Abstract
The present study was performed to examine how transforming growth factor β (TGF-β) in root-surrounding tissues on deciduous teeth regulates the differentiation induction into odontoclasts during physiological root resorption. We prepared root-surrounding tissues with (R) or without (N) physiological root resorption scraped off at three regions (R1–R3 or N1–N3) from the cervical area to the apical area of the tooth and measured both TGF-β and the tartrate-resistant acid phosphatase (TRAP) activities. The TGF-β activity level was increased in N1–N3, whereas the TRAP activity was increased in R2 and R3. In vitro experiments for the receptor activator of nuclear factor-κB (NF-κB) ligand (RANKL)-mediated osteoclast differentiation revealed that proteins from N1–N3 and R1–R3 enhanced the TRAP activity in RAW264 cells. A genetic study indicated that the mRNA levels of TGF-β1 in N1 and N2 were significantly increased, and corresponded with levels of osteoprotegerin (OPG). In contrast, the expression level of RANKL was increased in R2 and R3. Our findings suggest that TGF-β is closely related to the regulation of OPG induction and RANKL-mediated odontoclast differentiation depending on the timing of RANKL and OPG mRNA expression in the root-surrounding tissues of deciduous teeth during physiological root resorption.
Highlights
Physiological root resorption of human deciduous teeth proceeds from a root non-resorption period to a root resorption period for the formation of permanent teeth
Since transforming growth factor-β (TGF-β) activity has been found in the pulp and periodontal ligaments [15], we initially attempted to detect in vivo TGF-β in root-surrounding tissues at the protein level
We have previously shown that TGF-β1 binds to both amelogenin, major enamel protein and dentin sialophosphoprotein (DSPP)-derived proteins, most abundant dentin non-collagenous proteins
Summary
Physiological root resorption of human deciduous teeth proceeds from a root non-resorption period to a root resorption period for the formation of permanent teeth This series of progressions is mediated by odontoclasts, which are produced in the root-surrounding tissues [1]. The receptor activator of nuclear factor-κB (NF-κB) ligand (RANKL) and its receptor (RANK) have been shown to play a crucial role in the induction of osteoclast differentiation [6], whereas osteoprotegerin (OPG) is a decoy receptor for RANKL and suppresses osteoclast differentiation [7]. This mechanism must be taken into consideration, even in odontoclastogenesis. Previous experiments by our group have shown that transforming growth factor-β (TGF-β), which is a multifunctional cytokine and is critical for cell differentiation, exists in the pulp and periodontal ligaments [15]
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