O papel do fator de transcrição AP2γ na modulação da neurogénese glutamatérgica adulta em depressão

Dissertação de mestrado em Ciências da SaúdeMajor depressive disorder (MDD) is a multidimensional psychiatric disease, considered by the World Health Organization as one of the leading causes of disability. Despite the importance of this disease in modern societies and the large investment of resources already made in its study, the processes underlying its pathophysiology remain poorly understood. Several hypotheses have been proposed to clarify the neurobiological mechanisms underlying this psychiatric disorder, being the link between adult hippocampal neurogenesis and MDD a central topic in the past decades. Previous studies have identified AP2γ as a key regulator of adult hippocampal neurogenesis in mice, being expressed in a subpopulation of adult transient amplifying progenitors, and acting as a regulator of basal progenitors, promoting proliferation and glutamatergic neuronal differentiation. Thus, we wanted to further explore the impact of AP2γ in brain neurophysiology and behavior during development and at adult stages, dissecting also its mechanisms both in healthy and depressive states. With this study, we were able to understand the impact of AP2γ in post-natal development and during juvenile age, through the AP2γ constitutive knockout (KO) model. In the developmental milestones assessment we did not find any major impairment in the behavioral performance of AP2γ KO mice, since all parameters analyzed, including the ones where we found differences, were within the typical range for appearance of the developmental milestones. However, in the juvenile behavior assessment and in the hippocampal glutamatergic neurogenesis process, impairments were found, since AP2γ KO mice showed anxious-like behavior and decreased proliferation of immature neurons. To study the impact of modulating the transcription factor AP2γ in depression we exposed both constitutive and conditional KO animal models to a chronic stress protocol, which efficiently induced core depressive-like symptoms. Through the conditional AP2γ KO mice, we were able to elucidate the impact of deleting AP2γ on behavior and neurogenesis in depressive-like conditions specifically in adult age, without the interference of potential functions of the gene during early development that may appear in the constitutive AP2γ model. Through a multidimensional behavioral analysis, we observed that both models presented similar results in the three most affected behavioral dimensions in depression, namely anxiety, mood and cognition. Regarding anxiety and mood no major differences were found between genotypes in both animal models. Moreover, AP2γ KO mice presented cognitive deficits in basal conditions, but when exposed to chronic mild stress no detrimental effects of deletion of the gene were observed. In this work, we also identified, through a broad analysis of the dentate gyrus neurogenic niche, alterations of epigenetic regulators in the AP2γ constitutive KO mice after uCMS exposure. The reported results not only support the involvement of AP2γ in the transcriptional network that modulates the juvenile and adult neurogenic process, but also highlight the potential of this molecule as a future therapeutical tool in neuropsychiatric disorders, in which neurogenesis is impaired.O transtorno depressivo persistente é uma doença psiquiátrica multidimensional, considerada pela Organização Mundial de Saúde como uma das principais causas de incapacidade. Apesar da importância desta doença na sociedade moderna, e do largo investimento de recursos já feitos no seu estudo, os processos subjacentes à sua patofisiologia continuam pouco percebidos. Várias hipóteses foram propostas para clarificar os mecanismos neurobiológicos implícitos nesta doença psiquiátrica, tendo sido o vínculo entre a neurogénese hipocampal adulta e a depressão um tópico central nas décadas passadas. Estudos anteriores identificaram o AP2γ como um regulador chave da neurogénese hipocampal adulta em ratinhos, sendo expresso numa subpopulação de células progenitoras de rápida amplificação adultas, e atuando como regulador de progenitores basais, promovendo a proliferação e a diferenciação neuronal glutamatérgica. Deste modo, propusemos continuar a explorar o impacto do AP2γ na neurofisiologia cerebral e no comportamento, durante a fase de desenvolvimento e na idade adulta, procurando entender também os seus mecanismos tanto no estado saudável como em depressão. Com este trabalho, fomos capazes de entender o impacto do AP2γ no desenvolvimento pós-natal e em idade juvenil, a partir do modelo animal de deleção constitutiva do AP2γ. Na avaliação dos marcos de desenvolvimento, não encontramos nenhuma alteração no desempenho comportamental nos animais com deleção de AP2γ, visto que todos os parâmetros analisados, incluindo os que encontramos alguma diferença, se encontravam dentro dos intervalos típicos de aparecimento dos marcos de desenvolvimento. Contudo, na avaliação do comportamento juvenil e no processo de neurogénese glutamatérgica hipocampal observamos défices, visto que os animais com deleção de AP2γ apresentaram comportamento ansioso e uma diminuição da proliferação de neurónios imaturos. Para estudar o impacto da modulação do fator de transcrição AP2γ em depressão expusemos tanto o modelo animal com deleção constitutiva bem como o modelo animal condicional do gene a um protocolo de stress crónico, o qual eficientemente induziu sintomas primários de depressão. Através do modelo animal condicional do AP2γ, conseguimos compreender o impacto da deleção do AP2γ na modulação do comportamento e neurogénese em condições depressivas especificamente em idade adulta, sem interferência das potenciais funções do gene durante o período de desenvolvimento dos animais, que poderão surgir no modelo animal constitutivo do AP2γ. Através, de uma análise comportamental multidimensional, observamos que ambos os modelos apresentaram resultados similares nas dimensões comportamentais mais afetadas na depressão, nomeadamente a ansiedade, o humor e a cognição. Relativamente à ansiedade e ao humor não encontramos grandes diferenças entre genótipos em ambos os modelos animais. Além disso, os modelos animais de deleção do AP2γ apresentaram défices cognitivos em condições basais, mas após exposição ao stress crónico não foram observados os efeitos prejudiciais da deleção do gene. Neste trabalho, também identificamos, através de uma análise abrangente do nicho neurogénico girus denteado, um reguladores epigenéticos alterados no animal constitutivo do AP2γ. Os resultados apresentados não só suportam o envolvimento do AP2γ na rede transcripcional responsável pela modulação do processo neurogénico juvenil e adulto, como também destacam o potencial desta molécula em abordagens terapêuticas futuras em doenças neuropsiquiátricas, nas quais a neurogénese se encontra afetada

Chronic stress targets adult neurogenesis preferentially in the suprapyramidal blade of the rat dorsal dentate gyrus

First Online: 29 August 2017The continuous generation of new neurons and glial cells in the adult hippocampal dentate gyrus (DG) represents an important form of adult neuroplasticity, involved in normal brain function and behavior but also associated with the etiopathogenesis and treatment of psychiatric disorders. Despite the large number of studies addressing cell genesis along the septotemporal axis, data on the anatomical gradients of cytogenesis along the DG transverse axis is scarce, especially after exposure to stress. As such, in this study we characterized both basal proliferation and survival of adult-born neural cells along the transverse axis of the rat dorsal DG, and after stress exposure. In basal conditions, both proliferating cells and newborn neurons and glial cells were preferentially located at the subgranular zone and suprapyramidal blade. Exposure to chronic stress induced an overall decrease in the generation of adult-born neural cells and, more specifically, produced a regional-specific decrease in the survival of adult-born neurons at the suprapyramidal blade. No particular region-specific alterations were observed on surviving adult-born glial cells. This work reveals, for the first time, a distinct survival profile of adult-born neural cells, neurons and glial cells, among the transverse axis of the DG, in both basal and stress conditions. Our results unveil that adult-born neurons are preferentially located in the suprapyramidal blade and suggest a regional-specific impact of chronic stress in this blade with potential repercussions for its functional significance.NDA, PP, AMP, ARMS, MM and LP received fellowships from the Portuguese Foundation for Science and Technology (FCT). This work was funded by FCT (IF/01079/2014). This article has been developed under the scope of the project NORTE-01-0145-FEDER-000013, supported by the Northern Portugal Regional Operational Programme (NORTE 2020), under the Portugal 2020 Partnership Agreement, through the European Regional Development Fund (FEDER). This work has been funded by FEDER funds, through the Competitiveness Factors Operational Programme (COMPETE), and by National funds, through the Foundation for Science and Technology (FCT), under the scope of the project POCI-01-0145-FEDER-007038.info:eu-repo/semantics/publishedVersio

Beyond new neurons in the adult hippocampus: imipramine acts as a pro-astrogliogenic factor and rescues cognitive impairments induced by stress exposure

Depression is a prevalent, socially burdensome disease. Different studies have demonstrated the important role of astrocytes in the pathophysiology of depression as modulators of neurotransmission and neurovascular coupling. This is evidenced by astrocyte impairments observed in brains of depressed patients and the appearance of depressive-like behaviors upon astrocytic dysfunctions in animal models. However, little is known about the importance of de novo generated astrocytes in the mammalian brain and in particular its possible involvement in the precipitation of depression and in the therapeutic actions of current antidepressants (ADs). Therefore, we studied the modulation of astrocytes and adult astrogliogenesis in the hippocampal dentate gyrus (DG) of rats exposed to an unpredictable chronic mild stress (uCMS) protocol, untreated and treated for two weeks with antidepressants—fluoxetine and imipramine. Our results show that adult astrogliogenesis in the DG is modulated by stress and imipramine. This study reveals that distinct classes of ADs impact differently in the astrogliogenic process, showing different cellular mechanisms relevant to the recovery from behavioral deficits induced by chronic stress exposure. As such, in addition to those resident, the newborn astrocytes in the hippocampal DG might also be promising therapeutic targets for future therapies in the neuropsychiatric field.ARMS: ELC, NDA, PP, AMP, JSC, MM, AJR, JFO, and L.P. received fellowships from the Portuguese Foundation for Science and Technology (FCT) (IF/00328/2015 to J.F.O.; 2020.02855.CEECIND to LP). This work was funded by FCT (IF/01079/2014, PTDC/MED-NEU/31417/2017 Grant to JFO), BIAL Foundation Grants (037/18 to J.F.O. and 427/14 to L.P.), “la Caixa” Foundation Health Research Grant (LCF/PR/HR21/52410024) and Nature Research Award for Driving Global Impact—2019 Brain Sciences (to L.P.). This was also co-funded by the Life and Health Sciences Research Institute (ICVS), and by FEDER, through the Competitiveness Internationalization Operational Program (POCI), and by National funds, through the Foundation for Science and Technology (FCT)—project UIDB/50026/2020 and UIDP/50026/2020. Moreover, this work has been funded by ICVS Scientific Microscopy Platform, member of the national infrastructure PPBI—Portuguese Platform of Bioimaging (PPBI-POCI-01-0145-FEDER-022122; by National funds, through the Foundation for Science and Technology (FCT)—project UIDB/50026/2020 and UIDP/50026/2020; “la Caixa” Foundation (ID 100010434 to A.J.R.), under the agreement LCF/PR/HR20/52400020; and the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (grant agreement No 101003187 to A.J.R.)

Treating Parkinson's Disease with Human Bone Marrow Mesenchymal Stem Cell Secretome: A Translational Investigation Using Human Brain Organoids and Different Routes of In Vivo Administration.

peer reviewedParkinson's disease (PD) is the most common movement disorder, characterized by the progressive loss of dopaminergic neurons from the nigrostriatal system. Currently, there is no treatment that retards disease progression or reverses damage prior to the time of clinical diagnosis. Mesenchymal stem cells (MSCs) are one of the most extensively studied cell sources for regenerative medicine applications, particularly due to the release of soluble factors and vesicles, known as secretome. The main goal of this work was to address the therapeutic potential of the secretome collected from bone-marrow-derived MSCs (BM-MSCs) using different models of the disease. Firstly, we took advantage of an optimized human midbrain-specific organoid system to model PD in vitro using a neurotoxin-induced model through 6-hydroxydopamine (6-OHDA) exposure. In vivo, we evaluated the effects of BM-MSC secretome comparing two different routes of secretome administration: intracerebral injections (a two-site single administration) against multiple systemic administration. The secretome of BM-MSCs was able to protect from dopaminergic neuronal loss, these effects being more evident in vivo. The BM-MSC secretome led to motor function recovery and dopaminergic loss protection; however, multiple systemic administrations resulted in larger therapeutic effects, making this result extremely relevant for potential future clinical applications

Abstracts

Tradução, para a língua inglesa, dos resumos dos artigos publicados nesta edição

Constitutive deficiency of the neurogenic hippocampal modulator AP2γ promotes anxiety-like behavior and cumulative memory deficits in mice from juvenile to adult periods

The transcription factor activating protein two gamma (AP2γ) is an important regulator of neurogenesis both during embryonic development as well as in the postnatal brain, but its role for neurophysiology and behavior at distinct postnatal periods is still unclear. In this work, we explored the neurogenic, behavioral, and functional impact of a constitutive and heterozygous AP2γ deletion in mice from early postnatal development until adulthood. AP2γ deficiency promotes downregulation of hippocampal glutamatergic neurogenesis, altering the ontogeny of emotional and memory behaviors associated with hippocampus formation. The impairments induced by AP2γ constitutive deletion since early development leads to an anxious-like phenotype and memory impairments as early as the juvenile phase. These behavioral impairments either persist from the juvenile phase to adulthood or emerge in adult mice with deficits in behavioral flexibility and object location recognition. Collectively, we observed a progressive and cumulative impact of constitutive AP2γ deficiency on the hippocampal glutamatergic neurogenic process, as well as alterations on limbic-cortical connectivity, together with functional behavioral impairments. The results herein presented demonstrate the modulatory role exerted by the AP2γ transcription factor and the relevance of hippocampal neurogenesis in the development of emotional states and memory processes.H2020 -“la Caixa” Foundation(101003187

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear un derstanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5–7 vast areas of the tropics remain understudied.8–11 In the American tropics, Amazonia stands out as the world’s most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepre sented in biodiversity databases.13–15 To worsen this situation, human-induced modifications16,17 may elim inate pieces of the Amazon’s biodiversity puzzle before we can use them to understand how ecological com munities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple or ganism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region’s vulnerability to environmental change. 15%–18% of the most ne glected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lostinfo:eu-repo/semantics/publishedVersio

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5,6,7 vast areas of the tropics remain understudied.8,9,10,11 In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepresented in biodiversity databases.13,14,15 To worsen this situation, human-induced modifications16,17 may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost