The expression of podoplanin, a small mucin-like protein, is upregulated in the invasive front of a number of human carcinomas. We have investigated podoplanin function in cultured human breast cancer cells, in a mouse model of pancreatic beta cell carcinogenesis, and in human cancer biopsies. Our results indicate that podoplanin promotes tumor cell invasion in vitro and in vivo. Notably, the expression and subcellular localization of epithelial markers are unaltered, and mesenchymal markers are not induced in invasive podoplanin-expressing tumor cells. Rather, podoplanin induces collective cell migration by filopodia formation via the downregulation of the activities of small Rho family GTPases. In conclusion, podoplanin induces an alternative pathway of tumor cell invasion in the absence of epithelial-mesenchymal transition (EMT).

The prevalence of diabetes is increasing constantly, resulting in a global epidemic 1 . Diabetes is a major cause of blindness, kidney failure, heart attacks, stroke or lower limb amputation; in large parts because of marked changes in blood vessels, defined by expansion of the basement membrane and a loss of vascular cells [2][3][4] . Diabetes also impairs endothelial cell (EC) function 5 and disturbs EC-pericyte communication 6 . How endothelial/pericyte dysfunction leads to diabetic vasculopathy remains largely elusive. Here we report the development of self-organizing 3D human blood vessel organoids from pluripotent stem cells. These human blood vessel organoids contain endothelial cells and pericytes that self-assemble into capillary networks enveloped by a basement membrane. Human blood vessel organoids transplanted into mice form a stable, perfused vascular tree, including arteries, arterioles and venules. Exposure of blood vessel organoids to hyperglycemia and inflammatory cytokines in vitro induced thickening of the vascular basement membrane. Human blood vessels, exposed in vivo to a diabetic milieu in mice, also mimick the microvascular changes in diabetic patients. Dll4-Notch3 were identified as key

De novo lymphangiogenesis influences the course of different human diseases as diverse as chronic renal transplant rejection and tumor metastasis. The cellular mechanisms of lymphangiogenesis in human diseases are currently unknown, and could involve division of local preexisting endothelial cells or incorporation of circulating progenitors. We analyzed renal tissues of individuals with gender-mismatched transplants who had transplant rejection and high rates of overall lymphatic endothelial proliferation as well as massive chronic inflammation. Donor-derived cells were detected by in situ hybridization of the Y chromosome. We compared these tissues with biopsies of essentially normal skin and intestine, and two rare carcinomas with low rates of lymphatic endothelial proliferation that were derived from individuals with gender-mismatched bone marrow transplants. Here, we provide evidence for the participation of recipient-derived lymphatic progenitor cells in renal transplants. In contrast, lymphatic vessels of normal tissues and those around post-transplant carcinomas did not incorporate donor-derived progenitors. This indicates a stepwise mechanism of inflammation-associated de novo lymphangiogenesis, implying that potential lymphatic progenitor cells derive from the circulation, transmigrate through the connective tissue stroma, presumably in the form of macrophages, and finally incorporate into the growing lymphatic vessel.

The in vivo functions of lymphatic endothelial cells depend on their microenvironment, which cannot be fully reproduced in vitro. Because of technical limitations, gene expression in uncultured, "ex vivo" lymphatic endothelial cells has not been characterized at the molecular level. We combined tissue micropreparation and direct cell isolation with DNA chip experiments to identify 159 genes differentiating human lymphatic endothelial cells from blood vascular endothelial cells ex vivo. The same analysis performed with cultured primary cells revealed that only 19 genes characteristic for lymphatic endothelium ex vivo retained this property upon culture, while 27 marker genes were newly induced. In addition, a set of panendothelial genes could be recognized. The propagation of lymphatic endothelial cells in culture stimulated transcription of genes associated with cell turnover, basic metabolism, and the cytoskeleton. On the other hand, there was downregulation of genes encoding extracellular matrix components, signaling via transmembrane tyrosine kinase pathways and the chemokine (C-C) ligand 21. Direct ex vivo analysis of the lymphatic endothelial cell transcriptome is helpful for the understanding of the physiology of the lymphatic vascular system and of the pathogenesis of its diseases.