Tau seeds from Alzheimer's disease brains trigger tau spread in macaques while oligomeric-Aβ mediates pathology maturation

INTRODUCTION: The “prion-like” features of Alzheimer's disease (AD) tauopathy and its relationship with amyloid-β (Aβ) have never been experimentally studied in primates phylogenetically close to humans. METHODS: We injected 17 macaques in the entorhinal cortex with nanograms of seeding-competent tau aggregates purified from AD brains or control extracts from aged-matched healthy brains, with or without intracerebroventricular co-injections of oligomeric-Aβ. RESULTS: Pathological tau injection increased cerebrospinal fluid (CSF) p-tau181 concentration after 18 months. Tau pathology spreads from the entorhinal cortex to the hippocampal trisynaptic loop and the cingulate cortex, resuming the experimental progression of Braak stage I to IV. Many AD-related molecular networks were impacted by tau seeds injections regardless of Aβ injections in proteomic analyses. However, we found mature neurofibrillary tangles, increased CSF total-tau concentration, and pre- and postsynaptic degeneration only in Aβ co-injected macaques. DISCUSSION: Oligomeric-Aβ mediates the maturation of tau pathology and its neuronal toxicity in macaques but not its initial spreading. Highlights: This study supports the “prion-like” properties of misfolded tau extracted from AD brains. This study empirically validates the Braak staging in an anthropomorphic brain. This study highlights the role of oligomeric Aβ in driving the maturation and toxicity of tau pathology. This work establishes a novel animal model of early sporadic AD that is closer to the human pathology

Pathophysiology of tauopathies and modeling in non-human primate

Mon travail de thèse s’est porté principalement sur l’étude des tauopathies. Les tauopathies sont un groupe de maladies neurodégénératives caractérisées par l’accumulation et l’agrégation de la protéine pathologique tau mal-repliée. Au sein de cette grande famille de pathologies, nous en retrouvons plusieurs qui diffèrent autant sur le plan clinique que neuropathologique avec une distribution spatio-temporelle de lésions typiques bien distinctes.Cependant, les mécanismes d’initiation et de progression des tauopathies restent encore peu compris. Des études récentes ont suggéré que le développement des tauopathies serait basé sur des caractéristiques similaires à celles des protéines Prions où un agrégat mal conformé de protéine tau aurait théoriquement la capacité de « contaminer » des protéines tau solubles non-pathologiques conduisant à la neurotoxicité. Les agrégats seraient ensuite transmis de cellules en cellules par voie trans-synaptique, expliquant de cette façon la propagation de la tauopathie dans différentes régions cérébrales connectées. Cette hypothèse « prion-like » repose uniquement sur des études in vitro et in vivo sur des rongeurs. Ces modèles expérimentaux présentent de nombreux avantages pour l’étude des tauopathies mais ne reproduisent pas entièrement la pathologie humaine. Dans un objectif d’études précliniques de ces pathologies, il semble aujourd’hui nécessaire de travailler sur des modèles expérimentaux au plus proche de l’Homme. Ainsi, dans mon projet de thèse, nous avons proposé de modéliser les tauopathies chez le macaque rhésus (Macaca mulatta), animal phylogénétiquement très proche de l’Homme.L’objectif principal a été de montrer la propagation « prion-like » de la tauopathie chez le macaque. Nous nous sommes concentrés sur deux tauopathies : la PSP et la maladie d’Alzheimer.A partir d’injections intracérébrales d’agrégats de protéines tau extraites et purifiées de patients atteints de PSP et de maladie d’Alzheimer, nous avons induit les pathologies. En effet, nous avons pu observer chez ces primates la présence de lésions typiques de ces deux tauopathies, inclusions de la protéine tau hyperphosphorylée dans les neurones et les cellules gliales pour la PSP et des lésions de DNFs et de fibres tortueuses du neuropile pour la maladie d’Alzheimer. L’observation de ces lésions autour des sites d’injections ainsi qu’au sein de structures connectées nous suggère le caractère « prion-like » de la protéine tau où la simple injection de matériel pathogénique permet la formation de nouveaux agrégats qui progressent de cellules en cellules.Mes différents projets nous ont ainsi permis d’avoir une meilleure compréhension de la physiopathologie et des mécanismes impliqués dans les troubles cognitifs et moteurs de ces deux tauopathies. De plus, développer un modèle animal proche de l’Homme ouvre la voie à de nouvelles thérapeutiques.My PhD project was dedicated to the study of tauopathies. Tauopathies are a group of neurodegenerative diseases characterized by the accumulation and aggregation of pathological misfolded tau proteins. Alzheimer's disease (AD), progressive supranuclear palsy (PSP), cortico-basal degeneration (CBD) and some frontotemporal lobar degenerations (FTLD) are part of the large family of tauopathies. These pathologies differ both clinically and anatomically, with a distinct anatomical distribution of typical lesions.However, the mechanisms of initiation and progression of tauopathies remain poorly understood for these pathologies. Recent studies have suggested that the development of tauopathies is based on “prion-like” features, where a single tau proteopathic seed would have the ability to transmit pathogenic information, to "contaminate" non-pathological soluble tau proteins leading to neurotoxicité. Tau aggregates would be transmitted from cell to cell, thus explaining the spreading of tauopathy in different connected brain regions. However, this hypothesis is based only on in vitro and vivo rodents experiments. These experimental models offer many advantages for the study of tauopathies, but they do not fully reproduce human pathologies. In order to develop relevant pre-clinical studies of these pathologies, it seems necessary today to work on experimental models as close as possible to human models.Thus, in my PhD project, we proposed to model tauopathies in rhesus macaques (Macaca mulatta), an animal phylogenetically closest to humans. We focused on two tauopathies: PSP and Alzheimer's disease.The main aim of my PhD was to demonstrate the “prion-like” propagation of these two tauopathies in non-human primates. We focused on two tauopathies : PSP and Alzheimer’s disease.Using intracerebral injections of tau proetopathic seeds extracted and purified from PSP and Alzheimer's disease patients, we induced the pathologies. Indeed, we were able to observe in these primates the presence of lesions typical of these two tauopathies, inclusions of hyperphosphorylated tau protein in neurons and glial cells for PSP, and lesions of NFTs and neuropils threads for Alzheimer's disease. The observation of these lesions around injection sites and within connected structures suggests the "prion-like" feature of tau protein, where the simple injection of pathogenic material allows the formation of new aggregates progressing from cell to cell.These various projects have enabled us to better understand the pathophysiology and mechanisms involved in the cognitive and motor disorders of these tauopathies. Furthermore, the development of an animal model close to humans pave the way to new therapies

Étude de la physiopathologie des tauopathies et modélisation chez le primate non-humain

My PhD project was dedicated to the study of tauopathies. Tauopathies are a group of neurodegenerative diseases characterized by the accumulation and aggregation of pathological misfolded tau proteins. Alzheimer's disease (AD), progressive supranuclear palsy (PSP), cortico-basal degeneration (CBD) and some frontotemporal lobar degenerations (FTLD) are part of the large family of tauopathies. These pathologies differ both clinically and anatomically, with a distinct anatomical distribution of typical lesions.However, the mechanisms of initiation and progression of tauopathies remain poorly understood for these pathologies. Recent studies have suggested that the development of tauopathies is based on “prion-like” features, where a single tau proteopathic seed would have the ability to transmit pathogenic information, to "contaminate" non-pathological soluble tau proteins leading to neurotoxicité. Tau aggregates would be transmitted from cell to cell, thus explaining the spreading of tauopathy in different connected brain regions. However, this hypothesis is based only on in vitro and vivo rodents experiments. These experimental models offer many advantages for the study of tauopathies, but they do not fully reproduce human pathologies. In order to develop relevant pre-clinical studies of these pathologies, it seems necessary today to work on experimental models as close as possible to human models.Thus, in my PhD project, we proposed to model tauopathies in rhesus macaques (Macaca mulatta), an animal phylogenetically closest to humans. We focused on two tauopathies: PSP and Alzheimer's disease.The main aim of my PhD was to demonstrate the “prion-like” propagation of these two tauopathies in non-human primates. We focused on two tauopathies : PSP and Alzheimer’s disease.Using intracerebral injections of tau proetopathic seeds extracted and purified from PSP and Alzheimer's disease patients, we induced the pathologies. Indeed, we were able to observe in these primates the presence of lesions typical of these two tauopathies, inclusions of hyperphosphorylated tau protein in neurons and glial cells for PSP, and lesions of NFTs and neuropils threads for Alzheimer's disease. The observation of these lesions around injection sites and within connected structures suggests the "prion-like" feature of tau protein, where the simple injection of pathogenic material allows the formation of new aggregates progressing from cell to cell.These various projects have enabled us to better understand the pathophysiology and mechanisms involved in the cognitive and motor disorders of these tauopathies. Furthermore, the development of an animal model close to humans pave the way to new therapies.Mon travail de thèse s’est porté principalement sur l’étude des tauopathies. Les tauopathies sont un groupe de maladies neurodégénératives caractérisées par l’accumulation et l’agrégation de la protéine pathologique tau mal-repliée. Au sein de cette grande famille de pathologies, nous en retrouvons plusieurs qui diffèrent autant sur le plan clinique que neuropathologique avec une distribution spatio-temporelle de lésions typiques bien distinctes.Cependant, les mécanismes d’initiation et de progression des tauopathies restent encore peu compris. Des études récentes ont suggéré que le développement des tauopathies serait basé sur des caractéristiques similaires à celles des protéines Prions où un agrégat mal conformé de protéine tau aurait théoriquement la capacité de « contaminer » des protéines tau solubles non-pathologiques conduisant à la neurotoxicité. Les agrégats seraient ensuite transmis de cellules en cellules par voie trans-synaptique, expliquant de cette façon la propagation de la tauopathie dans différentes régions cérébrales connectées. Cette hypothèse « prion-like » repose uniquement sur des études in vitro et in vivo sur des rongeurs. Ces modèles expérimentaux présentent de nombreux avantages pour l’étude des tauopathies mais ne reproduisent pas entièrement la pathologie humaine. Dans un objectif d’études précliniques de ces pathologies, il semble aujourd’hui nécessaire de travailler sur des modèles expérimentaux au plus proche de l’Homme. Ainsi, dans mon projet de thèse, nous avons proposé de modéliser les tauopathies chez le macaque rhésus (Macaca mulatta), animal phylogénétiquement très proche de l’Homme.L’objectif principal a été de montrer la propagation « prion-like » de la tauopathie chez le macaque. Nous nous sommes concentrés sur deux tauopathies : la PSP et la maladie d’Alzheimer.A partir d’injections intracérébrales d’agrégats de protéines tau extraites et purifiées de patients atteints de PSP et de maladie d’Alzheimer, nous avons induit les pathologies. En effet, nous avons pu observer chez ces primates la présence de lésions typiques de ces deux tauopathies, inclusions de la protéine tau hyperphosphorylée dans les neurones et les cellules gliales pour la PSP et des lésions de DNFs et de fibres tortueuses du neuropile pour la maladie d’Alzheimer. L’observation de ces lésions autour des sites d’injections ainsi qu’au sein de structures connectées nous suggère le caractère « prion-like » de la protéine tau où la simple injection de matériel pathogénique permet la formation de nouveaux agrégats qui progressent de cellules en cellules.Mes différents projets nous ont ainsi permis d’avoir une meilleure compréhension de la physiopathologie et des mécanismes impliqués dans les troubles cognitifs et moteurs de ces deux tauopathies. De plus, développer un modèle animal proche de l’Homme ouvre la voie à de nouvelles thérapeutiques

J Parkinsons Dis

Evidence shows that altered retinoic acid signaling may contribute to the pathogenesis and pathophysiology of Parkinson's disease (PD). Retinoic acid is the bioactive derivative of the lipophilic vitamin A. Vitamin A is involved in several important homeostatic processes, such as cell differentiation, antioxidant activity, inflammation and neuronal plasticity. The role of vitamin A and its derivatives in the pathogenesis and pathophysiology of neurodegenerative diseases, and their potential as therapeutics, has drawn attention for more than 10 years. However, the literature sits in disparate fields. Vitamin A could act at the crossroad of multiple environmental and genetic factors of PD. The purpose of this review is to outline what is known about the role of vitamin A metabolism in the pathogenesis and pathophysiology of PD. We examine key biological systems and mechanisms that are under the control of vitamin A and its derivatives, which are (or could be) exploited for therapeutic potential in PD: the survival of dopaminergic neurons, oxidative stress, neuroinflammation, circadian rhythms, homeostasis of the enteric nervous system, and hormonal systems. We focus on the pivotal role of ALDH1A1, an enzyme expressed by dopaminergic neurons for the detoxification of these neurons, which is under the control of retinoic acid. By providing an integrated summary, this review will guide future studies on the potential role of vitamin A in the management of symptoms, health and wellbeing for PD patients

Preventive Vitamin A Supplementation Improves Striatal Function in 6-Hydroxydopamine Hemiparkinsonian Rats

International audienceBackgroundThe mechanisms leading to a loss of dopaminergic (DA) neurons from the substantia nigra pars compacta (SNc) in Parkinson's disease (PD) have multifactorial origins. In this context, nutrition is currently investigated as a modifiable environmental factor for the prevention of PD. In particular, initial studies revealed the deleterious consequences of vitamin A signaling failure on dopamine-related motor behaviors. However, the potential of vitamin A supplementation itself to prevent neurodegeneration has not been established yet.Objective: The hypothesis tested in this study is that preventive vitamin A supplementation can protect DA neurons in a rat model of PD.Methods: The impact of a 5-week preventive supplementation with vitamin A (20 IU/g of diet) was measured on motor and neurobiological alterations induced by 6-hydroxydopamine (6-OHDA) unilateral injections in the striatum of rats. Rotarod, step test and cylinder tests were performed up to 3 weeks after the lesion. Post-mortem analyses (retinol and monoamines dosages, western blots, immunofluorescence) were performed to investigate neurobiological processes.Results: Vitamin A supplementation improved voluntary movements in the cylinder test. In 6-OHDA lesioned rats, a marked decrease of dopamine levels in striatum homogenates was measured. Tyrosine hydroxylase labeling in the SNc and in the striatum was significantly decreased by 6-OHDA injection, without effect of vitamin A. By contrast, vitamin A supplementation increased striatal expression of D2 and RXR receptors in the striatum of 6-OHDA lesioned rats.Conclusions: Vitamin A supplementation partially alleviates motor alterations and improved striatal function, revealing a possible beneficial preventive approach for PD

Lack of Limbic-predominant Age-related TDP-43 Encephalopathy (LATE) neuropathological changes in aged macaques with memory impairment

International audience1Lack of Limbic-predominant Age-related TDP-43 Encephalopathy (LATE) neuropathological changes in agedmacaques with memory impairmentMorgane Darricau1,Marie-Hélène Canron1, Marion Bosc2, Marie-Laure Arotçarena1, Mégane Le Quang1,3,Benjamin Dehay1,Erwan Bezard1,2and Vincent Planche1,31. Univ. Bordeaux, CNRS, IMN, UMR 5293, F-33000Bordeaux, France. 2. Motac Neuroscience, F-33000 Bordeaux, France3. Centre Mémoire Ressources Recherches, Pôle de Neurosciences Cliniques, CHU de Bordeaux, F-33000 Bordeaux, FranceAbstractThe neuropathological changes of limbic-predominant age-related TDP-43 encephalopathy (LATE) arefrequent inthe agedpopulationand arenow recognized as a cause of memory impairment. However, it remains unknown if this proteinopathy is also present in other primate species. We thus investigated the presence and distribution of TDP-43 pathology in the hippocampus and amygdala of 7 agedmemory-impaired rhesus macaques (Macacamulatta,18 to 32years old) from two different cohorts. While present in anFTLD-TDP case used as a positive control for immunostaining, we found no TDP-43 or phosphorylated TDP-43immunoreactive neuronal cytoplasmic inclusion in the amygdala or the hippocampus of these aged animals (as well as in young and mature macaquesused as negative controls). We concluded that LATE is probablya human-specific condition, such as many other proteinopathies, and does not participate in age-related memory impairment in non-human primates

Tau seeds from patients induce progressive supranuclear palsy pathology and symptoms in primates

International audienceAbstract Progressive supranuclear palsy (PSP) is a primary tauopathy affecting both neurons and glia and is responsible for both motor and cognitive symptoms. Recently, it has been suggested that PSP tauopathy may spread in the brain from cell to cell in a “prion-like” manner. However, direct experimental evidence of this phenomenon, and its consequences on brain functions, is still lacking in primates. In this study, we first derived sarkosyl-insoluble tau fractions from post-mortem brains of PSP patients. We also isolated the same fraction from age-matched control brains. Compared to control extracts, the in vitro characterization of PSP-tau fractions demonstrated a high seeding activity in P301S-tau expressing cells, displaying after incubation abnormally phosphorylated (AT8- and AT100-positivity), misfolded, filamentous (pFTAA positive), and sarkosyl-insoluble tau. We bilaterally injected two male rhesus macaques in the supranigral area with this fraction of PSP-tau proteopathic seeds, and two other macaques with the control fraction. The quantitative analysis of kinematic features revealed that PSP-tau injected macaques exhibited symptoms suggestive of parkinsonism as early as six months after injection, remaining present until sacrifice at 18 months. Object retrieval task showed the progressive appearance of a significant dysexecutive syndrome in PSP-tau injected macaques compared to controls. We found AT8-positive staining and 4R-tau inclusions only in PSP-tau injected macaques. Characteristic pathological hallmarks of PSP, including globose and neurofibrillary tangles, tufted astrocytes, and coiled bodies, were found close to the injection sites but also in connected brain regions that are known to be affected in PSP (striatum, pallidum, thalamus). Interestingly, while glial AT8-positive lesions were the most frequent near the injection site, we found mainly neuronal inclusions in the remote brain area, consistent with a neuronal transsynaptic spreading of the disease. Our results demonstrate that PSP patient-derived tau aggregates can induce motor and behavioral impairments in non-human primates related to the prion-like seeding and spreading of typical pathological PSP lesions. This pilot study pave the way for supporting PSP-tau injected macaque as a relevant animal model to accelerate drug development targeting this rare and fatal neurodegenerative disease

FASEB J

The striatum is a brain structure involved in the control of voluntary movement. Striatum contains high amounts of retinoic acid, the active metabolite of vitamin A, as well as retinoid receptors, RARβ and RXRγ. Previous studies revealed that disruption of retinoid signaling initiated during development is deleterious for striatal physiology and related motor functions. However, the alteration of retinoid signaling, and the importance of vitamin A supply during adulthood on striatal physiology and function has never been established. In the present study, we investigated the impact of vitamin A supply on striatal function. Adult Sprague-Dawley rats were fed with three specific diets, either sub-deficient, sufficient, or enriched in vitamin A (0.4, 5, and 20 international units [IU] of retinol per g of diet, respectively) for 6 months. We first validated that vitamin A sub-deficient diet in adult rats constitutes a physiological model of retinoid signaling reduction in the striatum. We then revealed subtle alterations of fine motor skills in sub-deficient rats using a new behavioral apparatus specifically designed to test forepaw reach-and-grasp skills relying on striatal function. Finally, we showed using qPCR analysis and immunofluorescence that the striatal dopaminergic system per se was not affected by vitamin A sub-deficiency at adult age. Rather, cholinergic synthesis in the striatum and μ-opioid receptor expression in striosomes sub-territories were the most affected by vitamin A sub-deficiency starting at adulthood. Taken together these results revealed that retinoid signaling alteration at adulthood is associated with motor learning deficits together with discrete neurobiological alterations in the striatum

Impact of dietary vitamin A on striatal function in adult rats

The striatum is a brain structure involved in the control of voluntary movement. Striatum contains high amounts of retinoic acid, the active metabolite of vitamin A, as well as retinoid receptors, RARβ and RXRγ. Previous studies revealed that disruption of retinoid signaling initiated during development is deleterious for striatal physiology and related motor functions. However, the alteration of retinoid signaling, and the importance of vitamin A supply during adulthood on striatal physiology and function has never been established. In the present study, we investigated the impact of vitamin A supply on striatal function. Adult Sprague Dawley rats were fed with three specific diets, either sub-deficient, sufficient, or enriched in vitamin A (0.4, 5 and 20 international units (IU) of retinol per g of diet, respectively) for 6 months. We first validated that vitamin A sub-deficient diet in adult rats constitutes a physiological model of retinoid signaling reduction in the striatum. We then revealed subtle alterations of fine motor skills in sub-deficient rats using a new behavioral apparatus specifically designed to test forepaw reach-and-grasp skills relying on striatal function. Finally, we showed using qPCR analysis and immunofluorescence that the striatal dopaminergic system per se was not affected by vitamin A sub-deficiency at adult age. Rather, cholinergic synthesis in the striatum and μ-opioid receptor expression in striosomes sub-territories were the most affected by vitamin A sub-deficiency starting at adulthood. Taken together these results revealed that retinoid signaling alteration at adulthood is associated with Amotor learning deficits together with discrete neurobiological alterations in the striatum

Tau seeds from Alzheimer's disease brains trigger tau spread in macaques while oligomeric-Aβ mediates pathology maturation.

Publication status: PublishedFunder: European Union's Horizon 2020 research and innovation program (IMI ‐ IMPRiND)Funder: Investments for the Future Program IdEx Bordeaux GPR BRAIN‐2030Funder: Bettencourt‐Schueller FoundationFunder: UK Dementia Research Institute; doi: http://dx.doi.org/10.13039/501100017510INTRODUCTION: The "prion-like" features of Alzheimer's disease (AD) tauopathy and its relationship with amyloid-β (Aβ) have never been experimentally studied in primates phylogenetically close to humans. METHODS: We injected 17 macaques in the entorhinal cortex with nanograms of seeding-competent tau aggregates purified from AD brains or control extracts from aged-matched healthy brains, with or without intracerebroventricular co-injections of oligomeric-Aβ. RESULTS: Pathological tau injection increased cerebrospinal fluid (CSF) p-tau181 concentration after 18 months. Tau pathology spreads from the entorhinal cortex to the hippocampal trisynaptic loop and the cingulate cortex, resuming the experimental progression of Braak stage I to IV. Many AD-related molecular networks were impacted by tau seeds injections regardless of Aβ injections in proteomic analyses. However, we found mature neurofibrillary tangles, increased CSF total-tau concentration, and pre- and postsynaptic degeneration only in Aβ co-injected macaques. DISCUSSION: Oligomeric-Aβ mediates the maturation of tau pathology and its neuronal toxicity in macaques but not its initial spreading. HIGHLIGHTS: This study supports the "prion-like" properties of misfolded tau extracted from AD brains. This study empirically validates the Braak staging in an anthropomorphic brain. This study highlights the role of oligomeric Aβ in driving the maturation and toxicity of tau pathology. This work establishes a novel animal model of early sporadic AD that is closer to the human pathology