Perivascular tissue resident memory T cells as therapeutic target in multiple sclerosis

Gemistocytic tumor cells programmed for glial scarring characterize T cell confinement in IDH-mutant astrocytoma

Isocitrate dehydrogenase 1/2 mutant (IDHmt) astrocytoma is considered a T cell-deprived tumor, yet little is known regarding the phenotypes underlying T cell exclusion. Using bulk, single nucleus and spatial RNA and protein profiling, we demonstrate that a distinct spatial organization underlies T cell confinement to the perivascular space (T cell cuff) in IDHmt astrocytoma. T cell cuffs are uniquely characterized by a high abundance of gemistocytic tumor cells (GTC) in the surrounding stroma. Integrative analysis shows that GTC-high tumors are enriched for lymphocytes and tumor associated macrophages (TAM) and express immune cell migration and activation programs. Specifically, GTCs constitute a distinct sub-cluster of the astrocyte-like tumor cell state that co-localizes with immune reactive TAMs. Neighboring GTCs and TAMs express receptor-ligand pairs characteristic of reactive astrogliosis and glial scarring, such as SPP1/CD44 and IL-1β/IL1R1. Collectively, we reveal that T cell confinement in IDHmt astrocytomas associates with GTC-TAM networks that mimic glial scarring mechanisms.

NLRX1 limits inflammatory neurodegeneration in the anterior visual pathway

Chronic innate immune activation in the central nervous system (CNS) significantly contributes to neurodegeneration in progressive multiple sclerosis (MS). Using multiple experimental autoimmune encephalomyelitis (EAE) models, we discovered that NLRX1 protects neurons in the anterior visual pathway from inflammatory neurodegeneration. We quantified retinal ganglion cell (RGC) density and optic nerve axonal degeneration, gliosis, and T-cell infiltration in Nlrx1-/- and wild-type (WT) EAE mice and found increased RGC loss and axonal injury in Nlrx1-/- mice compared to WT mice in both active immunization EAE and spontaneous opticospinal encephalomyelitis (OSE) models. To minimize the effects of Nlrx1-/- on peripheral lymphocyte priming during EAE, we performed adoptive transfer experiments, in which activated myelin-specific T cells were transferred into lymphocyte-deficient Rag-/- or Nlrx1-/-Rag-/- mice. In this model, we found more severe microgliosis and astrogliosis in the optic nerve of Nlrx1-/-Rag-/- mice compared to Rag-/- mice, suggesting a regulatory role of NLRX1 in innate immune cells. Transcriptome analysis in primary astrocytes activated with LPS and IFNγ demonstrated that NLRX1 suppresses NF-κB activation and regulates mitochondrial oxidative phosphorylation in inflammatory reactive astrocytes. The novel pharmacologic NLRX1 activators NX-13 and LABP-66 decreased LPS-mediated gene expression of inflammatory cytokines and chemokines in mixed glial cultures. Moreover, treating EAE mice with oral LABP-66, compared to vehicle, after the onset of paralysis resulted in less anterior visual pathway neurodegeneration. These data suggest that pharmacologic NLRX1 activators have the potential to limit inflammatory neurodegeneration. This study highlights that NLRX1 could serve as a promising target for neuroprotection in progressive MS and other neurodegenerative diseases. Further studies are needed to better understand the cell-specific mechanisms underlying the neuroprotective role of NLRX1 in response to inflammation in the CNS.

Tissue-Resident Memory T Cells in Gastrointestinal Cancers: Prognostic Significance and Therapeutic Implications

Gastrointestinal cancers, which include a variety of esophageal and colorectal malignancies, present a global health challenge and require effective treatment strategies. In the evolving field of cancer immunotherapy, tissue-resident memory T cells (Trm cells) have emerged as important players in the immune response within nonlymphoid tissues. In this review, we summarize the characteristics and functions of Trm cells and discuss their profound implications for patient outcomes in gastrointestinal cancers. Positioned strategically in peripheral tissues, Trm cells have functions beyond immune surveillance, affecting tumor progression, prognosis, and response to immunotherapy. Studies indicate that Trm cells are prognostic markers and correlate positively with enhanced survival. Their presence in the tumor microenvironment has sparked interest in their therapeutic potential, particularly with respect to immune checkpoint inhibitors, which may improve cancer treatment. Understanding how Trm cells work will not only help to prevent cancer spread through effective treatment but will also contribute to disease prevention at early stages as well as vaccine development. The role of Trm cells goes beyond just cancer, and they have potential applications in infectious and autoimmune diseases. This review provides a thorough analysis of Trm cells in gastrointestinal cancers, which may lead to personalized and effective cancer therapies.

The dilated veins surrounding the cord in multiple sclerosis suggest elevated pressure and obstruction of the glymphatic system

Recently, Clarke et al. published a study using spinal cord susceptibility weighted imaging in multiple sclerosis patients at 7T. They discovered dilated intradural extramedullary veins surrounding the cord. The purpose of this commentary is to point out some recent research by our group, which suggests this dilatation also occurs in the bridging cortical veins surrounding the brain. The dilatation indicates a focal elevation in the venous pressure secondary to impedance mismatching. Due to the shared outflow geometry, dilatation of the outflow veins will obstruct the glymphatic pathway of the spinal cord altering the immune response.

Osteopontin associates with brain TRM-cell transcriptome and compartmentalization in donors with and without multiple sclerosis

The human brain is populated by perivascular T cells with a tissue-resident memory T (T_RM)-cell phenotype, which in multiple sclerosis (MS) associate with lesions. We investigated the transcriptional and functional profile of freshly isolated T cells from white and gray matter. RNA sequencing of CD8⁺ and CD4⁺ CD69⁺ T cells revealed T_RM-cell signatures. Notably, gene expression hardly differed between lesional and normal-appearing white matter T cells in MS brains. Genes up-regulated in brain T_RM cells were MS4A1 (CD20) and SPP1 (osteopontin, OPN). OPN is also abundantly expressed by microglia and has been shown to inhibit T cell activity. In line with their parenchymal localization and the increased presence of OPN in active MS lesions, we noticed a reduced production of inflammatory cytokines IL-2, TNF, and IFNγ by lesion-derived CD8⁺ and CD4⁺ T cells ex vivo. Our study reports traits of brain T_RM cells and reveals their tight control in MS lesions.

Autoreactive lymphocytes in multiple sclerosis: Pathogenesis and treatment target

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) characterized by destruction of the myelin sheath structure. The loss of myelin leads to damage of a neuron’s axon and cell body, which is identified as brain lesions on magnetic resonance image (MRI). The pathogenesis of MS remains largely unknown. However, immune mechanisms, especially those linked to the aberrant lymphocyte activity, are mainly responsible for neuronal damage. Th1 and Th17 populations of lymphocytes were primarily associated with MS pathogenesis. These lymphocytes are essential for differentiation of encephalitogenic CD8⁺ T cell and Th17 lymphocyte crossing the blood brain barrier and targeting myelin sheath in the CNS. B-lymphocytes could also contribute to MS pathogenesis by producing anti-myelin basic protein antibodies. In later studies, aberrant function of Treg and Th9 cells was identified as contributing to MS. This review summarizes the aberrant function and count of lymphocyte, and the contributions of these cell to the mechanisms of MS. Additionally, we have outlined the novel MS therapeutics aimed to amend the aberrant function or counts of these lymphocytes.

T cell-neuron interaction in inflammatory and progressive multiple sclerosis biology

Multiple sclerosis (MS) is a chronic autoimmune condition of the central nervous system (CNS) characterized by acute inflammatory relapses, chronic neuro-axonal degeneration, and subsequent disability progression. T cells - in interaction with B cells and CNS-resident glial cells - are key initiators and drivers of neurodegeneration in MS. However, it is not entirely clear how encephalitogenic T cells orchestrate the local immune response within the brain and how they overtake disease stage-specific roles in MS pathogenesis. This review highlights recent advances in understanding direct and indirect T cell-neuron interactions in inflammatory and progressive MS. Finally, we discuss new diagnostic tools such as neurofilament light chain (NfL), which is on the cusp of becoming a key factor in clinical and therapeutic decision-making.

Single-cell profiling reveals periventricular CD56bright NK cell accumulation in multiple sclerosis

Multiple sclerosis (MS) is a chronic demyelinating disease characterised by immune cell infiltration resulting in lesions that preferentially affect periventricular areas of the brain. Despite research efforts to define the role of various immune cells in MS pathogenesis, the focus has been on a few immune cell populations while full-spectrum analysis, encompassing others such as natural killer (NK) cells, has not been performed. Here, we used single-cell mass cytometry (CyTOF) to profile the immune landscape of brain periventricular areas - septum and choroid plexus - and of the circulation from donors with MS, dementia and controls without neurological disease. Using a 37-marker panel, we revealed the infiltration of T cells and antibody-secreting cells in periventricular brain regions and identified a novel NK cell signature specific to MS. CD56bright NK cells were accumulated in the septum of MS donors and displayed an activated and migratory phenotype, similar to that of CD56bright NK cells in the circulation. We validated this signature by multiplex immunohistochemistry and found that the number of NK cells with high expression of granzyme K, typical of the CD56bright subset, was increased in both periventricular lesions and the choroid plexus of donors with MS. Together, our multi-tissue single-cell data shows that CD56bright NK cells accumulate in the periventricular brain regions of MS patients, bringing NK cells back to the spotlight of MS pathology.

A systematic review of clinical and preclinical evidences for Janus kinase inhibitors in large vessel vasculitis

Corticosteroid-sparing disease-modifying anti-rheumatic drugs are an area of active exploration in large vessel vasculitis (LVV), i.e., Takayasu arteritis (TAK) and Giant Cell Arteritis (GCA). The role of Janus kinase (JAK) inhibitors has been recently identified in different inflammatory rheumatic diseases. We conducted a systematic review of the use of JAK inhibitors in LVV across MEDLINE, Scopus, Web of Science, EMBASE, PubMed Central, Cochrane database of controlled trials, clinicaltrials.gov, and major recent international conferences. We identified four cohort studies and ten case reports. The JAK inhibitors used in these studies were tofacitinib, baricitinib, and ruxolitinib. A cohort study in TAK compared 27 patients treated with tofacitinib with 26 others treated with methotrexate, with better clinical outcomes with tofacitinib but similar angiographic stabilization, relapses, corticosteroid-sparing effect, and adverse events in both groups. Most of the other studies favored clinical responses with JAK inhibitors in LVV but with a paucity of data on other outcomes. Most of the included studies were of moderate quality. Evidence from pre-clinical models of LVV as well as limited in vivo data in patients with TAK appears to suggest that JAK inhibition reduces adventitial fibrosis, intimal proliferation, and inflammatory T lymphocyte infiltration in the media as well as reduces resident memory T cells in the vascular wall (which are otherwise resistant to corticosteroids). Ongoing clinical trials of tofacitinib, baricitinib, and upadacitinib in LVV shall help to further clarify the potential promise of JAK inhibitors for LVV (PROSPERO registration number CRD42021273359). KEY POINTS : •Tofacitinib appeared to associate with better clinical outcomes than methotrexate in TAK. •JAKinibs reduce adventitial fibrosis, intimal proliferation, and inflammatory vascular infiltrate in pre-clinical models of LVV. •Tofacitinib downregulates resident memory vascular T lymphocytes in pre-clinical models of LVV.

Emerging role of Tissue Resident Memory T cells in vitiligo: From pathogenesis to therapeutics

Vitiligo is an acquired depigmenting disorder which affects both skin and mucous membranes and autoimmunity has been strongly suggested to play a role in loss of melanocytes. The recurrence of skin macules at the same sites where they were observed prior to the treatment, suggests the existence of Tissue Resident Memory T cells (TRMs) that persist within the skin or peripheral tissues with a longer survivability. Emerging studies have shown that reactivation of these skin TRMs results into autoreactive TRM cells in various autoimmune diseases including vitiligo. This review focuses on different subsets (CD8⁺ TRMs and CD4⁺ TRMs) of TRM cells, their retention and survivability in the skin along with their pathomechanisms leading to melanocyte death and progression of vitiligo. In addition, the review describes the TRM cells as potential targets for developing effective therapeutics of vitiligo.

Cerebral Organoids-Challenges to Establish a Brain Prototype

The new cellular models based on neural cells differentiated from induced pluripotent stem cells have greatly enhanced our understanding of human nervous system development. Highly efficient protocols for the differentiation of iPSCs into different types of neural cells have allowed the creation of 2D models of many neurodegenerative diseases and nervous system development. However, the 2D culture of neurons is an imperfect model of the 3D brain tissue architecture represented by many functionally active cell types. The development of protocols for the differentiation of iPSCs into 3D cerebral organoids made it possible to establish a cellular model closest to native human brain tissue. Cerebral organoids are equally suitable for modeling various CNS pathologies, testing pharmacologically active substances, and utilization in regenerative medicine. Meanwhile, this technology is still at the initial stage of development.

CD8+ T Cell-Mediated Mechanisms Contribute to the Progression of Neurocognitive Impairment in Both Multiple Sclerosis and Alzheimer's Disease?

Neurocognitive impairment (NCI) is one of the most relevant clinical manifestations of multiple sclerosis (MS). The profile of NCI and the structural and functional changes in the brain structures relevant for cognition in MS share some similarities to those in Alzheimer's disease (AD), the most common cause of neurocognitive disorders. Additionally, despite clear etiopathological differences between MS and AD, an accumulation of effector/memory CD8+ T cells and CD8+ tissue-resident memory T (Trm) cells in cognitively relevant brain structures of MS/AD patients, and higher frequency of effector/memory CD8+ T cells re-expressing CD45RA (TEMRA) with high capacity to secrete cytotoxic molecules and proinflammatory cytokines in their blood, were found. Thus, an active pathogenetic role of CD8+ T cells in the progression of MS and AD may be assumed. In this mini-review, findings supporting the putative role of CD8+ T cells in the pathogenesis of MS and AD are displayed, and putative mechanisms underlying their pathogenetic action are discussed. A special effort was made to identify the gaps in the current knowledge about the role of CD8+ T cells in the development of NCI to "catalyze" translational research leading to new feasible therapeutic interventions.

Different Perivascular Space Burdens in Idiopathic Rapid Eye Movement Sleep Behavior Disorder and Parkinson's Disease

BACKGROUND

Excessive aggregation of α-synuclein is the key pathophysiological feature of Parkinson's disease (PD). Rapid eye movement sleep behavior disorder (RBD) is also associated with synucleinopathies and considered as a powerful predictor of PD. Growing evidence suggests the diminished clearance of α-synuclein may be partly attributable to poor interstitial fluid drainage, which can be reflected by magnetic resonance imaging (MRI)-visible enlarged perivascular space (EPVS). However, the effect of MRI-visible EPVS on iRBD and PD, and their correlation with clinical characteristics remain unclear.

OBJECTIVE

To evaluate the clinical and neuroimaging significance of MRI-visible EPVS in iRBD and PD patients.

METHODS

We enrolled 33 iRBD patients, 82 PD (with and without RBD) patients, and 35 healthy controls (HCs), who underwent clinical evaluation and 3.0 Tesla MRI. Two neurologists assessed MRI-visible EPVS in centrum semiovale (CSO), basal ganglia (BG), substantia nigra (SN), and brainstem (BS). Independent risk factors for iRBD and PD were investigated using multivariable logistic regression analysis. Spearman analysis was used to test the correlation of MRI-visible EPVS with clinical characteristics of patients.

RESULTS

iRBD patients had significantly higher EPVS burdens (CSO, BG, SN, and BS) than PD patients. Higher CSO-EPVS and BS-EPVS burdens were independent risk factors for iRBD. Furthermore, higher CSO-EPVS and SN-EPVS burdens were positively correlated with the severity of clinical symptom in iRBD patients, and higher BG-EPVS burden was positively correlated with the severity of cognitive impairment in PD patients.

CONCLUSION

iRBD and PD patients have different MRI-visible EPVS burdens, which may be related with a compensatory mechanism in glymphatic system. Lower MRI-visible EPVS burden in PD patients may be a manifestation of severe brain waste drainage dysfunction. These findings shed light on the pathophysiologic relationship between iRBD and PD with respect to neuroimaging marker of PD.