue replacement. In light of these indirect effects, combination of the imaging methods developed in this dissertation with other functional and structural imaging methods is suggested in order to further elucidate interactions of NSCs with the vasculature

Mapping microstructural dynamics in a mouse stroke model using advanced diffusion MRI

Tese de mestrado integrado em Engenharia Biomédica e Biofísica (Sinais e Imagens Médicas), Universidade de Lisboa, Faculdade de Ciências, 2020O acidente vascular cerebral (AVC) corresponde a uma das principais causas de morte e invalidez a nível mundial, sendo o AVC isquémico o mais predominante, perfazendo mais de 80% dos casos. Este traduz-se no bloqueio de um ou mais vasos sanguíneos devido à formação de coágulos, comprometendo a oxigenação no local e o fornecimento de nutrientes como consequência da redução do fluxo sanguíneo. O único tratamento aceite para o AVC baseia-se na administração de agentes trombolíticos. Porém, a sua aplicabilidade é muito reduzida pois o intervalo de tempo exigido para a sua atuação é demasiado curto (menos de 4 horas desde a última vez em que o sujeito se apresentou assintomático). De momento, o desenvolvimento de técnicas inovadoras encontra-se dependente de um conhecimento mais aprofundado do tecido envolvente no decorrer do acidente isquémico. Posto tal, as técnicas de neuroimagiologia de cariz não invasivo, como a imagem por ressonância magnética (IRM), apresentam um papel crucial na investigação nesta área. A importância da ressonância magnética de difusão (dMRI, do inglês diffusion MRI) tem vindo a ser cada vez mais favorecida, especialmente na deteção do enfarte e no estudo do microambiente na zona respetiva. Contudo, as métricas convencionais de dMRI apenas disponibilizam informação relativa, no máximo, a um sumatório de efeitos não Gaussianos da difusão da água nos tecidos, o que a torna numa técnica consideravelmente inespecífica. Esta falta de especificidade pode então refletir-se numa incorreta caraterização do núcleo da lesão, de tecido recuperável e da resposta ao tratamento, no sentido em que os mecanismos subjacentes ao contraste de dMRI obtido são desconhecidos. No âmbito deste trabalho, de forma a aumentar a sensibilidade e especificidade da dMRI na informação obtida em contexto de AVC isquémico, a metodologia de imagem por contraste do tensor de correlação (CTI, do inglês Correlation Tensor Imaging), desenvolvida no nosso laboratório, foi aplicada num modelo de AVC isquémico em murganho (Mus musculus). A CTI permite a obtenção de informações mais específicas acerca de efeitos de difusão provenientes das fontes de curtose (relativos a anisotropia, dispersão na orientação, variância na difusão nos tecidos e propriedades não Gaussianas). Esta técnica baseia-se na expansão cumulativa do sinal adquirido em sequências avançadas de codificação de difusão dupla (DDE, do inglês Double Diffusion Encoding), em que ambas as codificações podem ser aplicadas em direções e magnitudes independentes (caraterizadas por vetores independentes q1 e q2). Todos os procedimentos em animais foram previamente aprovados pelas autoridades nacionais e internacionais competentes, e foram realizados de acordo com a Diretiva EU 2010/63. Murganhos macho C57BL/6J (N = 12; 26,4 ± 6,5 g) com 11 semanas foram utilizados. O modelo fototrombótico de Rose Bengal foi usado de forma a induzir um enfarte focalizado na região do cortéx de barril com uma solução de um corante fotossensível (15 mg/ml). Em animais do grupo experimental (N = 5), a solução foi administrada de forma intravenosa (10 μl/g peso do animal) e a zona cortical de interesse foi irradiada com uma fonte de luz fria durante 15 minutos. Os animais do grupo de controlo (N = 5) foram submetidos a procedimentos idênticos, à exceção da irradiação responsável pelo desencadeamento da lesão, mantendo o tempo de espera suposto. Os cérebros do grupo de AVC e do grupo de controlo foram perfundidos 3 h após o fim do período com ou sem iluminação e utilizados para aquisições ex vivo. Além disso, dois animais foram usados para examinação in vivo: um submetido à indução do AVC para validação com os resultados ex vivo, e outro animal saudável foi usado para efeitos corroborativos com estudos anteriores. Os cérebros foram examinados no scanner Aeon da Bruker de 16.4 T. As imagens por difusão ex vivo foram adquiridas com sequências de DDE com base em EPI (do inglês Echo Planar Imaging) escritas in house. Usou-se um protocolo com um total de 5 combinações q1-q2 de magnitudes diferentes (1498,0 – 0; 1059,2 – 1059,2; 1059,2 – 0; 749,0 – 749,0 e 749,0 - 0 mT/m), associando cada combinação a uma aquisição. Para combinações em que as magnitudes eram iguais entre vetores, foram usadas 135 direções paralelas e perpendiculares, resultando em 7 aquisições com valor b total de 750, 1500 ou 3000 mm/s2 . Os restantes parâmetros foram: TR/TE = 3000/49 ms, FOV = 11 × 11 mm2 , matriz = 78 × 78, resolução de voxel no plano de 141 × 141 μm2 , 25 fatias coronais com espessura de 0,5 mm, δ/Δ/τm = 1,5/10/10 ms e 2 segmentos. 20 imagens foram adquiridas sem gradientes de difusão aplicados (i.e., b = 0 mm/s2 ). Cada examinação durou aproximadamente 14 h na totalidade. No caso das aquisições in vivo, os animais foram sedados (isoflurano 2,5%) e examinados no scanner Biospec da Bruker de 9.4 T. As imagens por difusão foram adquiridas com um protocolo otimizado em comparação com o utilizado nas sequências ex vivo, diferindo nos seguintes parâmetros: as combinações q1-q2 de magnitude foram de 518,79 – 0; 366,84 – 366,84; 366,84 – 0; 259,4 – 259,4 e 259,4 - 0 mT/m. As combinações de direções foram idênticas às utilizadas nas aquisições ex vivo, resultando também em 7 aquisições com valor b total de 625, 1250 ou 1500 mm/s2 , TR/TE = 2800/44,5 ms, FOV = 12 × 12 mm2 , matriz = 78 × 78, resolução de voxel no plano de 181 × 181 μm2 , 5 fatias coronais com espessura de 0,85 mm, δ/Δ/τm = 4/10/10 ms e 1 segmento. Cada examinação durou aproximadamente 1 h e 15 min. O processamento dos dados englobou a correção do sinal ao nível do ruído, alinhamento dos dados e correção ao nível de Gibbs ringing. As métricas de difusão convencionais, tais como a difusão média, a anisotropia fracional, a difusão radial e axial (MD, FA, RD e AD, respetivamente) foram extraídas pelo tensor de difusão (D). No âmbito das fontes resolvidas pela CTI, a fonte de curtose excedente total (KT) foi obtida a partir de D e do tensor de curtose (W), as curtoses anisotrópica e isotrópica ( e ), ditas fontes intercompartimentais, foram extraídas a partir do tensor D e do tensor de correlação do deslocamento Z (de quarta ordem na expansão cumulativa), e a fonte de curtose intracompartimental () foi extraída a partir da subtração das fontes intercompartimentais à fonte KT. De forma a analisar os mapas obtidos para as métricas de curtose 3 h após enfarte ao nível de substância branca e cinzenta, regiões de interesse foram definidas (com base nos mapas de MD e FA) no hemisfério ipsilateral ou ipsilesional (relativo à lesão), e no hemisfério contralateral (não afetado), dos animais que sofreram o AVC. Regiões de interesse no grupo de controlo foram também definidas no hemisfério ipsilateral. Após associar os dados obtidos de cada hemisfério a diferentes subgrupos, foram realizadas comparações entre subgrupos para as diferentes métricas de curtose e uma análise ANOVA para testar diferenças significativas entre subgrupos, permitindo assim uma análise de especificidade de cada métrica aos efeitos do AVC. Foi ainda realizada uma análise da sensibilidade de cada métrica perante a lesão no hemisfério ipsilesional para todos os animais do grupo de AVC através da quantificação de voxeis sensíveis à lesão em cada animal, quer ao nível da lesão total, quer ao nível das substâncias branca e cinzenta. Uma breve análise histológica foi produzida para uma comparação qualitativa com os mapas das diferentes fontes de curtose e associação com degeneração e perda celular. Os resultados indicaram diferenças significativas (p < 0,05) para as métricas KT e entre o hemisfério ipsilateral do grupo de AVC e o hemisfério contralateral do mesmo grupo, bem como entre o hemisfério ipsilaterial do grupo de AVC e o hemisfério ipsilateral do grupo de controlo (em substância substância cinzenta e substância branca). Porém, a métrica de foi a que mais se destacou, visto ter mostrado sensibilidade para o AVC na substância cinzenta perante outras métricas. Os mapas de curtose in vivo mostraram-se consistentes com os mapas ex vivo. Em comparação com estudos anteriores, os resultados obtidos nas métricas de difusão (MD, FA, RD e AD) demonstraram congruência com a literatura, tendo os valores de KT seguido a tendência dos valores de curtose média (MK) obtidos noutros estudos de AVC em murganho. A menor sensibilidade para o AVC em KT, quando comparada com , por exemplo, sugere que certos efeitos de curtose se poderão anular, informação essa anteriormente desconhecida. Os nossos resultados, além de favorecerem maior sensibilidade comparativamente às métricas convencionais em contexto de AVC, acentuam também a especificidade de cada fonte de curtose perante o tecido isquémico, permitindo uma possível relação com mecanismos patofisiológicos a ocorrer na fase aguda-subaguda do AVC, tais como fenómenos citotóxicos e vasogénicos. Ao resolver as fontes de curtose em tecido isquémico, foi-nos possibilitada uma maior compreensão dos mecanismos microscópicos subjacentes, que, num formato mais sensível e específico, propicia uma caraterização de AVC inovadora e uma maior eficácia no tratamento associado.Stroke is a leading cause of long-term disability and death worldwide, with ischaemic infarct accounting for approximately 80% of all cases. Currently, novel treatments depend on a deeper understanding of the local tissue milieu following ischemia. Therefore, non-invasive neuroimaging plays a crucial role in stroke research. Diffusion MRI (dMRI) is one of the most reliable imaging techniques, mainly for the early detection of ischemic stroke via detection of microstructural changes. However, dMRI is critically unspecific, thereby hampering the conclusive characterization of infarct core, salvageable tissue and response to treatment. To overcome this drawback, Correlation Tensor Imaging (CTI) – a ground-breaking approach enhancing sensitivity and specificity towards tissue microstructure via the resolution of non-Gaussian diffusion sources – was applied for the first time towards the characterization of ischemic tissue (ex vivo and in vivo) and assessment of the mechanisms underlying dMRI contrasts in a mouse stroke model at an early stage post ischemic insult. In this study, a photothrombotic stroke model was used to induce a focal infarct in the barrel cortex and dMRI ex vivo datasets were acquired with CTI pulse sequences written in house. For corroboration of results, in vivo datasets were additionally acquired. The stroke model reproducibly induced well-delimited infarction cores in the targeted region in all animals. Our results suggest that CTI is capable of resolving microscopic features of ischemic tissue in-vivo, which until now were obfuscated or conflated in conventional dMRI measurements. Particularly, intra-compartmental kurtosis (), one of the resolved sources, shows higher sensitivity and specificity towards ischemic alterations when compared to other sources of kurtosis. These are critical first steps towards resolving the contributions of cytotoxic and vasogenic edema sources as well as potential for revealing salvageable tissue or ongoing excitotoxicity

Diffusion and perfusion magnetic resonance imaging in human ischaemic stroke analysis strategies and measurement isues in the assessment of lesion evolution

Stroke is the third most common cause of death in the developed world, and is the major cause of long term disability in the U.K. Eighty percent of strokes are ischaemic, or caused by vascular occlusion. Magnetic resonance imaging (MRI) provides stroke researchers with an invaluable tool to visualise ischaemic processes non-invasively from very early times after stroke onset. However, despite major progress, it is still unclear to what degree particular appearances on MRI relate to the underlying pathophysiological state of the ischaemic lesion, or the clinical outcome of the stroke patient.The aim of this thesis is to explore the evolution and issues affecting the analysis of ischaemic lesions on diffusion- and perfusion-weighted MRI (DWI and PWI) from acute (< 24 hours) to chronic (90 days) times after stroke onset. This thesis includes a review of previous human studies of acute DWI and PWI appearance versus final lesion outcome, a review of the 'DWI/PWI mismatch' model (thought to represent the ischaemic penumbra, or 'tissue at risk' of infarction), and a systematic review of previous animal studies of the pathophysiology associated with particular lesion appearances on DWIThe methodological problems raised by these reviews are addressed in this thesis using a large cohort of stroke patients with serial DWI and PWI. The interrater variability of manual lesion measurements on acute DWI is investigated, and factors affecting this variability are discussed. The effect of lesion oedema (swelling) on measurements of ischaemic lesions on MRI is investigated. This thesis also investigates the tissue state underlying persistent hyperintensity on late DWI, and whether this is just T₂ 'shine through', or indicates distinct features in the evolution v of the lesion. A novel grid-based analysis method is developed and employed to track serial DWI and PWI changes more effectively, and the effect of observer variability on diffusion and perfusion parameters measured by this method is assessed. Lastly, this thesis discusses the concept of using 'threshold' values to predict tissue infarction or survival

Watching the Healing Brain: Multimodal and Non-invasive Imaging of Regenerative Processes after Experimental Cerebral Ischemia

Stroke is a severe disease of the brain, which leads to cell death and loss of function. Neuroprotective therapy to prevent neuronal loss has not been effective in human stroke patients. Therefore, new therapeutic strategies are needed. Spontaneous recovery can be observed in some patients. However, the basis of this phenomenon is not completely understood yet. Several endogenous regenerative processes have been observed following cerebral ischemia, which may be the reason for functional recovery and can be used as a basis for new therapeutic strategies. Shortly after the insult, endothelial cells start to proliferate and eventually lead to revascularization of ischemic brain tissue (angiogenesis). Furthermore, resident neural progenitor cells increase their proliferative activity, migrate towards the ischemic tissue and even differentiate into new neurons (neurogenesis). Detailed knowledge about the molecular mechanisms and interactions between angiogenesis and neurogenesis in response to stroke is needed in order to reveal new therapeutic targets. This PhD thesis established novel non-invasive imaging strategies to followed post-stroke angiogenesis and neurogenesis with particular regard to their dynamic temporal profiles. Bioluminescence imaging and magnetic resonance imaging were chosen for this purpose. The vascular endothelial growth factor receptor 2 was used as a molecular marker for angiogenesis, and for the first time the molecular basis of post-stroke vascular remodelling was observed non-invasively with bioluminescence imaging in an angiogenesis-specific reporter mouse. Structural changes of the vascular system were monitored with a magnetic resonance imaging strategy. Initial pronounced decrease of vessel density in ischemic tissue was followed by vessel density normalization. Non-invasive observation of endogenous neurogenesis is limited by the small number of neural progenitor cells within the adult brain. This work established the first bioluminescence protocol optimized for highly sensitive bioluminescence imaging of neurogenesis in a neurogenesis-specific reporter mouse. For the first time, increased proliferation of neural progenitor cells after stroke was observed with bioluminescence imaging. As post-stroke angiogenesis and neurogenesis may lead to regeneration of brain function, this PhD thesis established the first functional magnetic resonance imaging protocol for the specific application in mice. First investigations of brain function after stroke were performed and future studies will have the opportunity to follow functional recovery in transgenic mouse models. All methods used in this thesis bear the exceptional potential to be combined into a multimodal approach. Screening for new therapeutic targets within the brain endogenous regenerative capacity will be possible non-invasively. Furthermore, the effect of new therapies on angiogenesis, neurogenesis or functional recovery can be quickly tested

Tracking endogenous and grafted neural progenitor cells in normal and ischaemic brains using MRI contrast agents and genetic labelling

Cerebral ischaemia is a major cause of mortality and morbidity globally. Neural stem and progenitor cells (NPC) have the potential to contribute to brain repair and regeneration after an ischaemic event. Both endogenous and grafted NPC have been shown to migrate towards the ischaemic lesion, and differentiate into neurons. This thesis investigates methods of labeling and tracking the migration neural progenitor cells to a site of cerebral ischaemic injury, using magnetic resonance imaging (MRI) contrast agents and transgenic lineage tracing techniques. First, labeling of exogenous NPC populations was investigated, for use in cell tracking in grafting studies. Cell labeling was optimized in vitro with fetal NPC using the iron oxide-based MRI contrast agent. A labeling method was developed using the FePro contrast agent, which maximized iron oxide uptake, was non-toxic to NPC, and did not interfere with NPC proliferation and differentiation. Labelled cells were then grafted into the brain after cerebral ischaemia, and imaged over four weeks using MRI. NPC migration was not observed in vivo, but an endogenous contrast evolved over time within the lesioned tissue, which presented a source of confounding signal for cell tracking. Endogenous ferric iron was observed in the lesion on histological sections. Several limitations of using MRI-based iron oxide contrast agents were highlighted in this study. To circumvent these limitations, we considered the development of gadolinium-based MRI contrast agents for cellular labeling and tracking, in collaboration with Imperial College chemistry department. Polymeric Gd-DOTA chelates were synthesized and designed for maximal r1 relaxivity, and their relaxivity and effects on cell viability were assessed. Through this approach, we identified a number of candidate polymeric Gd-DOTA chelates with high relaxivity and low cytotoxicity for use in cellular imaging and tracking studies. Next, cell tracking of endogenous NPC was investigated, using MRI contrast agent and transgenic lineage tracing approaches. A method of in situ labeling of endogenous NPC with the MRI contrast agent FePro was developed. NPC were labeled with FePro in situ, and their normal migration to the olfactory bulb, where they contribute to neurogenesis, could be imaged in vivo and ex vivo. In a second study, the migration of NPC constitutively expressing green fluorescent protein (GPF) under the promoters of genes of two developmentally distinct cortical and striatal NPC populations, was investigated following cerebral ischaemia. Both cortical and striatal populations of NPC were observed to contribute to the migrating streams of NPC that were observed in the striatum after five weeks post-ischaemia. These studies demonstrate that MRI contrast agents offer the potential for in vivo, longitudinal tracking of NPC migration, in both grafted and endogenous NPC populations. Coupled with transgenic lineage tracing, and used in animal models of CNS injury such as cerebral ischaemia, labeling and tracking the migration of NSC with MRI contrast agents can contribute to our understanding of NPC biology in pathological environments

Cerebral blood flow and glucose metabolism in ischemic stroke : multimodal imaging investigations in a clinically relevant rat model

Ischemic stroke is one of the leading causes of death worldwide. Ischemic stroke is also a major cause of long-term disability with vast socioeconomic results for patients, their relatives and health services. Over the last decades, experimental research has resulted in significant progress of our understanding of mechanisms leading to brain injury after ischemic stroke. However, so far, translational research targeting these mechanisms has failed. This failure has resulted in a general consensus that a more integrative approach is needed to account for not only neurobiology under ischemia, but also the ischemic impact on the neurovascular interface. Accordingly, new tools for simultaneously imaging and perturbing this interface needs to be established. The aims of the present work were firstly to develop an ischemic stroke model in rats that more closely mimics human stroke. Secondly, our goal was to incorporate the model with perfusion- and metabolic imaging using high-field magnetic resonance imaging (HF-MRI) and positron emission tomography (PET). Finally we wanted to apply the model in a treatment study targeting the neurovascular interface, and use HF-MRI and PET to assess treatment outcome. We translated endovascular techniques from bedside to bench in the interest of realizing a new rat model for focal cerebral ischemia, in which a microwire is navigated under X-ray fluoroscopy to an occluding position in the middle cerebral artery (MCA). Furthermore, we were able to use the endovascular technique to facilitate intra-arterial microcatheter access to the cerebrovascular system in the rat accommodating injections with varying degree of selectivity. Next, we established protocols for HF-MRI and PET to obtain imaging of pathophysiological events following acute and subacute ischemic stroke. Finally we applied the aforementioned techniques in a treatment study targeting vascular endothelial growth factor B (VEGF-B) in ischemic stroke. We found that the translation of clinical endovascular techniques to the experimental setting opened up several possibilities to access and perturb the neurovascular interface. In comparison with earlier models for focal stroke in the rat, the model for ischemic stroke presented in Paper I produces an injury and pathophysiology more resembling human stroke. Furthermore, the model showed to be highly compatible with small animal imaging systems with the possibility to occlude the MCA and to inject substances directly to the cerebrovascular supply before, during and after imaging (Paper II). The model also makes it possible to control blood flow during scanning with various modalities. HF-MRI and [2-18F]- 2-Fluoro-2-deoxy-D-glucose PET investigations of acute ischemia in Paper III provided evidence for hypermetabolism of glucose occurring in parallel with diffusion restriction of brain water, suggesting an extension of the current paradigm of the mechanisms behind infarct-related diffusion restriction of water. In Paper IV, we found that VEGF-B antagonism result in a reduction of stroke volume, indicating a mechanism of action of VEGF-B in ischemic stroke warranting further treatment studies targeting VEGF-B in ischemic stroke

Biological Implications of a Stroke Therapy Based in Neuroglobin Hyaluronate Nanoparticles. Neuroprotective Role and Molecular Bases

This research was funded by Ministerio de Economia y Competitividad, grant number BFU-2016-80316-R.Exogenous neuroprotective protein neuroglobin (Ngb) cannot cross the blood–brain barrier. To overcome this difficulty, we synthesized hyaluronate nanoparticles (NPs), able to deliver Ngb into the brain in an animal model of stroke (MCAO). These NPs effectively reached neurons, and were microscopically identified after 24 h of reperfusion. Compared to MCAO non-treated animals, those treated with Ngb-NPs showed survival rates up to 50% higher, and better neurological scores. Tissue damage improved with the treatment, but no changes in the infarct volume or in the oxidative/ nitrosative values were detected. A proteomics approach (p-value < 0.02; fold change = 0.05) in the infarcted areas showed a total of 219 proteins that significantly changed their expression after stroke and treatment with Ngb-NPs. Of special interest, are proteins such as FBXO7 and NTRK2, which were downexpressed in stroke, but overexpressed after treatment with Ngb-NPs; and ATX2L, which was overexpressed only under the effect of Ngb. Interestingly, the proteins affected by the treatment with Ngb were involved in mitochondrial function and cell death, endocytosis, protein metabolism, cytoskeletal remodeling, or synaptic function, and in regenerative processes, such as dendritogenesis, neuritogenesis, or sinaptogenesis. Consequently, our pharmaceutical preparation may open new therapeutic scopes for stroke and possibly for other neurodegenerative pathologies.Spanish Government BFU-2016-80316-

Role of magnetic resonance imaging and in vivo MR spectroscopy in clinical, experimental and biological research

Magnetic resonance imaging, a noninvasive imaging modality in clinical medicine produces soft tissue anatomical pictures in any desired plane that are exquisite representation of the spatial distribution of mobile protons present in human/animal tissues. In vivo magnetic resonance spectroscopy, on the other hand, is a useful technique for studying metabolic processes in biological systems. In the last decade, magnetic resonance imaging and in vivo spectroscopy methods have become an established tool in many areas of biomedical research for example, in understanding the physiology of several disease processes, tumor metabolism, and drug discovery process. In fact, in vivo magnetic resonance spectroscopy can be used for diagnosis of a specific disease pattern with biochemical/metabolic signature (marker), assessment of tumor response to different treatment regimens, drug concentrations in tissues, drug efficacy and metabolism. The advantage of in vivo magnetic resonance is its versatility and comprehensive characterization of normal and diseased tissues. In this article, a few examples of in vivo magnetic resonance methods and their utility in clinical, experimental and biological research are presented