Anti-inflammatory and joint-protective effects of blueberries in a monosodium iodoacetate (MIA) induced rat model of osteoarthritis
The purpose of this dissertation project was to investigate the anti-inflammatory and joint-protective effects of blueberries and its polyphenols using an in vitro and in vivo study design. The in vitro design used rabbit synoviocytes stimulated with tumor necrosis factor alpha (TNFα). Rabbit synoviocytes (HIG-82) were treated with 0, 100, 150, and 200 µg/mL of blueberry polyphenols (BBPs) and stimulated with 10ng/ml TNFα. The in vivo study design employed a monosodium iodoacetate (MIA) induced rat model of osteoarthritis. Forty, 45-day-old female CD rats were used where thirty rats were injected with MIA to induce joint destruction associated with osteoarthritis and ten rats served as control without induction of joint destruction. The MIA injected rats were randomized into three groups consisting of 10 animals. All groups were fed a casein-based diet with two of the MIA induced groups receiving an addition of whole blueberry powder at 5% and 10%, respectively for 48 days. The animals were weighed weekly throughout the study period and food intake monitored and recorded. Fasted blood specimens and other tissues were collected after euthanasia for analysis. Mechanical allodynia and joint width were assessed at four timepoint throughout the study to evaluate changes in pain behaviors and edema. Results from the in vitro study showed TNFα increased cell proliferation by ~ 19% compared to the non-stimulated control. This was significantly decreased in a dose-dependent manner with the treatment of blueberry polyphenols. TNFα stimulated, cells treated with BBP resulted in decreases in interleukin 1 beta (IL-1β) and Nuclear Factor Kappa B (NF-κB) concentration. The expression of metalloproteinase 3 (MMP3) increased 5-fold in the TNFα stimulated synoviocytes but was decreased by 3-fold in the blueberry treated cells. Findings in the MIA rat study demonstrated significant (p ≤ 0.05) mechanical allodynia in the MIA group compared to the control group at baseline. Mechanical allodynia was significantly (p ≤ 0.05) reduced after 40 days in the 10% whole blueberry treated group but no effects was seen in the 5% whole blueberry group. There was no effect of edema in the MIA induced groups compared to the control. There was no significant difference in average weight between the four groups at baseline and at the end of the study. The addition of whole blueberry into the diet of the MIA injected animals resulted in decreased serum concentrations of hyaluronic acid, and IL-10 concentrations. Protein expression of COMP and NFĸB were downregulated in cartilage samples. The gene expression of MMP3 and Col1a1 were significantly upregulated in the MIA group compared to the control group. A non-significant decrease was observed with blueberry treatment in MMP2, MMP3, Sufl 1 and NFĸB expression. These results suggest that whole blueberries with its naturally occurring bioactives incorporated into the diet may be a potential complimentary therapeutic agent for reducing inflammation, improving joint health, and alleviating pain associated with osteoarthritis.