Project description:The lineage and developmental trajectory of a cell are key determinant s of cellular identity. In the vascular system, endothelial cells (ECs) of blood and lymphatic vessels (LVs) differentiate and diversify to cater the different physiological demands of each organ . While LVs are known to originate from multiple origins , lymphatic ECs (LECs) themselves are not known to generate other cell - types . Here, we u s e recurrent imaging and lineage - tracing of ECs in zebrafish anal fins (AF) from early development through adulthood , to uncover an unexpected mechanism of specialized blood vessel formation through transdifferentiation of LECs . Moreover, we demonstrate distinct functional implications for deriving AF vessels from either LECs or blood ECs, uncovering a link between cell ontogeny and functionality. We further use scRNA - seq to characterize the different cellular populations and transition states involved in the transdifferentiation process . Finally, we show that akin to its normal development, the vasculature is re - derived from lymphatics during AF regeneration, demonstr ating that LECs in adult fish retain both potency and plasticity for generating blood ECs . Overall, our work highlights a new innate mechanism of blood vess el formation through LEC trans differentiation, and provides in vivo evidence for a link between cell ontogeny and functionality in ECs
Project description:Lymphogenous metastasis is an important event in the progression of many human cancers, and is associated with expression of vascular endothelial growth factor-D (VEGF-D). Changes to the lymphatic vasculature can occur during metastasis, and may aid metastatic spread. We investigated the effect of tumour derived VEGFD on the endothelium of the collecting lymphatic vessels draining primary tumors. We used microarrays to detail the changes in gene expression in the collecting lymphatic endothelium of mice with 293EBNA xenografts compared to 293EBNA xenografts overexpressing VEGFD. Mice were injected with 293EBNA cells (transfected with either empty APEX vector, or vector containing VEGFD) and tumours were allowed to grow to size. Mice were sacrificed and collecting lymphatic vessels were dissected. The endothelial cell population was isolated and RNA was extracted and hybridized on Affymetrix microarrays.
Project description:Lymphogenous metastasis is an important event in the progression of many human cancers, and is associated with expression of vascular endothelial growth factor-D (VEGF-D). Changes to the lymphatic vasculature can occur during metastasis, and may aid metastatic spread. We investigated the effect of tumour derived VEGFD on the endothelium of the collecting lymphatic vessels draining primary tumors. We used microarrays to detail the changes in gene expression in the collecting lymphatic endothelium of mice with 293EBNA xenografts compared to 293EBNA xenografts overexpressing VEGFD.
Project description:Antigen-specific CD8+ T cell accumulation in tumors is a prerequisite for effective immunotherapy, and yet, the mechanisms of lymphocyte transit remain poorly defined. We find that tumor-associated lymphatic vessels control T cell exit from tumors via the chemokine CXCL12, and intratumoral antigen encounter tunes CXCR4 expression on effector CD8+ T cells. Only high affinity antigen downregulates CXCR4 and upregulates the CXCL12 decoy receptor, ACKR3, thereby reducing CXCL12 sensitivity and promoting T cell retention. A diverse repertoire of functional tumor-specific CD8+ T cells exit the tumor, thereby limiting tumor control. CXCR4 inhibition and loss of lymphatic-specific CXCL12 boosts T cell retention and enhances tumor control. Strategies that limit T cell egress, therefore, provide a new tool to boost the response to immunotherapy.
Project description:The lymphatic vascular system plays important roles in the maintenance of interstitial fluid pressure, the afferent immune response and the absorption of dietary lipids. However, the molecular mechanisms that control lymphatic vessel network maturation and function remain largely unknown. To identify novel players in lymphatic vessel function, we isolated pure populations of lymphatic and blood vascular endothelial cells from mouse intestine using fluorescence-activated high-speed cell sorting and performed transcriptional profiling. We found that the axonal guidance molecules semaphorin 3A (Sema3A) and Sema3D were specifically expressed by lymphatic vessels. Quantitative PCR of ex vivo isolated cells and immunohistochemical analysis confirmed these results. Importantly, we found that the semaphorin receptor neuropilin-1 (Nrp-1) is expressed on the valves of collecting lymphatic vessels. Treatment of mice in utero (E12.5-E16.5) with an antibody that blocks Sema3A binding to Nrp-1, but not with an antibody that blocks VEGFA binding to Nrp-1, resulted in abnormal development of collecting lymphatic vessels and valves, and aberrant smooth muscle cell coverage. Conversely, Sema3A-deficient mice displayed branching defects of collecting lymphatic vessels as well as impaired valve development. Together, these results reveal an unanticipated role of Sema3A/Nrp-1 signaling in the maturation of the lymphatic vascular network.
Project description:The lymphatic vascular system plays important roles in the maintenance of interstitial fluid pressure, the afferent immune response and the absorption of dietary lipids. However, the molecular mechanisms that control lymphatic vessel network maturation and function remain largely unknown. To identify novel players in lymphatic vessel function, we isolated pure populations of lymphatic and blood vascular endothelial cells from mouse intestine using fluorescence-activated high-speed cell sorting and performed transcriptional profiling. We found that the axonal guidance molecules semaphorin 3A (Sema3A) and Sema3D were specifically expressed by lymphatic vessels. Quantitative PCR of ex vivo isolated cells and immunohistochemical analysis confirmed these results. Importantly, we found that the semaphorin receptor neuropilin-1 (Nrp-1) is expressed on the valves of collecting lymphatic vessels. Treatment of mice in utero (E12.5-E16.5) with an antibody that blocks Sema3A binding to Nrp-1, but not with an antibody that blocks VEGFA binding to Nrp-1, resulted in abnormal development of collecting lymphatic vessels and valves, and aberrant smooth muscle cell coverage. Conversely, Sema3A-deficient mice displayed branching defects of collecting lymphatic vessels as well as impaired valve development. Together, these results reveal an unanticipated role of Sema3A/Nrp-1 signaling in the maturation of the lymphatic vascular network. Colon single-cell suspensions were prepared by a fast protocol that minimizes the RNA degradation. Fluorescence-activated cell sorting (FACS) was used to sort blood vascular endothelial cells (BEC) and lymphatic endothelial cells (LEC). 4 animal-matched pairs of LEC and BEC were chosen based on the quality of extracted and amplified material to provide homogenous groups of biological replicates. This gave 8 samples to analyze. Samples present LEC and BEC isolated from 4 healthy normal mice. The 4 mice used present the 4 biological replicates.
Project description:How cells acquire their fate is a fundamental question in both developmental and regenerative biology. Multipotent progenitors undergo gradual cell fate restriction in response to temporal and positional cues from the microenvironment, the nature of which is far from being clear. In the case of the lymphatic system, venous endothelial cells are thought to give rise to lymphatic vessels, through a process of trans-differentiation. Upon expression of a set of transcription factors, venous cells acquire a lymphatic fate, and bud out to generate the lymphatic vasculature. In this work we challenge this view and show that while lymphatic endothelial cells (LECs) do arise in the Cardinal Vein (CV), they do so from a previously uncharacterized pool of multipotent angioblasts. Using lymphatic-specific transgenic zebrafish, in combination with endothelial photoconvertible reporters, and long-term live imaging, we demonstrate that these multipotent angioblasts can generate not only lymphatic, but also arterious, and venous fates. We further reveal that the underlying endoderm serves as a source of Wnt5b, which acts as a lymphatic inductive signal, promoting the angioblast-to-lymphatic transition. Moreover, Wnt5b induced lymphatic specification in human embryonic stem cells- derived vascular progenitors, suggesting that this process is evolutionary conserved. Our results uncover a novel mechanism of lymphatic vessel formation, whereby multipotent angioblasts and not venous endothelial cells give rise to the lymphatic endothelium, and provide the first characterization of their inductive niche. More broadly, our findings highlight the CV as a plastic and heterogeneous structure containing different cell populations, analogous to the hematopoietic niche in the aortic floor. Following Kaede photoconversion of dorsal or ventral halves of the PCV in Tg(fli1:gal4;uasKaede) embryos at 24 hpf, 6 embryos per group were used for FACS isolation of Kaede photconverted (red) ECs.
Project description:Afferent lymphatic vessels (LVs) connect peripheral tissues with draining lymph nodes (dLNs) and are important for immune-surveillance and tissue drainage. They begin in the tissue as initial lymphatic capillaries, which are highly permeable and branched vessels specialized in the uptake of macromolecules, fluids and immune cells. Conversely, the downstream collecting LVs are impermeable and contractile structures that transport the taken up lymph and immune cells to the dLN. We and others have recently observed that intralymphatic leukocytes actively migrate within lymphatic capillaries but de-adhere and are passively transported by flow once they have reached in the collecting vessels. Besides potential differences in lymph flow we hypothesize that gene expression differences between capillaries and collectors could account for this transition from a crawling to a flowing mode of migration. In this project we aimed to perform a sequencing-based gene expression analysis of lymphatic endothelial cells (LECs) isolated from lymphatic capillaries and collectors, in order to identify new genes involved in leukocyte migration, as well as genes involved in shaping the morphologic phenotype of capillaries and collectors. For this, murine skin was enzymatically digested and LECs from capillaries or collectors were FACS-sorted and their RNA extracted and subjected to sequencing.
Project description:The goal and objective of this study was to identify the transcriptional profiles differentiating the artery, vein, and lymphatic lineages in the adult rat vasculature with particular emphasis on the unique elements of the collecting lymphatic vessel transcriptome. A 2 x 3 experimental design was utilized in which parallel arteries, veins, and lymphatics from two different tissue beds were examined. The rat thoracic duct was selected as a large, post-nodal collecting lymphatic vessel that exhibits excellent conduit-type behavior while the rat mesenteric lymphatic was selected as a smaller, pre-nodal collecting lymphatic vessel that exhibits excellent pump behavior (see Gashev AA, et al. Microcirculation. 2004 Sep;11(6):477-92. [PMID: 15371129]). The axillary artery and vein were selected for comparison to the thoracic duct due to their similar anatomical position distal to the common junction of the lymphatic and venous vascular trees and represent a large artery and large vein, respectively. The mesentery artery and vein were selected for comparison to the mesenteric lymphatic vessels due to their parallel position within the mesenteric vasculature and represent a small atery and small vein, respectively. A 2 x 3, reference-based, experimental design was utilized consisting of both large (thoracic) and small (mesenteric) arteries, veins, and collecting lymphatic vessels for a total of 6 sample groups with n=6 biological replicates present in each group. All vessels acquired from the same donor animal have the same numerical label and were handled in parallel through all experimental steps. Each vessel sample RNA sample was amplified, labeled with Cy5, and compared to the same Rat Universal Reference RNA sample (Stratagene, La Jolla, CA) that was amplified and labeled with Cy3 dye. No dye swaps were utilized.