Osteogenesis with coral is increased by BMP and BMC in a rat cranioplasty

Autologous bone marrow cells (BMC), bone morphogenetic protein (BMP) and natural coral exoskeleton (CC) were used to enhance the repair of large skull bone defects in a craniotomy model. Nine millimeter calvarial defects were created in adult rats and were either left empty (control defects) or implanted with CC alone, CC–BMC, CC–BMP, or CC–BMC–BMP. After 1 or 2 months, osteogenesis was insufficient to allow union when defects were left empty or filled with CC. Addition of BMC alone to CC had no positive influence on osteogenesis at any time and increased CC resorption at 2 months (0.1±0.1 mm2 versus 0.5±0.3 mm2). In contrast addition of BMP or BMP/BMC to CC led to a significant increase in osteogenesis and allowed bone union after 1 month. At 2 months, the combination of CC–BMP–BMC was the most potent activator of osteogenesis. Filling a defect with CC–BMP–BMC resulted in significantly increased bone surface area (11±2.7 mm2) in comparison to filling a defect with CC–BMP (7.0±1.4 mm2), CC–BMC (3.5±1.1 mm2) or CC (4.5±0.4 mm2). CC resorption was significantly decreased in the presence of BMP with or without BMC at both times. These data are in accordance with the presence of progenitor cells in bone marrow that are inducible by BMP to the osteogenic pathway in a cranial site. The increase in material resorption in defects filled with CC–BMC could suggest that cells from the granulocyte–macrophage lineage survived the grafting procedure and were still active after 2 months.