Bienvenue sur le site de l'université Paris Descartes

février 2012

  • 24 févSéminaire du Centre de Recherche des Cordeliers

    24 fév 2012
    Séminaires/Colloques

    A 12hSéminaire de l’équipe 5 avec :

    Werner E.G. Müller
     Université Johannes Gutenberg à Mainz, Allemagne

     

    Bio-silica: applications in biomedicine (bone formation)
     Bio-silica represents the main mineral component of the sponge skeletal elements (siliceous spicules), while bio-polyphosphate (bio-polyP), a multifunctional polymer existing in microorganisms and animals acts, among others, as reinforcement for pores in cell membranes. These natural inorganic bio-polymers which can be readily prepared, either by recombinant enzymes (bio-silica and bio-polyP) or chemically (polyP), are promising materials/substances for the amelioration and/or treatment of human bone diseases and dysfunctions. It has been demonstrated that bio-silica causes in vitro a differential effect on the expression of the genes OPG and RANKL, encoding two mediators that control the tuned interaction of the anabolic (osteoblasts) and catabolic (osteoclasts) pathways in human bone cells. Since bio-silica and bio-polyP also induce the expression of the key mediator BMP2 which directs the differentiation of bone-forming progenitor cells to mature osteoblasts and in parallel inhibits the function of osteoclasts, they are promising candidates for treatment of osteoporosis.  
     

     

    et Heinz C. Schröder
     Université Johannes Gutenberg à Mainz, Allemagne

    Polyphosphate and Osteoblast-Osteoclast Cross-talk
    Inorganic polymeric phosphate/polyphosphate [polyP] is a natural polymer existing in both pro- and eukaryotic systems. In the present study the effect of polyP as well as of polyP supplied in a stoichiometric ratio of 2 moles of polyP:1 mole of CaCl2 [polyP (Ca2+ complex)] on the osteoblast-like SaOS-2 cells and the osteoclast-like RAW 264.7 cells was determined. Both polymers are non-toxic for these cells up to a concentration of 100 µM. In contrast to polyP, polyP (Ca2+ complex) significantly induced hydroxyapatite formation at concentrations above 10 µM, as documented by Alizarin Red S staining and scanning electron microscopic inspection. Furthermore polyP (Ca2+ complex) triggered in SaOS-2 cells transcription of BMP2 [bone morphogenetic protein 2], a cytokine involved in maturation of hydroxyapatite-forming cells. An additional activity of polyP (Ca2+ complex) is described by showing that this polymer impairs osteoclastogenesis. At concentrations > 10 µM polyP (Ca2+ complex) slows down the progression of RAW 264.7 cells to functional osteoclasts, as measured by the expression of TRAP [tartrate-resistant acid phosphatase]. Finally it is shown that 10 to 100 µM of polyP (Ca2+ complex) inhibited phosphorylation of IκBα by the respective kinase in RAW 264.7 cells. We concluded that polyP (Ca2+ complex) displays a dual effect on bone metabolizing cells. It promotes hydroxyapatite formation in SaOS-2 cells (osteoblasts) and impairs maturation of the osteoclast-related RAW 264.7 cells.
      

    Invités par Ariane BERDAL

    Lieu : Centre de Recherche des Cordeliers
     Amphithéâtre BILSKI-PASQUIER
     15 rue de l’Ecole de médecine,
     Paris 75006