Lymphangiogenèse et progression tumorale

National audienceNumerous data show a functional link between lymphangiogenesis, lymph node invasion by tumoral cells and metastasis. During the last decade, the identification of lymphatic endothelial cell-specific markers has allowed the investigation of lymphangiogenesis regulatory mechanisms and the analysis of its involvement in tumoral progression. Among regulatory systems, the growth factors VEGF-C and D, that bind and activate their common receptor VEGFR3, appear to play an important role in this process. Therapeutic strategies targeting this pathway or, in a general manner, aiming at inhibiting tumoral lymphangiogenesis are now considered to block the development of tumoral metastasis. Further fundamental and clinical studies are clearly needed to establish the pronostic value of lymphangiogenesis and to validate anti-lymphangiogenic therapies in the treatment of metastatic cancers

Development of a one-step embryonic stem cell-based assay for the screening of sprouting angiogenesis

BACKGROUND: Angiogenesis assays are important tools for the identification of regulatory molecules and the potential development of therapeutic strategies to modulate neovascularization. Although numerous in vitro angiogenesis models have been developed in the past, they exhibit limitations since they do not recapitulate the entire angiogenic process or correspond to multi-step procedures that are not easy to use. Convenient, reliable, easily quantifiable and physiologically relevant assays are still needed for pharmacological screenings of angiogenesis. RESULTS: Here, we have optimized an angiogenesis model based on ES cell differentiation for screening experiments. We have established conditions leading to angiogenic sprouting of embryoid bodies during ES cell differentiation in type I three-dimensional collagen gels. Immunostaining experiments carried out during these cultures showed the formation of numerous buds comprising CD31 positive cells, after 11 days of culture of ES cells. Moreover, this one-step model has been validated in response to activators and inhibitors of angiogenesis. Sprouting was specifically stimulated in the presence of VEGF and FGF2. Alternatively, endothelial sprouting induced by angiogenic activators was inhibited by angiogenesis inhibitors such as angiostatin, TGFβ and PF4. Sprouting angiogenesis can be easily quantified by image analysis after immunostaining of endothelial cells with CD31 pan-endothelial marker. CONCLUSION: Taken together, these data clearly validate that this one-step ES differentiation model constitutes a simple and versatile angiogenesis system that should facilitate, in future investigations, the screening of both activators and inhibitors of angiogenesis

Activation des plaquettes sanguines humaines par la vasopressine : caracterisation du recepteur et voies de transduction du signal hormonal

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Cellules souches embryonnaires et étude du développement du système vasculaire

GRENOBLE1-BU Sciences (384212103) / SudocSudocFranceF

Lymphatics in Eye Fluid Homeostasis: Minor Contributors or Significant Actors?

Lymphatic vessels exert major effects on the maintenance of interstitial fluid homeostasis, immune cell trafficking, lipid absorption, tumor progression and metastasis. Recently, novel functional roles for the lymphatic vasculature have emerged, which can be associated with pathological situations. Among them, lymphatics have been proposed to participate in eye aqueous humor drainage, with potential consequences on intraocular pressure, a main risk factor for progression of glaucoma disease. In this review, after the description of eye fluid dynamics, we provide an update on the data concerning the distribution of ocular lymphatics. Particular attention is given to the results of investigations allowing the three dimensional visualization of the ocular surface vasculature, and to the molecular mechanisms that have been characterized to regulate ocular lymphatic vessel development. The studies concerning the potential role of lymphatics in aqueous humor outflow are reported and discussed. We also considered the novel studies mentioning the existence of an ocular glymphatic system which may have, in connection with lymphatics, important repercussions in retinal clearance and in diseases affecting the eye posterior segment. Some remaining unsolved questions and new directions to explore are proposed to improve the knowledge about both lymphatic and glymphatic system interactions with eye fluid homeostasis

TGFbeta1 induces vasculogenesis and inhibits angiogenic sprouting in an embryonic stem cell differentiation model: respective contribution of ALK1 and ALK5.

International audienceTransforming growth factor-beta1 (TGFbeta1) is a multipotent cytokine that is involved in the regulation of vasculogenesis and angiogenesis. However, the actions of TGFbeta1 on vascular cells in vitro and in vivo are extremely complex and still incompletely understood. The aim of the present study was to investigate the role of TGFbeta1 and its two type I receptors, activin receptor-like kinase-1 (ALK1) and ALK5, in an embryonic stem cell (ESC) differentiation model that recapitulates the developmental steps of vasculogenesis and sprouting angiogenesis. We show that TGFbeta1 increases endothelial cell differentiation in a vascular endothelial growth factor (VEGF)-independent manner and inhibits endothelial tube formation. Furthermore, we demonstrate that undifferentiated ESCs express ALK5 but do not express ALK1, with ALK1 being expressed only after day 5 of differentiation. Finally, we demonstrate that constitutively active forms of ALK1 and ALK5 both inhibit growth factor-induced endothelial sprouting from embryoid bodies. In conclusion, the use of this ESC differentiation model allowed us to propose the following model: at early stages of development, TGFbeta1, through the ALK5 receptor, is provasculogenic in a VEGF-independent manner. Later, in differentiated endothelial cells in which both ALK1 and ALK5 are expressed, both receptors are implicated in inhibition of sprouting angiogenesis

Eye lymphatic defects induced by bone morphogenetic protein 9 deficiency have no functional consequences on intraocular pressure

International audienceAqueous humor drainage is essential for the regulation of intraocular pressure (IOP), a major risk factor for glaucoma. The Schlemm’s canal and the non-conventional uveoscleral pathway are known to drain aqueous humor from the eye anterior chamber. It has recently been reported that lymphatic vessels are involved in this process, and that the Schlemm’s canal responds to some lymphatic regulators. We have previously shown a critical role for bone morphogenetic protein 9 (BMP9) in lymphatic vessel maturation and valve formation, with repercussions in drainage efficiency. Here, we imaged eye lymphatic vessels and analyzed the consequences of Bmp9 (Gdf2) gene invalidation. A network of lymphatic vessel hyaluronan receptor 1 (LYVE-1)-positive lymphatic vessels was observed in the corneolimbus and the conjunctiva. In contrast, LYVE-1-positive cells present in the ciliary bodies were belonging to the macrophage lineage. Although enlarged conjunctival lymphatic trunks and a reduced valve number were observed in Bmp9-KO mice, there were no morphological differences in the Schlemm’s canal compared to wild type animals. Moreover, there were no functional consequences on IOP in both basal control conditions and after laser-induced ocular hypertonia. Thus, the BMP9-activated signaling pathway does not constitute a wise target for new glaucoma therapeutic strategies

Bone morphogenetic protein 9 regulates early lymphatic-specified endothelial cell expansion during mouse embryonic stem cell differentiation

International audienceExogenous cues involved in the regulation of the initials steps of lymphatic endothelial development remain largely unknown. We have used an in vitro model based on the co-culture of vascular precursors derived from mouse ES (embryonic stem) cell differentiation and OP9 stromal cells to examine the first steps of lymphatic specification and expansion. We found that Bone Morphogenetic protein 9 (BMP9) induced a dose-dependent biphasic effect on ES cell-derived vascular precursors. At low concentrations, below 1 ng/mL, BMP9 expands the LYVE-1-positive lymphatic progeny and activates the calcineurin phosphatase/NFATc1 signaling pathway. In contrast, higher BMP9 concentrations, preferentially enhance the formation of LYVE-1-negative endothelial cells. This effect results from an OP9 stromal cell-mediated VEGF-A secretion. RNA silencing experiments indicate specific involvement of ALK1 and ALK2 receptors in these different BMP9 responses. BMP9 at low concentrations may be a useful tool to generate lymphatic endothelial cells from stem cells for cell replacement strategies