Immunolocalization of vacuolar‐type H⁺‐ATPase, cathepsin K, matrix metalloproteinase‐9, and receptor activator of NFkB ligand in odontoclasts during physiological root resorption of human deciduous teeth

Abstract

To investigate the cellular mechanisms of physiological root resorption in human deciduous teeth, the authors examined the immunocytochemical localization of vacuolar-type H ϩ -ATPase, a lysosomal cysteine proteinase, cathepsin K, matrix metalloproteinase-9 (MMP-9), and receptor activator of NFKB ligand (RANKL) in odontoclasts. H ϩ -ATPase, cathepsin K, and MMP-9 are the most important enzymes for decalcification of apatite crystals and degradation of type-I collagen. In addition, RANKL is one of the key regulatory molecules in osteoclast formation and functions. Odontoclasts developed extensive ruffled borders and clear zones apposed to the resorbing root dentine surfaces. On immunoelectron microscopy, the expression of vacuolar-type H ϩ -ATPase was detected along the limiting membranes of pale vacuoles and the ruffled border membranes of odontoclasts. Cathepsin K in odontoclasts was localized within pale vacuoles, lysosomes, the extracellular canals of ruffled borders, and the underlying resorbing dentine surfaces. MMP-9 localization in odontoclasts was similar to those of cathepsin K. RANKL was detected in both mononuclear stromal cells and odontoclasts located on resorbing dentine surfaces. These results suggest that (1) odontoclasts are directly involved in decalcification of apatite crystals by active extrusion of proton ions mediated by H ϩ -ATPase and (2) extracellular degradation of dentine type-I collagen by both cathepsin K and MMP-9, and (3) odontoclast differentiation and activity are regulated, at least in part, by RANKL, possibly produced by mononuclear stromal cells and odontoclasts themselves in the resorbing tissues. Thus, the cellular mechanisms of physiological root resorption appear to be quite similar to those of osteoclastic bone resorption.

Differentiation and functions of osteoclasts and odontoclasts in mineralized tissue resorption

“…In this regard, it was a very interesting finding that RANKL expression was detected in OdC and some of the adjacent stromal cells located on resorbing root dentine (Fig. 15d) (Oshiro et al, 2001). All these results suggest that there is a common regulatory mechanism of cellular resorption of mineralized tissues such as bone and teeth.…”

“…We further clarified the subcellular localization of H ϩ -ATPase and cathepsin K in human OdC during physiological root resorption (Fig. 15a,b) (Oshiro et al, 2001). Localization of cathepsin K and MMP-9 and their functions in osteoclastic degradation of bone type-I collagen have been well documented (Everts et al, 1992(Everts et al, , 1998Inui et al, 1997;Kamiya et al, 1998;Littlewood-Evans et al, 1997;Okada et al, 1995;Reponen et al, 1994;Wucherpfennig et al, 1994;Yazawa et al, 1998).…”

“…15b,c). It is, therefore, suggested that, as in osteoclastic bone resorption, OdC are directly involved in demineralization of apatite crystals in dental hard tissues by H ϩ -ATPase and the subsequent collagen degradation by cathepsin K and MMP-9 (Oshiro et al, 2001). As in OC, OdC in root resorption were inactivated and lacked ruffled border structure and expression of H ϩ -ATPase and cathepsin K by bisphosphonate (pamidronate) administration (Sato et al, 2000a,b).…”

“…OdC are responsible for resorption of such dental hard tissues as cementum, dentine, and enamel; but no difference has ever been recognized between OdC and OC in the structural and cytochemical properties (Matsuda, 1992;Sahara, 1998;Sahara et al, 1994Sahara et al, , 1996Sasaki et al, 1988aSasaki et al, ,b, 1990Sasaki and Ueno-Matsuda, 1992). Although it has been uncertain whether OdC involved in root resorption possess functional features identical to those of OC, Oshiro et al (2001) recently reported that the expression of enzyme proteins described above and RANKL was detected in human OdC during root resorption. Based on our recent ultrastructural and immunocytochemical studies, these aspects will be discussed in the following sections.…”

HIV-1 Nef Triggers Macrophage Fusion in a p61Hck- and Protease-Dependent Manner

“…We wondered whether lysosome enzymes such as proteases might contribute to macrophage fusion, because they have been implicated in the formation of multinucleated myotubes (60,61). Therefore, we used a protease inhibitor mix, mostly non-cellpermeant, containing pepstatin A (inhibitor of aspartic proteases including cathepsin D), leupeptin (a broad inhibitor of cysteine proteases and cathepsin B), aprotinin (inhibitor of serine proteases), E64C (inhibitor of cysteine proteases such as cathepsins B, L, H, and K), and GM6001 (a broad metalloproteases inhibitor) (62)(63)(64). As shown in Fig.…”