Project description:The meninges are critical for the brain functions, but the diversity of meningeal cell types and intercellular interactions have yet to be thoroughly examined. Here we identify a population of meningeal lymphatic supporting cells (mLSCs) in the zebrafish leptomeninges, which are specifically labeled by ependymin. Morphologically, mLSCs form membranous structures that enwrap the majority of leptomeningeal blood vessels and all the mural lymphatic endothelial cells (muLECs). Based on its unique cellular morphologies and transcriptional profile, mLSC is characterized as a unique cell type different from all the currently known meningeal cell types. Because of the formation of supportive structures and production of pro-lymphangiogenic factors, mLSCs not only promote muLEC development and maintain the dispersed distributions of muLECs in the leptomeninges, but also are required for muLEC regeneration after ablation. This study characterizes a newly identified cell type in leptomeninges, mLSC, which is required for muLEC development, maintenance, and regeneration.
Project description:Pericytes/vascular smooth muscle cells (VSMCs), regulated by platelet-derived growth factor receptor β (PDGFRβ) signaling, play important roles in endothelial survival and vascular stability. Here we report that treatment with imatinib, an inhibitor of PDGFRβ, led to significant tumor growth impairment associated with increased apoptosis in human lymphoma xenografts including Farage, Karpas422 and OCI-Ly7 in SCID mice. Confocal analysis of the tumor tissue showed decreased microvessel density, decreased vascular flow, and increased vascular leak in the imatinib-treated cohorts. Imatinib targeted tumor-associated PDGFRβ+ pericytes in vivo by inducing apoptosis and disruption of the PDGFRβ+ perivascular network, and PDGFRβ+ VSMC in vitro by inhibition of proliferation. FACS analysis of mononuclear cell suspension of tumor tissues revealed decreased mature pericytes and endothelial cells, as well as their progenitors with imatinib treatment. Compared to imatinib, treatment with anti-PDGFRβ monoclonal antibody partially inhibited the growth of Farage lymphomas. Lastly, microarray analysis of differentially expressed genes in PDGFRβ+ VSMC following imatinib treatment showed significant down-regulation of genes implicated in proliferation, survival and angiogenesis, including those within PI3K/AKT and MAPK/ERK1/2 pathways downstream of PDGFRβ signaling. Taken together, targeting PDGFRβ+ pericytes in lymphoma presents a novel and complementary target to endothelial cells for efficacious antiangiogenic therapy. PDGFRb+ murine vascular smooth muscle cells (VSMCs) were treated in 10 uM imatinib for 24 or 48 hours. Gene expression changes in response to imatinib treatment were examined using NimbleGen MM8_60mer gene expression microarrays by comparing expression patterns at 24- and 48-hours treatment to the baseline level (0 hours).
Project description:Recent studies have shown that meningeal lymphatic vessels (MLVs), which are located both dorsally and basally beneath the skull, provide a route for draining macromolecules and trafficking immune cells from the central nervous system (CNS) into cervical lymph nodes (CLNs), and thus represent a potential therapeutic target for treating neurodegenerative and neuroinflammatory diseases. However, the roles of MLVs in brain tumor drainage and immunity remain unexplored. Here we show that dorsal MLVs undergo extensive remodeling in mice with intracranial gliomas or metastatic melanomas. RNA-seq analysis of MLV endothelial cells revealed changes in the gene sets involved in lymphatic remodeling, fluid drainage, as well as inflammatory and immunological responses. Disruption of dorsal MLVs alone impaired intratumor fluid drainage and the dissemination of brain tumor cells to deep CLNs (dCLNs). Notably, the dendritic cell (DC) trafficking from intracranial tumor tissues to dCLNs decreased in mice with defective dorsal MLVs, and increased in mice with enhanced dorsal meningeal lymphangiogenesis. Strikingly, disruption of dorsal MLVs alone, without affecting basal MLVs or nasal LVs, significantly reduced the efficacy of combined anti-PD-1/CTLA-4 checkpoint therapy in striatal tumor models. Furthermore, mice bearing tumors overexpressing VEGF-C displayed a better response to anti-PD-1/CTLA-4 combination therapy, and this was abolished by CCL21/CCR7 blockade, suggesting that VEGF-C potentiates checkpoint therapy via the CCL21/CCR7 pathway. Together, the results of our study not only demonstrate the functional aspects of MLVs as classic lymphatic vasculature, but also highlight that they are essential in generating an efficient immune response against brain tumors.
Project description:Pericytes/vascular smooth muscle cells (VSMCs), regulated by platelet-derived growth factor receptor β (PDGFRβ) signaling, play important roles in endothelial survival and vascular stability. Here we report that treatment with imatinib, an inhibitor of PDGFRβ, led to significant tumor growth impairment associated with increased apoptosis in human lymphoma xenografts including Farage, Karpas422 and OCI-Ly7 in SCID mice. Confocal analysis of the tumor tissue showed decreased microvessel density, decreased vascular flow, and increased vascular leak in the imatinib-treated cohorts. Imatinib targeted tumor-associated PDGFRβ+ pericytes in vivo by inducing apoptosis and disruption of the PDGFRβ+ perivascular network, and PDGFRβ+ VSMC in vitro by inhibition of proliferation. FACS analysis of mononuclear cell suspension of tumor tissues revealed decreased mature pericytes and endothelial cells, as well as their progenitors with imatinib treatment. Compared to imatinib, treatment with anti-PDGFRβ monoclonal antibody partially inhibited the growth of Farage lymphomas. Lastly, microarray analysis of differentially expressed genes in PDGFRβ+ VSMC following imatinib treatment showed significant down-regulation of genes implicated in proliferation, survival and angiogenesis, including those within PI3K/AKT and MAPK/ERK1/2 pathways downstream of PDGFRβ signaling. Taken together, targeting PDGFRβ+ pericytes in lymphoma presents a novel and complementary target to endothelial cells for efficacious antiangiogenic therapy.
Project description:Mural cells are critically important for the development, maturation, and maintenance of the blood vasculature. Pericytes are predominantly observed in capillaries and venules, while vascular smooth muscle cells (VSMCs) are found in arterioles, arteries, and veins. In this study, we have investigated functional differences between human pericytes and human coronary artery smooth muscle cells (CASMCs) as a model VSMC type. We compared the ability of these two mural cells to invade three-dimensional (3D) collagen matrices, recruit to developing human endothelial cell (EC)-lined tubes in 3D matrices and induce vascular basement membrane matrix assembly around these tubes. Here, we show that pericytes selectively invade, recruit, and induce basement membrane deposition on EC tubes under defined conditions, while CASMCs fail to respond equivalently. Pericytes dramatically invade 3D collagen matrices in response to the EC-derived factors, platelet-derived growth factor (PDGF)-BB, PDGF-DD, and endothelin-1, while minimal invasion occurs with CASMCs. Furthermore, pericytes recruit to EC tube networks, and induce basement membrane deposition around assembling EC tubes (narrow and elongated tubes) when these cells are co-cultured. In contrast, CASMCs are markedly less able to perform these functions showing minimal recruitment, little to no basement membrane deposition, with wider and shorter tubes. Our new findings suggest that pericytes demonstrate much greater functional ability to invade 3D matrix environments, recruit to EC-lined tubes and induce vascular basement membrane matrix deposition in response to and in conjunction with ECs.
Project description:Pericytes adhere to the abluminal surface of endothelial tubules and are required for the formation of stable vascular networks. Defective endothelial cell-pericyte interactions are frequently observed in diseases characterized by compromised vascular integrity such as diabetic retinopathy. Many functional properties of pericytes and their exact role in the regulation of angiogenic blood vessel growth remain elusive. Here we show that pericytes promote endothelial sprouting in the postnatal retinal vasculature. Using genetic and pharmacological approaches, we show that the expression of vascular endothelial growth factor receptor 1 (VEGFR1) by pericytes spatially restricts VEGF signalling. Angiogenic defects caused by pericyte depletion are phenocopied by intraocular injection of VEGF-A or pericyte-specific inactivation of the murine gene encoding VEGFR1. Our findings establish that pericytes promote endothelial sprouting, which results in the loss of side branches and the enlargement of vessels when pericyte function is impaired or lost.
Project description:Vascular physiology relies on the concerted dynamics of several cell types, including pericytes, endothelial, and vascular smooth muscle cells. The interactions between such cell types are inherently dynamic and are not easily described with static, fixed, experimental approaches. Pericytes are mural cells that support vascular development, remodeling, and homeostasis, and are involved in a number of pathological situations including cancer. The dynamic interplay between pericytes and endothelial cells is at the basis of vascular physiology and few experimental tools exist to properly describe and study it. Here we employ a previously developed ex vivo murine aortic explant to study the formation of new blood capillary-like structures close to physiological situation. We develop several mouse models to culture, identify, characterize, and follow simultaneously single endothelial cells and pericytes during angiogenesis. We employ microscopy and image analysis to dissect the interactions between cell types and the process of cellular recruitment on the newly forming vessel. We find that pericytes are recruited on the developing sprout by proliferation, migrate independently from endothelial cells, and can proliferate on the growing capillary. Our results help elucidating several relevant mechanisms of interactions between endothelial cells and pericytes.
Project description:Tumor neo-vasculature is characterized by spatial coordination of endothelial cells with mural cells, which delivers oxygen and nutrients. Here, we explored a key role of the secreted glycoprotein YKL-40, a mesenchymal marker, in the interaction between endothelial cells and mesenchymal mural-like cells for tumor angiogenesis. Xenotransplantation of tumor-derived mural-like cells (GSDCs) expressing YKL-40 in mice developed extensive and stable blood vessels covered with more GSDCs than those in YKL-40 gene knockdown tumors. YKL-40 expressed by GSDCs was associated with increased interaction of neural cadherin/β-catenin/smooth muscle alpha actin; thus, mediating cell-cell adhesion and permeability. YKL-40 also induced the interaction of vascular endothelial cadherin/β-catenin/actin in endothelial cells (HMVECs). In cell co-culture systems, YKL-40 enhanced both GSDC and HMVEC contacts, restricted vascular leakage, and stabilized vascular networks. Collectively, the data inform new mechanistic insights into the cooperation of mural cells with endothelial cells induced by YKL-40 during tumor angiogenesis, and also enhance our understanding of YKL-40 in both mural and endothelial cell biology.
Project description:Meningeal lymphatic vessels transport both the cerebrospinal fluid and interstitial fluid to the deep cervical lymph nodes. Traumatic brain injury (TBI) is accompanied by meningeal injury. We hypothesized that the TBI-induced meningeal injury would damage lymphatic vessels and affect brain function. We observed altered gene expression in meningeal lymphatic endothelial cells (LECs) in a mouse model of TBI. Through flow cytometry-based cell sorting, meningeal LECs were obtained from a mouse model of controlled cortical impact 3 days after TBI. Microarray analysis, real-time polymerase chain reaction assays, and enzyme-linked immunosorbent assays were performed to determine mRNA and protein expression levels in meningeal LECs. The number of meningeal LECs was significantly lower in the injury group than in the sham group 3 days after TBI. Additionally, the mRNA expression of lymphatic vessel endothelial hyaluronan receptor 1 (a specific marker of lymphatic vessels) in meningeal LECs was significantly lower in the injury group than in the sham group. The mRNA and protein expression of FMS-like tyrosine kinase 4 and neuropilin 2 (markers of lymphangiogenesis) in meningeal LECs was significantly higher in the injury group than in the sham group. Our findings indicate that TBI is associated with the impairment of meningeal LECs and meningeal lymphangiogenesis, which implicates lymphatic vessel injury in the pathogenesis of this condition.