Project description:The lymphatic system is formed during embryonic development by the commitment of specialized lymphatic endothelial cells (LECs) and their subsequent assembly in primary lymphatic vessels. While lymphatic cells are in continuous contact with mesenchymal cells during development and in adult tissues, the role of mesenchymal cells in lymphatic vasculature development remains poorly characterized. Here, we show that a subpopulation of mesenchymal cells expressing the transcription factor Osr1 are in close association with migrating LECs and established lymphatic vessels in mice. Lineage tracing experiments revealed that Osr1+ cells precede LEC arrival during lymphatic vasculature assembly in the back of the embryo. Using Osr1-deficient embryos and functional in vitro assays, we show that Osr1 acts in a non-cell autonomous manner controlling proliferation and early migration of LECs to peripheral tissues. Thereby, mesenchymal Osr1+ cells control in a bimodal manner the production of extracellular matrix scaffold components and signal ligands critical for lymphatic vessel formation.
Project description:Complex lymphatic anomalies (CLAs) are sporadically occurring diseases caused by the maldevelopment of lymphatic vessels. We and others recently reported that somatic activating mutations in KRAS can cause CLAs. However, the mechanisms by which activating KRAS mutations cause CLAs are poorly understood. Here we show that KRASG12D expression in lymphatic endothelial cells (LECs) during embryonic development impairs the formation of lymphovenous valves and causes the enlargement of lymphatic vessels. We demonstrate that KRASG12D expression in primary human LECs induces cell spindling, proliferation, and migration. It also increases AKT and ERK1/2 phosphorylation and decreases the expression of genes that regulate lymphatic vessel maturation. We show that MEK1/2 inhibition with the FDA-approved drug trametinib suppresses KRASG12D-induced morphological changes, proliferation, and migration. Trametinib also decreases ERK1/2 phosphorylation and increases the expression of genes that regulate the maturation of lymphatic vessels. We also show that trametinib and Cre-mediated expression of a dominant-negative form of MEK1 (Map2k1K97M) suppresses KRASG12D-induced lymphatic vessel hyperplasia in embryos. Last, we demonstrate that conditional knockout of wild-type Kras in LECs does not affect the formation or function of lymphatic vessels. Together, our data indicate that KRAS/MAPK signaling must be tightly regulated during embryonic development for the proper development of lymphatic vessels and further support the testing of MEK1/2 inhibitors for treating CLAs.
Project description:We did three sets of microarrays with three replicates each for a total of 9 arrays. Each array was run using pooled RNA from three animals. The three conditions were Normal tail skin (no intervention), Lymphedema tail skin(due to surgical lymphatic vessel blockage), and Surgical Sham control tail skin(surgical incision with no lymphatic vessel blockage). 15ug of test and reference (e17.5 mouse whole embryo) RNA was used for labeling.
Project description:Tissue lymphatic vessels network plays critical roles in immune surveillance and tissue homeostasis in response to pathogen invasion, but how lymphatic system per se is remolded during infection is less understood. Here, we observed that influenza infection induces a significant increase of lymphatic vessel numbers in the lung, accompanied with extensive proliferation of lymphatic endothelial cells (LECs). Single-cell RNA sequencing illustrated the heterogeneity of LECs, identifying a novel PD-L1+ subpopulation that is present during viral infection but not at steady state. Specific deletion of Pd-l1 in LECs elevated the expansion of lymphatic vessel numbers during viral infection. Together these findings elucidate a dramatic expansion of lung lymphatic network in response to viral infection, and reveal a PD-L1+ LEC subpopulation that potentially modulates lymphatic vessel remolding.
Project description:We developed a large animal model, with clinically relevant gravitational loading on the lymphatic vasculature, that enables longitudinal tracking of lymphatic function in vivo as well as end-point analysis of vessel function and mechanics. One of two parallel lymphatic vessels in the sheep hind limb was ligated with the contralateral limb acting as an internal control. To determine the changes in the protein expression profiles in the lymphatic muscle cells from the remodeled vessel compared to the control, we expanded isolated LMC in vitro and performed bottom-up proteomic analysis using a Q Exactive Plus mass spectrometer. Label-free quantitative (LFQ) methods directly used the raw spectral data from parallel MS runs to determine relative protein abundances. We used both “MS/MS (MS2) spectral counting” and “precursor MS1 area” methods for label free quantitation and further contrasting the differentially expressed proteomic profiles across the control and remodeled lymphatic muscle samples to determine the alterations in mitochondrial dysfunction and elevated oxidative stress within the lymphatic muscle.
Project description:Kaposi sarcoma is the most common cancer in AIDS patients and is typified by red skin lesions. The disease is caused by the KSHV virus (HHV8) and is recognisable by its distinctive red skin lesions. The lesions are KSHV-infected spindle cells, most commonly the lymphatic endothelial and blood vessel endothelial cells (LEC and BEC), plus surrounding stroma. The effects of KSHV infection of both LEC and BEC were assayed using Affymetrix hgu133plus2 chips at 72 hours post infection.