gms | German Medical Science

Objectives: Increasing life expectancy, associated with physical inactivity and supernutrition, lead to obesity and elevated blood sugar and insulin levels, not only in older but increasingly in young people. To date, there is evidence that diabetes mellitus (DM) patients have an imbalance in IL-10 expression. However, little is known about the role and mechanisms of this antiinflammatory and chondroprotective cytokine. In order to understand the interplay of OA and DM, we examined in a cell model the effects of hyperglycemia and hyperinsulinemia on human articular chondrocytes and a human chondrosarcoma cell line (OUMS-27) and considered the role of IL-10 as potential therapeutic starting point.

Methods: Human articular cartilage for enzymatic isolation of human articular chondrocytes (hACs) was obtained from OA patients undergoing total hip and knee replacement surgeries (male, female, mean age: 74 years). In comparison to primary cells OUMS-27 chondrosarcoma cells were used (IFO 50488, JCRB Cell Bank, Japan). Cells were seeded with an initial cell number of 1x104 cm-2 and cultured in normo- (1.0 g/L glucose, NG) and hyperglycemic (4.5 g/L, HG) conditions. Prior to stimulation with insulin (10 µg mL-1) or IL-10 (10 ng mL-1) or co-stimulation (insulin+IL-10), cells were allowed to attach and serum-starved for 24 h. Cell responses to differing glucose contents such as cell metabolism (CellTiter-Blue® Cell Viability Assay), cell survival (Live/dead staining), proliferation (CyQuant Assay) and ECM neo-synthesis were examined on protein level and by immunocytochemical staining.

Results and conclusion: After stimulation with insulin or/and IL-10, a significant reduction in metabolic activity was observed for hACs and OUMS-27. In hAC, a reduced metabolic activity was detected under HG compared to NG conditions. It was found that insulin and IL-10 alone as well as co-stimulation impair the metabolic rate of hAC significantly less in NG than in HG. Cell survival was high under NG and HG conditions. Cell viability was high, but under NG and HG the cell density increased after treatment with insulin and insulin+IL-10, but not with IL-10 alone. Most of these observations were confirmed by the measured DNA content. HG conditions lead to significantly reduced proliferation and DNA content in OUMS-27. Furthermore, reduced collagen type I and II synthesis was detected for cells in HG. Treated with insulin and insulin+IL-10, cells exhibited a higher collagen type I synthesis, while stimulation with IL-10 increased collagen type II synthesis.

In summary, hyperglycemia and hyperinsulinemia affect hACs and OUMS-27 metabolism and IL-10 has a modulatory effect.

Acknowledgements: The authors thank the Kerscher Foundation for their financial support.