Proteolytic enzymes in otosclerosis. Significance of proteolytic enzymes in otosclerotic bone remodelling.

The otosclerotic stapes footplate exhibits higher activities of cathepsin D and H and collagenase-like peptidase than those of normal cortical bone. The elevated enzyme activities of osteoblastic origin (Cl-peptidase and cathepsin D) emphasize the essential and probably primary role of the bone-forming cells, not only in bone formation, but in resorption as well. The highest activity of cathepsin D from among the measured enzymes highlights the adjuvant role of acidic glucosaminoglycans in the otosclerotic demineralization process. As the osteoblastic osteoid synthesis is known to be sharply reduced in otosclerotic bone remodelling, and the above data emphasize the role of proteolytic enzymes of osteoblastic origin too, indirectly, osteoblasts seem to be the otosclerosis signal-transducing cells.