Abstract: BACKGROUND: Decalcified bone matrix is a commonly used bone repair material in clinical practice, but it has been found to have the problem of insufficient osteogenic ability in clinical application. Combining with cells with osteogenic potential can effectively improve the osteogenic ability of scaffolds.
OBJECTIVE: To investigate the feasibility of decalcified bone matrix combined with adipose-derived stem cells to improve the repair ability of radial segmental bone defects. 
METHODS: Decalcified bone matrix was prepared using porcine bone as raw material. Adipose-derived stem cells of New Zealand white rabbits were isolated and cultured in vitro by enzymatic hydrolysis and adherence method. Cell phenotypes were detected by flow cytometry, and osteogenic and adipogenic differentiation was performed. Then adipose-derived stem cells were seeded into decalcified bone matrix. Three days later, the growth of adipose-derived stem cells on decalcified bone matrix was observed by inverted microscope and scanning electron microscope. Twenty-four New Zealand white rabbits were used to establish bilateral radial segmental defects (12 mm), which were randomly divided into blank control group, decalcified bone matrix group, adipose-derived stem cells-decalcified bone matrix group, and autologous bone group. The corresponding materials were implanted according to the groups. X-ray examination and hematoxylin-eosin staining were used to evaluate bone repair at 4, 8, and 12 weeks after surgery. 
RESULTS AND CONCLUSION: (1) The cultured cells adhered to the wall and grew together in a long spindle shape, with high expression of CD44 and CD71 and low expression of CD34, CD45 and CD106. In cultured cells induced by osteogenic differentiation, alizarin red staining showed mineralized nodules stained orange-red. Lipid induced differentiation cultured cells were stained with oil red O, and bright red lipid droplets could be seen in the cells. (2) Adipose-derived stem cells were tightly compounded on the surface of decalcified bone matrix, with good growth status, and grew into the pores. (3) X-ray examination and histological observation showed that the repair of bone defects in adipose-derived stem cells-decalcified bone matrix group was better than that in the blank control group and decalcified bone matrix group. The results confirm that loading with adipose-derived stem cells can effectively compensate for the lack of osteogenic ability of decalcified bone matrix. 

Key words: adipose-derived stem cell, decalcified bone matrix, radius, segmental bone defect, osteogenesis, New Zealand rabbit, tissue engineering