Background Signalling through insulin-like growth factor (IGF) 1 receptor is essential for cell survival, but may turn pathogenic in uncontrolled tissue growth in tumours. In rheumatoid arthritis (RA), the IGF-1R signalling is activated supporting expansion of the inflamed synovia.

The aim of the present study was to understand the place of IGF-1R expression and signalling for development of adaptive immune responses in the setting of prospective RA cohort and in experimental arthritis.

Material and methods Clinical associations of IGF1R expression in leukocytes of the peripheral blood were studied in 84 female RA patients with mean disease duration 8 years, all treated with methotrexate at the time of enrolment. Consequences of the IGF1R signalling inhibition for arthritis were studied in mBSA immunised Balb/c mice treated with NT157 compound promoting degradation of IRS-1/2.

Results In RA patients, high expression of IGF1R in leukocytes was associated with and systemic inflammation as verified by higher transcription factor NF-kB, serum levels of IL-6 and erythrocyte sedimentation rate, and higher pain perception. Additionally, phosphorylated IGF1R and STAT3 enriched T cells infiltrate in RA synovia. Treatment with NT157 inhibited the phosphorylation of IGF1R and STAT3 in synovia, and alleviated arthritis and erosions in mice. It also reduced expression of IGF1R in spleen T cells and despaired ERK and Akt signalling. This limited the ability of mBSA-specific T cells to produce IL-6, IFNg and IL-17. The reduction of IL-6 and IL-17 levels was associated with changed RoRgt/FoxP3 balance.

Conclusion IGF1R signalling contributes to T cell dependent inflammation in arthritis. Inhibition of IGF1R signalling alleviates arthritis by restricting IL-6 dependent formation of Th17 cells and may open for new treatment strategies in RA.