Low‐level laser therapy (780 nm) combined with collagen sponge scaffold promotes repair of rat cranial critical‐size defects and increases TGF ‐β, FGF ‐2, OPG / RANK and osteocalcin expression

Summary The aim of this study was to evaluate the effect of collagen sponge scaffold ( CSS ) implantation associated with low‐level laser therapy ( LLLT ) on repairing bone defects. A single 5‐mm cranial defect was surgically created in forty Wistar rats, which then received one of the following four interventions ( n  =   10 per group): no treatment (G0); bone defect implanted with collagen sponge scaffold ( CSS ) alone (G1); defect treated with low‐level laser therapy ( LLLT ) (wavelength 780 nm; total energy density 120 J/cm 2 ; power 50 mW) alone (G2); and CSS associated with LLLT treatment (G3). After surgery, animals in each group were euthanized at 21 days and 30 days ( n  = 5 per euthanasia time group). Bone formation was monitored by X‐ray imaging analysis. Biopsies were collected and processed for histological analysis and immunohistochemical evaluation of transforming growth factor‐beta ( TGF ‐β), fibroblast growth factor‐2 ( FGF ‐2), osteoprotegerin ( OPG ) and receptor activator of nuclear factor ƙ ( RANK ). Osteocalcin ( OCN ) was detected by immunofluorescence analysis. Compared to the G0 group, defects in the 30‐day G3 group exhibited increased bone formation, both by increase in radiopaque areas ( P  < 0.01) and by histomorphometric analysis ( P  < 0.001). The histopathological analysis showed a decreased number of inflammatory cells ( P  < 0.001). The combined CCS  +  LLLT (G3) treatment also resulted in the most intense immunostaining for OPG , RANK , FGF ‐2 and TGF ‐β, and the most intense and diffuse OCN immunofluorescent labelling at 30 days postsurgery (G3 vs . G0 group, P  < 0.05). Therefore, the use of CCS associated with LLLT could offer a synergistic advantage in improving the healing of bone fractures.