Endocytosis in Odontoclasts and Osteoclasts Using Microperoxidase as a Tracer

Abstract

Microperoxidase (MP, a peptide tracer) was intravenously injected into rats after six days of tooth movement by the Waldo method. Bone resorption was seen along the distal bone surface of the inter-radicular septum of the upper first molar, and tooth root resorption occurred along the mesial and distal surfaces of the distal root of the same molar. Odontoclasts were smaller in size and numbers than osteoclasts, but had the same organelles [multiple nuclei, ruffled borders (RB), clear zones, vacuoles, mitochondria, and specific granules] as osteoclasts. MP was deposited on the resorbed area through the clear zone and was transported into the vacuoles along the channels of the RB. The uptake of MP by odontoclasts was small, compared with that by osteoclasts. Collagen fibrils were found in the channels of the RB but were not detected in the vacuoles. Instead, filament-like structures were seen in the vacuoles and were located very near the collagen fibrils in the channels. Fibroblasts outside the resorbed lacunae had endocytosed collagen. In contrast, some cells close to odontoclasts (osteoclasts) in the dentin (bone)-resorbed lacunae had not endocytosed any collagen fibrils. These findings suggest (1) that odontoclasts resorb the dentin or cementum just as osteoclasts do in bone resorption, (2) that the resorbed area connects with the extracellular spaces of the odontoclasts or osteoclasts, and (3) that the organic components (e.g., collagen fibrils) of dentin or cementum are endocytosed through the channels of the RB in the same manner as that for MP. However, the endocytotic ability of odontoclasts appears inferior to that of osteoclasts.

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

“…The presence of cementoblast-like or fibroblast-like stromal cells in association with odontoclasts has been reported in root resorption of deciduous teeth (Sasaki et al, 1990a,b;Tanaka et al, 1990;Sahara, 1998). Similarity of the tooth resorption-repair sequence (i.e., root resorption and cementum formation) to the bone remodeling sequence has also been pointed out (Sasaki et al, 1990a,b;Sahara, 1998).…”

Cementum‐like tissue deposition on the resorbed enamel surface of human deciduous teeth prior to shedding

“…Thus, some authors considered that these mononuclear cells might scavenge the bone surface at the end of osteoclastic resorption (Heersche, 1978; Tran Van et al, 1982;Everts et al, 2002) and that the cement line/reversal line seen on the resorbed surface might be formed by these mononuclear cells (Heersche, 1978; Tran Van et al, 1982;McKee and Nanci, 1996a;Everts et al, 2002). In the case of tooth resorption, it was also reported that similar kinds of mononuclear cell types, e.g., cementoblast-like cells (Sasaki et al, 1990), machrophage-like cells or fibroblast-like cells (Tanaka et al, 1990;Okamura et al, 1993), and a special class of mononuclear cells (Bosshardt and Schroeder, 1998) were seen lining the resorption surface. In the present study, we also found that numerous mononuclear cells was seen to populate the resorbed enamel surface after the withdrawal of the odontoclasts and prior to the onset of repair cementum-like tissue formation.…”

Comparison of expression patterns of cathepsin K and MMP-9 in odontoclasts and osteoclasts in physiological root resorption in the rat molar

“…It has been proposed that osteoclasts undergoing even more differentiation have a greater number of nuclei with a higher bone resorption activity (Teti et al, 1991;Lees et al, 2001;Manolson et al, 2003). Since odontoclasts normally have fewer nuclei and less clear zones compared with osteoclasts (Tanaka et al, 1990;Ne et al, 1999), we hypothesized that odontoclasts possess less cell differentiation in their matrix resorption characteristics than osteoclasts. This may be a fundamental difference that explains why the dental root is less susceptible to resorption by multinucleated cells as compared with alveolar bone.…”