Degenerative knee osteoarthritis animal model and changes in intraosseous pressure during pathological processes

Background Degenerative knee osteoarthritis (KOA) is a common clinical disease which affecting patients' quality of life. However, there is currently no standard animal model for KOA research. The purpose of this study was to find a reasonable age range of animal model for the studying of KOA pathological process, and to investigate Intraosseous pressure (IOP) in the process during different degeneration stages of KOA. Methods Male Dunkin-Hartley guinea pigs were selected and divided into groups of 3, 6, 9, 12, 18 months old by age, 10 in each group. All knees underwent imaging examination including X-ray, Micro CT and MRI. Observed the imaging findings with the use of Kellgren-Lawrence (K-L) classification and knee osteoarthritis MRI scores. Measured the IOP of distal femur and proximal tibia in each group, and observed the differences of bilateral tibiofemoral articular cartilage in histological and immunohistochemistry, staining results were evaluated by using Mankin’s score. Using one-way ANOVA and T-test were used to compare the differences indicators between groups. Results With the increase of age, changes in X-ray, Micro-CT and MRI imaging findings and pathological staining results of articular cartilage in all stages were consistent with the changing of degenerative KOA process. The IOP of distal femur and proximal tibia increased gradually with age, and reached its peak in 12-month age group, and then gradually decreased, there was a statistically significant difference of IOP between each group (femur side: F=8.261, P=0.000; tibial side: F=8.469, P=0.000). The IOP of the distal femur was slightly higher than that of proximal tibia, but the difference was not statistically significant (P>0.05). Conclusions Dunkin-Hartley guinea pig can be used as an animal model to study different pathological stages of KOA. And there might be a correlation between the changes of IOP and the pathological progress of articular cartilage and subchondral bone in distal femur and proximal tibia.