To determine the in vivo effects of intraarticular MMP-13.
Human recombinant MMP-13 was injected intraarticularly (i.a. ) into the hamster knee joint. MMP-13 activity, collagen and proteoglycan fragments, and hyaluronan were measured in synovial fluid. Antibody 9A4 was used to localize collagen damage. Western blotting was used to determine the size of type II collagen fragments.
MMP-13 activity measurements showed greater than 98% of MMP-13 to be cleared instantly from the joint cavity. The remainder was cleared with a t(1/2)of 2 h. Immunohistochemical staining demonstrated collagen cleavage was limited to a thin superficial band on the surface of the articular cartilage whereas collagen damage extended more deeply into the synovial capsule and the menisci. The elevation of proteoglycan and hyaluronan in synovial fluid after MMP-13 was modest. Collagen fragments appeared in synovial fluid within 15 min following MMP-13. They were cleared with a half-life of circa 1.8 h and the predominant fragment was 32 kDa.
Activated MMP-13 leads to tissue collagen damage with the release of collagen fragments. These fragments are measurable and could provide a method for assessment of cartilage collagen damage.