Bone morphogenetic protein-2 stimulates cell recruitment and cementogenesis during early wound healing

Background: The unique action of bone morphogenetic proteins (BMPs) on mine ralised tissue formation indicates that BMPs are good candidates for use in stimulating periodontal regeneration. Relatively little is known about the mechanisms of actions of BMPs during periodontal regeneration. although re cent evidence from our laboratory suggests that the effects of BMPs may be profoundly influenced by various factors including root surface conditionin g, delivery systems and masticatory forces. Aim: The aim of this study tvas to investigate the effect of rhBMP-2 on cel l recruitment during periodontal regeneration using a pulse-chase technique where cells are labelled with a thymidine analogue (BrdU) (pulse) and the migration of their progeny is followed (chase) during early wound healing. The relationship between the rhBMP-2 influence on cell recruitment from the periodontal ligament (PDL) and its ability to stimulate cementogenesis was also evaluated. Method: The buccal aspect of the distal root of the first molar was denuded of its PDL, cementum and superficial dentine through a bony window created in the mandible of 64 Wistar rats under general anaesthesia. Test animals were treated with 10 muL of 500 mug/ml rhBMP-2 in a collagen membrane spong e (n=32) and control defects received 10 mul of saline in a collagen sponge (n=32). All animals received an intraperitoneal single pulse injection of 40 mg/kg BrdU label 2 days postoperatively. Groups of test and control anim als (n=8) were killed 2 hours later on dw 2 and at 4, 7 and 10 days postope ratively. Mandibles were processed for histological examination. Results: The results show that rhBMP-2 had a profound effect on proliferati on and migration of cells in the adjacent and deeper aspects of the PDL at 7 and 10 days post periodontal wounding (p<0.05). Significantly greater new cementum formation occurred in the test group at 10 days (p=0.03). Conclusion: This study shows that following periodontal wounding rhBMP-2 st imulates cell recruitment by increasing proliferation and migration of cell s from the adjacent unwounded PDL into the wounded area, thus promoting per iodontal regeneration by increasing new cementum formation.