Correlating Global Gene Regulation to Angiogenesis in the Developing Chick Extra-Embryonic Vascular System

International audienceBACKGROUND: Formation of blood vessels requires the concerted regulation of an unknown number of genes in a spatial-, time- and dosage-dependent manner. Determining genes, which drive vascular maturation is crucial for the identification of new therapeutic targets against pathological angiogenesis. METHOLOGY/PRINCIPAL FINDINGS: We accessed global gene regulation throughout maturation of the chick chorio-allantoic membrane (CAM), a highly vascularized tissue, using pan genomic microarrays. Seven percent of analyzed genes showed a significant change in expression (>2-fold, FDR<5%) with a peak occurring from E7 to E10, when key morphogenetic and angiogenic genes such as BMP4, SMO, HOXA3, EPAS1 and FGFR2 were upregulated, reflecting the state of an activated endothelium. At later stages, a general decrease in gene expression occurs, including genes encoding mitotic factors or angiogenic mediators such as CYR61, EPAS1, MDK and MYC. We identified putative human orthologs for 77% of significantly regulated genes and determined endothelial cell enrichment for 20% of the orthologs in silico. Vascular expression of several genes including ENC1, FSTL1, JAM2, LDB2, LIMS1, PARVB, PDE3A, PRCP, PTRF and ST6GAL1 was demonstrated by in situ hybridization. Up to 9% of the CAM genes were also overexpressed in human organs with related functions, such as placenta and lung or the thyroid. 21-66% of CAM genes enriched in endothelial cells were deregulated in several human cancer types (P<.0001). Interfering with PARVB (encoding parvin, beta) function profoundly changed human endothelial cell shape, motility and tubulogenesis, suggesting an important role of this gene in the angiogenic process. CONCLUSIONS/SIGNIFICANCE: Our study underlines the complexity of gene regulation in a highly vascularized organ during development. We identified a restricted number of novel genes enriched in the endothelium of different species and tissues, which may play crucial roles in normal and pathological angiogenesis

Developmental and pathological lymphangiogenesis: from models to human disease.

The lymphatic vascular system, the body's second vascular system present in vertebrates, has emerged in recent years as a crucial player in normal and pathological processes. It participates in the maintenance of normal tissue fluid balance, the immune functions of cellular and antigen trafficking and absorption of fatty acids and lipid-soluble vitamins in the gut. Recent scientific discoveries have highlighted the role of lymphatic system in a number of pathologic conditions, including lymphedema, inflammatory diseases, and tumor metastasis. Development of genetically modified animal models, identification of lymphatic endothelial specific markers and regulators coupled with technological advances such as high-resolution imaging and genome-wide approaches have been instrumental in understanding the major steps controlling growth and remodeling of lymphatic vessels. This review highlights the recent insights and developments in the field of lymphatic vascular biology

THE DETECTION OF AXILLARY LYMPH-NODE METASTASES FROM BREAST-CANCER BY RADIOLABELED MONOCLONAL-ANTIBODIES - A PROSPECTIVE-STUDY

In a prospective study to assess the accuracy of monoclonal immunoscintigraphy for the detection of axillary lymph node metastases in breast cancer, two murine monoclonal antibodies that react with human breast cancer (3E1.2 and RCC-1) were labelled with 131iodine, and the radiolabelled antibody was injected subcutaneously into the interdigital spaces of both hands of 40 patients, 36 of whom had breast cancer and the remaining four of whom had fibroadenoma (the normal, contralateral axilla was used as a control). Of the patients with breast cancer, the findings from the scintigraphy images were correlated with histopathology or cytology of the axillary lymph nodes; images were regarded as positive and hence indicative of lymph node metastases if the amount of background-subtracted radioactive count in axilla on the side of breast cancer exceeded the contralateral normal side by a ratio greater than or equal to 1.5:1.0 as assessed by computer analysis. Using this method, immunoscintigraphy had an overall sensitivity of 33% (23% with 131I-3E1.2 and 50% with 131I-RCC-1) for the detection of lymph node metastases and a specificity of 63% (67% with 131I-3E1.2 and 60% with 131I-RCC-1) with problems of non-specific uptake by presumably normal lymph nodes. The results of immunoscintigraphy obtained with 131I-RCC-1 (IgG) were superior to 131I-3E1.2 (IgM) although the accuracy of immunoscintigraphy using 131I-RCC-1 (56%) was not much better than preoperative clinical assessment (50%). However, there were cases when immunoscintigraphy using radiolabelled antibody (IgM or IgG) detected axillary lymph node metastases not suspected by clinical examination. Thus it appears that while immunoscintigraphy may be a useful adjunct to preoperative clinical assessment and is simple and safe, a major improvement in its accuracy is needed before it can replace axillary dissection and histological examination in the accurate staging of axilla in breast cancer

Sox18 induces development of the lymphatic vasculature in mice

The lymphatic system plays a key role in tissue fluid regulation and tumour metastasis, and lymphatic defects underlie many pathological states including lymphoedema, lymphangiectasia, lymphangioma and lymphatic dysplasia1, 2, 3. However, the origins of the lymphatic system in the embryo, and the mechanisms that direct growth of the network of lymphatic vessels, remain unclear. Lymphatic vessels are thought to arise from endothelial precursor cells budding from the cardinal vein under the influence of the lymphatic hallmark gene Prox1 (prospero homeobox 1; ref. 4). Defects in the transcription factor gene SOX18 (SRY (sex determining region Y) box 18) cause lymphatic dysfunction in the human syndrome hypotrichosis-lymphoedema-telangiectasia5, suggesting that Sox18 may also play a role in lymphatic development or function. Here we use molecular, cellular and genetic assays in mice to show that Sox18 acts as a molecular switch to induce differentiation of lymphatic endothelial cells. Sox18 is expressed in a subset of cardinal vein cells that later co-express Prox1 and migrate to form lymphatic vessels. Sox18 directly activates Prox1 transcription by binding to its proximal promoter. Overexpression of Sox18 in blood vascular endothelial cells induces them to express Prox1 and other lymphatic endothelial markers, while Sox18-null embryos show a complete blockade of lymphatic endothelial cell differentiation from the cardinal vein. Our findings demonstrate a critical role for Sox18 in developmental lymphangiogenesis, and suggest new avenues to investigate for therapeutic management of human lymphangiopathies

Hepatocyte growth factor promotes lymphatic vessel formation and function

The lymphatic vascular system plays a pivotal role in mediating tissue fluid homeostasis and cancer metastasis, but the molecular mechanisms that regulate its formation and function remain poorly characterized. A comparative analysis of the gene expression of purified lymphatic endothelial cells (LEC) versus blood vascular endothelial cells (BVEC) revealed that LEC express significantly higher levels of hepatocyte growth factor receptor (HGF-R). Whereas little or no HGF-R expression was detected by lymphatic vessels of normal tissues, HGF-R was strongly expressed by regenerating lymphatic endothelium during tissue repair and by activated lymphatic vessels in inflamed skin. Treatment of cultured LEC with HGF promoted LEC proliferation, migration and tube formation. HGF-induced proliferation of LEC did not require vascular endothelial growth factor receptor-3 activation, and HGF-induced cell migration was partially mediated via integrin alpha-9. Transgenic or subcutaneous delivery of HGF promoted lymphatic vessel formation in mice, whereas systemic blockade of HGF-R inhibited lymphatic function. These results identify HGF as a novel, potent lymphangiogenesis factor, and also indicate that HGF-R might serve as a new target for inhibiting pathological lymphangiogenesis