Protective effects of interleukin-10 and insulin-like growth factor-1 gene combination therapy on islet β cells of non-obese diabetic mice

Abstract

Objective To investigate whether IL-10 gene combined with insulin-like growth factor-1(IGF-1) gene transfer could attenuate pancreatic insulitis, increase the percentage of CD4+ CD25+ Foxp3+ regulatory T cells, and protect β cells from autoimmune destruction. Methods An adenoviral vector containing IL-10 gene(Ad-IL-10) or IGF-1 gene(Ad-IGF-1) was constructed separately.Forty female non-obese diabetic(NOD) mice were injected intra-peritoneally with Ad-IL-10 and/or Ad-IGF-1, Ad-green fluorescent protein(GFP) and phosphate buffered saline(PBS)separately, repeated after 3 weeks. Blood glucose concentration was measured weekly.Serum insulin, cytokine production were tested by enzyme-linked immunosorbent assay.CD4+ CD25+ Foxp3+ Treg cells were determined by flow cyto-metry.Pancreatic histology was measured for determination of insulitis grades.Pancreatic insulin content and β-cell mass, proliferation were measured.Apoptosis was measured by using a terminal deoxynucleotidyl transferase dUTP nick end labeling assay. Results A significantly lower diabetes incidence(P<0.01) was observed in NOD mice treated with Ad-IL-10 and/or Ad-IGF-1, compared with mice treated with Ad-GFP or PBS alone, especially combined group.Lower insulitis score compared to control mice was found in Ad-IL-10+ Ad-IGF-1 group(all P<0.01). The serum level of TNF-α and IFN-γ were decreased and the level of IL-10 increased in combination therapy.The CD4+ CD25+ Foxp3+ cells was (7.17±0.38)% in combined group, higher than that in the control groups.There was significantly less β-cell apoptosis(10.29±2.20)% in combined group than that in other groups(all P<0.05). Conclusions Combination therapy with IL-10 and IGF-1 gene is able to increase the percentage of CD4+ CD25+ Foxp3+ regulatory T cells, reduce autoimmunity and increase pancreatic β-cell mass, indicating promising potential of these therapies as a new treatment strategy for diabetes mellitus. Key words: Immunotherapy; Type 1 diabetes mellitus; T regulatory cells; Islet βcell