Dose-Dependent Osteoinduction by rhBMP-2-Loaded β-Tricalcium Phosphate Scaffolds in Rabbit Critical-Sized Calvarial Defects: Histological, Histomorphometric, CD31 Immunohistochemical Evaluation

Critical-sized bone defects represent a major clinical challenge, as bone gaps of this magnitude are unable to heal spontaneously without regenerative intervention. The present study aimed to evaluate the dose-dependent osteoinductive effect of rhBMP-2–loaded β-TCP scaffolds on bone regeneration in critical-sized calvarial defects in a rabbit model. Eighteen adult male New Zealand White rabbits were used, and four circular defects (5 mm in diameter) were surgically created in the calvaria of each animal, resulting in a total of 72 defects. The animals were divided into four groups: control, β-TCP + 5 μg rhBMP-2, β-TCP + 10 μg rhBMP-2, and β-TCP + 20 μg rhBMP-2. Bone healing was evaluated at 2, 4, and 8 weeks postoperatively using histological and histomorphometric analyses. Masson’s trichrome staining was performed to assess collagen deposition and maturation, while CD31 immunohistochemical staining was used to evaluate vascularization. The results demonstrated rhBMP-2–loaded β-TCP scaffolds significantly enhanced bone regeneration in a dose-dependent manner, with the β-TCP + 20 μg rhBMP-2 group demonstrating the greatest new bone formation and more mature bone architecture. In addition, BMP-2 treatment promoted osteoblastic activity, improved collagen maturation, and increased vascularization within the defect area. These findings indicate that rhBMP-2–loaded β-TCP scaffolds enhance bone regeneration in a dose-dependent manner, with higher rhBMP-2 doses resulting in greater bone formation and more mature bone architecture.