title: Characterization of human mesenchymal stem cell secretome at early steps of adipocyte and osteoblast differentiation.
abstract: BACKGROUND
  It is well established that adipose tissue plays a key role in energy storage and release but is also a secretory organ and a source of stem cells. Among different lineages, stem cells are able to differentiate into adipocytes and osteoblasts. As secreted proteins could regulate the balance between both lineages, we aimed at characterizing the secretome of human multipotent adipose-derived stem cell (hMADS) at an early step of commitment to adipocytes and osteoblasts.
  
  
  RESULTS
  A proteomic approach, using mono-dimensional electrophoresis and tandem mass spectrometry, allowed us to identify a total of 73 proteins at day 0 and day 3 of adipocyte and osteoblast differentiation. Analysis of identified proteins showed that 52 % corresponded to classical secreted proteins characterized by a signal peptide, that 37 % previously described in the extracellular compartment were devoid of signal peptide and that 11 % neither exhibited a signal peptide nor had been previously described extracellularly. These proteins were classified into 8 clusters according to their function. Quantitative analysis has been performed for 8 candidates: PAI-1, PEDF, BIGH3, PTX3, SPARC, ENO1, GRP78 and MMP2. Among them, PAI-1 was detected at day 0 and day 3 of osteoblast differentiation but never in adipocyte secretome. Furthermore we showed that PAI-1 mRNA was down-regulated in the bone of ovariectomized mice.
  
  
  CONCLUSIONS
  Given its regulation during the early events of hMADS cell differentiation and its status in ovariectomized mice, PAI-1 could play a role in the adipocyte/osteoblast balance and thus in bone diseases such as osteoporosis.
authors.affiliation: ISBDC, Université de Nice Sophia-Antipolis, CNRS ; 28 avenue de Valrose, 06100 Nice, France. Chiara.Chiellini@gmail.com
authors.forename: Chiara
authors.initials: C
authors.lastname: Chiellini
authors.forename: Olivia
authors.initials: O
authors.lastname: Cochet
authors.forename: Luc
authors.initials: L
authors.lastname: Negroni
authors.forename: Michel
authors.initials: M
authors.lastname: Samson
authors.forename: Marjorie
authors.initials: M
authors.lastname: Poggi
authors.forename: Gérard
authors.initials: G
authors.lastname: Ailhaud
authors.forename: Marie-Christine
authors.initials: MC
authors.lastname: Alessi
authors.forename: Christian
authors.initials: C
authors.lastname: Dani
authors.forename: Ez-Zoubir
authors.initials: EZ
authors.lastname: Amri
mesh_terms: D017667:Adipocytes / Q000502:physiology*; D000818:Animals; D002454:Cell Differentiation; D002478:Cells, Cultured; D000091342:Endoplasmic Reticulum Chaperone BiP; D005260:Female; D006801:Humans; D008297:Male; D059630:Mesenchymal Stem Cells / Q000378:metabolism* / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D010006:Osteoblasts / Q000502:physiology*; D010052:Ovariectomy; D010958:Plasminogen / Q000502:physiology; D017395:Plasminogen Activator Inhibitor 1 / Q000378:metabolism; D020543:Proteome / Q000032:analysis*; D013997:Time Factors
chemical_list: D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; C000717248:Hspa5 protein, mouse; D017395:Plasminogen Activator Inhibitor 1; D020543:Proteome; D010958:Plasminogen