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Down syndrome (DS) is caused by trisomy of human chromosome 21 (Hsa21). The understanding of genotype-phenotype relationships, the identification of driver genes and various proofs of concept for therapeutics have benefited from mouse models. The premier model, named Ts(1716)65Dn/J (Ts65Dn), displayed phenotypes related to human DS features. It carries an additional minichromosome with the Mir155 to Zbtb21 region of mouse chromosome 16, homologous to Hsa21, encompassing around 90 genes, fused to the centromeric part of mouse chromosome 17 from Pisd-ps2/Scaf8 to Pde10a, containing 46 genes not related to Hsa21. Here, we report the investigation of a new model, Ts66Yah, generated by CRISPR/Cas9 without the genomic region unrelated to Hsa21 on the minichromosome. As expected, Ts66Yah replicated DS cognitive features. However, certain phenotypes related to increased activity, spatial learning and molecular signatures were changed, suggesting genetic interactions between the Mir155-Zbtb21 and Scaf8-Pde10a intervals. Thus, Ts66Yah mice have stronger construct and face validity than Ts65Dn mice for mimicking consequences of DS genetic overdosage. Furthermore, this study is the first to demonstrate genetic interactions between triplicated regions homologous to Hsa21 and others unrelated to Hsa21. This article has an associated First Person interview with the first author of the paper.
Assuntos
Síndrome de Down , Humanos , Camundongos , Animais , Síndrome de Down/genética , Diester Fosfórico HidrolasesRESUMO
With the aim of designing a preclinical study evaluating an intracerebral cell-based therapy for stroke, an observational study was performed in the rat suture model of ischemic stroke. Objectives were threefold: (i) to characterize neurofunctional and imaging readouts in the first weeks following transient ischemic stroke, according to lesion subtype (hypothalamic, striatal, corticostriatal); (ii) to confirm that intracerebral administration does not negatively impact these readouts; and (iii) to calculate sample sizes for a future therapeutic trial using these readouts as endpoints. Our results suggested that the most relevant endpoints were side bias (staircase test) and axial diffusivity (AD) (diffusion tensor imaging). Hypothalamic-only lesions did not affect those parameters, which were close to normal. Side bias in striatal lesions reached near-normal levels within 2 weeks, while rats with corticostriatal lesions remained impaired until week 14. AD values were decreased at 4 days and increased at 5 weeks post-surgery, with a subtype gradient: hypothalamic < striatal < corticostriatal. Intracerebral administration did not impact these readouts. After sample size calculation (18-147 rats per group according to the endpoint considered), we conclude that a therapeutic trial based on both readouts would be feasible only in the framework of a multicenter trial.
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AVC Isquêmico , Acidente Vascular Cerebral , Animais , Terapia Baseada em Transplante de Células e Tecidos , Imagem de Difusão por Ressonância Magnética , Imagem de Tensor de Difusão , Ratos , Acidente Vascular Cerebral/diagnóstico por imagem , Acidente Vascular Cerebral/patologia , Acidente Vascular Cerebral/terapiaRESUMO
Lyme borreliosis is the most prevalent vector-borne disease in northern hemisphere. Borrelia burgdorferi sensu lato spirochetes are transmitted by Ixodes species ticks. During a blood meal, these spirochetes are inoculated into the skin where they multiply and often spread to various target organs: disseminated skin sites, the central nervous system, the heart and large joints. The usual diagnosis of this disease relies on serological tests. However, in patients presenting persistent clinical manifestations, this indirect diagnosis is not capable of detecting an active infection. If the serological tests are positive, it only proves that exposure of an individual to Lyme spirochetes had occurred. Although culture and quantitative PCR detect active infection, currently used tests are not sensitive enough for wide-ranging applications. Animal models have shown that B. burgdorferi persists in the skin. We present here our targeted proteomics results using infected mouse skin biopsies that facilitate detection of this pathogen. We have employed several novel approaches in this study. First, the effect of lidocaine, a local anesthetic used for human skin biopsy, on B. burgdorferi presence was measured. We further determined the impact of topical corticosteroids to reactivate Borrelia locally in the skin. This local immunosuppressive compound helps follow-up detection of spirochetes by proteomic analysis of Borrelia present in the skin. This approach could be developed as a novel diagnostic test for active Lyme borreliosis in patients presenting disseminated persistent infection. Although our results using topical corticosteroids in mice are highly promising for recovery of spirochetes, further optimization will be needed to translate this strategy for diagnosis of Lyme disease in patients.
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Corticosteroides/uso terapêutico , Grupo Borrelia Burgdorferi/efeitos dos fármacos , Lidocaína/uso terapêutico , Doença de Lyme/tratamento farmacológico , Pele/microbiologia , Corticosteroides/administração & dosagem , Animais , Borrelia burgdorferi , Lidocaína/administração & dosagem , Camundongos , Pele/efeitos dos fármacosRESUMO
Rationale: The role of Monosodium Urate (MSU) crystals in gout pathophysiology is well described, as is the major impact of IL-1ß in the inflammatory reaction that constitutes the hallmark of the disease. However, despite the discovery of the NLRP3 inflammasome and its role as a Pattern Recognition Receptor linking the detection of a danger signal (MSU) to IL-1ß secretion in vitro, the precise mechanisms leading to joint inflammation in gout patients are still poorly understood. Methods: Acute urate crystal inflammation was obtained by subcutaneous injections of MSU crystals in mice. Symptoms were followed by scoring, cytokine quantification by ELISA and western blot, gene expression by RT-qPCR and RNAseq; Magnetic Resonance Imaging was also used to assess inflammation. Results: We provide an extensive clinical, biological and molecular characterization of an acute uratic inflammation mouse model which accurately mimics human gout. We report the efficacy of topical imiquimod treatment and its impact on Interferon-dependent down modulation of Il-1ß gene expression in this experimental model. Conclusion: Our work reveals several key features of MSU-dependent inflammation and identifies novel therapeutic opportunities for gout patients.
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Gota/tratamento farmacológico , Imiquimode/farmacologia , Inflamação/induzido quimicamente , Interleucina-1beta/efeitos dos fármacos , Ácido Úrico/efeitos adversos , Doença Aguda , Adjuvantes Imunológicos/administração & dosagem , Adjuvantes Imunológicos/farmacologia , Adjuvantes Imunológicos/uso terapêutico , Administração Tópica , Animais , Antioxidantes/administração & dosagem , Antioxidantes/efeitos adversos , Citocinas/metabolismo , Modelos Animais de Doenças , Gota/metabolismo , Gota/patologia , Imiquimode/administração & dosagem , Imiquimode/uso terapêutico , Inflamação/diagnóstico , Inflamação/imunologia , Injeções Subcutâneas , Imageamento por Ressonância Magnética/métodos , Camundongos , Camundongos Knockout , Ácido Úrico/administração & dosagemRESUMO
Rheumatoid arthritis (RA) is an autoimmune disease affecting 1% of the world population and is characterized by chronic inflammation of the joints sometimes accompanied by extra-articular manifestations. K/BxN mice, originally described in 1996 as a model of polyarthritis, exhibit knee joint alterations. The aim of this study was to describe temporomandibular joint (TMJ) inflammation and damage in these mice. We used relevant imaging modalities, such as micro-magnetic resonance imaging (µMRI) and micro-computed tomography (µCT), as well as histology and immunofluorescence techniques to detect TMJ alterations in this mouse model. Histology and immunofluorescence for Col-I, Col-II, and aggrecan showed cartilage damage in the TMJ of K/BxN animals, which was also evidenced by µCT but was less pronounced than that seen in the knee joints. µMRI observations suggested an increased volume of the upper articular cavity, an indicator of an inflammatory process. Fibroblast-like synoviocytes (FLSs) isolated from the TMJ of K/BxN mice secreted inflammatory cytokines (IL-6 and IL-1ß) and expressed degradative mediators such as matrix metalloproteinases (MMPs). K/BxN mice represent an attractive model for describing and investigating spontaneous damage to the TMJ, a painful disorder in humans with an etiology that is still poorly understood.
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Artrite Experimental/patologia , Artrite Reumatoide/patologia , Osso e Ossos/diagnóstico por imagem , Articulação Temporomandibular/diagnóstico por imagem , Articulação Temporomandibular/lesões , Microtomografia por Raio-X/métodos , Animais , Artrite Experimental/imunologia , Artrite Reumatoide/imunologia , Osso e Ossos/metabolismo , Osso e Ossos/patologia , Modelos Animais de Doenças , Humanos , Imageamento por Ressonância Magnética , Metaloproteinase 8 da Matriz/imunologia , Camundongos , Camundongos Transgênicos , Articulação Temporomandibular/metabolismo , Tomografia Computadorizada por Raios XRESUMO
Current treatments in multiple sclerosis (MS) are modulating the inflammatory component of the disease, but no drugs are currently available to repair lesions. Our study identifies in MS patients the overexpression of Plexin-A1, the signalling receptor of the oligodendrocyte inhibitor Semaphorin 3A. Using a novel type of peptidic antagonist, we showed the possibility to counteract the Sema3A inhibitory effect on oligodendrocyte migration and differentiation in vitro when antagonizing Plexin-A1. The use of this compound in vivo demonstrated a myelin protective effect as shown with DTI-MRI and confirmed at the histological level in the mouse cuprizone model of induced demyelination/remyelination. This effect correlated with locomotor performances fully preserved in chronically treated animals. The administration of the peptide also showed protective effects, leading to a reduced severity of demyelination in the context of experimental autoimmune encephalitis (EAE). Hence, the disruption of the inhibitory microenvironmental molecular barriers allows normal myelinating cells to exert their spontaneous remyelinating capacity. This opens unprecedented therapeutic opportunity for patients suffering a disease for which no curative options are yet available.
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Esclerose Múltipla/fisiopatologia , Proteínas do Tecido Nervoso/metabolismo , Oligodendroglia/fisiologia , Receptores de Superfície Celular/metabolismo , Remielinização , Semaforina-3A/metabolismo , Transdução de Sinais , Animais , Encéfalo/diagnóstico por imagem , Linhagem Celular , Movimento Celular , Proliferação de Células , Modelos Animais de Doenças , Imageamento por Ressonância Magnética , Camundongos Endogâmicos C57BL , Proteínas do Tecido Nervoso/antagonistas & inibidores , Receptores de Superfície Celular/antagonistas & inibidoresRESUMO
It took decades to arrive at the general consensus dismissing the notion that the immune system is independent of the central nervous system. In the case of uncontrolled systemic inflammation, the relationship between the two systems is thrown off balance and results in cognitive and emotional impairment. It is specifically true for autoimmune pathologies where the central nervous system is affected as a result of systemic inflammation. Along with boosting circulating cytokine levels, systemic inflammation can lead to aberrant brain-resident immune cell activation, leakage of the bloodâ»brain barrier, and the production of circulating antibodies that cross-react with brain antigens. One of the most disabling autoimmune pathologies known to have an effect on the central nervous system secondary to the systemic disease is systemic lupus erythematosus. Its neuropsychiatric expression has been extensively studied in lupus-like disease murine models that develop an autoimmunity-associated behavioral syndrome. These models are very useful for studying how the peripheral immune system and systemic inflammation can influence brain functions. In this review, we summarize the experimental data reported on murine models developing autoimmune diseases and systemic inflammation, and we explore the underlying mechanisms explaining how systemic inflammation can result in behavioral deficits, with a special focus on in vivo neuroimaging techniques.
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Inflamação/imunologia , Inflamação/metabolismo , Animais , Barreira Hematoencefálica/metabolismo , Humanos , Lúpus Eritematoso Sistêmico/imunologia , Lúpus Eritematoso Sistêmico/metabolismo , Vasculite Associada ao Lúpus do Sistema Nervoso Central/imunologia , Vasculite Associada ao Lúpus do Sistema Nervoso Central/metabolismo , Imageamento por Ressonância MagnéticaRESUMO
The family of WD40-repeat (WDR) proteins is one of the largest in eukaryotes, but little is known about their function in brain development. Among 26 WDR genes assessed, we found 7 displaying a major impact in neuronal morphology when inactivated in mice. Remarkably, all seven genes showed corpus callosum defects, including thicker (Atg16l1, Coro1c, Dmxl2, and Herc1), thinner (Kif21b and Wdr89), or absent corpus callosum (Wdr47), revealing a common role for WDR genes in brain connectivity. We focused on the poorly studied WDR47 protein sharing structural homology with LIS1, which causes lissencephaly. In a dosage-dependent manner, mice lacking Wdr47 showed lethality, extensive fiber defects, microcephaly, thinner cortices, and sensory motor gating abnormalities. We showed that WDR47 shares functional characteristics with LIS1 and participates in key microtubule-mediated processes, including neural stem cell proliferation, radial migration, and growth cone dynamics. In absence of WDR47, the exhaustion of late cortical progenitors and the consequent decrease of neurogenesis together with the impaired survival of late-born neurons are likely yielding to the worsening of the microcephaly phenotype postnatally. Interestingly, the WDR47-specific C-terminal to LisH (CTLH) domain was associated with functions in autophagy described in mammals. Silencing WDR47 in hypothalamic GT1-7 neuronal cells and yeast models independently recapitulated these findings, showing conserved mechanisms. Finally, our data identified superior cervical ganglion-10 (SCG10) as an interacting partner of WDR47. Taken together, these results provide a starting point for studying the implications of WDR proteins in neuronal regulation of microtubules and autophagy.
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Autofagia/fisiologia , Encéfalo/crescimento & desenvolvimento , Encéfalo/metabolismo , Proteínas dos Microfilamentos/metabolismo , Proteínas Associadas aos Microtúbulos/metabolismo , Repetições WD40/fisiologia , Animais , Movimento Celular/fisiologia , Proliferação de Células/fisiologia , Células Cultivadas , Feminino , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Microtúbulos/metabolismo , Microtúbulos/fisiologia , Neurogênese/fisiologia , Neurônios/metabolismo , Neurônios/fisiologia , Fenótipo , Células-Tronco/metabolismo , Células-Tronco/fisiologiaRESUMO
Today, molecular imaging of neurodegenerative diseases is mainly based on small molecule probes. Alternatively, antibodies are versatile tools that may be developed as new imaging agents. Indeed, they can be readily obtained to specifically target any antigen of interest and their scaffold can be functionalized. One of the critical issues involved in translating antibody-based probes to the clinic is the design and synthesis of perfectly-defined conjugates. Camelid single-domain antibody-fragments (VHHs) are very small and stable antibodies that are able to diffuse in tissues and potentially cross the blood brain barrier (BBB). Here, we selected a VHH (R3VQ) specifically targeting one of the main lesions of Alzheimer's disease (AD), namely the amyloid-beta (Aß) deposits. It was used as a scaffold for the design of imaging probes for magnetic resonance imaging (MRI) and labeled with the contrastophore gadolinium using either a random or site-specific approach. In contrast to the random strategy, the site-specific conjugation to a single reduced cysteine in the C-terminal part of the R3VQ generates a well-defined bioconjugate in a high yield process. This new imaging probe is able to cross the BBB and label Aß deposits after intravenous injection. Also, it displays improved r1 and r2 relaxivities, up to 30 times higher than a widely used clinical contrast agent, and it allows MRI detection of amyloid deposits in post mortem brain tissue of a mouse model of AD. The ability to produce chemically-defined VHH conjugates that cross the BBB opens the way for future development of tailored imaging probes targeting intracerebral antigens.
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Transgenic and gene knockout rodent models are primordial to study pathophysiological processes in cardiovascular research. Over time, cardiac MRI has become a gold standard for in vivo evaluation of such models. Technical advances have led to the development of magnets with increasingly high field strength, allowing specific investigation of cardiac anatomy, global and regional function, viability, perfusion or vascular parameters. The aim of this report is to provide a review of the various sequences and techniques available to image mice on 7-11.7 T magnets and relevant to the clinical setting in humans. Specific technical aspects due to the rise of the magnetic field are also discussed.
Assuntos
Doenças Cardiovasculares/diagnóstico por imagem , Coração/diagnóstico por imagem , Imageamento por Ressonância Magnética/métodos , Animais , Modelos Animais de Doenças , Humanos , CamundongosRESUMO
A molecular theranostic agent for magnetic resonance imaging (MRI) and photodynamic therapy (PDT) consisting of four [GdDTTA](-) complexes (DTTA(4-) = diethylenetriamine-N,N,Nâ³,Nâ³-tetraacetate) linked to a meso-tetraphenylporphyrin core, as well as its yttrium(III) analogue, was synthesized. A variety of physicochemical methods were used to characterize the gadolinium(III) conjugate 1 both as an MRI contrast agent and as a photosensitizer. The proton relaxivity measured in H2O at 20 MHz and 25 °C, r1 = 43.7 mmol(-1) s(-1) per gadolinium center, is the highest reported for a bishydrated gadolinium(III)-based contrast agent of medium size and can be related to the rigidity of the molecule. The complex displays also a remarkable singlet oxygen quantum yield of ÏΔ = 0.45 in H2O, similar to that of a meso-tetrasulfonated porphyrin. We also evidenced the ability of the gadolinium(III) conjugate to penetrate in cancer cells with low cytotoxicity. Its phototoxicity on Hela cells was evaluated following incubation at low micromolar concentration and moderate light irradiation (21 J cm(-2)) induced 50% of cell death. Altogether, these results demonstrate the high potential of this conjugate as a theranostic agent for MRI and PDT.
Assuntos
Complexos de Coordenação/farmacologia , Gadolínio/química , Fármacos Fotossensibilizantes/farmacologia , Porfirinas/farmacologia , Nanomedicina Teranóstica , Morte Celular/efeitos dos fármacos , Complexos de Coordenação/síntese química , Complexos de Coordenação/toxicidade , Células HeLa , Humanos , Luz , Lisossomos/metabolismo , Imageamento por Ressonância Magnética , Fármacos Fotossensibilizantes/síntese química , Fármacos Fotossensibilizantes/toxicidade , Porfirinas/síntese química , Porfirinas/efeitos da radiação , Porfirinas/toxicidade , Espectroscopia de Prótons por Ressonância Magnética , Solubilidade , Água/química , Ítrio/químicaRESUMO
In recent clinical studies, vascular disrupting agents (VDAs) are mainly used in combination with chemotherapy. However, an often overlooked concern in treatment combination is the VDA-induced impairment of chemotherapy distribution in the tumor. The work presented here investigated the impact of blood flow shutdown induced by Combretastatin A4 (CA4) on gemcitabine uptake into mouse hepatocarcinoma. At 2 h after CA4 treatment, using DCE-MRI, a significant decrease in the perfusion-relevant parameters Ktrans and Vp were observed in treated group compared with the control group. The blood flow shutdown was indeed confirmed by a histology study. In a third experiment, the total gemcitabine uptake was found to be significantly lower in treated tumors, as assessed in a separate experiment using ex vivo fluorine nuclear magnetic resonance spectroscopy. The amount of active metabolite gemcitabine triphosphate was also lower in treated tumors. In conclusion, the blood flow shutdown induced by VDAs can impact negatively on the delivery of small cytotoxic agents in tumors. The present study outlines the importance of monitoring the tumor vascular function when designing drug combinations.
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STUDY QUESTION: Does the endometrial functionalis have the potential to undergo self-renewal after menstruation and how is this process controlled by ovarian steroids? SUMMARY ANSWER: Endometrial xenografts subjected to withdrawal of estradiol and progesterone shrink but also show signs of proliferation and tissue repair; new estradiol supply prevents atrophy but is not sufficient to increase graft volume. WHAT IS KNOWN ALREADY: Menstruation, i.e. cyclic proteolysis of the extracellular matrix of endometrial functionalis, is induced by a fall in estrogen and progesterone concentration and is followed by tissue regeneration. However, there is debate about whether regenerating cells must originate from the basalis or from stem cells and whether new estrogen supply is required for the early repair concomitant with menstruation. STUDY DESIGN, SIZE, DURATION: Fragments from human endometrial functionalis (from 24 hysterectomy specimens) were xenografted in ovariectomized SCID mice and submitted to a 4-day estradiol and progesterone withdrawal (to mimic menstruation) followed by re-exposure to estradiol (to mimic the proliferative phase). We measured signs of proliferation and changes in graft volume. PARTICIPANTS/MATERIALS, SETTING, METHODS: Endometrium was collected from spontaneously cycling women. Cell proliferation was examined by immunolabeling Ki-67, cyclin D1 and phosphorylated-histone H3. Xenograft volume was measured by magnetic resonance imaging. Xenograft histomorphometry was performed to determine how the different tissue compartments contributed to volume change. MAIN RESULTS AND THE ROLE OF CHANCE: Hormone withdrawal induced a rapid decrease in graft volume mainly attributable to stroma condensation and breakdown, concomitant with an increase of proliferation markers. Reinsertion of estradiol pellets after induced menstruation blocked volume decrease and stimulated epithelial and stromal growth, but, surprisingly, did not induce graft enlargement. Reinsertion of both estradiol and progesterone pellets blocked apoptosis. LIMITATIONS, REASONS FOR CAUTION: Mechanisms of endometrial remodeling are different in women and mice and the contribution of circulating inflammatory cells in both species remains to be clarified. Moreover, during human menstruation, endometrial fragments resulting from tissue proteolysis can be expelled by the menstrual flow, unlike in this model. WIDER IMPLICATIONS OF THE FINDINGS: Menstruation is a multifocal event within the functionalis. This is the first evidence that endometrial fragments that are not shed after menstrual tissue breakdown can support endometrial regeneration. Endometriosis is commonly thought to result from the retrograde migration of menstrual fragments of the degraded functionalis into the peritoneal cavity. Our study supports their potential to regenerate as ectopic endometrium. STUDY FUNDING/COMPETING INTERESTS: This work was supported by the Fonds de la Recherche Scientifique Médicale, Concerted Research Actions, Communauté Française de Belgique, Région wallonne, Région bruxelloise and Loterie nationale. P.H. and B.F.J. are research associates of the Belgian Fonds de la Recherche Scientifique (F.R.S.-F.N.R.S.). E.M. is Associate Editor at Human Reproduction. There is no conflict of interest to declare.
Assuntos
Endométrio/fisiologia , Endométrio/transplante , Ovário/metabolismo , Esteroides/química , Animais , Apoptose , Proliferação de Células , Ciclina D1/metabolismo , Endometriose/metabolismo , Estradiol/metabolismo , Receptor alfa de Estrogênio/metabolismo , Feminino , Xenoenxertos/metabolismo , Humanos , Histerectomia , Antígeno Ki-67/metabolismo , Imageamento por Ressonância Magnética , Camundongos , Camundongos SCID , Pós-Menopausa , Progesterona/metabolismo , Regeneração , Transplante HeterólogoRESUMO
Our aims were to assess the spatiotemporal development of brain pathology in a mouse model of chronic hypoperfusion using magnetic resonance imaging (MRI), and to test whether the renin-angiotensin system (RAS) can offer therapeutic benefit. For the first time, different patterns of cerebral blood flow alterations were observed in hypoperfused mice that ranged from an immediate and dramatic to a delayed decrease in cerebral perfusion. Diffusion tensor imaging revealed increases in several quantitative parameters in different brain regions that are indicative of white-matter degeneration; this began around 3 weeks after induction of hypoperfusion. While this model may be more variable than previously reported, neuroimaging tools represent a promising way to identify surrogate markers of pathology. Vascular remodelling was observed in hypoperfused mice, particularly in the anterior part of the Circle of Willis. While the angiotensin II receptor type 2 agonist, Compound 21 (C21), did not influence this response, it did promote expansion of the basilar artery in microcoil animals. Furthermore, C21-treated animals exhibited increased brain lymphocyte infiltration, and importantly, C21 had opposing effects on spatial reference memory in hypoperfused and sham mice. These results suggest that the RAS may have a role in vascular cognitive impairment.
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Encéfalo/patologia , Circulação Cerebrovascular/fisiologia , Demência Vascular/patologia , Receptor Tipo 2 de Angiotensina/metabolismo , Bloqueadores do Receptor Tipo 2 de Angiotensina II/farmacologia , Animais , Encéfalo/efeitos dos fármacos , Encéfalo/metabolismo , Circulação Cerebrovascular/efeitos dos fármacos , Demência Vascular/metabolismo , Modelos Animais de Doenças , Citometria de Fluxo , Processamento de Imagem Assistida por Computador , Imageamento por Ressonância Magnética , Masculino , Camundongos , Camundongos Endogâmicos C57BLRESUMO
Multifunctional nanoparticles combining therapy and imaging have the potential to improve cancer treatment by allowing personalized therapy. Herein, we aimed to compare in vivo different strategies in terms of targeting capabilities: (1) passive targeting via the EPR effect, (2) active targeting of αvß3 integrin via RGD grafting, (3) magnetic targeting via a magnet placed on the tumor and (4) the combination of magnetic targeting and active targeting of αvß3 integrin. For a translational approach, PLGA-based nanoparticles loaded with paclitaxel and superparamagnetic iron oxides were used. Electron Spin Resonance spectroscopy and Magnetic Resonance Imaging (MRI) were used to both quantify and visualize the accumulation of multifunctional nanoparticles into the tumors. We demonstrate that compared to untargeted or single targeted nanoparticles, the combination of both active strategy and magnetic targeting drastically enhanced (i) nanoparticle accumulation into the tumor tissue with an 8-fold increase compared to passive targeting (1.12% and 0.135% of the injected dose, respectively), (ii) contrast in MRI (imaging purpose) and (iii) anti-cancer efficacy with a median survival time of 22 days compared to 13 for the passive targeting (therapeutic purpose). Double targeting of nanoparticles to tumors by different mechanisms could be a promising translational approach for the management of therapeutic treatment and personalized therapy.
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Antineoplásicos Fitogênicos/administração & dosagem , Antineoplásicos Fitogênicos/farmacocinética , Sistemas de Liberação de Medicamentos/métodos , Compostos Férricos/química , Magnetismo , Neoplasias/tratamento farmacológico , Neoplasias/metabolismo , Paclitaxel/administração & dosagem , Paclitaxel/farmacocinética , Animais , Antineoplásicos Fitogênicos/farmacologia , Ácido Láctico , Imageamento por Ressonância Magnética , Nanopartículas Metálicas , Camundongos , Camundongos Endogâmicos BALB C , Paclitaxel/farmacologia , Tamanho da Partícula , Ácido Poliglicólico , Copolímero de Ácido Poliláctico e Ácido Poliglicólico , Distribuição Tecidual , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
Longitudinal studies on brain pathology and assessment of therapeutic strategies rely on a fully mature adult brain to exclude confounds of cerebral developmental changes. Thus, knowledge about onset of adulthood is indispensable for discrimination of developmental phase and adulthood. We have performed a high-resolution longitudinal MRI study at 11.7T of male Wistar rats between 21days and six months of age, characterizing cerebral volume changes and tissue-specific myelination as a function of age. Cortical thickness reaches final value at 1month, while volume increases of cortex, striatum and whole brain end only after two months. Myelin accretion is pronounced until the end of the third postnatal month. After this time, continuing myelination increases in cortex are still seen on histological analysis but are no longer reliably detectable with diffusion-weighted MRI due to parallel tissue restructuring processes. In conclusion, cerebral development continues over the first three months of age. This is of relevance for future studies on brain disease models which should not start before the end of month 3 to exclude serious confounds of continuing tissue development.
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Envelhecimento/patologia , Córtex Cerebral/anatomia & histologia , Corpo Estriado/anatomia & histologia , Fibras Nervosas Mielinizadas/ultraestrutura , Envelhecimento/fisiologia , Animais , Córtex Cerebral/fisiologia , Corpo Estriado/fisiologia , Imagem de Tensor de Difusão , Masculino , Fibras Nervosas Mielinizadas/fisiologia , Tamanho do Órgão , Ratos , Ratos WistarRESUMO
Functional connectivity networks derived from resting-state functional MRI (rsfMRI) have received increasing interest to further our understanding of brain function. The anesthesia in rodent models may influence the interpretation and comparison of results from functional connectivity MRI (fcMRI). More research is required on this aspect. In this study, we investigated rat brain connectivity networks under 1.5% isoflurane anesthesia in comparison with medetomidine sedation. rsfMRI data were acquired under both anesthesia conditions within one imaging session. Male Wistar rats (n = 17) were scanned at 11.7 T with focus on the sensorimotor system. The data underwent a per-subject independent component analysis (ICA), after which individual components were grouped using hierarchical clustering. Consistent and reliable networks were identified under medetomidine in sensorimotor cortex (three networks) and striatum (two networks). The incidence of these networks was drastically reduced under isoflurane. Seed correlation analysis confirmed these results and revealed globally elevated correlations with low topical specificity under isoflurane, stemming from low-frequency global signal fluctuations. Global signal removal thus enhanced slightly regional specificity under isoflurane and showed anti-correlations of cortico-striatal connections in both anesthesia regimes. Functional connectivity networks are thus reliably detected in medetomidine-sedated animals on an individual basis using ICA. Their occurrence, however, is heavily compromised under isoflurane as a result of global signal fluctuations potentially stemming from burst-suppression-like neural activity. Anesthesia and pharmacologically induced modulations may provide insight into network mechanisms in the future. As an agent for fcMRI in brain disease studies, light sedation using medetomidine preserves connectivity networks in a greater level of detail, and may therefore be considered superior to standard isoflurane anesthesia.
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Anestesia Geral , Encéfalo/fisiologia , Sedação Consciente , Imageamento por Ressonância Magnética/métodos , Rede Nervosa/fisiologia , Animais , Mapeamento Encefálico , Córtex Cerebral/fisiologia , Corpo Estriado/fisiologia , Isoflurano/farmacologia , Masculino , Medetomidina/farmacologia , Ratos , Ratos Wistar , Reprodutibilidade dos TestesRESUMO
After stroke, the brain has shown to be able to achieve spontaneous functional recovery despite severe cerebral damage. This phenomenon is poorly understood. To address this issue, focal transient ischemia was induced by 60 min middle cerebral artery occlusion in Wistar rats. The evolution of stroke was followed using two magnetic resonance imaging modalities: diffusion spectrum imaging (acquired before, one and four weeks after stroke) and functional magnetic resonance imaging (acquired before and five weeks after stroke). To confirm the imaging observations, immunohistochemical staining for myelin, astrocytes and macrophages/microglia was added. At four weeks after stroke, a focal alteration of the diffusion anisotropy was observed between the ipsilesional ventricle and the lesion area. Using tractography this perturbation was identified as reorganization of the ipsilesional internal capsule. Functional imaging at five weeks after ischemia demonstrated activation of the primary sensorimotor cortex in both hemispheres in all rats except one animal lacking a functional response in the ipsilesional cortex. Furthermore, fiber tracking showed a transhemispheric fiber connection through the corpus callosum, which-in the rat without functional recovery-was lost. Our study shows the influence of the internal capsule reorganization, combined with inter-hemispheric connections though the corpus callosum, on the functional activation of the brain from stroke. In conclusion, tractography opens a new door to non-invasively investigate the structural correlates of lack of functional recovery after stroke.
Assuntos
Córtex Motor/fisiopatologia , Animais , Isquemia Encefálica/patologia , Isquemia Encefálica/fisiopatologia , Imageamento por Ressonância Magnética , Masculino , Córtex Motor/patologia , Ratos , Ratos WistarRESUMO
Fiber tracking in combination with functional MRI has recently attracted strong interest, as it may help to elucidate the structural basis for functional connectivities and may be selective in the determination of the fiber bundles responsible for a particular circuit. Diffusion spectrum imaging provides a more complex analysis of fiber circuits than the commonly used diffusion tensor imaging approach, also allowing the discrimination of crossing fibers in the brain. For the understanding of pathophysiological alterations during brain lesion and recovery, such studies need to be extended to small-animal models. In this article, we present the first study combining functional MRI with high-resolution diffusion spectrum imaging in vivo. We have chosen the well-characterized electrical forepaw stimulation paradigm in the rat to examine the thalamo-cortical pathway. Using the functionally activated areas in both thalamus and somatosensory cortex as seed and target regions for fiber tracking, we are able to characterize the fibers responsible for this stimulation pathway. Moreover, we show that the selection of the thalamic nucleus and primary somatosensory cortex on the basis of anatomical description results in a larger fiber bundle, probably encompassing connectivities between the thalamus and other areas of the somatosensory cortex, such as the hindpaw and large barrel field cortex.