Monosodium iodoacetate-induced subchondral bone microstructure and inflammatory changes in an animal model of osteoarthritis

Abstract

The monosodium iodoacetate (MIA)-induced osteoarthritis (OA) may lead to cartilage degeneration and histopathological lesions. However, the correlation between inflammatory reaction and subchondral bone remodeling in a rodent osteoarthritic model is ambiguous. In this study, intra-articular injection of MIA was performed in 36 four-week-old specific pathogen-free male Wistar rats to induce OA. After 4 weeks of intervention, changes in intrinsic structural properties of the subchondral bones were measured, and the histological evaluation, as well as biochemical analysis, was conducted. We found that intra-articular injection of MIA increased chondrocyte apoptosis and promoted cartilage matrix degradation, such as cartilage surface defects and shallow or disappearing staining. MIA also induced inflammation, improved the expression of IL-1β, TNF-α, and matrix metalloproteinase, and decreased the expression of cartilage-specific proteins with the extension of modeling time. Meanwhile, the MIA also significantly accelerated the subchondral bone remodeling, as shown by the decreased subchondral bone density, thinning of trabeculae, disordered cartilage structure, and morphology. In conclusion, we have shown that MIA-induced rodent osteoarthritic model would cause decreased subchondral bone density, sparse trabecular bone, and other manifestations of osteoporosis accompanied by an inflammatory response, which would worsen with the progression of modeling time. Our results suggest that different phases of MIA-induced OA are associated with the changes in subchondral bone microstructure and the progression of local inflammation.

Keywords: animal model; bone microarchitecture; iodoacetic acid; osteoarthritis.

Figure 1

Representative micrographs of rat tibial joints receiving different treatments. Red arrow: a rough surface with fibrous degeneration; black arrow: absence of staining in cartilage surface; black triangle: increased trabecular space; red triangle: hypertrophy and vacuolated chondrocytes Abbreviation: SBP: subchondral bone plate; AC, articular cartilage. Sham group: animals received sterile saline 0.9% for 4 weeks; OA-2W group: animals received MIA for 2 weeks; OA-4W group: animals received MIA for 4 weeks. Scale bar, 100 μm.

Figure 2

OOCHAS scores in the three groups. n = 12 per group. **P < 0.01 compared to the sham group and **** P < 0.0001 compared to the sham group. Sham: animals received sterile saline 0.9% for 4 weeks; OA-2W: animals received MIA for 2 weeks; OA-4W: animals received MIA for 4 weeks.

Figure 3

(a) Representative micro-CT three-dimensional images of rat tibial bone in three groups. (b) Representative micro-CT two-dimensional sectional view of the knee. (c) Representative micro-CT three-dimensional sectional view of the knee. Red arrow: The MIA groups exhibited a rough surface on the cartilage and an extensive area of cartilage defects. Black arrow: There was significant cartilage loss and trabeculae missing together with widening of Tb.Sp in the MIA-injected group. Sham: animals received sterile saline 0.9% for 4 weeks; OA-2W: animals received MIA for 2 weeks; OA-4W: animals received MIA for 4 weeks.

Figure 4

Quantitative micro-CT analysis of various parameters of tibial subchondral bone. BMD, BV/TV, Tb. Th, Tb. SP, and Conn. D. n = 9 per group. *P < 0.05 compared to the sham group, **P < 0.01 compared to the sham group, and **** P < 0.0001 compared to the sham group, ns stands for no statistical significance compared to the sham group. Sham: animals received sterile saline 0.9% for 4 weeks; OA-2W: animals received MIA for 2 weeks; OA-4W: animals received MIA for 4 weeks.

Figure 5

Relative mRNA expression of genes: (a) IL1-β, (b) TNF-α, (c) MMP-13, and (d) collagen II in distal femur containing cartilage and subchondral region. All values are expressed as Mean ± SD. (n = 9/group). **P < 0.01, ***P < 0.001, and ****P < 0.0001 compared to the sham group. IL-1β, TNF-α, Matrix metalloproteinase 13(MMP-13). Sham: animals received sterile saline 0.9% for 4 weeks; OA-2W: animals received MIA for 2 weeks; OA-4W: animals received MIA for 4 weeks.

Figure 6

Effect of MIA treatment on cartilage inflammatory and degradative proteins. Western blot analysis of (a) MMP-13, (b) TNF-α in the distal femur containing cartilage and subchondral region is represented after treatment in rat articular. All values are expressed as Mean ± SD. (n = 6/group). **P < 0.01, ****P < 0.0001 compared to the sham group. TNF-α, MMP-13. Sham: animals received sterile saline 0.9% for 4 weeks; OA-2W: animals received MIA for 2 weeks; OA-4W: animals received MIA for 4 weeks.

Figure A1

Effects of MIA treatment on the expression of IL-1β in the tibial plateau. Vision: 400× magnification. IL-1β of the tibial plateau was sparsely expressed in the sham group. The expression of IL-1β was improved by MIA treatment with the prolonging of modeling time. Sham: animals received sterile saline 0.9% for 4 weeks; OA-2W: animals received MIA for 2 weeks; OA-4W: animals received MIA for 4 weeks.