Biogran Grafting in Rat Tibia Defects - A Model of High Bone Metabolism Site

We investigated the Biogran on bone repair and metabolism at several time -intervals upon grafting into rat tibia artificial defects. The biomaterial was thoroughly characterized in vitro, and its dissolution behavior upon immersion was assessed in simulated body fluid (SBF) solution for 1, 3, 7, 14, and 30 days. Biogran was also assessed by in vitro hydroxyapatite formation in SBF solution, which is a marker for bioactive behavior. In vivo, distal and proximal bone defects were performed in the Wistar rat's right tibia and filled according to the experimental groups: I) negative control, no filling; II) positive control, 10 mg of autogenous bone; and III) 10 mg of Biogran. Animals were euthanized at 1, 2, 3, 4, 7, and 10 weeks. Bone neoformation was analyzed using histomorphometry (proximal defect), and local levels of bone morphogenetic protein 2 (BMP-2) were measured using the ELISA assay (distal defect). In vitro, the Biogran sample showed a fast dissolution rate within the first 7 days, parallel to the formation of the hydroxyapatite layer. In vivo, the sample was progressively resorbed at a higher rate within the first month until it became almost absent at week 10th. The sample presented similar or higher bone neoformation concerning the autogenous bone. BMP-2 levels were sustained in the Biogran group (around 200 pg/mg) and detected until the last experimental time with a significant difference compared with the controls. Results suggest Biogran is a candidate for hard tissue even in active bone sites.