Resolving the cellular specificity of TSPO imaging in a rat model of peripherally-induced neuroinflammation
Brain, behavior, and immunity
Vicente-Rodríguez, M;Singh, N;Turkheimer, F;Peris-Yague, A;Randall, K;Veronese, M;Simmons, C;Karim Haji-Dheere, A;Bordoloi, J;Sander, K;Awais, RO;Årstad, E;Consortium, N;Cash, D;Parker, CA;
PMID: 34052363 | DOI: 10.1016/j.bbi.2021.05.025
the increased expression of 18kDa Translocator protein (TSPO) is one of the few available biomarkers of neuroinflammation that can be assessed in humans in vivo by positron emission tomography (PET). TSPO PET imaging of the central nervous system (CNS) has been widely undertaken, but to date no clear consensus has been reached about its utility in brain disorders. One reason for this could be because the interpretation of TSPO PET signal remains challenging, given the cellular heterogeneity and ubiquity of TSPO in the brain. the aim of the current study was to ascertain if TSPO PET imaging can be used to detect neuroinflammation induced by a peripheral treatment with endotoxin lipopolysaccharide (LPS) in a rat model (ip LPS), and investigate the origin of TSPO signal changes in terms of their cellular sources and regional distribution. An initial pilot study utilising both [18F]DPA-714 and [11C]PK11195 demonstrated [18F]DPA-714 to exhibit a significantly higher lesion-related signal in the intracerebral LPS rat model (ic LPS) than [11C]PK11195. Subsequently, [18F]DPA-714 was selected for use in the ip LPS study. twenty-four hours after ip LPS, there was an increased uptake of [18F]DPA-714 across the whole brain. Further analyses of regions of interest, using immunohistochemistry and RNAscope Multiplex fluorescence V2 in situ hybridization technology, showed TSPO expression in microglia, monocyte derived-macrophages, astrocytes, neurons and endothelial cells. The expression of TSPO was significantly increased after ip LPS in a region-dependent manner; with microglia, monocyte-derived macrophages and astrocytes in the substantia nigra, in contrast to the hippocampus where TSPO was mostly confined to microglia and astrocytes. in summary, our data demonstrate the robust detection of peripherally-induced neuroinflammation in the CNS utilizing the TSPO radioligand [18F]DPA-714, and importantly, confirm that the TSPO signal increase arises mostly from a combination of microglia, astrocytes and monocyte-derived macrophages.
Mao F, Holmlund C, Faraz M, Wang W, Bergenheim T, Kvarnbrink S, Johansson M, Henriksson R, Hedman H.
PMID: - | DOI: 10.1038/s41389-017-0012-8
Recently, a genome-wide association study showed that a single nucleotide polymorphism (SNP) —rs11706832—in intron 2 of the human LRIG1 (Leucine-rich repeats and immunoglobulin-like domains 1) gene is associated with susceptibility to glioma. However, the mechanism by which rs11706832 affects glioma risk remains unknown; additionally, it is unknown whether the expression levels of LRIG1 are a relevant determinant of gliomagenesis. Here, we investigated the role of Lrig1 in platelet-derived growth factor (PDGF)-induced experimental glioma in mice by introducing mono-allelic and bi-allelic deletions of Lrig1followed by inducing gliomagenesis via intracranial retroviral transduction of PDGFB in neural progenitor cells. Lrig1 was expressed in PDGFB-induced gliomas in wild-type mice as assessed using in situ hybridization. Intriguingly, Lrig1-heterozygous mice developed higher grade gliomas than did wild-type mice (grade IV vs. grade II/III, p = 0.002). Reciprocally, the ectopic expression of LRIG1 in the TB107 high-grade human glioma (glioblastoma, grade IV) cell line decreased the invasion of orthotopic tumors in immunocompromised mice in vivo and reduced cell migration in vitro. Concomitantly, the activity of the receptor tyrosine kinase MET was downregulated, which partially explained the reduction in cell migration. In summary, Lrig1 is a haploinsufficient suppressor of PDGFB-driven glioma, possibly in part via negative regulation of MET-driven cell migration and invasion. Thus, for the first time, changes in physiological Lrig1 expression have been linked to gliomagenesis, whereby the SNP rs11706832 may affect glioma risk by regulating LRIG1 expression.
Translatomic analysis of regenerating and degenerating spinal motor neurons in injury and ALS
Shadrach, J;Stansberry, W;Milen, A;Ives, R;Fogarty, E;Antonellis, A;Pierchala, B;
| DOI: 10.1016/j.isci.2021.102700
The neuromuscular junction is a synapse critical for muscle strength and coordinated motor function. Unlike CNS injuries, motor neurons mount robust regenerative responses after peripheral nerve injuries. Conversely, motor neurons selectively degenerate in diseases such as amyotrophic lateral sclerosis (ALS). To assess how these insults affect motor neurons in vivo, we performed ribosomal profiling of mouse motor neurons. Motor neuron-specific transcripts were isolated from spinal cords following sciatic nerve crush, a model of acute injury and regeneration, and in the SOD1G93A ALS model. Of the 267 transcripts upregulated after nerve crush, 38% were also upregulated in SOD1G93A motor neurons. However, most upregulated genes in injured and ALS motor neurons were context specific. Some of the most significantly upregulated transcripts in both paradigms were chemokines such as Ccl2 and Ccl7, suggesting an important role for neuroimmune modulation. Collectively these data will aid in defining pro-regenerative and pro-degenerative mechanisms in motor neurons.
De Schepper, S;Ge, JZ;Crowley, G;Ferreira, LSS;Garceau, D;Toomey, CE;Sokolova, D;Rueda-Carrasco, J;Shin, SH;Kim, JS;Childs, T;Lashley, T;Burden, JJ;Sasner, M;Sala Frigerio, C;Jung, S;Hong, S;
PMID: 36747024 | DOI: 10.1038/s41593-023-01257-z
Alzheimer's disease (AD) is characterized by synaptic loss, which can result from dysfunctional microglial phagocytosis and complement activation. However, what signals drive aberrant microglia-mediated engulfment of synapses in AD is unclear. Here we report that secreted phosphoprotein 1 (SPP1/osteopontin) is upregulated predominantly by perivascular macrophages and, to a lesser extent, by perivascular fibroblasts. Perivascular SPP1 is required for microglia to engulf synapses and upregulate phagocytic markers including C1qa, Grn and Ctsb in presence of amyloid-β oligomers. Absence of Spp1 expression in AD mouse models results in prevention of synaptic loss. Furthermore, single-cell RNA sequencing and putative cell-cell interaction analyses reveal that perivascular SPP1 induces microglial phagocytic states in the hippocampus of a mouse model of AD. Altogether, we suggest a functional role for SPP1 in perivascular cells-to-microglia crosstalk, whereby SPP1 modulates microglia-mediated synaptic engulfment in mouse models of AD.
Krawczyk, MC;Pan, L;Zhang, AJ;Zhang, Y;
PMID: 36827449 | DOI: 10.1371/journal.pone.0279736
Though the brain was long characterized as an immune-privileged organ, findings in recent years have shown extensive communications between the brain and peripheral immune cells. We now know that alterations in the peripheral immune system can affect the behavioral outputs of the central nervous system, but we do not know which brain cells are affected by the presence of peripheral immune cells. Glial cells including microglia, astrocytes, oligodendrocytes, and oligodendrocyte precursor cells (OPCs) are critical for the development and function of the central nervous system. In a wide range of neurological and psychiatric diseases, the glial cell state is influenced by infiltrating peripheral lymphocytes. However, it remains largely unclear whether the development of the molecular phenotypes of glial cells in the healthy brain is regulated by lymphocytes. To answer this question, we acutely purified each type of glial cell from immunodeficient Rag2-/- mice. Interestingly, we found that the transcriptomes of microglia, astrocytes, and OPCs developed normally in Rag2-/- mice without reliance on lymphocytes. In contrast, there are modest transcriptome differences between the oligodendrocytes from Rag2-/- and control mice. Furthermore, the subcellular localization of the RNA-binding protein Quaking, is altered in oligodendrocytes. These results demonstrate that the molecular attributes of glial cells develop largely without influence from lymphocytes and highlight potential interactions between lymphocytes and oligodendrocytes.
Shi, Z;Yu, P;Lin, WJ;Chen, S;Hu, X;Chen, S;Cheng, J;Liu, Q;Yang, Y;Li, S;Zhang, Z;Xie, J;Jiang, J;He, B;Li, Y;Li, H;Xu, Y;Zeng, J;Huang, J;Mei, J;Cai, J;Chen, J;Wu, LJ;Ko, H;Tang, Y;
PMID: 36603584 | DOI: 10.1016/j.neuron.2022.12.009
The crosstalk between the nervous and immune systems has gained increasing attention for its emerging role in neurological diseases. Radiation-induced brain injury (RIBI) remains the most common medical complication of cranial radiotherapy, and its pathological mechanisms have yet to be elucidated. Here, using single-cell RNA and T cell receptor sequencing, we found infiltration and clonal expansion of CD8+ T lymphocytes in the lesioned brain tissues of RIBI patients. Furthermore, by strategies of genetic or pharmacologic interruption, we identified a chemotactic action of microglia-derived CCL2/CCL8 chemokines in mediating the infiltration of CCR2+/CCR5+ CD8+ T cells and tissue damage in RIBI mice. Such a chemotactic axis also participated in the progression of cerebral infarction in the mouse model of ischemic injury. Our findings therefore highlight the critical role of microglia in mediating the dysregulation of adaptive immune responses and reveal a potential therapeutic strategy for non-infectious brain diseases.
Choi E, Lantz TL, Vlacich G, Keeley TM, Samuelson LC, Coffey RJ, Goldenring JR, Powell AE.
PMID: 28814482 | DOI: 10.1136/gutjnl-2017-313874
Abstract
OBJECTIVE:
Lrig1 is a marker of proliferative and quiescent stem cells in the skin and intestine. We examined whether Lrig1-expressing cells are long-lived gastric progenitors in gastric glands in the mouse stomach. We also investigated how the Lrig1-expressing progenitor cells contribute to the regeneration of normal gastric mucosa by lineage commitment to parietal cells after acute gastric injury in mice.
DESIGN:
We performed lineage labelling using Lrig1-CreERT2/+;R26R-YFP/+ (Lrig1/YFP) or R26R-LacZ/+ (Lrig1/LacZ) mice to examine whether the Lrig1-YFP-marked cells are gastric progenitor cells. We studied whether Lrig1-YFP-marked cells give rise to normal gastric lineage cells in damaged mucosa using Lrig1/YFP mice after treatment with DMP-777 to induce acute injury. We also studied Lrig1-CreERT2/CreERT2 (Lrig1 knockout) mice to examine whether the Lrig1 protein is required for regeneration of gastric corpus mucosa after acute injury.
RESULTS:
Lrig1-YFP-marked cells give rise to gastric lineage epithelial cells both in the gastric corpus and antrum, in contrast to published results that Lgr5 only marks progenitor cells within the gastric antrum. Lrig1-YFP-marked cells contribute to replacement of damaged gastric oxyntic glands during the recovery phase after acute oxyntic atrophy in the gastric corpus. Lrig1 null mice recovered normally from acute gastric mucosal injury indicating that Lrig1 protein is not required for lineage differentiation. Lrig1+ isthmal progenitor cells did not contribute to transdifferentiating chief cell lineages after acute oxyntic atrophy.
CONCLUSIONS:
Lrig1 marks gastric corpus epithelial progenitor cells capable of repopulating the damaged oxyntic mucosa by differentiating into normal gastric lineage cells in mouse stomach.
The Journal of clinical investigation
Yan, P;Kim, KW;Xiao, Q;Ma, X;Czerniewski, LR;Liu, H;Rawnsley, DR;Yan, Y;Randolph, GJ;Epelman, S;Lee, JM;Diwan, A;
PMID: 35511433 | DOI: 10.1172/JCI152565
Microglia, the parenchymal tissue macrophages in the brain, surround amyloid plaques in brains of individuals with Alzheimer's disease (AD) but are ineffective at clearing amyloid to mitigate disease progression. Recent studies in mice indicate that microglia are derived exclusively from primitive yolk sac hematopoiesis and self-renew without contribution from ontogenically distinct monocytes/macrophages of definitive adult hematopoietic origin. Using a genetic fate-mapping approach to label cells of definitive hematopoietic origin throughout life span, we discovered that circulating monocytes contribute 6% of plaque-associated macrophages in aged AD mice. Moreover, peripheral monocytes contributed to a higher fraction of macrophages in the choroid plexus, meninges, and perivascular spaces of aged AD mice versus WT control mice, indicating enrichment at potential sites for entry into the brain parenchyma. Splenectomy, which markedly reduced circulating Ly6Chi monocytes, also reduced abundance of plaque-associated macrophages of definitive hematopoietic origin, resulting in increased amyloid plaque load. Together, these results indicate that peripherally derived monocytes invade the brain parenchyma, targeting amyloid plaques to reduce plaque load.
Xie, Y;Kuan, AT;Wang, W;Herbert, ZT;Mosto, O;Olukoya, O;Adam, M;Vu, S;Kim, M;Tran, D;Gómez, N;Charpentier, C;Sorour, I;Lacey, TE;Tolstorukov, MY;Sabatini, BL;Lee, WA;Harwell, CC;
PMID: 35196485 | DOI: 10.1016/j.celrep.2022.110416
Neuron-glia interactions play a critical role in the regulation of synapse formation and circuit assembly. Here we demonstrate that canonical Sonic hedgehog (Shh) pathway signaling in cortical astrocytes acts to coordinate layer-specific synaptic connectivity. We show that the Shh receptor Ptch1 is expressed by cortical astrocytes during development and that Shh signaling is necessary and sufficient to promote the expression of genes involved in regulating synaptic development and layer-enriched astrocyte molecular identity. Loss of Shh in layer V neurons reduces astrocyte complexity and coverage by astrocytic processes in tripartite synapses; conversely, cell-autonomous activation of Shh signaling in astrocytes promotes cortical excitatory synapse formation. Furthermore, Shh-dependent genes Lrig1 and Sparc distinctively contribute to astrocyte morphology and synapse formation. Together, these results suggest that Shh secreted from deep-layer cortical neurons acts to specialize the molecular and functional features of astrocytes during development to shape circuit assembly and function.
Stogsdill, JA;Kim, K;Binan, L;Farhi, SL;Levin, JZ;Arlotta, P;
PMID: 35948630 | DOI: 10.1038/s41586-022-05056-7
Microglia are specialized macrophages in the brain parenchyma that exist in multiple transcriptional states and reside within a wide range of neuronal environments1-4. However, how and where these states are generated remains poorly understood. Here, using the mouse somatosensory cortex, we demonstrate that microglia density and molecular state acquisition are determined by the local composition of pyramidal neuron classes. Using single-cell and spatial transcriptomic profiling, we unveil the molecular signatures and spatial distributions of diverse microglia populations and show that certain states are enriched in specific cortical layers, whereas others are broadly distributed throughout the cortex. Notably, conversion of deep-layer pyramidal neurons to an alternate class identity reconfigures the distribution of local, layer-enriched homeostatic microglia to match the new neuronal niche. Leveraging the transcriptional diversity of pyramidal neurons in the neocortex, we construct a ligand-receptor atlas describing interactions between individual pyramidal neuron subtypes and microglia states, revealing rules of neuron-microglia communication. Our findings uncover a fundamental role for neuronal diversity in instructing the acquisition of microglia states as a potential mechanism for fine-tuning neuroimmune interactions within the cortical local circuitry.
Pluvinage JV, Haney MS, Smith BAH, Sun J, Iram T, Bonanno L, Li L, Lee DP, Morgens DW, Yang AC, Shuken SR, Gate D, Scott M, Khatri P, Luo J, Bertozzi CR, Bassik MC, Wyss-Coray T.
PMID: 30944478 | DOI: 10.1038/s41586-019-1088-4
Microglia maintain homeostasis in the central nervous system through phagocytic clearance of protein aggregates and cellular debris. This function deteriorates during ageing and neurodegenerative disease, concomitant with cognitive decline. However, the mechanisms of impaired microglial homeostatic function and the cognitive effects of restoring this function remain unknown. We combined CRISPR-Cas9 knockout screens with RNA sequencing analysis to discover age-related genetic modifiers of microglial phagocytosis. These screens identified CD22, a canonical B cell receptor, as a negative regulator of phagocytosis that is upregulated on aged microglia. CD22 mediates the anti-phagocytic effect of α2,6-linked sialic acid, and inhibition of CD22 promotes the clearance of myelin debris, amyloid-β oligomers and α-synuclein fibrils in vivo. Long-term central nervous system delivery of an antibody that blocks CD22 function reprograms microglia towards a homeostatic transcriptional state and improves cognitive function in aged mice. These findings elucidate a mechanism of age-related microglial impairment and a strategy to restore homeostasis in the ageing brain.
Bennett FC, Bennett ML, Yaqoob F, Mulinyawe SB, Grant GA, Hayden Gephart M, Plowey ED, Barres BA.
PMID: 29861285 | DOI: 10.1016/j.neuron.2018.05.014
Microglia, the brain's resident macrophages, are dynamic CNS custodians with surprising origins in the extra-embryonic yolk sac. The consequences of their distinct ontogeny are unknown but critical to understanding and treating brain diseases. We created a brain macrophage transplantation system to disentangle how environment and ontogeny specify microglial identity. We find that donor cells extensively engraft in the CNS of microglia-deficient mice, and even after exposure to a cell culture environment, microglia fully regain their identity when returned to the CNS. Though transplanted macrophages from multiple tissues can express microglial genes in the brain, only those of yolk-sac origin fully attain microglial identity. Transplanted macrophages of inappropriate origin, including primary human cells in a humanized host, express disease-associated genes and specific ontogeny markers. Through brain macrophage transplantation, we discover new principles of microglial identity that have broad applications to the study of disease and development of myeloid cell therapies.
