Inflammatory response of cultured rat synoviocytes challenged with synovial fluid from osteoarthritis patients correlates with their radiographic grading: a pilot study.

The inflammatory nature of synovial fluid (SF) of varying grade osteoarthritis (OA) patients was estimated by measuring pro-inflammatory factors and through a unique cell-challenge experiment. SF samples were collected from six OA and one non-OA patient; spanning Kellgren-Lawrence (KL) grades were analyzed for interlukin-1-beta (IL-1β), nitric oxide (NO) and its derivatives, and glycosaminoglycan (GAG). Levels of IL-1β, NO, and GAG in SF did not correlate with KL grades of the patients studied. In the cell-challenge experiment, cultured rat synoviocyte fibroblasts (RSFs) were challenged by the patient's SFs with and without pre-treatment of IL-1β and lipopolysaccharide (LPS). NO released by the cells was taken as an indicator of inflammation. SFs from KL grades 2 and 3 induced maximum inflammation in cultured RSFs (grade 2 64.61 ± 4.8 and 89.51 ± 5.6 μM/ml after 48 and 72 h, grade 3 58.27 ± 2.7 and 64.22 ± 2.8 μM/ml after 48 and 72 h, respectively). Similar trend was observed in RSF pretreated with either recombinant IL-1β or LPS suggesting that SF from patients KL grades 2 and 3 accumulates more pro-inflammatory factors. IL-1β-pre-treated RSFs challenged by SF for 72 h showed 234.41 ± 17.6 μM/ml increase (patient 3, grade 3), whereas higher NO after LPS pre-treatment was recorded (118.92 ± 6.2 μM/ml; patient 3, grade 3). Interestingly, SFs from grade 1 and non-OA patient could reduce released NO to 27.10 ± 2.2 μM/ml showing potency to alleviate inflammation. These interesting findings, however, need to be confirmed on a wider number of patients, which may offer significant therapeutic application in treatment of OA.