Exploratory study on the effect of osteoactivin on bone formation in the rat critical-size calvarial defect model

Background and Objective: Osteoactivin is a novel glycoprotein shown to exhibit an important role in regulating osteoblast differentiation and function. The aim of the present study was to evaluate the potential of osteoactivin to support bone regeneration using an established defect model. Material and Methods: Critical-size, 8-mm-diameter through-and-through calvarial osteotomy defects were created in 60 adult male Sprague-Dawley rats. Test animals received 0.1mL of osteoactivin in phosphate-buffered saline (50μg/mL) soak-loaded onto an absorbable collagen sponge. Controls received 0.1mL of phosphate-buffered saline soak-loaded onto the absorbable collagen sponge or no further intervention (sham-surgery). The animals were euthanized 2 and 4wk after treatment and histometric analyses were performed. Results: The absorbable collagen sponge control (mean±standard deviation: 40.9±26.9%) showed borderline significant greater bone fill compared with sham-surgery (22.9±15.8%; p=0.10) and osteoactivin (20.2±11.8%; p=0.07) treatments at 2wk. In contrast, osteoactivin (84.7±15.8%) showed significantly greater bone fill than sham-surgery (28.4±9.6%; p<0.001) and absorbable collagen sponge (41.8±22.1%; p<0.001) at 4wk. No animals receiving sham-surgery or absorbable collagen sponge exhibited complete bone fill at 4wk while 70% of the animals receiving osteoactivin showed complete bone fill. Conclusion: Osteoactivin demonstrates a significant potential to support bone regeneration/formation. Studies using discriminating large animal models are necessary to explore clinical application for periodontal and craniofacial indications.