Tissue-engineered bone from BMP-2-transduced stem cells derived from human fat

Background: Progenitor cells capable of induction into multiple mesenchymal lineages have been isolated from human liposuction aspirates. These cells, named processed lipoaspirate cells, have previously shown in vitro osteogenic capacity. The purpose of this study was to examine the in vivo bone induction capacity of bone morphogenetic protein-2 (BMP-2)-transduced processed lipoaspirate cells using adipose tissue from multiple harvest sites. Methods: Processed lipoaspirate cells extracted from human abdominal and buttock liposuction aspirates (n = 5) and from infrapatellar fat pads (n = 5) were placed in osteogenic media containing Dulbecco's Modified Eagle Medium with 10% fetal bovine serum supplemented with 50 mu M ascorbic acid-2-phosphate and 10 mM beta-glycerol phosphate. Half of these cells were transfected with an adenovirus carrying the cDNA for bone morphogenetic protein-2 (adBMP-2). These transfected cells were then seeded onto collagen I matrices at a concentration of 2 X 10(6) cells/matrix and were placed into the hind limbs of severe combined immunodeficient mice (n = 10). Nontransfected processed lipoaspirate cells were placed in the contralateral limb as a control. After 6 weeks, specimens were analyzed by radiographs, densitometry, and hematoxylin and eosin and von Kossa staining. Results: The average number of cells extracted from the abdominal/buttock lipoaspirates was 3.4 X 10(7) cells/100 ml fat aspirate and 5.5 X 10(6) cells per infrapatellar fat pad (average volume, 20.6 cc). All 10 BMP-2 transfected processed lipoaspirate constructs produced abundant radiographic and histologic bone. The bone was adequately mineralized and was beginning to establish a marrow cavity. There was no quantitative difference in bone production between harvest sites [mean, 2.0 +/- 0.1 aluminum units (knee) versus 2.1 +/- 0.1 aluminum units (abdomen/buttock); p = 0.14]. No bone was produced in the negative controls. Conclusions: Multipotential processed lipoaspirate cells can be extracted from adipose tissue harvested from liposuction aspirates or from the infrapatellar fat pad of the knee. Processed lipoaspirate cells can be transduced,with the BMP-2 gene to produce abundant in vivo bone. These cells appear to be clinically useful for bone tissue engineering applications either as osteoprogenitor cells or as delivery vehicles for BMP-2.