Human adipose tissue-derived multipotent stem cells differentiate in vitro and in vivo into osteocyte-like cells Christian Elabd a , Chiara Chiellini a , Ali Massoudi a , Olivia Cochet a , Laure-Emmanuelle Zaragosi a , Christophe Trojani b , Jean-Franc ¸ois Michiels c , Pierre Weiss d , Georges Carle b , Nathalie Rochet b , Claude A. Dechesne a , Ge ´rard Ailhaud a , Christian Dani a , Ez-Zoubir Amri a, * a ISBDC, Universite ´ de Nice Sophia-Antipolis, CNRS, 28 Avenue de Valrose, 06100 Nice, France b CNRS/UNSA FRE 2943, IFR50, Faculte ´ de Me ´decine, Avenue de Valombrose, 06107 Nice, France c Service d 0 Anatomopathologie, CHU de Nice, 30 Avenue de la Voie Romaine, 06002 Nice, France d Inserm, U791, LIOAD, Laboratoire d’inge ´nierie Oste ´o-Articulaire et Dentaire, Universite ´ Nantes 1 place A. Ricordeau, Faculte ´ de chirurgie dentaire, BP 84215 Nantes, F-44042, France Received 28 June 2007 Available online 20 July 2007 Abstract Cell-based therapies are used to treat bone defects. We recently described that human multipotent adipose-derived stem (hMADS) cells, which exhibit a normal karyotype, self renewal, and the maintenance of their differentiation properties, are able to differentiate into different lineages. Herein, we show that hMADS cells can differentiate into osteocyte-like cells. In the presence of a low amount of serum and EGF, hMADS cells express specific molecular markers, among which alkaline phosphatase, CBFA-1, osteocalcin, DMP1, PHEX, and podoplanin and develop functional gap-junctions. When loaded on a hardening injectable bone substitute (HIBS) biomaterial and injected subcutaneously into nude mice, hMADS cells develop mineralized woven bone 4 weeks after implantation. Thus hMADS cells represent a valuable tool for pharmacological and biological studies of osteoblast differentiation in vitro and bone development in vivo. Ó 2007 Elsevier Inc. All rights reserved. Keywords: Stem cells; Osteoblast; Osteocyte; Differentiation; Injectable; Biomaterial Bone diseases, such as osteopenia and osteoporosis, affect several millions of patients throughout the world. Ongoing studies for repairing bone defects are performed in pharmacology, gene, and cell therapies. Suitable cells needed for tissue engineering should exhibit immunocom- patibility and self-regenerative potential. Mesenchymal stem cells have recently received widespread interest in this respect. Multipotent mesenchymal stem cells, which differ- entiate in vitro into osteoblasts, chondrocytes, adipocytes, myoblasts, cardiomyocytes, endothelial, and neuronal cells [1–3], have been mainly isolated from adult marrow. Other tissues, i.e., adipose tissue, muscle, periosteum and synovial tissue contain also cells with similar properties but the lim- ited life span and amount of cells as well as their heteroge- neity, worsened by their inability to support successive freezing/thawing steps, limit the use of these cells [1,4–7]. Recently, we described the isolation of mesenchymal stem cell populations from human adipose tissue that are able, at a clonal level, to differentiate into various mesodermal lineages [8,9]. Human multipotent adipose-derived stem (hMADS) cells exhibit potent self-renewal capacity, main- tain clonogenicity and multipotency after expansion, and promote long-term expression of human dystrophin when transplanted into muscle of immunocompetent mdx mice [9,10]. 0006-291X/$ - see front matter Ó 2007 Elsevier Inc. All rights reserved. doi:10.1016/j.bbrc.2007.06.180 * Corresponding author. Fax: +33 492 07 64 04. E-mail address: amri@unice.fr (E.-Z. Amri). www.elsevier.com/locate/ybbrc Biochemical and Biophysical Research Communications 361 (2007) 342–348