Elevated level of
interleukin (IL)-17, predominantly produced by T helper (Th) 17 cells, has been implicated in
diabetic retinopathy (DR), but it remains unclear whether
IL-17 is involved in the pathogenesis of DR. Ins2Akita (Akita) mice spontaneously develop diabetes, and show early pathophysiological changes in
diabetic complications. On the other hand,
interferon-γ knock out (GKO) mice exhibit high differentiation and activation of Th2 and Th17 cells as a result of Th1 cell inhibition. In this study, Ins2Akita IFN-γ-deficient (Akita-GKO) mice were established by crossbreeding Akita mice with GKO mice, and Th17-mediated immune responses on DR were investigated.
Blood glucose levels (BGL) of Akita mice and Akita-GKO mice were significantly higher than those of age-matched wild type (WT) or GKO mice, and there was no significant difference in BGL between Akita and Akita-GKO mice. Relative
mRNA expression of ROR-γt that is a transcriptional factor of Th17 cells but not GATA-3 that is for Th2 cells was significantly upregulated only in Akita-GKO mice compared with WT mice, and the proportions of
IL-17 and IL-22-producing splenic CD4+ cells were significantly higher in Akita-GKO mice than in wild type (WT), Akita, or GKO mice. In the retina,
mRNA expression of
vascular endothelial growth factor (
VEGF) and
intercellular adhesion molecule-1 (ICAM-1) were increased in Akita-GKO mice more than in Akita or GKO mice, and statistically significant differences were observed between Akita-GKO mice and WT mice.
Leukostasis in retinal vessels and ocular level of
VEGF protein increased significantly in Akita-GKO mice compared with the other groups. Edematous change in the
retinal surface layer,
retinal exudative lesions depicted as areas of hyperfluorescence in
fluorescein angiography (FA), and vascular basement membrane thickening in all layers of the retina were also observed in Akita-GKO mice at 9-week-old but not in age-matched Akita or GKO mice. These results suggested that Th17 cell-mediated immune responses might be involved in promotion of functional and morphological changes in the retina of mice spontaneously developing diabetes.