The role of adipose protein derived hydrogels in adipogenesis Shiri Uriel a , Jung-Ju Huang b , Monica L. Moya a , Megan E. Francis a, c , Rui Wang a , Shu-ying Chang b , Ming-Huei Cheng b, * , Eric M. Brey a, c a Pritzker Institute of Biomedical Science and Engineering, Department of Biomedical Engineering, Illinois Institute of Technology,10 W. 32nd Street, Engineering 1 Room 116, Chicago, IL 60616-3793, USA b Chung Gung Memorial Hospital, Chang Gung Medical College, Chang Gung University, Department of Plastic and Reconstructive Surgery, Taoyuan, 5, Fu-Hsing Street, Kweishan, Taiwan c Department of Research, Hines V.A. Hospital, Hines, IL, USA article info Article history: Received 26 March 2008 Accepted 23 May 2008 Available online 24 June 2008 Keywords: Preadipocytes Extracellular matrix Basement membrane Adipogenesis Angiogenesis Differentiation abstract Biomaterials that induce adipogenesis may ultimately serve as alternatives to traditional tissue reconstruction and regeneration techniques. In addition, these materials can provide environments for studying factors that regulate adipogenesis. The present study investigates the potential of adipose- derived matrices to induce adipogenesis in vitro and in vivo. Solutions containing basement membrane proteins and growth factors were extracted from subcutaneous adipose tissue. These extracts could be induced to form gels by either incubating the solutions at 37  C or adjusting the pH to 4.0. The adipose extracts promoted rapid preadipocyte aggregation and formation of lipid-loaded colonies in vitro. Dif- ferentiation on adipose-derived gels was greater than tissue culture dishes and the tumor-derived product MatrigelÔ (p < 0.05). Significant adipose formation was observed when adipose-derived gels were implanted around a rat epigastric pedicle bundle. Adipose levels in these gels were significantly greater than MatrigelÔ (p < 0.05). The duration of adipose formation depended on the mechanism for gelling the solutions, with acid gelled matrices having greater adipose levels at 6 weeks than temper- ature gelled matrices. These adipose-derived hydrogels promote rapid adipogenesis in vitro and in vivo. They may lead to new materials for adipose tissue engineering, and provide an environment for studying cell–matrix interactions in adipogenesis. Published by Elsevier Ltd. 1. Introduction The ability to engineer vascularized adipose tissue may offer an alternative to traditional approaches to tissue reconstruction fol- lowing tumor resection and for treatment of congenital defects. While progress has been made in adipose tissue engineering, our incomplete knowledge of the factors regulating adipogenesis limits the ability to design appropriate conditions for promoting rapid and stable vascularized adipose tissue formation. Adipose formation is regulated by factors in the tissue micro- environment, including growth factors, hormones, and extracellu- lar matrices (ECMs). ECM plays an important role in adipogenesis by influencing cellular function through mechanical and bio- chemical mechanisms [1,2]. Basement membranes (BMs) play a particularly important role in adipogenesis [3]. BMs are a spe- cialized layer of the ECM that surround adipocytes and regulate differentiation, migration and adhesion [4,5]. The predominant components of BM are isoforms of laminin, collagen, nidogen/ entactin and proteoglycans [6]. Laminins are BM glycoproteins consisting of a, b, and g chains assembled into a cross-shaped heterotrimer that play an important role in BM function. The cur- rently accepted laminin nomenclature is to define heterotrimers by sequential Arabic numerals based on their chains (e.g. laminin a4, b1, and g1 chains and laminin a1, b1, and g1 chains are denoted as laminin-411 and laminin-111, respectively) [7]. Studies have shown that BM deposition, synthesis and remodeling are enhanced during adipogenesis and are essential for adipocyte maturation [8,9]. Dif- ferentiated adipocytes first degrade the BM and subsequently synthesize new BM components including collagen type IV, lam- inins and fibronectin [10,11]. The new BM influences the initiation and maintenance of adipogenesis and remodeling of adipose tissue. Studies have demonstrated that MatrigelÔ, a commercially available BM isolated from a rat sarcoma, supports adipogenesis in vivo [12–15]. MatrigelÔ supplemented with fibroblast growth factor-2 (FGF-2) (more than 1 ng/ml) and subcutaneously injected * Corresponding author. Division of Reconstructive Microsurgery, Department of Plastic and Reconstructive Surgery, Chang Gung Memorial Hospital, Chang Gung Medical College, Chang Gung University, 5, Fu-Hsing Street, Kweishan, Taoyuan 333, Taiwan. Tel.: þ886 3 3281200x3355; fax: þ886 3 3287260. E-mail address: minghueicheng@gmail.com (M.-H. Cheng). Contents lists available at ScienceDirect Biomaterials journal homepage: www.elsevier.com/locate/biomaterials 0142-9612/$ – see front matter Published by Elsevier Ltd. doi:10.1016/j.biomaterials.2008.05.028 Biomaterials 29 (2008) 3712–3719