Abstract
Introduction
Bone grafts play an important role in spinal fusion surgery. Despite tremendous research efforts, synthetic or biological grafting materials equaling autologous bone habe not been developed so far. One of the major reasons is the achievement of sufficient graft vascularization. Aim of the presented study ist to test the concept of an autologous, scaffold-free, vascularized bone graft by converting the patient's fat tissue into bone.
Methods and Materials: 10 fat tissue biopsies deriving from surgical waste material were used for the experiments. Samples were washed in sterile saline solution and divided into two parts. Part A served as control group and was cultivated in DMEM-F12 medium supplemented with 10% fetal calf serum and 2 mM L-Glutamine. Part B was transdifferentiated in toto using osteogenic differentiation medium and cultivated at 37°C, 95% humidity and 5% CO2 for 3 weeks. Histological evaluation of tissue mineralization was performed using H/E, van Kossa and Alizarin Red staining. Mineralization was quantified and angiogenesis and tissue integration were evaluated using the chick chorionallantoic membrane assay. Quantitative analysis were performed in triplicates. Statistical evaluation was performed using the Student's T-Test at a 0,05 level of significany.
Results
The osteogenic transdifferentiated fat graft showed an increase in collagen content and signs of mineralization as indicated by positive van Kossa and Alizarin Red staining. Average Calcium OD/mm sample was 50 for the transdifferentiated grafts after 3 weeks vs 24 for the corresponding control tissue (p < 0,005). Transplantation onto the chick chorionallantoic membrane demonstrated excellent tissue integration and connection to the recipients vascular system after 5 days in vivo. Numerous small blood vessels were visible within the graft. Despite the deprivation of osteogenic differentiation factors, the osteogenic phenotype was maintained after heterotopic implantation.
Conclusion
The patient's own fat tissue can be transdifferented toward an osteogenic phenotype in vitro and demonstrates excellent angiogenetic properties after in vivo implantation without losing the osteogenic phenotype. A transdifferentiated fat pat might therefore have the potential to serve as a fully autologous, vascularized graft to enhance osteogenesis in spinal fusion surgery.