Blockade of interleukin 6 by rat anti-mouse interleukin 6 receptor antibody promotes fracture healing

Abstract

Level of interleukin 6 (IL-6) is associated with fracture healing. This study was performed to explore the effect of IL-6 blockade on fracture healing. Clinical serum levels of IL-6 and tumor necrosis factor-α (TNF-α) were evaluated by enzyme-linked immunosorbent assay (ELISA). For animal experiments, the IL-6 levels after fracture and treatment with rat anti-mouse IL-6 receptor antibody (MR16-1) were assessed. Then, mice were assigned into four or seven groups: control group, fracture group, isotype IgG group, and MR16-1 groups. Serum levels of IL-6 and TNF-α, relative flexural rigidity, and mRNA levels of osteoblast-specific genes were respectively assayed by ELISA, three-point bending test, and quantitative reverse transcription PCR (qRT-PCR). Serum levels of IL-6 and TNF-α after fracture in humans and mice were increased. The increase in IL-6 and TNF-α levels in murine serum was attenuated by MR16-1 treatment. The three-point bending test showed the relative flexural rigidity of the femur was decreased after fracture, whereas the decrease was alleviated by MR16-1 treatment. The qRT-PCR results demonstrated mRNA levels of osteoblast-specific genes were upregulated after fracture and then further upregulated by MR16-1 treatment in a dose-dependent manner. Collectively, the serum level of IL-6 was elevated after fracture both in clinical and murine samples. IL-6 blockade by MR16-1 promoted fracture healing, which might be associated with changes in expression of osteoblast-specific genes.