Histological Analysis of In Vitro Co-Culture and In Vivo Mice Co-Transplantation of Stem Cell-Derived Adipocyte and Osteoblast

Abstract

Many researchers have focused on the role of adipocytes in increasing efficient bone tissue engineering and osteogenic differentiation of stem cells. Previous reports have not reached a definite consensus on whether adipocytes positively influence in vitro osteogenic differentiation and in vivo bone formation. We investigated the adipocyte influence on osteogenic differentiation from adipose-derived stromal cells (ADSCs) and bone formation through histological analysis in vitro and in vivo. Using the direct co-culture system, we analyzed the influence of adipocytes to promote the differentiation fate of ADSCs. Using co-transplantation of ADSC-derived adipocytes and osteoblasts into the dorsal region of mice, the osteogenesis and bone quality were determined by histological morphology, radiography, and the measurement of the Ca2+ concentration. The adipocyte negatively affected the osteoblast differentiation of ADSCs in the in vitro system and induced osteogenesis of osteoblasts in the in vivo system through co-transplantation. Interestingly, in the co-transplanted adipocytes and osteoblasts, the bone formation areas decreased in the osteoblast only group compared with the mixed adipocytes and osteoblast group 6 weeks after transplantation. Conversely, co-transplantation and osteoblast transplantation had similar degrees of calcification as observed from radiography analysis and the measurement of the Ca2+ concentrations. Our results revealed that adipocytes inhibited osteoblast differentiation in vitro but enhanced the efficacy of osteogenesis in vivo. In addition, the adipocytes controlled the activity of osteoclasts in the newly formed bone tissue. Our approach can be used to reconstruct bone using stem cell-based tissue engineering and to enhance the understanding of the role adipocytes play.