Vidar Isaksen's research while affiliated with University Hospital of North Norway and other places

Osteoarthritis (OA) is a common joint disorder found mostly in elderly people. The role of mechanical behavior in the progression of OA is complex and remains unclear. The stress-relaxation behavior of human articular cartilage in clinically defined osteoarthritic stages may have importance in diagnosis and prognosis of OA. In this study we investigated differences in the biomechanical responses among human cartilage of ICRS grades I, II and III using polymer dynamics theory. We collected 24 explants of human articular cartilage (eight each of ICRS grade I, II and III) and acquired stress-relaxation data applying a continuous load on the articular surface of each cartilage explant for 1180 s. We observed a significant decrease in Young’s modulus, stress-relaxation time, and stretching exponent in advanced stages of OA (ICRS grade III). The stretch exponential model speculated that significant loss in hyaluronic acid polymer might be the reason for the loss of proteoglycan in advanced OA. This work encourages further biomechanical modelling of osteoarthritic cartilage utilizing these data as input parameters to enhance the fidelity of computational models aimed at revealing how mechanical behaviors play a role in pathogenesis of OA.

Osteoarthritis (OA) is a common joint disorder found mostly in elderly people. The role of mechanical behavior in the progression of OA is complex and remains unclear. The stress-relaxation behavior of human articular cartilage in clinically defined osteoarthritic stages may have importance in diagnosis and prognosis of OA. In this study we investigated differences in the biomechanical responses among human cartilage of ICRS grades I, II and III using polymer dynamics theory. We collected 24 explants of human articular cartilage (eight each of ICRS grade I, II and III) and acquired stress-relaxation data applying a continuous load on the articular surface of each cartilage explant for 1180 s. We observed a significant decrease in Young’s modulus, stress-relaxation time, and stretching exponent in advanced stages of OA (ICRS grade III). The stretch exponential model indicated that significant loss in hyaluronic acid polymer might be the reason for the loss of proteoglycan in advanced OA. This work encourages further biomechanical modelling of osteoarthritic cartilage utilizing these data as input parameters to enhance the fidelity of computational models aimed at revealing how mechanical behaviors play a role in pathogenesis of OA.

Biomolecular changes in the cartilage matrix during the early stage of osteoarthritis may be detected by Raman spectroscopy. The objective of this investigation was to determine vibrational spectral differences among different grades (grades I, II, and III) of osteoarthritis in human osteoarthritic cartilage, which was classified according to the International Cartilage Repair Society (ICRS) grading system. Degenerative articular cartilage samples were collected during total joint replacement surgery and were classified according to the ICRS grading system for osteoarthritis. Twelve cartilage sections (4 sections of each ICRS grades I, II, and III) were selected for Raman spectroscopic analysis. Safranin-O/Fast green was used for histological staining and assignment of the Osteoarthritis Research Society International (OARSI) grade. Multivariate principal component analysis (PCA) was used for data analysis. Spectral analysis indicates that the content of disordered coil collagen increases significantly during the early progression of osteoarthritis. However, the increase was not statistically significant during later stages of the disease. A decrease in the content of proteoglycan was observed only during advanced stages of osteoarthritis. Our investigation shows that Raman spectroscopy can classify the different stage of osteoarthritic cartilage and can provide details on biochemical changes. This proof-of-concept study encourages further investigation of fresh cartilage on a larger population using fiber-based miniaturized Raman probe for the development of in vivo Raman arthroscopy as a potential diagnostic tool for osteoarthritis.