Osteoblastic STAT3 Is Crucial for Orthodontic Force Driving Alveolar Bone Remodeling and Tooth Movement

METTL14-mediated m6A modification of ZFP14 inhibits clear cell renal cell carcinoma progression via promoting STAT3 ubiquitination

Therapeutic options for advanced clear cell renal cell carcinoma (ccRCC) are currently inadequate. Earlier research has shown that the enzyme methyltransferase-like 14 (METTL14) can suppress ccRCC development through the modification of N6-methyladenosine (m6A). This study further explored its complex biological functions and underlying molecular mechanisms. Here, we identified zinc finger protein 14 (ZFP14) as a novel target of METTL14-mediated m6A, and its under-expression was associated with ccRCC tumourigenesis and progression. Detailed investigations revealed that METTL14 interacted directly with the 3' untranslated region of ZFP14 mRNA, promoting m6A modification at two specific sites. These modifications were recognised by the protein insulin-like growth factor 2 mRNA-binding protein 2 (IGF2BP2), which stabilised and enhanced the expression of ZFP14 mRNA. Functionally, the METTL14/ZFP14 axis suppressed in vitro growth, migration and invasiveness and in vivo proliferation and metastasis of ccRCC cells. ZFP14 potentially regulated numbers of transcripts, among which matrix metalloproteinase 1/3 (MMP1/3) were validated to be under-expressed by ZFP14. Crucially, ZFP14 interacted with the signal transducer and activator of transcription 3 (STAT3), augmenting its K48-linked ubiquitination and destabilising it via the proteasome pathway. Moreover, ZFP14 repressed ccRCC cell in vivo growth and metastasis as well as decreasing MMP1/3 levels by under-expressing STAT3. These observations confirmed that ZFP14 served as both a novel target for METTL14-mediated m6A modification and a significant tumour suppressor in ccRCC, shedding light on the cellular and molecular operations in ccRCC and opening up possibilities for novel therapeutic strategies. KEY POINTS: ZFP14 under-expression is associated with ccRCC tumourigenesis and progression. METTL14-mediated m6A enhances ZFP14 mRNA stability and expression with IGF2BP2 as the reader in ccRCC. ZFP14 promotes the degradation of STAT3 by enhancing its K48-linked ubiquitination, inhibiting ccRCC progression.

Measurement of the root surface area in rat molars through three-dimensional modeling

OBJECTIVES

Rats are used as animal models for basic and applied research related to orthodontic tooth movement (OTM). The magnitude of mechanical force in OTM rat models mainly depends on the supporting capability of the periodontal ligament (PDL), which is highly associated with the root surface area (RSA). But the size of rat RSA remains unknown, which is the reason why there are still debates on the magnitude of mechanical force in OTM rat models. This study aimed to explore a method for measuring the RSA in rat molars.

DESIGN

The maxillary and mandibular samples of rats were scanned by Micro-CT to generate three-dimensional (3D) images, followed by 3D reconstruction of every molar through Mimics Medical 21.0. Geomagic Wrap 2021 and Unigraphics NX 12.0 were utilized to smooth teeth surface and mark the cementoenamel junction (CEJ). Finally, the RSA in rat molars was measured.

RESULTS

The results showed that for the six-, eight-, or ten-week-old rats, the average RSA of maxillary first, second, and third molars was 25.90 ± 2.29 mm2, 15.92 ± 2.14 mm2, and 10.34 ± 1.94 mm2. The RSA of mandibular first, second, and third molars was 27.03 ± 2.63 mm2, 17.16 ± 1.61 mm2, and 11.39 ± 2.13 mm2.

CONCLUSIONS

Through 3D modelling, we provided data of rat RSA, and observed the trend of increasing RSA mean values with age. These data are pivotal for determining the magnitude of mechanical force required to move rat molars, especially when conducting research related to OTM using rat models.

Periodontal response to nonsurgical accelerated orthodontic tooth movement

Tooth movement is a complex process involving the vascularization of the tissues, remodeling of the bone cells, and periodontal ligament fibroblasts under the hormonal and neuronal regulation mechanisms in response to mechanical force application. Therefore, it will inevitably impact periodontal tissues. Prolonged treatment can lead to adverse effects on teeth and periodontal tissues, prompting the development of various methods to reduce the length of orthodontic treatment. These methods are surgical or nonsurgical interventions applied simultaneously within the orthodontic treatment. The main target of nonsurgical approaches is modulating the response of the periodontal tissues to the orthodontic force. They stimulate osteoclasts and osteoclastic bone resorption in a controlled manner to facilitate tooth movement. Among various nonsurgical methods, the most promising clinical results have been achieved with photobiomodulation (PBM) therapy. Clinical data on electric/magnetic stimulation, pharmacologic administrations, and vibration forces indicate the need for further studies to improve their efficiency. This growing field will lead to a paradigm shift as we understand the biological response to these approaches and their adoption in clinical practice. This review will specifically focus on the impact of nonsurgical methods on periodontal tissues, providing a comprehensive understanding of this significant and understudied aspect of orthodontic care.

AGEs impair osteogenesis in orthodontic force-induced periodontal ligament stem cells through the KDM6B/Wnt self-reinforcing loop

BACKGROUND

Diabetes, occasionally diagnosed in orthodontic patients, can impede orthodontic tooth movement (OTM) by accumulating advanced glycation end products (AGEs) in the periodontium. This accumulation impairs the osteogenic differentiation of periodontal ligament stem cells (PDLSCs) due to alterations in the force-loaded microenvironment, yet the underlying mechanisms remain elusive.

METHODS

Bioinformatics analysis of GSE112122 identified alterations in the mechanical regulation of histone methylation enzyme Lysine Demethylase 6B (KDM6B). OTM models were established in healthy and Nicotinamide/ Streptozotocin-induced type II diabetic rats. The impact of AGEs on mechanically induced osteogenesis and its correlation with KDM6B were evaluated by assessing the therapeutic effects of periodontal ligament injections of the AGEs/RAGE inhibitor FPS-ZM1. To investigate transcriptomic changes, we extracted human PDLSCs, which were subjected to RNA sequencing following the overexpression of KDM6B. Experimental validation further identified potential self-reinforcing loops and their associated antioxidative mechanisms.

RESULTS

Mechanical forces upregulated KDM6B expression and function in PDLSCs, modulating extensive downstream osteogenesis-related transcriptional changes. Experiments with AGEs-treated and FPS-ZM1-treated samples demonstrated that AGEs impaired osteogenesis by compromising KDM6B mechanical responsiveness. A positive feedback loop between KDM6B and Wnt pathways was identified, inhibited by AGEs. This loop regulated superoxide dismutase 2 (SOD2), facilitating antioxidative stress and preventing stem cell ageing.

CONCLUSIONS

This study elucidates a novel mechanism by which AGEs influence the osteogenic process and antioxidative capacity of PDLSCs through the KDM6B/Wnt self-reinforcing loop under orthodontic force. Targeting the AGE/RAGE pathway or enhancing KDM6B may enhance orthodontic treatments for diabetic patients.

Exploring biological mechanisms in orthodontic tooth movement: Bridging the gap between basic research experiments and clinical applications - A comprehensive review

OBJECTIVES

The molecular mechanisms behind orthodontic tooth movements (OTM) were investigated by clarifying the role of chemical messengers released by cells.

METHODS

Using the Cochrane library, Google scholar, and PubMed databases, a literature search was conducted, and studies published from 1984 to 2024 were considered.

RESULTS

Both bone growth and remodeling may occur when a tooth is subjected to mechanical stress. These chemicals have a significant effect on the stimulation and regulation of osteoblasts, osteoclasts, and osteocytes during alveolar bone remodeling. This regulation can take place in pathological conditions, such as periodontal diseases, or during OTM alone. This comprehensive review outlines key molecular mechanisms underlying OTM and explores various clinical assumptions associated with specific molecules and their functional domains during this process. Furthermore, clinical applications of certain molecules such as relaxin, prostaglandin E (PGE), and interleukin-1β (IL-1β) in accelerating OTM have been reported. Our findings underscore the existing gap between OTM clinical applications and basic research investigations.

CONCLUSION

A comprehensive understanding of orthodontic treatment is enriched by insights into biological systems. We reported the activation of osteoblasts, osteoclast precursor cells, osteoclasts, and osteocytes in response to mechanical stress, leading to targeted cellular and molecular interventions and facilitating rapid and regulated alveolar bone remodeling during tooth movement. Despite the shortcomings of clinical studies in accelerating OTM, this review highlights the crucial role of biological agents in this process and advocates for prioritizing high-quality human studies in future research to gain further insights from clinical trials.

Targeting phosphatidylinositol-3-kinase for inhibiting maxillary bone resorption

Previous studies have suggested a role of phosphatidylinositol-3-kinase gamma (PI3Kγ) in bone remodeling, but the mechanism remains undefined. Here, we explored the contribution of PI3Kγ in the resorption of maxillary bone and dental roots using models of orthodontic tooth movement (OTM), orthodontic-induced inflammatory root resorption, and rapid maxillary expansion (RME). PI3Kγ-deficient mice (PI3Kγ-/- ), mice with loss of PI3Kγ kinase activity (PI3KγKD/KD ) and C57BL/6 mice treated with a PI3Kγ inhibitor (AS605240) and respective controls were used. The maxillary bones of PI3Kγ-/- , PI3KγKD/KD , and C57BL/6 mice treated with AS605240 showed an improvement of bone quality compared to their controls, resulting in reduction of the OTM and RME in all experimental groups. PI3Kγ-/- mice exhibited increased root volume and decreased odontoclasts counts. Consistently, the pharmacological blockade or genetic deletion of PI3K resulted in increased numbers of osteoblasts and reduction in osteoclasts during OTM. There was an augmented expression of Runt-related transcription factor 2 (Runx2) and alkaline phosphatase (Alp), a reduction of interleukin-6 (Il-6), as well as a lack of responsiveness of receptor activator of nuclear factor kappa-Β (Rank) in PI3Kγ-/- and PI3KγKD/KD mice compared to control mice. The maxillary bones of PI3Kγ-/- animals showed reduced p-Akt expression. In vitro, bone marrow cells treated with AS605240 and cells from PI3Kγ-/- mice exhibited significant augment of osteoblast mineralization and less osteoclast differentiation. The PI3Kγ/Akt axis is pivotal for bone remodeling by providing negative and positive signals for the differentiation of osteoclasts and osteoblasts, respectively.

Mechanisms of Osteoclastogenesis in Orthodontic Tooth Movement and Orthodontically Induced Tooth Root Resorption

Orthodontic tooth movement (OTM) is achieved by the simultaneous activation of bone resorption by osteoclasts and bone formation by osteoblasts. When orthodontic forces are applied, osteoclast-mediated bone resorption occurs in the alveolar bone on the compression side, creating space for tooth movement. Therefore, controlling osteoclastogenesis is the fundamental tenet of orthodontic treatment. Orthodontic forces are sensed by osteoblast lineage cells such as periodontal ligament (PDL) cells and osteocytes. Of several cytokines produced by these cells, the most important cytokine promoting osteoclastogenesis is the receptor activator of nuclear factor-κB ligand (RANKL), which is mainly supplied by osteoblasts. Additionally, osteocytes embedded within the bone matrix, T lymphocytes in inflammatory conditions, and PDL cells produce RANKL. Besides RANKL, inflammatory cytokines, such as interleukin-1, tumor necrosis factor-α, and prostaglandin E2 promote osteoclastogenesis under OTM. On the downside, excessive osteoclastogenesis activation triggers orthodontically-induced external root resorption (ERR) through pro-osteoclastic inflammatory cytokines. Therefore, understanding the mechanisms of osteoclastogenesis during OTM is essential in reducing the adverse effects of orthodontic treatment. Here, we review the current concepts of the mechanisms underlying osteoclastogenesis in OTM and orthodontically induced ERR.

Cyclic tensile force modifies calvarial osteoblast function via the interplay between ERK1/2 and STAT3

BACKGROUND

Mechanical therapies, such as distraction osteogenesis, are widely used in dental clinics. During this process, the mechanisms by which tensile force triggers bone formation remain of interest. Herein, we investigated the influence of cyclic tensile stress on osteoblasts and identified the involvement of ERK1/2 and STAT3.

MATERIALS AND METHODS

Rat clavarial osteoblasts were subjected to tensile loading (10% elongation, 0.5 Hz) for different time periods. RNA and protein levels of osteogenic markers were determined using qPCR and western blot after inhibition of ERK1/2 and STAT3. ALP activity and ARS staining revealed osteoblast mineralization capacity. The interaction between ERK1/2 and STAT3 was investigated by immunofluorescence, western blot, and Co-IP.

RESULTS

The results showed that tensile loading significantly promoted osteogenesis-related genes, proteins and mineralized nodules. In loading-induced osteoblasts, inhibition of ERK1/2 or STAT3 decreased osteogenesis-related biomarkers significantly. Moreover, ERK1/2 inhibition suppressed STAT3 phosphorylation, and STAT3 inhibition disrupted the nuclear translocation of pERK1/2 induced by tensile loading. In the non-loading environment, inhibition of ERK1/2 hindered osteoblast differentiation and mineralization, while STAT3 phosphorylation was elevated after ERK1/2 inhibition. STAT3 inhibition also increased ERK1/2 phosphorylation, but did not significantly affect osteogenesis-related factors.

CONCLUSION

Taken together, these data suggested that ERK1/2 and STAT3 interacted in osteoblasts. ERK1/2-STAT3 were sequentially activated by tensile force loading, and both affected osteogenesis during the process.

Suppressing STAT3 activation impairs bone formation during maxillary expansion and relapse

OBJECTIVES

The mid-palatal expansion technique is commonly used to correct maxillary constriction in dental clinics. However, there is a tendency for it to relapse, and the key molecules responsible for modulating bone formation remain elusive. Thus, this study aimed to investigate whether signal transducer and activator of transcription 3 (STAT3) activation contributes to osteoblast-mediated bone formation during palatal expansion and relapse.

METHODOLOGY

In total, 30 male Wistar rats were randomly allocated into Ctrl (control), E (expansion only), and E+Stattic (expansion plus STAT3-inhibitor, Stattic) groups. Micro-computed tomography, micromorphology staining, and immunohistochemistry of the mid-palatal suture were performed on days 7 and 14. In vitro cyclic tensile stress (10% magnitude, 0.5 Hz frequency, and 24 h duration) was applied to rat primary osteoblasts and Stattic was administered for STAT3 inhibition. The role of STAT3 in mechanical loading-induced osteoblasts was confirmed by alkaline phosphatase (ALP), alizarin red staining, and western blots.

RESULTS

The E group showed greater arch width than the E+Stattic group after expansion. The differences between the two groups remained significant after relapse. We found active bone formation in the E group with increased expression of ALP, COL-I, and Runx2, although the expression of osteogenesis-related factors was downregulated in the E+stattic group. After STAT3 inhibition, expansive force-induced bone resorption was attenuated, as TRAP staining demonstrated. Furthermore, the administration of Stattic in vitro partially suppressed tensile stress-enhanced osteogenic markers in osteoblasts.

CONCLUSIONS

STAT3 inactivation reduced osteoblast-mediated bone formation during palatal expansion and post-expansion relapse, thus it may be a potential therapeutic target to treat force-induced bone formation.