OSTEOARTHRITIS - DIFFERENTIAL EXPRESSION OF MATRIX METALLOPROTEINASE-9 MESSENGER-RNA IN NONFIBRILLATED AND FIBRILLATED CARTILAGE

Expression of matrix metalloproteinase-9 mRNA in osteoarthritic and no rmal cartilage was analyzed using reverse transcription-polymerase cha in reaction and in situ hybridization. Fifty-four osteoarthritic carti lage samples were obtained from 24 patients undergoing total knee arth roplasty. Sixteen normal cartilage samples were obtained from non-oste oarthritic knees of four autopsy cases. With normal cartilage, reverse transcription-polymerase chain reaction analysis for matrix metallopr oteinase-9 mRNA showed that chondrocytes exhibited only a trace signal . In analysis of osteoarthritic cartilage, chondrocytes of moderately and severely fibrillated cartilage exhibited a 73-fold and 110-fold in crease in matrix metalloproteinase-9 mRNA signal, respectively, relati ve to normal cartilage. Chondrocytes of nonfibrillated osteoarthritic cartilage exhibited a 6-fold increase (p < 0.02) in matrix metalloprot einase-9 mRNA signal relative to normal cartilage. Analysis of matrix metalloproteinase-9 mRNA expression in fresh-frozen sections of normal and osteoarthritic cartilage by in situ hybridization confirmed these results. This study showed that reverse transcription-polymerase chai n reaction provides a sensitive index of mRNA levels in normal and ost eoarthritic cartilage samples and suggests that increased expression o f matrix metalloproteinase-9 precedes fibrillation of cartilage in the development of osteoarthritis.