Objectives—To determine concentrations of matrix
metalloproteinase (MMP)-2 and -9 in synovial fluid;
and mRNA expression of MMP-1, -13, and -3; interleukin[
IL]-1α and β; and tumor necrosis factor(TNF)-α
in synovial membrane and articular cartilage from
horses with naturally occurring joint disease.
Sample Population—Synovial fluid (n = 76), synovial
membrane (59), and articular cartilage (45) from 5 clinically
normal horses and 55 horses with joint disease
categorized as traumatic (acute [AT] or chronic [CT]),
osteochondritis dissecans (OCD), or septic (S).
Procedure—Synovial fluid gelatinase concentrations
were analyzed, using zymography. Synovial membrane
and articular cartilage mRNA expression for
MMP-1, -3, and -13, IL-1α and β, TNF-α, type-II collagen,
and aggrecan were analyzed, using quantitative
reverse transcriptase-polymerase chain reaction.
Results—Synovial fluid pro-MMP-2 concentration
was significantly higher in diseased joints than normal
joints. Septic joints had significantly higher concentrations
of pro and active MMP-9. Stromelysin-1 was
expressed in ≥ 80% of synovial membrane and articular
cartilage samples and was strongly influenced by
age. Collagenases were rarely expressed, with MMP-
13 expressed only in diseased joints. Interleukin-1β
expression was significantly higher in all OCD samples
and was influenced by age. Tumor necrosis factor-
α expression was significantly higher in cartilage
from joints with AT and OCD. There was no correlation
between MMP or cytokines and type-II collagen
or aggrecan expression.
Conclusions and Clinical Relevance—Matrix metalloproteinase-
2 and -3 are abundant in naturally occurring
joint disease and normal joints. Interleukin-1β and
TNF-α may be important in the pathogenesis of OCD.
Age affects MMP and IL-1β concentrations. (Am J Vet