Calcified Tissue International

, Volume 56, Issue 6, pp 566–570

An ultrastructural evaluation of the effects of cysteine-proteinase inhibitors on osteoclastic resorptive functions


  • K. Debari
    • Department of Anatomy, School of Medicine and Central Laboratory for Electron MicroscopyShowa University
  • T. Sasaki
    • Department of Oral AnatomyShowa University
  • N. Udagawa
    • Department of Biochemistry, School of DentistryShowa University
  • B. R. Rifkin
    • Basic Sciences Division, College of DentistryNew York University
Laboratory Investigations

DOI: 10.1007/BF00298591

Cite this article as:
Debari, K., Sasaki, T., Udagawa, N. et al. Calcif Tissue Int (1995) 56: 566. doi:10.1007/BF00298591


This study was designed to evaluate the effects of specific and potent cathepsin inhibitors on osteoclastic resorptive functions in vitro by means of a novel ultrastructural assay system. Mouse bone marrow cell-derived osteoclasts were suspended on dentine slices and cultured for 48 hours in the presence of either E-64 (a generalized cysteine proteinase inhibitor) or Z-Phe-Phe-CHN2 (a selective cathepsin L inhibitor). After the removal of cultured osteoclasts, co-cultured dentine slices were examined using electron microscopy: backscattered (BSEM), scanning (SEM), and atomic force (AFM). In morphometric analyses of BSEM images, there were no significant differences in the areas of demineralized dentine surfaces between control and inhibitor-treated groups, suggesting that cathepsin inhibitors had no effect on dentine demineralization by cultured osteoclasts. However, in SEM and AFM observations, both inhibitors remarkably reduced to the same extent, the formation of deep resorption lacunae on dentine slices that had resulted from degradation of matrix collagen. In addition, Z-Phe-Phe-CHN2 treatment produced deeper, ring-like grooves with little collagen exposure in shallow resorption lacunae. These results strongly suggest that (1) cathepsins released by osteoclasts are involved in the formation of deep resorption lacunae, and (2) cathepsin L plays a key role in bone resorption.

Key words

Cathepsin inhibitorsOsteoclastsResorptionElectron microscopy

Copyright information

© Springer-Verlag New York Inc 1995