Calcium-Chitosan Scaffolds With Simvastatin Enhance Bone Regeneration in Critical-Sized Calvarial Defects in Rats

Bone regeneration in critical defects remains a clinical challenge, motivating the development of biomaterials capable of supporting osteogenesis and modulating local biological responses. This study investigated the regenerative potential of chitosan-calcium (CH-Ca) scaffolds functionalized with simvastatin (SV) in rat calvarial critical-sized defects. Forty male Wistar rats were randomly assigned to four groups (n = 5 per group/experimental period): SHAM (coagulum), Bio-Oss (xenograft), CH-Ca, and CH-Ca + SV. Defects of 5 mm were surgically created and filled according to group allocation. Animals were euthanized at 14 and 30 days, and samples were processed for histological, histomorphometric, Picrosirius Red, and immunohistochemical (BMP-2 and osteocalcin [OCN]) analyses. Histologically, the SHAM group showed bone restricted to the defect margins with persistent inflammation, while Bio-Oss exhibited partial bone extension and residual particles surrounded by connective tissue. In contrast, CH-Ca and CH-Ca + SV scaffolds supported linear bone formation progressing toward the defect center, with more pronounced mineralization in CH-Ca + SV. Histomorphometry confirmed higher new bone formation (NBF%) in CH and CH + SV compared with SHAM and Bio-Oss at both time points, with CH + SV surpassing CH at 30 days. Picrosirius Red revealed greater collagen fiber maturation in CH + SV, whereas SHAM maintained a higher proportion of immature fibers. Immunohistochemistry demonstrated increased BMP-2 and OCN expression in CH and CH + SV, particularly in CH + SV, at both 14 and 30 days. These findings indicate that SV-loaded CH-Ca scaffolds enhance bone regeneration by promoting osteogenesis, collagen maturation, and the expression of osteogenic proteins, suggesting their potential as a cost-effective and biologically favorable strategy for the treatment of critical-sized bone defects.