bims-microg 2024-07-21 papers

bims-microg

Biomed News

on Microglia in health and disease

Issue of 2024‒07‒21
25 papers selected by
Marcus Karlstetter, Universität zu Köln

Therapeutic targeting of immunometabolism reveals a critical reliance on hexokinase 2 dosage for microglial activation and Alzheimer's progression.
Morphotype-specific calcium signaling in human microglia.
PARK7/DJ-1 deficiency impairs microglial activation in response to LPS-induced inflammation.
LRRK2 kinase activity restricts NRF2-dependent mitochondrial protection in microglia.
Breaking the vicious cycle: Targeting the NLRP3 inflammasome for treating sepsis-associated encephalopathy.
The A53T mutation in α-synuclein enhances pro-inflammatory activation in human microglia upon inflammatory stimulus.
Organelle phenotyping and multi-dimensional microscopy identify C1q as a novel regulator of microglial function.
Synergism of ApoE4 and systemic infectious burden is mediated by the APOE-NLRP3 axis in Alzheimer's disease.
Pathogenic variants associated with speech/cognitive delay and seizures affect genes with expression biases in excitatory neurons and microglia in developing human cortex.
Development of a high-throughput pipeline to characterize microglia morphological states at a single-cell resolution.
The emerging role of brain neuroinflammatory responses in Alzheimer's disease.
Co-Transplantation-Based Human-Mouse Chimeric Brain Models to Study Human Glial-Glial and Glial-Neuronal Interactions.
Microglia depletion leads to increased susceptibility to ocular hypertension-dependent glaucoma.
Microglia mediate the early-life programming of adult glucose control.
Single-cell RNA Sequencing Identifies a Novel Subtype of Microglia with High Cd74 Expression that Facilitates White Matter Inflammation During Chronic Cerebral Hypoperfusion.
Developmental Functions of Microglia: Impact of Psychosocial and Physiological Early Life Stress.
Minocycline prevents photoreceptor degeneration in Retinitis pigmentosa through modulating mitochondrial homeostasis.
ID2-ETS2 axis regulates the transcriptional acquisition of pro-tumoral microglia phenotype in glioma.
Role of inflammation in diabetic macular edema and neovascular age-related macular degeneration.
Rod-shaped microglia interact with neuronal dendrites to regulate cortical excitability in TDP-43 related neurodegeneration.
Microglia Morphological Response to Mesenchymal Stromal Cell Extracellular Vesicles Demonstrates EV Therapeutic Potential for Modulating Neuroinflammation.
The impact of interleukin-6 (IL-6) and mesenchymal stem cell-derived IL-6 on neurological conditions.
SDS3 regulates microglial inflammation by modulating the expression of the upstream kinase ASK1 in the p38 MAPK signaling pathway.
N-Glycan profile of the cell membrane as a probe for lipopolysaccharide-induced microglial neuroinflammation uncovers the effects of common fatty acid supplementation.
Cerebral Microvascular Density, Permeability of the Blood-Brain Barrier, and Neuroinflammatory Responses Indicate Early Aging Characteristics in a Marfan Syndrome Mouse Model.

Cell Rep. 2024 Jul 11. pii: S2211-1247(24)00817-9. [Epub ahead of print]43(7): 114488

Therapeutic targeting of immunometabolism reveals a critical reliance on hexokinase 2 dosage for microglial activation and Alzheimer's progression.

Juan F Codocedo, Claudia Mera-Reina, Peter Bor-Chian Lin, Paul B Fallen, Shweta S Puntambekar, Brad T Casali, Nur Jury-Garfe, Pablo Martinez, Cristian A Lasagna-Reeves, Gary E Landreth.

  Neuroinflammation is a prominent feature of Alzheimer's disease (AD). Activated microglia undergo a reprogramming of cellular metabolism necessary to power their cellular activities during disease. Thus, selective targeting of microglial immunometabolism might be of therapeutic benefit for treating AD. In the AD brain, the levels of microglial hexokinase 2 (HK2), an enzyme that supports inflammatory responses by promoting glycolysis, are significantly increased. In addition, HK2 displays non-metabolic activities that extend its inflammatory role beyond glycolysis. The antagonism of HK2 affects microglial phenotypes and disease progression in a gene-dose-dependent manner. HK2 complete loss fails to improve pathology by exacerbating inflammation, while its haploinsufficiency reduces pathology in 5xFAD mice. We propose that the partial antagonism of HK2 is effective in slowing disease progression by modulating NF-κB signaling through its cytosolic target, IKBα. The complete loss of HK2 affects additional inflammatory mechanisms related to mitochondrial dysfunction.

Keywords:  Alzheimer’s disease; CP: Metabolism; CP: Neuroscience; NF-κB; amyloid; hexokinase 2; inflammation; lonidamine; microglia; mitochondria

DOI:  https://doi.org/10.1016/j.celrep.2024.114488
J Neuroinflammation. 2024 Jul 17. 21(1): 175

Morphotype-specific calcium signaling in human microglia.

Sofia Nevelchuk, Bianca Brawek, Niklas Schwarz, Ariel Valiente-Gabioud, Thomas V Wuttke, Yury Kovalchuk, Henner Koch, Anke Höllig, Frederik Steiner, Katherine Figarella, Oliver Griesbeck, Olga Garaschuk.

  BACKGROUND: Key functions of Ca2+ signaling in rodent microglia include monitoring the brain state as well as the surrounding neuronal activity and sensing the danger or damage in their vicinity. Microglial Ca2+ dyshomeostasis is a disease hallmark in many mouse models of neurological disorders but the Ca2+ signal properties of human microglia remain unknown.METHODS: We developed a novel genetically-encoded ratiometric Ca2+ indicator, targeting microglial cells in the freshly resected human tissue, organotypically cultured tissue slices and analyzed in situ ongoing Ca2+ signaling of decades-old microglia dwelling in their native microenvironment.
RESULTS: The data revealed marked compartmentalization of Ca2+ signals, with signal properties differing across the compartments and resident morphotypes. The basal Ca2+ levels were low in ramified and high in ameboid microglia. The fraction of cells with ongoing Ca2+ signaling, the fraction and the amplitude of process Ca2+ signals and the duration of somatic Ca2+ signals decreased when moving from ramified via hypertrophic to ameboid microglia. In contrast, the size of active compartments, the fraction and amplitude of somatic Ca2+ signals and the duration of process Ca2+ signals increased along this pathway.

Keywords:  Human microglia; In vitro human brain tissue model; Morphotypes of resident microglia; Native microglial microenvironment; microRNA-9-assisted labeling

DOI:  https://doi.org/10.1186/s12974-024-03169-6
J Neuroinflammation. 2024 Jul 16. 21(1): 174

PARK7/DJ-1 deficiency impairs microglial activation in response to LPS-induced inflammation.

Frida Lind-Holm Mogensen, Carole Sousa, Corrado Ameli, Katja Badanjak, Sandro L Pereira, Arnaud Muller, Tony Kaoma, Djalil Coowar, Andrea Scafidi, Suresh K Poovathingal, Maria Tziortziou, Paul M A Antony, Nathalie Nicot, Aurélien Ginolhac, Daniela M Vogt Weisenhorn, Wolfgang Wurst, Aurélie Poli, Petr V Nazarov, Alexander Skupin, Anne Grünewald, Alessandro Michelucci.

  BACKGROUND: Specific microglia responses are thought to contribute to the development and progression of neurodegenerative diseases, including Parkinson's disease (PD). However, the phenotypic acquisition of microglial cells and their role during the underlying neuroinflammatory processes remain largely elusive. Here, according to the multiple-hit hypothesis, which stipulates that PD etiology is determined by a combination of genetics and various environmental risk factors, we investigate microglial transcriptional programs and morphological adaptations under PARK7/DJ-1 deficiency, a genetic cause of PD, during lipopolysaccharide (LPS)-induced inflammation.METHODS: Using a combination of single-cell RNA-sequencing, bulk RNA-sequencing, multicolor flow cytometry and immunofluorescence analyses, we comprehensively compared microglial cell phenotypic characteristics in PARK7/DJ-1 knock-out (KO) with wildtype littermate mice following 6- or 24-h intraperitoneal injection with LPS. For translational perspectives, we conducted corresponding analyses in human PARK7/DJ-1 mutant induced pluripotent stem cell (iPSC)-derived microglia and murine bone marrow-derived macrophages (BMDMs).
RESULTS: By excluding the contribution of other immune brain resident and peripheral cells, we show that microglia acutely isolated from PARK7/DJ-1 KO mice display a distinct phenotype, specially related to type II interferon and DNA damage response signaling, when compared with wildtype microglia, in response to LPS. We also detected discrete signatures in human PARK7/DJ-1 mutant iPSC-derived microglia and BMDMs from PARK7/DJ-1 KO mice. These specific transcriptional signatures were reflected at the morphological level, with microglia in LPS-treated PARK7/DJ-1 KO mice showing a less amoeboid cell shape compared to wildtype mice, both at 6 and 24 h after acute inflammation, as also observed in BMDMs.
CONCLUSIONS: Taken together, our results show that, under inflammatory conditions, PARK7/DJ-1 deficiency skews microglia towards a distinct phenotype characterized by downregulation of genes involved in type II interferon signaling and a less prominent amoeboid morphology compared to wildtype microglia. These findings suggest that the underlying oxidative stress associated with the lack of PARK7/DJ-1 affects microglia neuroinflammatory responses, which may play a causative role in PD onset and progression.

Keywords:   PARK7/DJ-1; Lipopolysaccharide; Microglia; Microglia morphology; Neuroinflammation; Parkinson’s disease

DOI:  https://doi.org/10.1186/s12974-024-03164-x
bioRxiv. 2024 Jul 13. pii: 2024.07.09.602769. [Epub ahead of print]

LRRK2 kinase activity restricts NRF2-dependent mitochondrial protection in microglia.

Chi G Weindel, Lily M Ellzey, Aja K Coleman, Kristin L Patrick, Robert O Watson.

Mounting evidence supports a critical role for central nervous system (CNS) glial cells in neuroinflammation and neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's Disease (PD), Multiple Sclerosis (MS), as well as neurovascular ischemic stroke. Previously, we found that loss of the PD-associated gene leucine-rich repeat kinase 2 ( Lrrk2 ) in macrophages, peripheral innate immune cells, induced mitochondrial stress and elevated basal expression of type I interferon (IFN) stimulated genes (ISGs) due to chronic mitochondrial DNA engagement with the cGAS/STING DNA sensing pathway. Here, we report that loss of LRRK2 results in a paradoxical response in microglial cells, a CNS-specific macrophage population. In primary murine microglia and microglial cell lines, loss of Lrrk2 reduces tonic IFN signaling leading to a reduction in ISG expression. Consistent with reduced type I IFN, mitochondria from Lrrk2 KO microglia are protected from stress and have elevated metabolism. These protective phenotypes involve upregulation of NRF2, an important transcription factor in the response to oxidative stress and are restricted by LRRK2 kinase activity. Collectively, these findings illustrate a dichotomous role for LRRK2 within different immune cell populations and give insight into the fundamental differences between immune regulation in the CNS and the periphery.

DOI: https://doi.org/10.1101/2024.07.09.602769
Biomed Pharmacother. 2024 Jul 13. pii: S0753-3322(24)00926-0. [Epub ahead of print]177 117042

Breaking the vicious cycle: Targeting the NLRP3 inflammasome for treating sepsis-associated encephalopathy.

Hui Zhong, Tianshu Liu, You Shang, Chaolin Huang, Shangwen Pan.

  Sepsis-associated encephalopathy (SAE) is a collection of clinical syndromes resulting from sepsis and characterized by widespread brain dysfunction. The high prevalence of SAE has adverse outcomes on the clinical management and prognosis of sepsis patients. However, currently, there are no effective treatments to ameliorate SAE. The pathogenesis of SAE is complex, including neuroinflammation and microglia activation, destruction of the blood-brain barrier (BBB), neurotransmitter dysfunction, cerebral metabolism and mitochondrial impairment, accumulation of amyloid beta and tauopathy, complement activation, among others. Furthermore, these mechanisms intertwine with each other, further complicating the comprehension of SAE. Among them, neuroinflammation mediated by hyperactivated microglia is considered the primary etiology of SAE. This instigates a detrimental cycle wherein BBB permeability escalates, facilitating direct damage to the central nervous system (CNS) by various neurotoxic substances. Activation of the NLRP3 inflammasome, situated within microglia, can be triggered by diverse danger signals, leading to cell pyroptosis, apoptosis, and tauopathy. These complex processes intricately regulate the onset and progression of neuroinflammation. In this review, we focus on elucidating the inhibitory regulatory mechanism of the NLRP3 inflammasome in microglia, which ultimately manifests as suppression of the inflammatory response. Our ultimate objective is to augment comprehension regarding the role of microglial NLRP3 inflammasome as we explore potential targets for therapeutic interventions against SAE.

Keywords:  Microglia; NLRP3 inflammasome; Negative regulation; Sepsis-associated encephalopathy

DOI:  https://doi.org/10.1016/j.biopha.2024.117042
Biol Psychiatry. 2024 Jul 17. pii: S0006-3223(24)01459-8. [Epub ahead of print]

The A53T mutation in α-synuclein enhances pro-inflammatory activation in human microglia upon inflammatory stimulus.

Marine Krzisch, Bingbing Yuan, Wenyu Chen, Tatsuya Osaki, Dongdong Fu, Carrie M Garrett-Engele, Devon S Svoboda, Kristin R Andrykovich, Michael D Gallagher, Mriganka Sur, Rudolf Jaenisch.

  BACKGROUND: Parkinson's disease (PD) is the second most common neurodegenerative disease, following Alzheimer's. It is characterized by the aggregation of α-synuclein into Lewy bodies and Lewy neurites in the brain. Microglia-driven neuroinflammation may contribute to neuronal death in PD, however the exact role of microglia remains unclear and has been understudied. The A53T mutation in the gene coding for α-synuclein has been linked to early-onset PD, and exposure to A53T-mutant human α-synuclein increases the potential for inflammation of murine microglia. To date, its effect has not been studied in human microglia.METHODS: Here, we used 2-dimensional cultures of human iPSC-derived microglia and transplantation of these cells into the mouse brain to assess the cell-autonomous effects of the A53T mutation on human microglia.
RESULTS: We found that A53T-mutant human microglia had an intrinsically increased propensity towards pro-inflammatory activation upon inflammatory stimulus. Additionally, transplanted A53T mutant microglia showed a strong decrease in catalase expression in non-inflammatory conditions, and increased oxidative stress.
CONCLUSIONS: Our results indicate that A53T mutant human microglia display cell-autonomous phenotypes that may worsen neuronal damage in early-onset PD.

Keywords:  Parkinson’s disease; disease modeling; human pluripotent stem cells; inflammation; microglia; xenotransplantation

DOI:  https://doi.org/10.1016/j.biopsych.2024.07.011
J Neurochem. 2024 Jul 17.

Organelle phenotyping and multi-dimensional microscopy identify C1q as a novel regulator of microglial function.

Pooja S Sakthivel, Lorenzo Scipioni, Josh Karam, Zahara Keulen, Mathew Blurton-Jones, Enrico Gratton, Aileen J Anderson.

  Microglia, the immune cells of the central nervous system, are dynamic and heterogenous cells. While single cell RNA sequencing has become the conventional methodology for evaluating microglial state, transcriptomics do not provide insight into functional changes, identifying a critical gap in the field. Here, we propose a novel organelle phenotyping approach in which we treat live human induced pluripotent stem cell-derived microglia (iMGL) with organelle dyes staining mitochondria, lipids, lysosomes and acquire data by live-cell spectral microscopy. Dimensionality reduction techniques and unbiased cluster identification allow for recognition of microglial subpopulations with single-cell resolution based on organelle function. We validated this methodology using lipopolysaccharide and IL-10 treatment to polarize iMGL to an "inflammatory" and "anti-inflammatory" state, respectively, and then applied it to identify a novel regulator of iMGL function, complement protein C1q. While C1q is traditionally known as the initiator of the complement cascade, here we use organelle phenotyping to identify a role for C1q in regulating iMGL polarization via fatty acid storage and mitochondria membrane potential. Follow up evaluation of microglia using traditional read outs of activation state confirm that C1q drives an increase in microglia pro-inflammatory gene production and migration, while suppressing microglial proliferation. These data together validate the use of a novel organelle phenotyping approach and enable better mechanistic investigation of molecular regulators of microglial state.

Keywords:  C1q; complement; inflammation; microglia; organelles

DOI:  https://doi.org/10.1111/jnc.16173
Psychiatry Clin Neurosci. 2024 Jul 16.

Synergism of ApoE4 and systemic infectious burden is mediated by the APOE-NLRP3 axis in Alzheimer's disease.

Xue-Ting Liu, Xiu Chen, Na Zhao, Fan Geng, Meng-Meng Zhu, Qing-Guo Ren.

  BACKGROUND: Systemic infections are associated with the development of AD, especially in individuals carrying the APOE4 genotype. However, the detailed mechanism through which APOE4 affects microglia inflammatory response remains unclear.METHODS: We obtained human snRNA-seq data from the Synapse AD Knowledge Portal and assessed the DEGs between APOE3 and APOE4 isoforms in microglia. To verify the interaction between ApoE and infectious products, we used ApoE to stimulate in vitro and in vivo models in the presence or absence of LPS (or ATP). The NLRP3 gene knockout experiment was performed to demonstrate whether the APOE-NLRP3 axis was indispensable for microglia to regulate inflammation and mitochondrial autophagy. Results were evaluated by biochemical analyses and fluorescence imaging.
RESULTS: Compared with APOE3, up-regulated genes in APOE4 gene carriers were involved in pro-inflammatory responses. ApoE4-stimulation significantly increased the levels of NLRP3 inflammasomes and ROS in microglia. Moreover, compared with ApoE4 alone, the co-incubation of ApoE4 with LPS (or ATP) markedly promoted pyroptosis. Both NF-κB activation and mitochondrial autophagy dysfunction were contributed by the increased level of NLRP3 inflammasomes induced by ApoE4. Furthermore, the pathological impairment induced by ApoE4 could be reversed by NLRP3 KO.
CONCLUSIONS: Our study highlights the importance of NLRP3 inflammasomes in linking ApoE4 with microglia innate immune function. These findings not only provide a molecular basis for APOE4-mediated neuroinflammatory but also reveal the potential reason for the increased risk of AD in APOE4 gene carriers after contracting infectious diseases.

Keywords:  Alzheimer's disease; NLRP3 inflammasome; activation of microglia; apolipoprotein E

DOI:  https://doi.org/10.1111/pcn.13704
bioRxiv. 2024 Jul 02. pii: 2024.07.01.601597. [Epub ahead of print]

Pathogenic variants associated with speech/cognitive delay and seizures affect genes with expression biases in excitatory neurons and microglia in developing human cortex.

Jeffrey B Russ, Alexa C Stone, Kayli Maney, Lauren Morris, Caroline F Wright, Jillian H Hurst, Jennifer L Cohen.

Background & Objective: Congenital brain malformations and neurodevelopmental disorders (NDDs) are common pediatric neurological disorders and result in chronic disability. With the expansion of genetic testing, new etiologies for NDDs are continually uncovered, with as many as one third attributable to single-gene pathogenic variants. While our ability to identify pathogenic variants has continually improved, we have little understanding of the underlying cellular pathophysiology in the nervous system that results from these variants. We therefore integrated phenotypic information from subjects with monogenic diagnoses with two large, single-nucleus RNA-sequencing (snRNAseq) datasets from human cortex across developmental stages in order to investigate cell-specific biases in gene expression associated with distinct neurodevelopmental phenotypes.Methods: Phenotypic data was gathered from 1) a single-institution cohort of 84 neonates with pathogenic single-gene variants referred to Duke Pediatric Genetics, and 2) a cohort of 4,238 patients with neurodevelopmental disorders and pathogenic single-gene variants enrolled in the Deciphering Developmental Disorders (DDD) study. Pathogenic variants were grouped into genesets by neurodevelopmental phenotype and geneset expression across cortical cell subtypes was compared within snRNAseq datasets from 86 human cortex samples spanning the 2nd trimester of gestation to adulthood.
Results: We find that pathogenic variants associated with speech/cognitive delay or seizures involve genes that are more highly expressed in cortical excitatory neurons than variants in genes not associated with these phenotypes (Speech/cognitive: p=2.25×10 -7 ; Seizures: p=7.97×10 -12 ). A separate set of primarily rare variants associated with speech/cognitive delay or seizures, distinct from those with excitatory neuron expression biases, demonstrated expression biases in microglia. We also found that variants associated with speech/cognitive delay and an excitatory neuron expression bias could be further parsed by the presence or absence of comorbid seizures. Variants associated with speech/cognitive delay without seizures tended to involve calcium regulatory pathways and showed greater expression in extratelencephalic neurons, while those associated with speech/cognitive delay with seizures tended to involve synaptic regulatory machinery and an intratelencephalic neuron expression bias (ANOVA by geneset p<2×10 -16 ).
Conclusions: By combining extensive phenotype datasets from subjects with neurodevelopmental disorders with massive human cortical snRNAseq datasets across developmental stages, we identified cell-specific expression biases for genes in which pathogenic variants are associated with speech/cognitive delay and seizures. The involvement of genes with enriched expression in excitatory neurons or microglia highlights the unique role both cell types play in proper sculpting of the developing brain. Moreover, this information begins to shed light on distinct cortical cell types that are more likely to be impacted by pathogenic variants and that may mediate the symptomatology of resulting neurodevelopmental disorders.

DOI: https://doi.org/10.1101/2024.07.01.601597
eNeuro. 2024 Jul 19. pii: ENEURO.0014-24.2024. [Epub ahead of print]

Development of a high-throughput pipeline to characterize microglia morphological states at a single-cell resolution.

Jennifer Kim, Paul Pavlidis, Annie Vogel Ciernia.

As rapid responders to their environments, microglia engage in functions that are mirrored by their cellular morphology. Microglia are classically thought to exhibit a ramified morphology under homeostatic conditions which switches to an ameboid form during inflammatory conditions. However, microglia display a wide spectrum of morphologies outside of this dichotomy, including rod-like, ramified, ameboid, and hypertrophic states, which have been observed across brain regions, neurodevelopmental timepoints, and various pathological contexts. We applied dimensionality reduction and clustering to consider contributions of multiple morphology measures together to define a spectrum of microglial morphological states in a mouse dataset we used to demonstrate the utility of our toolset. Using ImageJ, we first developed a semi-automated approach to characterize 27 morphology features from hundreds to thousands of individual microglial cells in a brain region-specific manner. Within this pool of features, we defined distinct sets of highly correlated features that describe different aspects of morphology, including branch length, branching complexity, territory span, and circularity. When considered together, these sets of features drove different morphological clusters. Our tools captured morphological states similarly and robustly when applied to independent datasets and using different immunofluorescent markers for microglia. We have compiled our morphology analysis pipeline into an accessible, easy-to-use, and fully open-source ImageJ macro and R package that the neuroscience community can expand upon and directly apply to their own analyses. Outcomes from this work will supply the field with new tools to systematically evaluate the heterogeneity of microglia morphological states across various experimental models and research questions.Significance Statement We developed an accessible, user-friendly, and open-source computational toolset for microglia morphology segmentation and analysis. While there has been considerable progress in the field to develop automated microglia morphology segmentation tools, the majority of published tools are not openly available nor well-documented and there has been less transparency about the methods used to analyze the resulting morphological measures. Using our toolset, we took a data-informed approach to characterize different classes of microglia morphologies and to statistically model how membership across these forms dynamically changes across brain regions in an experimental mouse model. Application of our toolset will yield novel insights into microglia morphology differences at a single-cell resolution and in a spatially-resolved manner across many different research questions.

DOI: https://doi.org/10.1523/ENEURO.0014-24.2024
Front Aging Neurosci. 2024 ;16 1391517

The emerging role of brain neuroinflammatory responses in Alzheimer's disease.

Mandana Amelimojarad, Melika Amelimojarad, Xiaonan Cui.

  As the most common cause of dementia, Alzheimer's disease (AD) is characterized by neurodegeneration and synaptic loss with an increasing prevalence in the elderly. Increased inflammatory responses triggers brain cells to produce pro-inflammatory cytokines and accelerates the Aβ accumulation, tau protein hyper-phosphorylation leading to neurodegeneration. Therefore, in this paper, we discuss the current understanding of how inflammation affects brain activity to induce AD pathology, the inflammatory biomarkers and possible therapies that combat inflammation for AD.

Keywords:  Alzheimer’s disease; NSAIDs; inflammation; microglia; neuroinflammation

DOI:  https://doi.org/10.3389/fnagi.2024.1391517
bioRxiv. 2024 Jul 06. pii: 2024.07.03.601990. [Epub ahead of print]

Co-Transplantation-Based Human-Mouse Chimeric Brain Models to Study Human Glial-Glial and Glial-Neuronal Interactions.

Mengmeng Jin, Ziyuan Ma, Haiwei Zhang, Ava V Papetti, Rui Dang, Alessandro C Stillitano, Steven A Goldman, Peng Jiang.

Human-mouse chimeric brain models, generated by transplanting human induced pluripotent stem cell (hiPSC)-derived neural cells, are valuable for studying the development and function of human neural cells in vivo. Understanding glial-glial and glial-neuronal interactions is essential for unraveling the complexities of brain function and developing treatments for neurological disorders. To explore these interactions between human neural cells within an intact brain environment, we employe a co-transplantation strategy involving the engraftment of hiPSC-derived neural progenitor cells along with primitive macrophage progenitors into the neonatal mouse brain. This approach creates human-mouse chimeric brains containing human microglia, macroglia (astroglia and oligodendroglia), and neurons. Using super-resolution imaging and 3D reconstruction techniques, we examine the dynamics between human neurons and glia, unveiling human microglia engulfing immature human neurons, microglia pruning synapses of human neurons, and significant interactions between human oligodendrocytes and neurons. Single-cell RNA sequencing analysis of the chimeric brain uncovers a close recapitulation of the human glial progenitor cell population, along with a dynamic stage in astroglial development that mirrors the processes found in the human brain. Furthermore, cell-cell communication analysis highlights significant neuronal-glial and glial-glial interactions, especially the interaction between adhesion molecules neurexins and neuroligins. This innovative co-transplantation model opens up new avenues for exploring the complex pathophysiological mechanisms underlying human neurological diseases. It holds particular promise for studying disorders where glial-neuronal interactions and non-cell-autonomous effects play crucial roles.

DOI: https://doi.org/10.1101/2024.07.03.601990
Front Aging Neurosci. 2024 ;16 1396443

Microglia depletion leads to increased susceptibility to ocular hypertension-dependent glaucoma.

Cory A Diemler, Michael MacLean, Sarah E Heuer, Amanda A Hewes, Olivia J Marola, Richard T Libby, Gareth R Howell.

  In recent years, microglia have been highlighted for playing integral roles in neurodegenerative diseases, like glaucoma. To better understand the role of microglia during chronic ocular hypertension, we depleted microglia from aged (9-12 months old) DBA/2 J (D2) mice, which exhibit age-related increases in intraocular pressure, using a dietary CSF1R antagonist, PLX5622. Retinal ganglion cell (RGC) somas were counted, and optic nerve cross-sections stained and assessed for glaucomatous damage. Sustained administration of dietary PLX5622 significantly reduced the numbers of retinal microglia. Dietary PLX5622 did not lead to changes in intraocular pressure in D2 or normotensive DBA/2 J-Gpnmb+ (D2-Gpnmb+ ) control mice. While PLX5622-treated D2-Gpnmb+ did not develop optic nerve damage, PLX5622-treated D2 mice showed a significant increase in moderate-to-severe optic nerve damage compared to D2 mice fed a control diet. In conclusion, global reduction of microglia exacerbated glaucomatous neurodegeneration in D2 mice suggesting microglia play an overall beneficial role in protecting from ocular hypertension associated RGC loss.

Keywords:  glaucoma; microglia; neuronflammation; optic nerve; retina; retinal ganglion cells

DOI:  https://doi.org/10.3389/fnagi.2024.1396443
bioRxiv. 2024 Jul 04. pii: 2024.07.02.601752. [Epub ahead of print]

Microglia mediate the early-life programming of adult glucose control.

M Valdearcos, E R McGrath, S M Brown Mayfield, A Folick, R T Cheang, L Li, T P Bachor, R N Lippert, A W Xu, S K Koliwad.

Mammalian glucose homeostasis is, in part, nutritionally programmed during early neonatal life, a critical window for the formation of synapses between hypothalamic glucoregulatory centers. Although microglia are known to prune synapses throughout the brain, their specific role in refining hypothalamic glucoregulatory circuits remains unknown. Here, we show that microglia in the mediobasal hypothalamus (MBH) of mice actively engage in synaptic pruning during early life. Microglial phagocytic activity is induced following birth, regresses upon weaning from maternal milk, and is exacerbated by feeding dams a high-fat diet while lactating. In particular, we show that microglia refine perineuronal nets (PNNs) within the neonatal MBH. Indeed, transiently depleting microglia before weaning (P6-16), but not afterward (P21-31), remarkably increased PNN abundance in the MBH. Furthermore, mice lacking microglia only from P6-16 had glucose intolerance due to impaired glucose-responsive pancreatic insulin secretion in adulthood, a phenotype not seen if microglial depletion occurred after weaning. Viral retrograde tracing revealed that this impairment is linked to a reduction in the number of neurons in specific hypothalamic glucoregulatory centers that synaptically connect to the pancreatic β-cell compartment. These findings show that microglia facilitate synaptic plasticity in the MBH during early life through a process that includes PNN refinement, to establish hypothalamic circuits that regulate adult glucose homeostasis.

DOI: https://doi.org/10.1101/2024.07.02.601752
Neurochem Res. 2024 Jul 16.

Single-cell RNA Sequencing Identifies a Novel Subtype of Microglia with High Cd74 Expression that Facilitates White Matter Inflammation During Chronic Cerebral Hypoperfusion.

Wenchao Cheng, Yuhan Wang, Chang Cheng, Xiuying Chen, Lan Zhang, Wen Huang.

  Vascular dementia (VaD) causes progressive cognitive decline in the elderly population, but there is short of available therapeutic measures. Microglia-mediated neuroinflammation is vigorously involved in the pathogenesis of VaD, but the traditional classification of microglial M1/M2 phenotypes remains restrictive and controversial. This study aims to investigate whether microglia transform into novel subtypes in VaD. Chronic cerebral hypoperfusion (CCH) rat model was constructed to mimic VaD. Microglia were isolated via magnetic-activated cell sorting and analyzed by single-cell RNA sequencing (scRNA-seq) and bioinformatics. The findings inferred from scRNA-seq and bioinformatics were further validated through in vivo experiments. In this study, microglia were divided into eight clusters. The proportion of MG5 cluster was significantly increased in the white matter of the CCH group compared with the Sham group and was named chronic ischemia-associated microglia (CIAM). Immunity- and inflammation-related genes, including RT1-Db1, RT1-Da, RT1-Ba, Cd74, Spp1, C3, and Cd68, were markedly upregulated in CIAM. Enrichment analysis illustrated that CIAM possessed the function of evoking neuroinflammation. Further studies unveiled that Cd74 is associated with the most abundant GO terms involved in inflammation as well as cell proliferation and differentiation. In addition, microglia-specific Cd74 knockdown mediated by adeno-associated virus decreased the abundance of CIAM in the white matter, thereby mitigating inflammatory cytokine levels, alleviating white matter lesions, and improving cognitive impairment for CCH rats. These findings indicate that Cd74 is the core molecule of CIAM to trigger neuroinflammation and induce microglial differentiation to CIAM, suggesting that Cd74 may be a potential therapeutic target for VaD.

Keywords:  Cd74; Chronic cerebral hypoperfusion; Microglia; Neuroinflammation; Single-cell RNA sequencing; Vascular dementia

DOI:  https://doi.org/10.1007/s11064-024-04206-9
Neuropharmacology. 2024 Jul 16. pii: S0028-3908(24)00253-3. [Epub ahead of print] 110084

Developmental Functions of Microglia: Impact of Psychosocial and Physiological Early Life Stress.

Marissa A Smail, Kathryn M Lenz.

  Microglia play numerous important roles in brain development. From early embryonic stages through adolescence, these immune cells influence neuronal genesis and maturation, guide connectivity, and shape brain circuits. They also interact with other glial cells and structures, influencing the brain's supportive microenvironment. While this central role makes microglia essential, it means that early life perturbations to microglia can have widespread effects on brain development, potentially resulting in long-lasting behavioral impairments. Here, we will focus on the effects of early life psychosocial versus physiological stressors in rodent models. Psychosocial stress refers to perceived threats that lead to stress axes activation, including prenatal stress, or chronic postnatal stress, including maternal separation and resource scarcity. Physiological stress refers to with physical threats, including maternal immune activation, postnatal infection, and traumatic brain injury. Differing sources of early life stress have varied impacts on microglia, and these effects are moderated by factors such as developmental age, brain region, and sex. Overall, these stressors appear to either 1) upregulate basal microglia numbers and activity throughout the lifespan, while possibly blunting their responsivity to subsequent stressors, or 2) shift the developmental curve of microglia, resulting in differential timing and function, impacting the critical periods they govern. Either could contribute to behavioral dysfunctions that occur after the resolution of early life stress. Exploring how different stressors impact microglia, as well as how the experience of multiple stressors interacts to alter microglia's developmental functions, could deepen our understanding of how early life stress changes the brain's developmental trajectory.

Keywords:  development; early life stress; maternal immune activation; maternal separation; microglia; traumatic brain injury

DOI:  https://doi.org/10.1016/j.neuropharm.2024.110084
Int Immunopharmacol. 2024 Jul 16. pii: S1567-5769(24)01224-4. [Epub ahead of print]139 112703

Minocycline prevents photoreceptor degeneration in Retinitis pigmentosa through modulating mitochondrial homeostasis.

Yuxun Shi, Yuxi Chen, Yuan Pan, Guanyu Chen, Zhiqiang Xiao, Xiaoqing Chen, Minzhen Wang, Dan Liang.

  Minocycline, a broad-spectrum tetracycline antibiotic, has been shown to possess anti-inflammatory and antioxidative effects in various neurodegenerative diseases. However, its specific effects on retinitis pigmentosa (RP) have not been thoroughly investigated. Therefore, the objective of this study was to explore the potential role of minocycline in treating RP. In this investigation, we used rd1 to explore the antioxidant effect of minocycline in RP. Minocycline therapy effectively restored retinal function and structure in rd1 mice at 14 days postnatal. Additionally, minocycline inhibited the activation of microglia. Moreover, RNA sequencing analysis revealed a significant downregulation in the expression of mitochondrial genes within the retina of rd1 mice. Further KEGG and GO pathway analysis indicated impaired oxidative phosphorylation and electron transport chain processes. TEM confirmed the presence of damaged mitochondria in photoreceptors, while JC-1 staining demonstrated a decrease in mitochondrial membrane potential, accompanied by an increase in mitochondrial reactive oxygen species (ROS) levels. However, treatment with minocycline successfully reversed the abnormal expression of mitochondrial genes and reduced the levels of mitochondrial ROS, thereby providing protection against photoreceptor degeneration. Collectively, minocycline demonstrated the ability to rescue photoreceptor cells in RP by effectively modulating mitochondrial homeostasis and subsequently inflammation. These findings hold significant implications for the development of potential therapeutic strategies for RP.

Keywords:  Microglia activation; Minocycline; Mitochondrial ROS; Photoreceptor degeneration; Retinitis pigmentosa

DOI:  https://doi.org/10.1016/j.intimp.2024.112703
Cell Death Dis. 2024 Jul 18. 15(7): 512

ID2-ETS2 axis regulates the transcriptional acquisition of pro-tumoral microglia phenotype in glioma.

Guillermo Vázquez-Cabrera, Martin Škandík, Noémie Roncier, Farah Real Oualit, Mireia Cruz De Los Santos, Austeja Baleviciute, Mathilde Cheray, Bertrand Joseph.

Glioblastoma is a highly aggressive brain tumour that creates an immunosuppressive microenvironment. Microglia, the brain's resident immune cells, play a crucial role in this environment. Glioblastoma cells can reprogramme microglia to create a supportive niche that promotes tumour growth. However, the mechanisms controlling the acquisition of a transcriptome associated with a tumour-supportive microglial reactive state are not fully understood. In this study, we investigated changes in the transcriptional profile of BV2 microglia exposed to C6 glioma cells. RNA-sequencing analysis revealed a significant upregulation of microglial inhibitor of DNA binding 1 (Id1) and Id2, helix-loop-helix negative transcription regulatory factors. The concomitant regulation of microglial ETS proto-oncogene 2, transcription factor (ETS2)-target genes, i.e., Dusp6, Fli1, Jun, Hmox1, and Stab1, led us to hypothesize that ETS2 could be regulated by ID proteins. In fact, ID2-ETS2 protein interactions increased in microglia exposed to glioma cells. In addition, perturbation of the ID2-ETS2 transcriptional axis influenced the acquisition of a microglial tumour-supportive phenotype. ID2 and ETS2 genes were found to be expressed by the tumour-associated microglia isolated from human glioblastoma tumour biopsies. Furthermore, ID2 and ETS2 gene expressions exhibited inverse prognostic values in patients with glioma in cohorts from The Cancer Genome Atlas. Collectively, our findings indicate that the regulation of ETS2 by ID2 plays a role in the transcriptional regulation of microglia in response to stimuli originating from glioblastoma cells, information that could lead to developing therapeutic strategies to manipulate microglial tumour-trophic functions.

DOI: https://doi.org/10.1038/s41419-024-06903-3
Surv Ophthalmol. 2024 Jul 17. pii: S0039-6257(24)00080-8. [Epub ahead of print]

Role of inflammation in diabetic macular edema and neovascular age-related macular degeneration.

Stela Vujosevic, Marco Lupidi, Simone Donati, Carlo Astarita, Valentina Gallinaro, Elisabetta Pilotto.

  Diabetic macular edema (DME) and neovascular age-related macular degeneration (nAMD) are multifactorial disorders that affect the macula and cause significant vision loss. Although inflammation and neoangiogenesis are hallmarks of DME and nAMD, respectively, they share some biochemical mediators. While inflammation is a trigger for the processes that lead to the development of DME, in nAMD inflammation seems to be the consequence of retinal pigment epithelium and Bruch membrane alterations. These pathophysiologic differences may be the key issue that justifies the difference in treatment strategies. Vascular endothelial growth factor inhibitors have changed the treatment of both diseases, however, many patients with DME fail to achieve the established therapeutic goals. From a clinical perspective, targeting inflammatory pathways with intravitreal corticosteroids has been proven to be effective in patients with DME. On the contrary, the clinical relevance of addressing inflammation in patients with nAMD has not been proven yet. We explore the role and implication of inflammation in the development of nAMD and DME and its therapeutical relevance.

Keywords:  Diabetic macular edema; Inflammation; Intravitreal corticosteroid implant; Neovascular age-related macular degeneration; VEGF inhibitors

DOI:  https://doi.org/10.1016/j.survophthal.2024.07.006
bioRxiv. 2024 Jul 02. pii: 2024.06.30.601396. [Epub ahead of print]

Rod-shaped microglia interact with neuronal dendrites to regulate cortical excitability in TDP-43 related neurodegeneration.

Manling Xie, Alessandra S Miller, Praveen N Pallegar, Anthony Umpierre, Yue Liang, Na Wang, Shuwen Zhang, Nagaswaroop Kengunte Nagaraj, Zachary C Fogarty, Nikhil B Ghayal, Björn Oskarsson, Shunyi Zhao, Jiaying Zheng, Fangfang Qi, Aivi Nguyen, Dennis W Dickson, Long-Jun Wu.

Motor cortical hyperexcitability is well-documented in the presymptomatic stage of amyotrophic lateral sclerosis (ALS). However, the mechanisms underlying this early dysregulation are not fully understood. Microglia, as the principal immune cells of the central nervous system, have emerged as important players in sensing and regulating neuronal activity. Here we investigated the role of microglia in the motor cortical circuits in a mouse model of TDP-43 neurodegeneration (rNLS8). Utilizing multichannel probe recording and longitudinal in vivo calcium imaging in awake mice, we observed neuronal hyperactivity at the initial stage of disease progression. Spatial and single-cell RNA sequencing revealed that microglia are the primary responders to motor cortical hyperactivity. We further identified a unique subpopulation of microglia, rod-shaped microglia, which are characterized by a distinct morphology and transcriptional profile. Notably, rod-shaped microglia predominantly interact with neuronal dendrites and excitatory synaptic inputs to attenuate motor cortical hyperactivity. The elimination of rod-shaped microglia through TREM2 deficiency increased neuronal hyperactivity, exacerbated motor deficits, and further decreased survival rates of rNLS8 mice. Together, our results suggest that rod-shaped microglia play a neuroprotective role by attenuating cortical hyperexcitability in the mouse model of TDP-43 related neurodegeneration.

DOI: https://doi.org/10.1101/2024.06.30.601396
bioRxiv. 2024 Jul 03. pii: 2024.07.01.601612. [Epub ahead of print]

Microglia Morphological Response to Mesenchymal Stromal Cell Extracellular Vesicles Demonstrates EV Therapeutic Potential for Modulating Neuroinflammation.

Kanupriya R Daga, Andrew M Larey, Maria G Morfin, Kailin Chen, Sara Bitarafan, Jana M Carpenter, Hannah M Hynds, Kelly M Hines, Levi B Wood, Ross A Marklein.

Background: Mesenchymal stromal cell derived extracellular vesicles (MSC-EVs) are a promising therapeutic for neuroinflammation. MSC-EVs can interact with microglia, the resident immune cells of the brain, to exert their immunomodulatory effects. In response to inflammatory cues, such as cytokines, microglia undergo phenotypic changes indicative of their function e.g. morphology and secretion. However, these changes in response to MSC-EVs are not well understood. Additionally, no disease-relevant screening tools to assess MSC-EV bioactivity exist, which has further impeded clinical translation. Here, we developed a quantitative, high throughput morphological profiling approach to assess the response of microglia to neuroinflammation-relevant signals and whether this morphological response can be used to indicate the bioactivity of MSC-EVs.Results: Using an immortalized human microglia cell-line, we observed increased size (perimeter, major axis length) and complexity (form factor) upon stimulation with interferon-gamma (IFN-γ) and tumor necrosis factor-alpha (TNF-α). Upon treatment with MSC-EVs, the overall morphological score (determined using principal component analysis) shifted towards the unstimulated morphology, indicating that MSC-EVs are bioactive and modulate microglia. The morphological effects of MSC-EVs in TNF-γ/IFN-α stimulated cells were concomitant with reduced secretion of 14 chemokines/cytokines (e.g. CXCL6, CXCL9) and increased secretion of 12 chemokines/cytokines (e.g. CXCL8, CXCL10). Proteomic analysis of cell lysates revealed significant increases in 192 proteins (e.g. HIBADH, MEAK7, LAMC1) and decreases in 257 proteins (e.g. PTEN, TOM1, MFF) with MSC-EV treatment. Of note, many of these proteins are involved in regulation of cell morphology and migration. Gene Set Variation Analysis revealed upregulation of pathways associated with immune response, such as regulation of cytokine production, immune cell infiltration (e.g. T cells, NK cells) and morphological changes (e.g. Semaphorin, RHO/Rac signaling). Additionally, changes in microglia mitochondrial morphology were measured suggesting that MSC-EV modulate mitochondrial metabolism.
Conclusion: This study comprehensively demonstrates the effects of MSC-EVs on human microglial morphology, cytokine secretion, cellular proteome, and mitochondrial content. Our high-throughput, rapid, low-cost morphological approach enables screening of MSC-EV batches and manufacturing conditions to enhance EV function and mitigate EV functional heterogeneity in a disease relevant manner. This approach is highly generalizable and can be further adapted and refined based on selection of the disease-relevant signal, target cell, and therapeutic product.

DOI: https://doi.org/10.1101/2024.07.01.601612
Front Immunol. 2024 ;15 1400533

The impact of interleukin-6 (IL-6) and mesenchymal stem cell-derived IL-6 on neurological conditions.

Irina Kerkis, Álvaro Prieto da Silva, Rodrigo Pinheiro Araldi.

  Interleukin-6 (IL-6) is a versatile cytokine crucial for immune response modulation, inflammation regulation, and various physiological processes in the body. Its wide-ranging functions underscore its importance in maintaining health. Dysregulated IL-6 is closely associated with many diseases, making it a key research and therapeutic target. Elevated IL-6 levels in the central nervous system worsen neuroinflammation in neurodegenerative diseases by activating microglia and astrocytes and releasing pro-inflammatory cytokines and neurotoxic molecules. Moreover, dysregulated IL-6 weakens the blood-brain barrier, exacerbating neuroinflammation and neuronal damage by allowing peripheral immune cells and inflammatory mediators to enter the brain. Mesenchymal stem cells (MSCs) show promise in modulating neuroinflammation by regulating IL-6 levels. They effectively suppress pro-inflammatory cytokines, including IL-6, while promoting anti-inflammatory factors. This therapeutic approach highlights the importance of targeting IL-6 and other inflammatory mediators to alleviate neuroinflammation and its adverse effects on neurological disorders. This review provides a comprehensive overview of IL-6's involvement in neurological disorders, examining endogenous IL-6 and IL-6 derived from MSCs. We explore IL-6's mechanisms affecting neuronal function, survival, and immune modulation in the central nervous system. Additionally, we discuss the potential of MSC-derived IL-6 in neuroregeneration and neuroprotection. By elucidating IL-6's interplay with neurological pathologies, this review offers insights into novel therapeutic strategies targeting IL-6 signaling pathways for neurological disorders.

Keywords:  Huntington disease (HD); IL-6 dysregulation; interleukin-6 (IL-6); mesenchymal stem cells (MSCs); neurodegenerative diseases; stroke

DOI:  https://doi.org/10.3389/fimmu.2024.1400533
Inflamm Res. 2024 Jul 15.

SDS3 regulates microglial inflammation by modulating the expression of the upstream kinase ASK1 in the p38 MAPK signaling pathway.

Jian Shen, Wenjia Lai, Zeyang Li, Wenyuan Zhu, Xue Bai, Zihao Yang, Qingsong Wang, Jianguo Ji.

  BACKGROUND: Microglia, the main innate immune cells in the central nervous system, are key drivers of neuroinflammation, which plays a crucial role in the pathogenesis of neurodegenerative diseases. The Sin3/histone deacetylase (HDAC) complex, a highly conserved multiprotein co-repressor complex, primarily performs transcriptional repression via deacetylase activity; however, the function of SDS3, which maintains the integrity of the complex, in microglia remains unclear.METHODS: To uncover the regulatory role of the transcriptional co-repressor SDS3 in microglial inflammation, we used chromatin immunoprecipitation to identify SDS3 target genes and combined with transcriptomics and proteomics analysis to explore expression changes in cells following SDS3 knocking down. Subsequently, we validated our findings through experimental assays.
RESULTS: Our analysis revealed that SDS3 modulates the expression of the upstream kinase ASK1 of the p38 MAPK pathway, thus regulating the activation of signaling pathways and ultimately influencing inflammation.
CONCLUSIONS: Our findings provide important evidence of the contributions of SDS3 toward microglial inflammation and offer new insights into the regulatory mechanisms of microglial inflammatory responses.

Keywords:  ASK1; Microglia; Neuroinflammation; SDS3; p38 MAPK

DOI:  https://doi.org/10.1007/s00011-024-01913-5
Food Funct. 2024 Jul 16.

N-Glycan profile of the cell membrane as a probe for lipopolysaccharide-induced microglial neuroinflammation uncovers the effects of common fatty acid supplementation.

Sheryl Joyce B Grijaldo-Alvarez, Michael Russelle S Alvarez, Ryan Lee Schindler, Armin Oloumi, Noah Hernandez, Tristan Seales, Jorge Gil C Angeles, Ruel C Nacario, Gladys C Completo, Angela M Zivkovic, J Bruce German, Carlito B Lebrilla.

Altered N-glycosylation of proteins on the cell membrane is associated with several neurodegenerative diseases. Microglia are an ideal model for studying glycosylation and neuroinflammation, but whether aberrant N-glycosylation in microglia can be restored by diet remains unknown. Herein, we profiled the N-glycome, proteome, and glycoproteome of the human microglia following lipopolysaccharide (LPS) induction to probe the impact of dietary and gut microbe-derived fatty acids-oleic acid, lauric acid, palmitic acid, valeric acid, butyric acid, isobutyric acid, and propionic acid-on neuroinflammation using liquid chromatography-tandem mass spectrometry. LPS changed N-glycosylation in the microglial glycocalyx altering high mannose and sialofucosylated N-glycans, suggesting the dysregulation of mannosidases, fucosyltransferases, and sialyltransferases. The results were consistent as we observed the restoration effect of the fatty acids, especially oleic acid, on the LPS-treated microglia, specifically on the high mannose and sialofucosylated glycoforms of translocon-associated proteins, SSRA and SSRB along with the cell surface proteins, CD63 and CD166. In addition, proteomic analysis and in silico modeling substantiated the potential of fatty acids in reverting the effects of LPS on microglial N-glycosylation. Our results showed that N-glycosylation is likely affected by diet by restoring alterations following LPS challenge, which may then influence the disease state.

DOI: https://doi.org/10.1039/d4fo01598c
bioRxiv. 2024 Jul 02. pii: 2024.06.30.601409. [Epub ahead of print]

Cerebral Microvascular Density, Permeability of the Blood-Brain Barrier, and Neuroinflammatory Responses Indicate Early Aging Characteristics in a Marfan Syndrome Mouse Model.

T Curry-Koski, L Curtin, M Esfandiarei, Thomas T Currier.

Marfan Syndrome (MFS) is a connective tissue disorder due to mutations in fibrillin-1 ( Fbn1 ), where a Fbn1 missense mutation ( Fbn1 C1039G/+ ) can result in systemic increases in the bioavailability and signaling of transforming growth factor-β (TGF-β). In a well-established mouse model of MFS ( Fbn1 C1041G/+ ), pre-mature aging of the aortic wall and the progression of aortic root aneurysm are observed by 6-months-of-age. TGF-β signaling has been implicated in cerebrovascular dysfunction, loss of blood-brain barrier (BBB) integrity, and age-related neuroinflammation. We have reported that pre-mature vascular aging in MFS mice could extend to cerebrovasculature, where peak blood flow velocity in the posterior cerebral artery (PCA) of 6-month-old (6M) MFS mice was reduced, similarly to 12-month-old (12M) control mice. Case studies of MFS patients have documented neurovascular manifestations, including intracranial aneurysms, stroke, arterial tortuosity, as well as headaches and migraines, with reported incidence of pain and chronic fatigue. Despite these significant clinical observations, investigation into cerebrovascular dysfunction and neuropathology in MFS remains limited. Using 6M-control ( C57BL/6 ) and 6M-MFS ( Fbn1 C1041G/+ ) and healthy 12M-control male and female mice, we test the hypothesis that abnormal Fbn1 protein expression is associated with altered cerebral microvascular density, BBB permeability, and neuroinflammation in the PCA-perfused hippocampus, all indicative of a pre-mature aging brain phenotype. Using Glut1 staining, 6M-MFS mice and 12M-CTRL similarly present decreased microvascular density in the dentate gyrus (DG), cornu ammonis 1 (CA1), and cornu ammonis 3 (CA3) regions of the hippocampus. 6M-MFS mice exhibit increased BBB permeability in the DG, CA1, and CA3 as evident by Immunoglobulin G (IgG) staining, which was more comparable to 12M-CTRL mice. 6M-MFS mice show a higher number of microglia in the hippocampus compared to age-matched control mice, a pattern resembling that of 12M-CTRL mice. This study represents the first known investigation into neuropathology in a mouse model of MFS and indicates that the pathophysiology underlying MFS leads to a systemic pre-mature aging phenotype. This study is crucial for identifying and understanding MFS-associated neurovascular and neurological abnormalities, underscoring the need for research aimed at improving the quality of life and managing pre-mature aging symptoms in MFS and related connective tissue disorders.

DOI: https://doi.org/10.1101/2024.06.30.601409