Long-term histopathological developments in knee-joint components in a rat model of osteoarthritis induced by monosodium iodoacetate

Abstract

[Purpose] This study was performed to evaluate the long-term histopathological changes in knee-joint components including synovial membrane and joint capsule in a rat model of osteoarthritis (OA) induced by monosodium iodoacetate (MIA). [Subjects and Methods] Fifty male rats were used. OA was induced through intra-articular injection of MIA, and ten rats were randomly allocated to each of five groups induced with OA for 1, 2, 4, 6, or 8 weeks. At the end of each period, the knee components were examined histopathologically. [Results] After 1 and 2 weeks, chondrocytes were weakly stained. After 4 weeks, fibrillation, fissuring, and eburnation were observed, whereas after 6 weeks, chondrocyte clustering and osteophyte formation were detected. In the synovial membrane, the proliferation of spindle-shaped cells and a multilayered structure of the surface cells were observed at 1 and 2 weeks, but the degree of these changes decreased over time. In the joint capsule, a narrowing of the space between collagen fiber bundles was observed at 4-8 weeks. [Conclusion] The long-term histopathological changes of the joint components observed in a rat model of OA induced by MIA were similar to those detected in OA, but differed at specific times and tissues.

Keywords: Histopathology; Monosodium iodoacetate; Osteoarthritis.

Fig. 1.

Histopathological analysis of normal joint components Articular cartilage stained with hematoxylin and eosin (H&E) (A) and toluidine blue (B). H&E staining of synovial membrane (C) and joint capsule (D). Scale bar=500 µm (A, B) and 50 µm (C, D)

Fig. 2.

Histopathological (H&E) staining of coronal sections of the medial femorotibial joint Scale bar=500 µm

Fig. 3.

Histopathological (toluidine blue) staining of coronal sections of the medial femorotibial joint. Scale bar=500 µm

Fig. 4.

Representative histopathological features of the articular cartilage The panels show weak staining of chondrocytes (A; black arrows), fibrillation and fissuring (B), eburnation (C), vascularization into the articular cartilage (D; white arrows), and osteophyte formation (E). Scale bar=50 µm (A), 200 µm (B, C, D), and 500 µm (E)

Fig. 5.

Histopathological (H&E) staining of the synovial membrane From 1 to 4 weeks, proliferation of spindle-shaped cells in the surface layer and a multilayered structure of the surface cells were observed (black arrows). Moreover, possible mild infiltration of inflammatory cells was detected (white arrows). Scale bar=50 µm

Fig. 6.

Histopathological (H&E) staining of the joint capsule A narrowing of the space between collagen fiber bundles was observed at 4 weeks. At 6 and 8 weeks, the degree of this narrowing of the space in the joint capsule had increased (black arrows). Scale bar=50 µm