慢性関節リウマチ（ＲＡ）関節破壊に関与する酸性プロテアーゼ（ｃａｔｈｅｐｓｉｎ Ｄ）の活性化機構に関する免疫組織化学的解析

Abstract

Objectives : In order to get an activating mechanism of cathepsin D, we immunohistochemically examined the production and transportation of H+ which activates an acid protease in pericellular region.Materials and methods : Synovial tissues used in this study were obtained at total knee replacement. They were fixed in 4% paraformaldehyde for 2-3 hours, embedded in paraffin. 3μm thickened sections were examined by immunohistochemical method. Antibodies used in this study were anti-cathepsin D (Cat-D), carbonic anhydraseII (CAII), vacuolar type ATPase (V-ATPase) and CD68 (macrophage) antibodies. Serial sections were prepared for Cat-D, CAII and V-ATPase for elucidating Cat-D activation mechanism by H+ which is produced by CAII and is transported by V-ATPase. Furthermore, for identify the Cat-D positive cells in synovial tissues in which there are many kinds of cells, we used Immunohistochemical method.Results : Osteoclasts and monocytes in granulation tissues around bony destruction (pannus), and chondrocytes neighboring to inflammatory region, and macrophages in synovial tissues intensively expressed Cat-D. The osteoclasts and chondrocytes intensively demonstrated CAII and V-ATPase, which indicated the Cat-D activation in pericellular region, however macrophages in synovial tissues did not always expressed CAII and V-ATPase intensively. Furthermore, immunoelectron microscopic study revealed that the macrophages with Cat-D had plenty of phagocytotic vacuoles, and these vacuoles fused with lysosomes containing Cat-D. These findings suggested that the Cat-D in macrophage of synovial tissues was utilized for digestive function of phagocytotic substance rather than deteriorating extracellular matrix.Conclusion : It was histochemically revealed that cathepsin D in osteoclasts and chondrocyte participates in deteriorating the matrix, while in synovial tissue, this enzyme may play a role in digestion of intracytoplasmic substances.