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Updated: Jul 20, 2026
Standardized Histomorphometric Evaluation of Osteoarthritis in a Surgical Mouse Model
Published on: May 6, 2020
Pathogenesis of osteoarthritis-like changes in the joints of mice deficient in type IX collagen
Objective:
To examine the pathogenetic mechanisms of osteoarthritis (OA)-like changes in Col9a1-/- mice, which are deficient in type IX collagen.
Methods:
Knee joints and temporomandibular joints (TMJs) from Col9a1-/- mice and their wild-type (Col9a1+/+) littermates were examined by light microscopy. Immunohistochemical staining was performed to examine the expression of matrix metalloproteinase 3 (MMP-3) and MMP-13, degraded type II collagen, and the discoidin domain receptor 2 (DDR-2) in knee joints. Cartilage mechanics were also evaluated for compressive properties by microindentation testing of the tibial plateau and for tensile properties by osmotic loading of the femoral condyle.
Results:
Histologic analysis showed age-dependent OA-like changes in the knee and TMJs of Col9a1-/- mice starting at the age of 3 months. At the age of 6 months, enhanced proteoglycan degradation was observed in the articular cartilage of the knee and TMJs of the mutant mice. The expression of MMP-13 and DDR-2 protein and the amount of degraded type II collagen were higher in the knee joints of Col9a1-/- mice than in their wild-type littermates at the age of 6 months. Changes in cartilage mechanics were observed in the femoral and tibial plateaus of Col9a1-/- mice at 6 months, including a decrease in the compressive modulus and uniaxial modulus. At 3 and 6 months of age, tibial cartilage in Col9a1-/- mice was found to be more permeable to fluid flow, with an associated compromise in the fluid pressurization mechanism of load support. All of these changes occurred only at medial sites.
Conclusion:
Lack of type IX collagen in Col9a1-/- mice results in age-dependent OA-like changes in the knee joints and TMJs.
Insights
Mice lacking type IX collagen develop osteoarthritis-like changes in their knee and temporomandibular joints. These age-dependent changes involve cartilage degradation and altered mechanics, particularly at medial sites.
Area of Science:
- Biochemistry
- Orthopedics
- Genetics
Background:
- Osteoarthritis (OA) is a degenerative joint disease.
- Type IX collagen is a crucial component of articular cartilage.
Purpose of the Study:
- To investigate the role of type IX collagen in OA pathogenesis.
- To elucidate the mechanisms behind OA-like changes in Col9a1-/- mice.
Main Methods:
- Histological and immunohistochemical analysis of knee and temporomandibular joints (TMJs) in Col9a1-/- and wild-type mice.
- Assessment of matrix metalloproteinase (MMP) expression, collagen degradation, and discoidin domain receptor 2 (DDR-2) levels.
- Evaluation of cartilage mechanical properties, including compressive and tensile strength, and fluid flow.
Main Results:
- Col9a1-/- mice exhibited age-dependent OA-like changes in knee and TMJs from 3 months of age.
- Increased proteoglycan degradation, MMP-13 and DDR-2 expression, and type II collagen breakdown were observed in mutant mice.
- Compromised cartilage mechanics, including reduced modulus and increased permeability, were noted in Col9a1-/- mice, primarily at medial sites.
Conclusions:
- Deficiency in type IX collagen leads to age-dependent osteoarthritis-like changes in the knee and TMJs.
- These findings highlight the critical role of type IX collagen in maintaining joint integrity and function.
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