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"PATHOLOGY"
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Pericyte-derived fibrotic scarring is conserved across diverse central nervous system lesions
Fibrotic scar tissue limits central nervous system regeneration in adult mammals. The extent of fibrotic tissue generation and distribution of stromal cells across different lesions in the brain and spinal cord has not been systematically investigated in mice and humans. Furthermore, it is unknown whether scar-forming stromal cells have the same origin throughout the central nervous system and in different types of lesions. In the current study, we compared fibrotic scarring in human pathological tissue and corresponding mouse models of penetrating and non-penetrating spinal cord injury, traumatic brain injury, ischemic stroke, multiple sclerosis and glioblastoma. We show that the extent and distribution of stromal cells are specific to the type of lesion and, in most cases, similar between mice and humans. Employing in vivo lineage tracing, we report that in all mouse models that develop fibrotic tissue, the primary source of scar-forming fibroblasts is a discrete subset of perivascular cells, termed type A pericytes. Perivascular cells with a type A pericyte marker profile also exist in the human brain and spinal cord. We uncover type A pericyte-derived fibrosis as a conserved mechanism that may be explored as a therapeutic target to improve recovery after central nervous system lesions.
Fibrotic scar tissue limits central nervous system regeneration. Here, Dias et al. show that fibrotic scarring is common in mice and humans, following distinct lesions to the adult brain and spinal cord, and derives from a discrete population of GLAST-expressing perivascular cells.
Journal Article
Flexible 19-Gauge Endobronchial Ultrasound-Guided Transbronchial Needle Aspiration Needle: First Experience
Background: Endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) is a well-established first-line invasive modality for mediastinal lymph node staging in lung cancer patients and in the diagnostic workup of patients with mediastinal adenopathy. With the current 21- and 22-gauge (G) EBUS-TBNA needles, the procedure can be limited by the degree of flexibility in the needle and the size of the lumen in tissue acquisition. Objective: We report our initial experience with a first-generation flexible 19-G EBUS-TBNA (Flex 19G; Olympus Respiratory America, Redmond, WA, USA) needle with regards to efficacy and safety. Methods: The Flex 19G EBUS-TBNA needle was used in 47 selected patients with enlarged hilar and/or mediastinal lymphadenopathy at 3 centers. The standard Olympus EBUS scope with a 2.2-mm working channel was used in all cases. Results: The diagnostic yield of the Flex 19G needle according to clinical cytopathology reports was 89% (42/47). The diagnosis and their respective diagnostic yield with the Flex 19G EBUS-TBNA needle were malignancy 24/27 (89%), sarcoidosis 13/14 (93%), and reactive lymph node hyperplasia 5/6 (83%). The mean short axis of the sampled lymph nodes was 19 ± 9 mm. No complications occurred except for 1 instance of moderate bleeding, which did not require intervention beyond suctioning and subsequently resolved. All 13 patients diagnosed with adenocarcinoma by the 19-G needle had sufficient tissue for genetic testing. Conclusion: EBUS-TBNA using the first-generation Flex 19G needle is feasible and safe with promising diagnostic yield while providing a greater degree of flexion with the Olympus EBUS scope. Additional clinical evaluations are warranted.
Journal Article
Microglia regulate central nervous system myelin growth and integrity
Myelin is required for the function of neuronal axons in the central nervous system, but the mechanisms that support myelin health are unclear. Although macrophages in the central nervous system have been implicated in myelin health
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, it is unknown which macrophage populations are involved and which aspects they influence. Here we show that resident microglia are crucial for the maintenance of myelin health in adulthood in both mice and humans. We demonstrate that microglia are dispensable for developmental myelin ensheathment. However, they are required for subsequent regulation of myelin growth and associated cognitive function, and for preservation of myelin integrity by preventing its degeneration. We show that loss of myelin health due to the absence of microglia is associated with the appearance of a myelinating oligodendrocyte state with altered lipid metabolism. Moreover, this mechanism is regulated through disruption of the TGFβ1–TGFβR1 axis. Our findings highlight microglia as promising therapeutic targets for conditions in which myelin growth and integrity are dysregulated, such as in ageing and neurodegenerative disease
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Resident microglia in the central nervous system are identified as the specific macrophage population that regulates myelin growth and integrity.
Journal Article
Histopathology and ultrastructural findings of fatal COVID-19 infections in Washington State: a case series
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the cause of an ongoing pandemic, with increasing deaths worldwide. To date, documentation of the histopathological features in fatal cases of the disease caused by SARS-CoV-2 (COVID-19) has been scarce due to sparse autopsy performance and incomplete organ sampling. We aimed to provide a clinicopathological report of severe COVID-19 cases by documenting histopathological changes and evidence of SARS-CoV-2 tissue tropism.
In this case series, patients with a positive antemortem or post-mortem SARS-CoV-2 result were considered eligible for enrolment. Post-mortem examinations were done on 14 people who died with COVID-19 at the King County Medical Examiner's Office (Seattle, WA, USA) and Snohomish County Medical Examiner's Office (Everett, WA, USA) in negative-pressure isolation suites during February and March, 2020. Clinical and laboratory data were reviewed. Tissue examination was done by light microscopy, immunohistochemistry, electron microscopy, and quantitative RT-PCR.
The median age of our cohort was 73·5 years (range 42–84; IQR 67·5–77·25). All patients had clinically significant comorbidities, the most common being hypertension, chronic kidney disease, obstructive sleep apnoea, and metabolic disease including diabetes and obesity. The major pulmonary finding was diffuse alveolar damage in the acute or organising phases, with five patients showing focal pulmonary microthrombi. Coronavirus-like particles were detected in the respiratory system, kidney, and gastrointestinal tract. Lymphocytic myocarditis was observed in one patient with viral RNA detected in the tissue.
The primary pathology observed in our cohort was diffuse alveolar damage, with virus located in the pneumocytes and tracheal epithelium. Microthrombi, where observed, were scarce and endotheliitis was not identified. Although other non-pulmonary organs showed susceptibility to infection, their contribution to the pathogenesis of SARS-CoV-2 infection requires further examination.
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Journal Article
Phagocyte-mediated synapse removal in cortical neuroinflammation is promoted by local calcium accumulation
Cortical pathology contributes to chronic cognitive impairment of patients suffering from the neuroinflammatory disease multiple sclerosis (MS). How such gray matter inflammation affects neuronal structure and function is not well understood. In the present study, we use functional and structural in vivo imaging in a mouse model of cortical MS to demonstrate that bouts of cortical inflammation disrupt cortical circuit activity coincident with a widespread, but transient, loss of dendritic spines. Spines destined for removal show local calcium accumulations and are subsequently removed by invading macrophages or activated microglia. Targeting phagocyte activation with a new antagonist of the colony-stimulating factor 1 receptor prevents cortical synapse loss. Overall, our study identifies synapse loss as a key pathological feature of inflammatory gray matter lesions that is amenable to immunomodulatory therapy.
Synapse loss is prominent in the cortex in multiple sclerosis (MS). In a cortical MS model, Jafari et al. show that phagocytes remove synapses by engulfment, which is triggered by local calcium accumulations and prevented by blocking colony-stimulating factor 1 signaling.
Journal Article