論文の公開元へLithium carbonate accelerates the healing of apical periodontitis
概要
Title
Lithium carbonate accelerates the healing of
apical periodontitis
Author(s)
Kagioka, Takumi; Itoh, Shousaku; Hue, Mai Thi et
al.
Citation
Scientific Reports. 2023, 13, p. 7886
Version Type VoR
URL
rights
https://hdl.handle.net/11094/92523
This article is licensed under a Creative
Commons Attribution 4.0 International License.
Note
Osaka University Knowledge Archive : OUKA
https://ir.library.osaka-u.ac.jp/
Osaka University
www.nature.com/scientificreports
OPEN
Lithium carbonate accelerates
the healing of apical periodontitis
Takumi Kagioka 1, Shousaku Itoh 1*, Mai Thi Hue 1, Makoto Abe 2 & Mikako Hayashi 1
Apical periodontitis is a disease caused by bacterial invasions through the root canals. Our previous
study reported that lithium chloride (LiCl) had a healing effect on apical periodontitis. The aim of
this report is to investigate the healing properties and mechanism of lithium ion (Li+) for apical
periodontitis using rat root canal treatment model. 10-week-old male Wistar rat’s mandibular
first molars with experimentally induced apical periodontitis underwent root canal treatment and
were applied lithium carbonate (Li2CO3) containing intracanal medicament. Base material of the
medicament was used as a control. Subject teeth were scanned by micro-CT every week and the
periapical lesion volume was evaluated. The lesion volume of Li2CO3 group was significantly smaller
than that of the control group. Histological analysis showed that in Li2CO3 group, M2 macrophages
and regulatory T cells were induced in the periapical lesion. In situ hybridization experiments
revealed a greater expression of Col1a1 in Li2CO3 group compared with the control group. At 24 h
after application of intracanal medicament, Axin2-positive cells were distributed in Li2CO3 group. In
conclusion, Li2CO3 stimulates Wnt/β-catenin signaling pathway and accelerate the healing process of
apical periodontitis, modulating the immune system and the bone metabolism.
Apical periodontitis is generally caused by the host’s immune response to bacterial invasions through the root
canals, resulting in the subsequent alveolar bone resorption by osteoclasts via immune cells’ production of
inflammatory cytokines1–4. In the case of apical periodontitis, the disrupted bone homeostasis causes alveolar
bone resorption, resulting in the formation of periapical lesion which is observed as a radiolucent area around
the root apex. Root canal treatment is intended to mechanically remove infected dentin and chemically reduce
the number of bacteria. One of the chemical methods to remove bacterial is the usage of intracanal medicaments
with bactericidal properties. Calcium hydroxide, which has antibacterial properties due to its high pH, is currently used as a common intracanal medicament in root canal t reatment5,6. However, the application of calcium
hydroxide, which is primarily an antibacterial agent, alone may cause prolonged healing of periapical lesions and,
in some cases, lesions may not heal. Currently, the success rate of root canal treatment, especially retreatment,
varies from one case to another; for example, the success rate for retreatment of teeth with periapical lesions is
reported to be 65.7–80%7–9. Since we speculated that there might be a new approach to heal apical periodontitis,
we tried to establish a new intracanal medicament.
In recent years, many disease-related genes have been identified in various multifactorial diseases by single
nucleotide polymorphisms (SNPs). Since some cases were observed in which root canal cleaning and filling
conditions were inadequate but no periapical lesions formed, it was speculated that there may be individual differences in the development of apical periodontitis. Our recent report demonstrated that the A1330V variant of
LDL Receptor Related Protein 5 (LRP5), which was one of the co-receptors of Wnt proteins in the canonical Wnt
pathway, was associated with apical p
eriodontitis10. Previous reports have shown that the Wnt/β-catenin signaling
pathway is involved in somatic axis formation during ontogeny and in the development of various diseases11–13.
This pathway also has important functions in maintaining bone homeostasis14–16. Wnt protein inhibits glycogen
synthase kinase-3β (GSK-3β)-mediated phosphorylation of β-catenin by binding to its frizzled receptor and coreceptor LRP 5/6. Stabilized β-catenin is accumulated in the cytoplasm. Accumulated β-catenin is transferred
into the nucleus where it associates with the transcription factor LEF-1/TCF. The complex of β-catenin and
LEF-1/TCF activates various target genes. Previous reports have shown that lithium chloride (LiCl) can stimulate the Wnt/β-catenin signaling pathway and promotes mineralization17. To determine the details of the role of
this pathway in the development of apical periodontitis, we performed the root canal treatment on mice with
induced apical periodontitis. The results of our in vivo experiments demonstrated that the application of LiCl
into the mice’s root canals accelerated the healing of apical periodontitis10. Thus, these results imply that lithium
ion (Li+) diffused from LiCl has the healing ability for apical periodontitis.
1
Department of Restorative Dentistry and Endodontology, Osaka University Graduate School of Dentistry, 1‑8
Yamadaoka, Suita, Osaka 565‑0871, Japan. 2Department of Oral Anatomy and Developmental Biology, Osaka
University Graduate School of Dentistry, Osaka, Japan. *email: itoh.shousaku.dent@osaka-u.ac.jp
Scientific Reports |
(2023) 13:7886
| https://doi.org/10.1038/s41598-023-34700-z
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Vol.:(0123456789)
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Moreover, the clinical use of LiCl was questionable in terms of its safety. In this report, we applied lithium
carbonate (Li2CO3) into root canals instead of LiCl aiming to confirm the safety of L
i+ in clinical application
+
and the healing ability of Li for apical periodontitis. This is because Li2CO3 has already been used as a primary
therapeutic agent for bipolar disorder. Furthermore, rats were used in this study to determine if the healing
ability of L
i+ can be also observed in another animal. Because of the larger size of mandibular first molar of rats
than that of mice, rubber dam could be used for root canal treatment, enabling treatment sterility. Alternatively,
another objective of our study was to analyze the mechanism of the healing ability of Li+ because the mechanism
remained unclear in our previous study. To elucidate this mechanism, histological analysis was performed on rat
mandibular tissue targeting immune cells, osteoblast, and the Wnt/β-catenin signaling pathway.
Results
Verify the safety during application of Li2CO3 into root canal. We applied a 12% Li2CO3 paste into
the root canals to verify the safety for periapical tissue. The experimental procedure is shown in Fig. 1a. The
hematoxylin and eosin (H&E) staining images showed that there was no difference in the periapical tissues
between the control group and the 12% Li2CO3 group (Fig. 1b). In detail, there was no inflammatory cell infiltration around the apical foramen and the area that came into contact with the intracanal medicament in both
the control and 12% L
i2CO3 groups. In addition, there was no pathological alveolar bone and root resorption in
these two groups. Further, to evaluate the systemic effects of the application of 12% L
i2CO3 paste into root canals,
we monitored the blood concentration of Li+ for 72 h. The intraperitoneal group showed the transient increase in
the blood concentration of Li+ up to around 2 mM at 1 h after the administration (Fig. 1c). After that, the blood
concentration of Li+ was gradually decreased until 72 h. On the other hand, in cases of the application of 12%
Li2CO3 into the root canals, there was no increase in the blood concentration of Li+ throughout the observation
period. These results demonstrated that applied Li+ did not diffuse into the blood (Fig. 1c); therefore, indicating
that the L
i2CO3 was safe to apply into the root canal.
Li2CO3 reduced the volume of periapical lesions. To evaluate the applicability of L i2CO3 for the treatment of apical periodontitis, we applied a 12% Li2CO3 paste into root canals using a rat root canal treatment
model. Figure 2a shows the experimental procedure. The results of H&E staining at 28 d after intracanal medication showed that the size of periapical lesions of the 12% Li2CO3 group was much smaller than that of the control
group (Fig. 2b,c). In the 12% L
i2CO3 group, there was hardly any infiltration of inflammatory cells. However,
in the control group, many inflammatory cells were observed inside the periapical lesion. Additionally, some
alveolar bone areas in the 12% Li2CO3 group appeared to have undergone healing of the lesions with bone tissue.
Next, we analyzed periapical lesion volumes using micro-CT. Throughout the study, we were able to check
whether the intracanal medicament reached the apex of the root canal because of the X-ray contrast given to
the base material of the control and 12% Li2CO3 paste (Fig. 2b,c). Periapical lesion volumes were not significantly different between the control and the 12% L
i2CO3 groups from 0 (p = 0.932) to 7 d (p = 0.075). In contrast,
the periapical lesion volume of the 12% Li2CO3 group was significantly smaller than that of the control group
(Fig. 2d) on 14 d (p = 0.022), 21 d (p = 0.005) and 28 d (p = 0.009).
Li2CO3 has the healing ability for apical periodontitis through the stimulation of Wnt/β‑catenin
signaling pathway. To elucidate the mechanism of the ameliorative effect of L i2CO3 on apical periodon-
titis, histological experiments were performed on periapical tissues. Though many CD86-positive cells were
observed in the control group at 7, 14, and 21 d, there were very few CD86-positive cells in the 12% Li2CO3
group at the same time points (Fig. 3). ...
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