Correlation of histomorphometry and inflammatory factor expression in hip osteoarthritis

Objective To investigate the expression of several cytokines,matrix metalloproteinas-es (MMPs) in osteoarthritis (OA) and control joint tissues,and explore the possible pathological mecha- nism of inflammation from subchondral bone to test the hypothesis that the severity of hip OA is related to local levels of inflammatory metabolites and their corresponding enzymes. Methods The cartilage,synovi-al and subobondral bone tissues were collected from patients undergoing operations for OA and femoral head trauma,and the latter worked as control subjects. HE stain was adopted for subchondral bone histo- morphometric analysis with 4 parameters including bone volume fraction, trabecular thinness, trabecular number, and trabecular separation. The inflammatory mediators in cartilage,synovial and subchondral bone tissues, such as tumor necrosis factor (TNF)-α and interleukin (IL)-1β were measured by radioimmuno- assay,and MMP-9 by ELISA. Correlation of bone tissue histomorphometry and inflammatory factor expres-sion in hip OA was analyzed. Results Increased subchondral bone formation and subc.hondral bone scle-rosis were observed in OA group. For bone tissue histomorphometry, there was significant difference in bone volume fraction,trabecular number and trabecular separation except trabeeular thinness. OA cartilage and synovium tissue revealed significantly higher level of M M P-9 expression, while IL-1β expression was signif- icantly higher in OA cartilage, lnteresiingly,MMP-9,TNP-α and IL-1β were all up-regnlated in OA sub-chondral bone,and had good correlation with joint tissue histomorphometric changes. Conclusion Inflam-matory factors were up-regulated in OA joint tissues especially in the subchondral bone,and had good cor-relation with tissue histomorphometric changes. It also supports the hypothesis that vascularized subchon-dral region may increase the synthesis of cytokines and M MPs,leading to degradation of adjacent cartilage. Key words: Osteoarthritis;  Cytokines ;  Metalloproteinases;  Hip joint;  Histology