Effects of remote ischemic post-conditioning on fracture healing in rats

Abstract

Remote ischemic post-conditioning (RIPC) is an established method to activate the hypoxia-inducible factor-1α (HIF-1α) pathway, which is involved in the impairment of fracture healing. However, the role of RIPC in fracture healing remains to be fully elucidated. In the present study, rats received fractures and were divided into two groups: Control and RIPC, in which hind limb occlusion was performed. Rats were sacrifced at 7, 14, 28 and 42 days subsequent to tibial fracture. Micro-computed tomography was performed to measure healing of the bone tissue and biomechanical testing was used to test mechanical strength. In addition, the effects of hind limb occlusion on the expression of two primary angiogenic mediators, HIF-1α and vascular endothelial growth factor (VEGF), as well as the osteoblast markers runt-related transcription factor 2 (Runx2), alkaline phosphatase (ALP) and osteocalcin (OCN), were determined at the mRNA and protein levels by reverse transcription-quantitative polymerase chain reaction, western blot analysis and immunohistochemistry. Systemic administration of hind limb occlusion (3 cycles/day, with each occlusion or release phase lasting 10 min) signifcantly promoted fracture healing and mechanical strength. The present study demonstrated that in rats treated with hind limb occlusion, the expression of HIF-1α, VEGF, Runx2, ALP and OCN was signifcantly increased at the mRNA and protein levels, and that RIPC enhances fracture repair in vivo.