Endocultivation: metabolism during heterotopic osteoinduction in vivo--monitoring with fiber optic detection devices.

Reconstructions of facial bone defects are one of the most challenging aspects in surgical treatment of malignant diseases, large facial traumata, or congenital anomalies. High-level reconstruction techniques are often associated with an elevated morbidity by the harvest of autologous bone grafts from the patient. Tissue engineering techniques may help to solve this problem. The aim of this study was to monitor metabolic processes during cellular colonization of matrices in vivo in an established rat model for endocultivation. After implantation of computer-designed hydroxyapatite scaffolds into the latissimus dorsi muscle of six rats, 100??g bone morphogenetic protein-2 (BMP-2) was injected twice, in week 1 and 2, directly into the center of the matrices. The development of pH value and oxygen (O?) saturation inside the matrix was followed by fiber optic detection technique over 8 weeks and analyzed by variance analyses. Bone density measurements were performed by computed tomography as well as histological evaluations. Two weeks after implantation, oxygen supply and pH value measurements had decreased significantly. In the following weeks both parameters increased and stabilized on higher levels. This is the first study reporting a reproducible method to follow metabolic processes during heterotopic osteoinduction in vivo. It was shown that in the beginning of the study pH value and O? saturation decreased and it took several weeks to regain physiological levels. This is an important step to further understand the physiological process of bone induction.