Despite the clinical need for reconstructive and plastic surgery, the supply of engineered adipose tissue equivalents still remains a challenge. As yet, only preadipocytes have been applied as a cell material for the in vitro tissue engineering of fat. Herein, we report the establishment of a three-dimensional (3-D) long-term cell culture, using bone marrow-derived mesenchymal stem cells (MSCs) as an alternative cell source and custom-made poly(lactic-co-glycolic acid) (PLGA) scaffolds as a cell carrier. Cell-polymer constructs were cultivated for 4 weeks in both the absence and presence of basic fibroblast growth factor (bFGF), which was previously shown to strongly enhance the adipogenesis of MSCs in conventional 2-D short-term culture. A striking enhancement of the adipogenic differentiation of MSCs and tissue development caused by bFGF in the 3-D culture was observed by osmium tetroxide histology and scanning electron microscopy. At the molecular level, reflecting the increased accumulation of lipids, bFGF increased the enzymatic activity of glycerol-3-phosphate dehydrogenase, a late marker of adipogenesis, and the expression of adipocyte-specific genes peroxisome proliferator activated receptor-gamma2 (PPARgamma2) and glucose transporter-4 (GLUT4), as assessed by reverse transcription-polymerase chain reaction. This study demonstrates that the use of bone marrow-derived MSCs, especially in combination with bFGF, may represent a promising approach to adipose tissue engineering.

Biodegradable polymers, such as poly(lactic acid) (PLA) and poly(lactic-coglycolic acid) (PLGA), are attractive materials for tissue engineering because of their degradative and mechanical properties, which permit scaffolds to be tailored to the individual requirements of different tissues. Although these materials support tissue development, their chemical properties offer no control of cell adhesion or function because their surfaces become immediately masked by adsorbing serum proteins when the materials come into contact with body fluids. Furthermore, adhesion proteins undergo conformational changes and a decrease in bioactivity when adsorbed to hydrophobic materials, such as PLA. To overcome these limitations, we modified the properties of PLA by synthesizing a diblock copolymer with poly(ethylene glycol) (PEG), which is known to reduce the amount of adsorbed proteins and to modify their conformation. By altering the PEG content of these diblock copolymers we were able to control the adsorption of adhesion proteins and, because cell adhesion takes place only in the presence of serum proteins, to control cell adhesion and cell shape. Marrow stromal cell differentiation to the osteoblastic phenotype was strongly improved on PEG-PLA compared with PLA, PLGA and tissue culture polystyrene and led to a 2-fold increase in alkaline phosphatase activity and mineralization.