AAV/hSTAT3-gene delivery lowers aortic inflammatory cell infiltration in LDLR KO mice on high cholesterol

Abstract 

Atherosclerosis is an inflammatory disorder of arteries. Signal transducer and activator of transcription-3 (STAT3), an important signal transduction molecule, responds to a number of interleukins (IL) including IL-10, and has a significant immunosuppressive phenotype. Several studies have suggested a correlation of STAT3 expression with a lower state of inflammation. To investigate the contribution of STAT3 in regulating atherogenesis, we delivered full-length wild type human (h) STAT3 gene by adeno-associated virus type 8 (AAV8) via tail vein into low density lipoprotein knockout (LDLR KO) mice which were then fed high cholesterol diet (HCD). Compared to neomycin resistance (Neo) gene delivery-HCD, hSTAT3 delivery-HCD treatment did not result in significant changes in high plasma cholesterol levels. However, while vessel wall lipids were not directly measured, hSTAT3 delivery did result a significant reduction in aortic anomalies, as determined by larger aortic lumen size, thinner aortic wall thickness, and lower blood velocity than the Neo control (all statistically significant). Moreover, measurements of inflammation/monocyte/macrophage (Mo/MФ) burden, including CD68, ITGAM, EMR-1 and nitrotyrosine were reduced in hSTAT3-HCD-treated animals, while foxp3 (Tregs) and SOCS1 expression were increased. An advantage hSTAT3-gene therapy would have over IL-10 would be a reduced chance of systemic effects as STAT3 is not a secreted protein. While hSTAT3-inhibitory gene delivery has been performed by several groups, delivery of the wild type STAT3 gene has never been attempted before. These data strongly suggest, for the first time, that STAT3 gene delivery can down-regulate Mo/MФ burden and atherosclerosis. These data also suggest the possibility that STAT3 and IL-10 dual gene delivery may result in higher efficacy than either one alone.

Keywords: Atherosclerosis, STAT3, Inflammation, Gene therapy, Adeno-associated virus