Localization of heat shock protein in osteoarthritic cartilage

In osteoarthritic (OA) chondrocytes, expression of 70 kD heat shock protein (HSP70) is enhanced under stress. The HSP70 level is also related to OA severity in humans. In the present study, specimens of OA cartilage were obtained from 14 surgically treated female patients. Their disease severity was evaluated according to Mankin's histological/histochemical grading scores. The ratio of HSP70-positive cells was examined by using immunohistochemistry. As OA became more severe, the ratio of HSP70-positive cells increased in deeper areas from the surface, and there was a positive correlation between the grade and the ratio. Distribution of cells expressing HSP70 mRNA detected by in situ hybridization was similar to the distribution of positive cells in the immunohistochemistry. It was presumed that HSP70 plays a role in cell protection from stress, and that mechanical and biological factors which are related to the enhancement of HSP70 expression, have a considerable influence on OA progressions.