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:The aim of this feasibility study was to assess whether inflammatory status of the lymphatic vessels (LVs) and/or changes in the miRNA profile of the LVs have potential prognostic and predictive value for overall outcome and risk of relapse. Tissue specimens were obtained from the external iliac vessels draining the pelvic region of patients undergoing debulking surgery (n=10). The tissue was transported directly from surgical theatre to the laboratory in ice-cold sterile Phosphate Buffered Saline. LVs were identified and isolated along with a small amount of surrounding tissue under a dissection microscope within a sterile laminar flow cabinet. Each vessel was divided into two sections. One half of each vessel was further cleaned of surrounding fatty tissue, placed in RNA stabilising solution, frozen on dry ice and stored at -20°C. The miRNAs were extracted with an miRNA easy kit and reverse-transcribed to cDNA using a miScript II RT Kit . Subsequent qPCR was carried out using a miScriptSybrGreen real-time PCR kit and pre-defined miScript miRNA PCR Array. Quantification of the inflammatory state (low, medium and high) and presence of cancer-infiltration of each LV was carried out using immunohistochemistry with the remaining half of each vessel. The LV miRNA expression profiling was then analysed in the context of high versus low inflammation, and cancer-infiltrated versus non-cancer-infiltrated. Results were correlated with clinical outcome data including relapse with an average follow-up time of 13.3 months.
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:The muscle cells within the wall of collecting lymphatic vessels exhibit tonic and autonomous phasic contractions, which drive active lymph transport to maintain tissue-fluid homeostasis and support immune surveillance. Damage to the lymphatic muscle cells (LMC) disrupts lymphatic function and is related to various diseases. Despite their importance, knowledge of the transcriptional signatures in LMC and how they relate to lymphatic function in normal and diseases contexts is largely missing. In this study, we have generated to date the most comprehensive transcriptional single-cell atlas—including LMC—of collecting lymphatic vessels in mouse dermis at various ages.
Project description:Somatic activating mutations in KRAS can cause complex lymphatic anomalies (CLAs). However, the specific cellular and molecular processes that drive KRAS-mediated CLAs have yet to be fully elucidated. Here, we use single-cell RNA sequencing to construct an atlas of normal and KrasG12D-malformed lymphatic vessels. We show that adult wild-type mice have six subtypes of lymphatic endothelial cells (LECs) in their lungs (Ptx3, capillary, collecting, valve, mixed, and proliferating). To determine when the LEC subtypes are specified during development, we integrated our data with data from four stages of development. We show that proliferating and Ptx3 LECs are prevalent during early lymphatic development and that collecting and valve LECs emerge later in development. Additionally, we demonstrate that the proportion of Ptx3 LECs decreases as the lymphatic network matures but remains high in KrasG12D mice. We also show that KrasG12D mice have fewer collecting and valve LECs than wild-type mice. Last, we demonstrate that immature lymphatic vessels in young mice are more sensitive to the pathologic effects of KrasG12D than mature lymphatic vessels in older mice. Together, our results expand the current model for the development of the lymphatic system and suggest that KRAS mutations impair the maturation of lymphatic vessels.
Project description:Background: Dysregulation of TRPV4-mediated signaling has been associated with inflammation and tissue fibrosis, both of which are key features in the pathophysiology of lymphatic system diseases; however, the expression and functional roles of lymphatic TRPV4 channels remain largely unexplored. Methods: We generated a single-cell RNA sequencing dataset from microdissected mouse collecting lymphatic vessels to characterize the expression of Trpv4. Using a novel Trpv4fx/fx mouse strain and the Cre-lines Prox1-CreERT2 and LysM-Cre we assessed the role of TRPV4 channels in lymphatic endothelial cells (LECs) and peri-lymphatic myeloid cells, respectively. Confocal microscopy and extensive functional experimentation on isolated and pressurized lymphatics, including measurements of intracellular calcium activity, were employed to validate our scRNAseq findings and to elucidate the underlying mechanisms. Clinical significance was assessed using biopsies from breast cancer-related lymphedema (BCRL) patients. Results: We characterized the single-cell transcriptome of collecting lymphatic vessels and surrounding tissues. Trpv4 was highly enriched in LECs and in a subset of Lyve1+ macrophages displaying a tissue-resident profile. In clinical samples, BCRL was associated with increased infiltration of macrophages co-expressing LYVE1 and TRPV4. Pharmacological activation of TRPV4 channels led to contractile dysregulation in isolated collecting lymphatics. The response was multi-phasic, including initial vasospasm and subsequent vasodilation and inhibition of contractions, which was associated with the activation of thromboxane A2 receptors (TXA2Rs) in lymphatic muscle cells (LMCs) by secreted prostanoids from TRPV4+ myeloid cells, and increased nitric oxide (and perhaps other vasodilatory prostanoids) from LECs. The TXA2R-mediated vasospasm resulted from increased mobilization of calcium from intracellular stores through IP3 receptors and store-operated calcium entry. Conclusions: Our results uncovered a novel mechanism of lymphatic contractile dysregulation mediated by the crosstalk between TRPV4-expressing myeloid cells, including LYVE1+ macrophages, and LMCs or LECs. These findings highlight potentially important roles of TRPV4 channels in lymphatic dysfunction associated with inflammation, including secondary lymphedema.
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:Collecting lymphatic vessels (cLVs) exhibit spontaneous contractions with a pressure-dependent frequency, but the identity of the lymphatic pacemaker cell is still debated. By analogy to pacemakers in the GI and lower urinary tracts, proposed cLV pacemaker cells include interstitial cells of Cajal like cells (ICLC) or the lymphatic muscle (LMCs) cells themselves. Here we examined the cellular constituents of the mouse cLV wall and assessed whether any cell type exhibited morphological and functional processes characteristic of pacemaker cells: a continuous if not contiguous network; spontaneous Ca2+ transients; and depolarization-induced propagated contractions. We employed inducible Cre (iCre) mouse models routinely used to target these specific cell populations including: c-kitCreERT2 to target ICLC; PdgfrβCreERT2 to target pericyte like cells; PdgfrαCreERTM to target CD34+ adventitial cells and ICLC; and Myh11CreERT2 to target LMCs directly. These specific inducible Cre lines were crossed to the fluorescent reporter ROSA26mT/mG, the genetically encoded Ca2+ sensor GCaMP6f, and the light-activated cation channel rhodopsin2 (ChR2). c-KitCreERT2 labeled both a sparse population of LECs and round adventitial cells that responded to the mast cell activator compound 48-80. PdgfrβCreERT2 drove recombination in both adventitial cells and LMCs, limiting its power to discriminate a pericyte specific population. PdgfrαCreERTM labeled a large population of interconnected, oak leaf-shaped cells primarily along the adventitial surface of the vessel. Of these cells, only LMCs consistently, but heterogeneously, displayed spontaneous Ca2+ events during the diastolic period of the contraction cycle, and whose frequency was modulated in a pressure-dependent manner. Optogenetic depolarization through the expression of ChR2 under control of Myh11CreERT2, but not PdgfrαCreERTM or c-KitCreERT2, resulted in a propagated contraction upon photo-stimulation. Membrane potential recording in LMCs demonstrated that the diastolic depolarization was significantly correlated with contraction frequency. These findings support the conclusion that LMCs, or a subset of LMCs, are responsible for mouse cLV pacemaking.