Characterization of human mesenchymal stem cell secretome at early steps of adipocyte and osteoblast differentiation

Chiara Chiellini¹ , Olivia Cochet¹ , Luc Negroni² , Michel Samson³ , Marjorie Poggi⁴ , Gérard Ailhaud¹ , Marie-Christine Alessi³ , Christian Dani¹ and Ez-Zoubir Amri¹

¹ISBDC, Université de Nice Sophia-Antipolis, CNRS ; 28 avenue de Valrose, 06100 Nice, France

²IFR 50, Faculté de Médecine, Plate-Forme Protéomique, Avenue de Valombrose, 06107 Nice, Cedex 02, France

³INSERM, Unité 638, Faculté de Médecine, Université de Nice Sophia Antipolis, Avenue de Valombrose, 06107 Nice, Cedex 02, France

⁴INSERM UMR 626; Faculté de Médecine Timone, 27 Boulevard Jean Moulin, 13385 Marseille, Cedex 5, France

author email corresponding author email

BMC Molecular Biology 2008, 9:26doi:10.1186/1471-2199-9-26


Published:	26 February 2008

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.

Conclusion

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.