Microscopic Change in Macroscopically Normal Equine Cartilage from Osteoarthritic Joints

Abstract

The objective of this study was to assess whether macroscopically normal articular cartilage taken from joints containing focal osteoarthritic lesions is histologically similar to articular cartilage taken from macroscopically normal joints. Metacarpophalangeal, proximal interphalangeal, and distal interphalangeal joints were obtained from 10 horses following euthanasia. Gross articular cartilage damage was scored and the cartilage assigned to one of two groups: (1) macroscopically normal cartilage from normal joints (control) and (2) macroscopically normal cartilage from diseased joints in which there were focal osteoarthritic lesions. Chondrocytes expressing specific cytokines and cytokine receptors were identified by immunohistochemistry. The total number of chondrocytes, and percentage of chondrocytes positive for these cytokines and receptors, was recorded in the superficial, middle, and deep cartilage zones. There was a significant increase in the expression of interleukin-1beta in the superficial and middle zones and interleukin-18 receptor in the superficial zone in Group 2 compared with Group 1 control samples. A significant positive correlation also was found between the grade of osteoarthritis and the percentage of chondrocytes positive for interleukin-1beta in the superficial and middle zones, and for interleukin-18 and interleukin-18R in the superficial zone. There was a significant increase in histology score for glycosaminoglycan loss in Group 2 compared with that in Group 1. In joints with focal osteoarthritis lesions, all the articular cartilage, even if macroscopically apparently normal, may have microscopic changes associated with osteoarthritis.

Interleukin‐1β–Induced Extracellular Matrix Degradation and Glycosaminoglycan Release Is Inhibited by Curcumin in an Explant Model of Cartilage Inflammation

“…Cartilage sections from OA patients positively stain for inflammatory mediators, such as the cytokines, IL‐1β, and TNF‐α, unlike sections from healthy cartilage 5 . This is supported by work from the equine field, which has demonstrated a positive correlation between grade of OA and percentage of chondrocytes positively staining for IL‐1β in cartilage from equine joints 6 . In addition, cells cultured from synovial tissue of human patients with OA produce IL‐1β and TNF‐α, most significantly in the early stages of OA 7 .…”

“…5 This is supported by work from the equine field, which has demonstrated a positive correlation between grade of OA and percentage of chondrocytes positively staining for IL-1β in cartilage from equine joints. 6 In addition, cells cultured from synovial tissue of human patients with OA produce IL-1β and TNF-α, most significantly in the early stages of OA. 7 These studies all contribute to the evidence for cytokine involvement in OA.…”

T2 mapping of cartilage in the equine distal interphalangeal joint with corresponding histology using 0.27 T and 3.0 T magnetic resonance imaging

“…See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License OARSI grade 0, despite sampling from macroscopically normal articular cartilage. The sample population has, however, confirmed the difficulty with ascertaining a normal control group in clinical research and that macroscopically normal articular cartilage is often not histologically normal, which has been described for other equine joints 33 . There were no samples with an OARSI grade higher than 3 however, the mean T2 relaxation time would have been extremely difficult to measure in OARSI grades 4 and 5 due to little or no cartilage presence.…”

Chondrocyte death by apoptosis is associated with the initiation and severity of articular cartilage degradation

“…This suggests that even though cartilage from osteoarthritic joints may appear macroscopically normal, it may have microscopic changes associated with ECM destruction. Accordingly, a recent study 17 demonstrated that macroscopically normal cartilage from joints with focal AC damage was structurally altered and showed increased expression of various cytokines and receptors (which may be expected as OA develops) when compared to normal cartilage from entirely macroscopically normal joints.…”