The additive effects of photobiomodulation and bioactive glasses on enhancing early angiogenesis

Bioactive glasses (BG) have been widely utilized as a biomaterial for bone repair. However, the early angiogenesis of BG may be inadequate, which weakens its osteogenic effects in large-sized bone defects and often leads to the failure of bone regeneration. In this study, we explored the effects of photobiomodulation (PBM) combined with BG on early angiogenesis to solve this bottleneck problem of insufficient early angiogenesis.In vitro, human umbilical vein endothelial cells (HUVECs) were cultured with BG extracts and treated with PBM using 1 J cm^-2. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, real-time reverse transcription-polymerase chain reaction (real-time RT-PCR) and tubule formation assay were utilized to detect HUVECs' proliferation, vascular growth factor genes expression and tubules formation.In vivo, bone defects at the femoral metaphysis in Sprague-Dawley rats were treated with BG particulates and PBM at 120 J cm^-2. Hematoxylin-eosin staining was used to observe the inflammatory response, tissue formation and biomaterial absorption of bone defects. Immunohistochemical staining was applied to observe the vascular-like structure formation. Thein vitroresults showed that PBM combined with BG significantly promoted HUVECs' proliferation, genes expression and mature tubules formation. On days 2, 4 and 7, the mRNA expression of VEGF in BG + PBM group was 2.70-, 2.59- and 3.05-fold higher than control (P< 0.05), and significantly higher than PBM and BG groups (P< 0.05). On days 4 and 7, the bFGF gene expression in BG + PBM group was 2.42- and 1.82-fold higher than control (P< 0.05), and also higher than PBM and BG groups (P< 0.05). Tube formation assay showed that mature tubules were formed in BG + PBM and PBM groups after 4 h, and the number in BG + PBM group was significantly higher than other groups (P< 0.05).In vivoresults further confirmed PBM induced early angiogenesis, with more vascular-like structures observed in BG + PBM and PBM groups 2 week post-surgery. With the optimum PBM fluence and BG concentration, PBM combined with BG exerted additive effects on enhancing early angiogenesis.