In vivo inhibition of angiogenesis by interleukin‐13 gene therapy in a rat model of rheumatoid arthritis

Objective Interleukin‐13 (IL‐13) is a pleiotropic cytokine that can affect vessel formation, an important component of the rheumatoid arthritis (RA) synovial tissue pannus. The purpose of this study was to use a gene therapy approach to investigate the role of IL‐13 in angiogenesis in vivo, using a rat adjuvant‐induced arthritis model of RA. Methods Ankle joints of female rats were injected preventatively with an adenovirus vector containing human IL‐13 (AxCAIL‐13), a control vector with no insert (AxCANI), or phosphate buffered saline (PBS). Joints were harvested at the peak of arthritis, and histologic and biochemical features were evaluated. Results AxCAIL‐13–treated joint homogenates had lower hemoglobin levels, suggesting reduced joint vascularity, and both endothelial cell migration and tube formation were significantly inhibited (P < 0.05). Similarly, AxCAIL‐13 inhibited capillary sprouting in the rat aortic ring assay and vessel growth in the Matrigel plug in vivo assay. IL‐13 gene delivery resulted in up‐regulation and association of phosphorylated ERK‐1/2 and protein kinase Cα/βII, suggesting a novel pathway in IL‐13–mediated angiostasis. The angiostatic effect of AxCAIL‐13 was associated with down‐regulation of proangiogenic cytokines (IL‐18, cytokine‐induced neutrophil chemoattractant 1/CXCL1, lipopolysaccharide‐induced CXC chemokine/CXCL5) and up‐regulation of the angiogenesis inhibitor endostatin. The expression and activity of matrix metalloproteinases 2 and 9, which participate in angiogenesis, was impaired in response to IL‐13 as compared with AxCANI and PBS treatment. Conclusion Our findings support a role for IL‐13 as an in vivo antiangiogenic factor and provide a rationale for its use in RA to control pathologic neovascularization.