Canine osteoarthritis: effects of endogenous neutral metalloproteoglycanases on articular cartilage proteoglycans
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Published on: March 18, 2022
J P Pelletier1, J Martel-Pelletier, C J Malemud
1Unité des Maladies Rhumatismales, Hôpital Notre-Dame, Montreal, QC, Canada.
Abstract:
The aim of this study was to analyze the mechanisms by which neutral metalloproteoglycanases (NMPE) degrade proteoglycans (PGs) in the cartilage of an experimental model of osteoarthritis (OA). We demonstrated that chondrocytes in osteoarthritic cartilage synthesize PGs with the same functional characteristics as those found in normal cartilage. Osteoarthritic cartilage contains NMPE in both active and latent forms. Both forms can degrade newly synthesized and endogenous PG macromolecules, as indicated by the reduced hydrodynamic size found in the two PG populations of osteoarthritic cartilage. PG monomers, derived from the included fraction of Sepharose CL2B chromatography, were unable to form aggregates with hyaluronic acid. Reduction and alkylation showed that PG monomers from osteoarthritic cartilage had a small hydrodynamic size, especially after activation with amino-phenylmercuric acetate. No significant differences were observed in the size of the chondroitin sulfate chain when normal cartilage was compared with its osteoarthritic equivalent. These results suggest that the proteolytic degradation of cartilage matrix PGs by NMPE occurs at both the hyaluronate-binding region and at the chondroitin sulfate-rich region of the core protein.
Insights
Neutral metalloproteoglycanases (NMPE) degrade proteoglycans (PGs) in osteoarthritis (OA) cartilage. NMPE targets both the hyaluronate-binding and chondroitin sulfate regions of the PG core protein, impacting cartilage matrix integrity.
Area of Science:
- Biochemistry
- Biomaterials Science
- Rheumatology
Background:
- Osteoarthritis (OA) is a degenerative joint disease characterized by cartilage breakdown.
- Proteoglycans (PGs) are crucial components of cartilage extracellular matrix, providing structural integrity and hydration.
- Neutral metalloproteoglycanases (NMPE) are implicated in cartilage degradation.
Purpose of the Study:
- To elucidate the mechanisms of proteoglycan (PG) degradation by neutral metalloproteoglycanases (NMPE) in experimental osteoarthritis (OA).
- To investigate the functional characteristics of PGs synthesized by chondrocytes in OA cartilage.
- To determine the specific sites of NMPE-mediated PG degradation within the cartilage matrix.
Main Methods:
- Analysis of PG synthesis and characteristics in osteoarthritic (OA) cartilage.
- Detection and characterization of active and latent NMPE in OA cartilage.
- Assessment of PG macromolecule degradation using hydrodynamic size analysis (Sepharose CL2B chromatography).
- Investigation of PG monomer aggregation with hyaluronic acid.
- Evaluation of PG core protein size after reduction, alkylation, and amino-phenylmercuric acetate activation.
- Comparison of chondroitin sulfate chain size between normal and OA cartilage.
Main Results:
- Chondrocytes in OA cartilage synthesize PGs with normal functional characteristics.
- Both active and latent forms of NMPE are present in OA cartilage.
- NMPE degrades both newly synthesized and endogenous PG macromolecules, evidenced by reduced hydrodynamic size.
- PG monomers from OA cartilage are unable to form aggregates with hyaluronic acid.
- PG monomers exhibit reduced hydrodynamic size, particularly after NMPE activation.
- No significant differences in chondroitin sulfate chain size were found between normal and OA cartilage.
Conclusions:
- NMPE actively degrades cartilage matrix PGs in an experimental OA model.
- The degradation occurs at both the hyaluronate-binding region and the chondroitin sulfate-rich region of the PG core protein.
- These findings highlight NMPE as a key enzyme in the pathogenesis of OA cartilage degradation.
