Low-dose X-ray irradiation promotes fracture healing through up-regulation of vascular endothelial growth factor.

Compared with high and medium dose irradiation, low-dose irradiation (LDI) revealed different yet healing promotion effects, such as hormesis and adaptive response. A recent milestone work by Zhou demonstrated that LDI at 1 Gy promoted callus formation and mineralization in a rat model, yet without being able to address the underlying mechanism. It is well known that vascular endothelial growth factor (VEGF) is a key cytokine that regulates angiogenesis, especially important found in the process of fracture healing to interplay with other molecules. Furthermore, recent studies revealed that tissue repair might be enhanced by LDI through up-regulation of the level of VEGF. In view of this general phenomenon, we propose the following hypothesis that low-dose X-ray irradiation at ≤ 1 Gy promotes fracture healing through up-regulation of VEGF.