Cell sheet techniques are widely used in bone engineering. However, vascularization remains a challenge in fabricating vascularized engineered bone. The goal of this study was to induce adipose-derived stem cell (ADSC) osteogenic and angiogenic lineage differentiation and investigate the use of bidiretionally differentiated ADSCs for bone regeneration. ADSCs were cultured to form an osteogenic cell sheet. Other ADSCs were induced to differentiate into endothelial progenitor cells (EPCs), which were identified and characterized by morphological observation and CD31 immunofluorescent staining. Then, the ADSC sheet-EPC complexes were implanted subcutaneously into nude mice, while ADSC sheets alone were implanted as a control. After 8 weeks of transplantation, microcomputed tomography (micro-CT) and histological observation were used to assess bone formation. We then implanted the complexes in calvarial defects in rabbits and assessed bone repair by micro-CT and histological analysis. The ADSC sheets consisted of multiple layers of cells and extracellular matrix. The obtained EPCs formed capillary-like structures and expressed the specific antigen marker CD31. The osteogenic ADSC sheet-EPC complexes formed dense and well-vascularized new bone tissue at 8 weeks after implantation. Bone density was significantly lower in the control group than in the complex group (p < .05). In addition, the reconstruction of calvarial defects in rabbits in complex group was obviously greater than that in the control group (p < .05). These results suggested that the approach of engineering bone tissue with bidiretionally differentiated ADSCs enabled bone regeneration, thus offering a promising strategy for repairing bone defects.
Keywords: adipose-derived stem cells; bone tissue engineering; cell sheet; endothelial progenitor cells.
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