Microscopic change in macroscopically normal equine cartilage from osteoarthritic joints.

This research investigates if visually normal cartilage in horse joints with osteoarthritic damage is histologically the same as cartilage from visually healthy joints. Findings reveal microscopic changes in the ‘normal’ cartilage from joint areas affected with osteoarthritis.

Research Background

• The aim of the study was to determine if cartilage that appears normal to the naked eye, but is situated in a joint with localized osteoarthritic lesions, is histologically similar to cartilage from joints without evidence of disease.
• This was tested by isolating joints from horses that had been euthanized, and scoring the degree of visible cartilage damage.

Methods

• Joints were extracted from 10 horses that had been euthanized.
• The researchers categorized the cartilage into two groups: visually normal cartilage from healthy joints (Group 1), and visually normal cartilage from joints with focal osteoarthritic lesions (Group 2).
• They used immunohistochemistry, a technique that uses antibodies to detect specific proteins in cells, to identify chondrocytes (cartilage cells) that were expressing specific cytokines (protein molecules used in cell signaling) and receptors. This would help establish any microscopic difference between the two groups.

Findings

• There was a significant increase in the expression of a particular protein (interleukin-1beta) in Group 2, specifically in the superficial and middle layers of the cartilage when compared to Group 1.
• Another protein (interleukin-18 receptor) also showed a significant increase in its expression in the superficial layer of Group 2 cartilage.
• Moreover, a positive correlation was found between the severity of osteoarthritis and the percentage of chondrocytes expressing these proteins in these specific layers of the cartilage.
• There was a significant increase in histology score for glycosaminoglycan (a type of molecule found in cartilage) loss in Group 2 compared to that in Group 1, indicating a degradation of the cartilage in joints with osteoarthritic lesions.

Conclusion

• The study concluded that in joints harboring osteoarthritic lesions, visually normal areas of cartilage also had microscopic changes consistent with the biochemical markers of osteoarthritis. This discovery could have significant implications for the early detection of osteoarthritis.