The activity of cathepsin D and alpha-1 antitrypsin in hip and knee osteoarthritis

The progress of cartilage decay during joint degeneration is not well monitored with biochemical methods. The role of cathepsin D (CAT-D) in articular cartilage deterioration remains unclear. The aim of this study is to assess the activity of CAT-D and alpha-1 antitrypsin (AAT) in blood in patients with hip or knee osteoarthritis. The activity of CAT-D and AAT in blood serum of 40 women and 21 men with hip or knee osteoarthritis was determined before total joint replacement, on the tenth day after surgery, and once in 54 healthy patients. The preoperative activity of CAT-D in patients with osteoarthritis was lower by 53.6% (11.00 ± 4.54 10-2 nM released tyrosine/mg protein/min, P < 0.001) and after surgery by 55.0% (10.67 ± 4.64 10-2 nM released tyrosine/mg protein/min, P < 0.001) when compared to its activity in healthy patients. There was no significant statistical difference between CAT-D activity before the surgery and its activity on the tenth day after it in the analyzed group (P< 0.496). Simultaneously, the preoperative activity of AAT in the OA (osteoarthritis) patients was by 25.5% (0.93 ± 0.32 mg inhibited trypsin/ml blood serum, P < 0.001) and postoperative was by 44.9% higher (1.26 ± 0.36 mg inhibited trypsin/ml blood serum, P < 0.001) than in healthy patients. The low CAT-D activity in osteoarthritis of big joints is associated with a decrease of cartilage cells during the degenerative process. The higher activity of acute phase protein AAT in OA patients' blood serum confirms the inflammatory component in the osteoarthritis process.