Taking the bait: exploiting new tools to capture, identify, and visualize active proteinases in osteoarthritic cartilage destruction

Osteoarthritis (OA) is a disease that affects approximately 10 million people in the UK (VersusArthritis, 2022). Public knowledge of this disease is generally accurate - with a firm understanding of osteoarthritis as the breakdown of the cartilage surrounding the affected joints in the body. However, the idea of osteoarthritis as stemming from joint overuse or as an inherent part of the general aging process is flawed. Past research has shown that cartilage breakdown in OA is driven by matrix metalloproteinases (MMPs). Subsequent research reveals a profound role for serine proteinases in the cellular processes leading to the destruction of cartilage in the joint (Wilkinson et al, 2019) and, more importantly, a synergistic relationship between serine proteinases and MMPs in the deterioration of cartilage (Wilkinson et al., 2017a; Wilkinson et al., 2017b; Wilkinson et al., 2021; Falconer et al., 2019). With these advances in research, the next logical step is to characterize the activity of proteinases within different areas of the joint as well as monitor the activity of proteinases throughout the various stages of OA. Therefore, the aim of this project is to design and utilize activity-based probes (ABPs) to form a coherent picture of serine proteinase activity within the osteoarthritic joint. These probes are the final product of a chemical process that results in an attractive target for active proteinases to bind to via a "warhead" (or bait). In addition, the contents of these probes, such as a biotin tag or fluorophore, can allow for the binding and characterization of proteinases through mass spectrometry or the characterization of proteinase activity via fluorescent imaging, respectively. There will be three distinct stages to the project wherein proteinase activity will be monitored via the use of ABPs: firstly, in cultured cellular populations, secondly, in synovial fluid, and finally, in OA mouse models. We are enthusiastic about the effectiveness of these investigatory procedures to advance the scientific understanding of osteoarthritis progression in the human body as well as the role of serine proteinases and matrix metalloproteinases in the breakdown of human cartilage.