0260 : Endoglin in adhesion between endothelial and mural cells

147 Archives of Cardiovascular Diseases Supplements (2015) 7, 146-147 catenin pathway) or Dll4 intraocular injection in fzd7iECKO and WT mice on vascular retinal phenotype. Our results showed that LiCl totally overrules the effects of Fzd7 deficiency in EC whereas Dll4 only partly rescues the phenotype observed in fzd7iECKO mice. The tip cells impairment in fzd7iECKO mice is overruled by Dll4 but not the delay of vascular growth. We then assessed whether fzd7 deletion impaired the expression of partners of βcatenin and Notch pathways by RT-qPCR. In vivo, deletion of fzd7 in EC induces a decrease in both partners of β-catenin and Notch pathways expression compared to control. Moreover this impairment of β-catenin and Notch pathways in vivo is totally rescue by LiCl injection. This study shows that fzd7 plays a crucial role during angiogenesis in postnatal mouse retina. Fzd7 controls vascular growth through a β-catenin signaling in a Notch independent way but also regulates the tip cells selection through a β-catenin signaling in a Notch dependent manner. associated with an impaired upregulation of Gli1. Sonic Hedgehog expression was not different in old mice compared to young mice while Desert Hedgehog (Dhh) expression was downregulated in skeletal muscle of old mice both in healthy and ischemic conditions. Rescue of Dhh expression by gene therapy in old mice increased nerve density and promoted ischemia-induced angiogenesis, nevertheless it failed to promote myogenesis. After further investigation, we found that, in addition to Dhh knockdown, Smoothened (Smo) expression was significantly downregulated in old mice. We used mice in which Hh signaling is specifically disrupted in myocytes (HSA Cre:Smoflox/flox) and demonstrated that Smo knockdown is sufficient to impair ischemiainduced myogenesis. Conclusion: The present study demonstrates that Hh signaling is impaired in aged mice which leads to impaired peripheral nerve survival and myogenesis in acute ischemic stress condition. Moreover, this study brings the new concept that it is necessary to restore both peripheral nerve integrity and myogenesis in elderly to promote revascularisation of ischemic tissues. 0260 Endoglin in adhesion between endothelial and mural cells Abstract 0048-Figure: Delayed retinal vascular formation in fzd7iECKO 0292 Blood vessels, muscle cells and peripheral nerves work together to regenerate ischemic muscles Marie-Ange Renault (1), Candice Chapouly (2), Qinyu Yao (1), Soizic Vandierdonck (2), Alain-Pierre Gadeau(1) (1) CHU Bordeaux, Hôpital Haut-Lévèque, INSERM U1034, Pessac, France – (2) CHU Bordeaux, Hôpital Haut-Lévêque, Pharmacie, INSERM U1034, Pessac, France Background: In elderly and diabetic patients, the increased risk of developing ischemic disease is associated with impaired regenerative properties of most tissues including skeletal muscle, which make those patients a challenging population to treat. We recently demonstrated that in skeletal muscle, Hedgehog (Hh) signaling promotes ischemia-induced angiogenesis by maintaining peripheral nerve and by promoting myogenesis. The objective of this study is to investigate the functionality of Hh dependent regulation of peripheral nerve survival and myogenesis in aged mice. Methods and Results: In the present study, we used 12 week old (young mice) and 20 to 24 month old C57BL/6 mice (old mice) to investigate the activity of Hh signaling in the setting of ischemic skeletal muscle regeneration. In this model, delayed ischemic muscle repair observed in old mice was Elisa Rossi (1), David Smadja (1), Elisa Boscolo (2), Carmen Langa (3), Miguel A. Arevalo (4), Miguel Pericacho (5), Alexandre Kauskot (6), Luisa M Botella (3), Pascale Gaussem (1), Joyce Bischoff (2), JosèMiguel Lopez-Novoa (4), Carmelo Bernabeu (3) (1) Université Paris Descartes, Hématologie – Faculté de Pharmacie, INSERM UMRS1140, Paris, France – (2) Harvard Medical School, Children’s Hospital, Surgery, Boston, Etats-Unis – (3) Centro de Investigaciones Biologicas CIB-CSIC, Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Espagne – (4) Universidad de Salamanca, Anatomía e Histología Humanas, Salamanca, Espagne – (5) Universidad de Salamanca, Fisiología y Farmacología, Salamanca, Espagne – (6) APHP-Hôpital Bicêtre – INSERM U770, Le KremlinBicêtre, France The interaction and interplay between endothelial cells (ECs) and mural cells (such as vascular smooth muscle cells -VSMCs- and pericytes) play a pivotal role in vascular biology. Endoglin is an RGD-containing ligand of β1 integrins highly expressed by ECs during angiogenesis. Our working hypothesis is that endothelial endoglin acts as an adhesion molecule via integrin recognition motifs, allowing the interaction between ECs and mural cells. We find that suppression of endoglin expression or addition of soluble endoglin inhibits the adhesion between ECs and VSMCs as shown by tubulogenesis assays on matrigel. The EC-VSMC adhesion was also abolished by an antiintegrin α5β1 inhibitory antibody, whereas it was markedly enhanced by the integrin activators MnCl2 or CXCL12. The CXCL12-dependent cell adhesion was abolished in the presence of soluble endoglin or a derived pentapeptide containing the RGD motif. Adhesion of cells overexpressing different endoglin mutant constructs, allowed the specific mapping of the endoglin RGD motif as involved in adhesion to VSMCs. Binding of soluble endoglin to VSMCs was markedly enhanced by MnCl2 and CXCL12 and this increase was inhibited by the RGD peptide. Moreover, transgenic mice overexpressing soluble endoglin show podocyturia and lower number of glomerular podocytes, suggesting that soluble endoglin induced the detachment of podocytes from glomerular capillaries. These results suggest a critical role for endoglin in integrin-mediated adhesion of mural cells and provide a better understanding on the mechanisms of vessel development and maturation in normal physiology as well as in pathologies such as preeclampsia, cancer or hereditary hemorrhagic telangiectasia.    © Elsevier Masson SAS. All rights reserved.