C2K77 ELISA detects cleavage of type II collagen by cathepsin K in equine articular cartilage

The ELISA C2K77 measured the activity of cathepsin K in equine cartilage which was unchanged in OA cartilage. Cytokines that upregulate MMP collagenase activity had no effect on endogenous cathepsin K activity, suggesting a different activation mechanism that requires further study.