Session Title: Rheumatoid Arthritis: Animal Models
Session Type: Abstract Submissions (ACR)
Background/Purpose: Rheumatoid arthritis (RA) is an autoimmune disease characterized by joint inflammation and connective tissue destruction. On the other hand, osteoarthritis (OA) is regarded as a joint disease with cartilage destruction, but the role of inflammation in OA is still debatable. During joint inflammation and destruction, a variety of proteases are upregulated, including different cathepsins and matrix-metalloproteinases (MMPs). MMPs are a large group of enzymes known to degrade the extracellular matrix during both RA and OA, causing cartilage proteoglycan depletion and breakdown of the collagen network, leading to erosion. Cathepsins are lysosomal proteases which are abundantly found in the synovial fluid and the lining tissue of arthritic joints. In this study we investigated cathepsin and MMP activity in the process of cartilage destruction, in both a RA and an OA model.
Methods: Collagen-induced arthritis (CIA) was induced in DBA1/J mice, mimicking a RA model. Destabilization of the medial meniscus (DMM) was induced in C57Bl6/N mice causing instability of the joint and subsequently osteoarthritic features. For the CIA model at day 30 and for the DMM model at day 56, fluorescent imaging was performed using Sense 680 probes (PerkinElmer, Massachusetts, USA) and enzyme activity was detected using the IVIS Lumina (Caliper Life Sciences). The ProSense 680 probe becomes activated upon enzymatic cleavage by cathepsins, whereas the MMPSense 680 can be activated by different MMPs. After imaging, mice were sacrificed and knee and ankle joints were dissected and processed for histology. Sections were also immunostained for VDIPEN, a neoepitope of aggrecan cleaved by MMPs.
Results: The ProSense as well as the MMPSense showed a 3 times higher fluorescent signal intensity during CIA, indicating both cathepsin and MMP activity in this model. Interestingly, on the other hand, only MMP activity (1,5 times higher), but no cathepsins activity, could be measured in the DMM model. On histological level, although different in severity, the CIA model and the DMM model both showed features of cartilage damage. In the CIA model, more VDIPEN staining was seen with increasing severity of the disease; on the other hand, in the DMM model no VDIPEN staining was seen above baseline levels.
Conclusion: In the CIA model, inflammation and destruction are correlated, while the DMM model showed MMP activity without inflammation. Mort et al. (1998) showed that cathepsin-B can also cleave aggrecan, and can thereby form the VDIPEN neoepitope. Because no cathepsin activity could be measured in the DMM model, this can explain the absence of the VDIPEN neoepitope. This argues for a role of cathepsins in cartilage destruction but their role in CIA remains to be determined. Combining the imaging of local enzyme activity using activatable fluorescent probes together with cartilage neoepitope immunolocalization may unravel the processes involved in joint destruction.
E. A. Vermeij,
M. I. Koenders,
O. J. Arntz,
M. B. Bennink,
A. B. Blom,
P. L. E. M. van Lent,
W. B. van den Berg,
F. A. J. van de Loo,
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/high-local-cathepsin-activity-in-a-murine-rheumatoid-arthritis-model-but-not-in-an-osteoarthritis-model-explains-the-difference-in-cartilage-vdipen-neoepitope-formation/