Expression of matrix metalloproteinases in normal and damaged articular cartilage from human knee and ankle joints.

The objectives of this study were the following: (a) describe the appearance of histopathologic changes observed in human articular cartilage from the knee and ankle joints of organ donors with no symptomatic joint disease; (b) compare by in situ hybridization mRNA expression of six matrix metalloproteinases (MMP) in these cartilages; (c) compare MMP mRNA expression with the histology of the cartilage; and (d) test whether the effect of interleukin-1beta (IL-1beta) on the MMP mRNA expression could be detected with in situ hybridization. Human articular cartilages from the knee (tibiofemoral) and ankle (talocrural) joints of 41 different donors (aged 18 to 84 years) were obtained through the Regional Organ Bank of Illinois. The microscopic appearance of the cartilages was graded on a histopathologic scale from 0 to 13 with the highest grade representing severely damaged cartilage. In situ hybridization was performed using oligonucleotide probes to three collagenases (MMP-1, MMP-8, MMP-13), gelatinase A (MMP-2), stromelysin (MMP-3), and matrix type-1 metalloproteinase (MMP-14). Cartilages from some donors were cultured with IL-1beta and then analyzed for MMP expression using in situ hybridization. The histopathology grades of the cartilages from the asymptomatic donors covered the entire scale even in the ankle. Based on their grades, the cartilages were described as either normal (grades 0 to 5) or damaged (grades 6 to 13). The cartilages contained message for all six MMP tested with no detectable differences in expression of MMP-1, -2, -13, and -14 between the normal and damaged cartilages. However the expression of MMP-3 and MMP-8 was elevated in the damaged cartilages. In normal knee cartilage, mRNA expression of MMP-3 and MMP-8 was low, whereas in normal ankle cartilage, MMP-8 expression was below the detection limit. MMP-3 and MMP-8 message was up-regulated in the damaged cartilage from both joints, or if the tissue was cultured in the presence of IL-1beta. From this study we conclude the following: (a) similar histopathologic changes occur in both knee and ankle cartilages; (b) MMP-1, -2, -13, and -14 are constitutively expressed in adult human cartilage; and (c) only up-regulation of mRNA expression of MMP-3 and MMP-8 could be detected with naturally occurring cartilage damage and IL-1beta induction.