Project description:Aging is a major risk factor for many neurological pathologies, including Alzheimer’s disease (AD). However, the mechanisms underlying brain aging and cognitive decline remain elusive. Body tissues are perfused by interstitial fluid (ISF), which is locally reabsorbed via the lymphatic vascular network. In contrast, the parenchyma of the central nervous system (CNS) is devoid of lymphatic vasculature; in the brain, removal of cellular debris and toxic molecules, such as amyloid beta (A) peptides, is mediated by a combination of transcellular mechanisms of transport across the blood−brain and blood−cerebrospinal fluid (CSF) barriers, phagocytosis and digestion by resident microglia and recruited monocytes/macrophages, and CSF influx and ISF efflux through a paravascular route. The recent characterization of meningeal lymphatic vessels prompted a reassessment of the conventional pathways of CNS waste clearance. The role of this vasculature in brain function, specifically in the context of aging and AD, is still poorly understood. Here we show that meningeal lymphatic vessels play an essential role in maintaining brain homeostasis by draining macromolecules from the CNS (CSF and ISF) into the cervical lymph nodes. Using pharmacological, surgical, and genetic models we show that impairment of meningeal lymphatic function in adult mice slows paravascular influx of CSF macromolecules and efflux of ISF macromolecules, and induces cognitive impairment. Treatment with a lymphangiogenic factor, vascular endothelial growth factor C (VEGF-C), enhances meningeal lymphatic drainage of CSF macromolecules, improving brain perfusion and learning and memory performance in aged mice. Disruption of meningeal lymphatic vessels in transgenic mouse models of AD promotes amyloid deposition in the meninges, which closely correlates with human meningeal pathology, and aggravates overall disease severity. Our findings suggest that meningeal lymphatic dysfunction may be an aggravating factor in AD pathology and in age-associated cognitive decline. Thus, augmentation of meningeal lymphatic function might be a promising therapeutic target for preventing or delaying age-associated neurological diseases.

Project description:Sphingosine 1-phosphate (S1P) influences T cell migration into and out of secondary lymphoid organs; however, its mechanism of action remains uncertain. Our previous research shows that agonism of the S1P receptor S1P1 inhibits the egress of T lymphocytes from the peripheral tissues into afferent lymphatics. To better define the mechanism of inhibition, we developed an in vitro model to characterize T cell transendothelial migration across lymphatics. Two commercially available endothelial cell lines (MS-1 and SVEC4-10) were characterized by flow cytometry, real time RT-PCR, and Affymetrix Gene Array. These cell lines were grown to confluent monolayers in transwell systems, on either the upper or lower surface of the transwell insert. T cells were isolated from the spleens of (C57BL/6 x C3H/HeJ)F1, S1P1 KO, or S1P1 KO littermate controls, and either treated with the S1P receptor modulator FTY720 or left untreated. Cells were migrated to chemokines (CCL19 or CCL21) for 4 hours, and migration quantified. Flow cytometry, RT-PCR, and array results identified MS-1 as a blood vascular endothelial cell line, expressing high levels of CD31, CD34, and ICAM-1 as well as other endothelial cell markers; while SVEC4-10 closely resemble a lymphatic phenotype, expressing LYVE-1, VEGFR-3, and podoplanin. T cells efficiently migrate across MS-1, whether grown on the upper or lower surface; whereas migration across SVEC4-10 only occurs when cells are grown on the lower surface of the transwell (iSVEC), recapitulating basal (abluminal) to apical (luminal) migration that occurs in vivo. FTY720 inhibits T cell migration across iSVEC, but not across MS-1. Inhibition is due to drug effects only on T cells but not endothelial cells. S1P1 KO T cells treated with FTY720 are not inhibited in their migration across the iSVEC line, showing that S1P1 stimulation is required for migration inhibition. The in vitro model developed here is the first to use endothelial cell lines to analyze the regulation of T cell migration across lymphatic endothelium. The results show there is directional control of T cell migration across lymphatic cells, such that T cells only migrate from a basal to apical direction. Agonism of S1P1 specifically inhibits migration, while absence of the receptor does not. These findings have important implications for the use of S1P1 agonists in transplantation, as inhibition of cell entry into afferent lymphatics and lymph nodes could impede the development of graft rejection. We used microarrays to detail the global gene expression of these two cell lines in order to beter determine their phenotype as blood vascular or lymphatic endothelial cell line for use in our newly-developed in vitro model. Experiment Overall Design: MS-1 or SVEC4-10 endothelial cell lines were grown in culture flasks for 3-5 days in standard culture medium (see protocol below) until reaching confluence. Cells were then gently dissociated from flask and cells were placed in Trizol reagent for RNA isolation.

Project description:Patient-derived cells hold great promise for precision medicine approaches in human health. Fibroblast cells have been a major source of human cells for reprogramming and differentiating into specific cell types for disease modeling. Such cells can be isolated at various stages during life (presymptomatic, symptomatic, and advanced disease) and thus can potentially be used to model different phases of disease progression. In certain circumstances, however, tissues are not collected during life and only postmortem tissues are the only available source of fibroblasts. Fibroblasts cultured from postmortem human dura mater of individuals with neurodegenerative diseases have been suggested as a primary source of cells for in vitro modeling of neurodegenerative diseases. Although fibroblast-like cells from human and mouse dura mater have been previously described, their utility for reprogramming and direct differentiation protocols requires further characterization. In this study, cells derived from dermal biopsies of living subjects were compared to cells derived from postmortem dura mater. In two instances, we have isolated and compared dermal and dural cell lines from the same subject. Notably, such striking differences were observed between cells of dermal and dural origin that their fibroblast nature was brought into question. Compared to dermal fibroblasts, postmortem dura mater-derived cells demonstrated different morphology, slower growth rates, and a higher rate of karyotype abnormality. Dura mater-derived cells also failed to express fibroblast protein markers. When dermal fibroblasts and dural-derived cells from the same subject were compared, they exhibited significant differences in gene expression profiles. Ultimately, dura mater-derived cells were found to originate from a mixed mural lineage consisting of smooth muscle cells and pericytes. Our study argues for rigorous karyotyping of all postmortem derived cell lines and highlights significant limitations of postmortem human dura mater-derived cells for modeling normal biology or disease-associated pathobiology.

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Cerebral Venous Blood Flow Regulates Brain Fluid Clearance via Dural Lymphatics

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