Both synovial and bone forms of osteoarthritis (OA) are characterized by inflammatory processes in the articular compartment. Increasing evidence suggests that changes in bone tissue are important for the deterioration or loss of joint function. Therefore it is reasonable to shift emphasis from research on cartilage to that on other articular tissues, particularly on subchondral bone. The aim of the study was to demonstrate the involvement of several cytokines in OA development and, on the basis of changes of joint markers, to assess the extent of inflammatory process.
A total of 60 patients with an osseous form of osteoarthritis of the knee joint (28 patients) or the hip joining (32 patients) underwent total knee or hip arthroplasty. The mean age of our patients was 66.7 +/- 10.4 years. Preoperative clinical and radiographic examinations were carried out as well as routine laboratory tests on blood and urine. Samples of urine, blood serum (BS) and synovial fluid (SF), extracts from cartilage (CA) and synovial membrane (SM) and granulation bone tissue were analysed for markers indicating the presence of inflammatory processes in joints.
The following markers of inflammatory activity in the bone compartment were investigated: pyridinoline (PYR), deoxypyridinoline (D-PYR), bone alkaline phosphatase (BAP) and chondrex (CHON). The levels of cytokines IL-1 alpha, IL-8, IL-10 and TNF-alpha were assayed by immunoanalysis (ELISA and IMMULITE system) in BS, CA, SM, GT and SF. The tissue samples were obtained during arthroplasty.
In the patients with osteoarthritis, the urinary levels of PYR and D-PYR were higher than control values (70.33 +/- 34.93 vs (41.6 +/- 10.6 nmol/mmol creatinine). No significant differences were found between pre- and post-operative levels. Similarly, the serum levels of BAP and CHON compared with control values were higher (27.65 +/- 12.21 vs 12.2 +/- 2.7 U/L and (96.35 +/- 58.83 vs 43.2 +/- 14.5 ng/ml, respectively). In all articular compartments and in synovial fluid, the level of cytokine IL-8 exceeded concentrations of the other cytokines. In blood serum, only IL-10 levels were markedly increased as against the control group (17.35 +/- 5.82 vs 9.80 +/- 4.40 pg/ml).
Primary osteoarthritis is the most common joint disease that deteriorates with age. Its symptoms are pain and a lower range of motion in the joint affected. The initial involvement of articular cartilage progresses to degenerative changes involving synovial and bony structures. This degenerative disease gradually develops into an inflammatory disease. At this stage, osseous tissue shows an increase in metabolism and bone destruction results. In the control of inflammatory reactions by the immune system, cytokines, among other proteins, play an important role: some may enhance inflammation by activating leukocytes (IL-1, TNF-alpha, IL-8) while others, such as IL-10, have anti-inflammatory effects.
During osteoarthritis, the articular compartment shows high metabolic processes that, in some patients, may increase and even persist some time after arthroplasty.