Mechanical-induced bone remodeling does not depend on Piezo1 in dentoalveolar hard tissue

Piezo Channels in Dentistry: Decoding the Functional Effects of Forces

The oral system is a highly complex mechanosensory structure that continuously adapts to changes in mechanical stimuli, exerting mechanical forces on cells and tissues. Understanding how these forces are converted into biochemical signals and how they mediate gene expression and cellular activities has been a significant focus in dentistry. Piezo channels, including Piezo1 and Piezo2, are mechanically activated cation channels characterized by an extracellular "cap" domain and 3 peripheral mechanosensitive blades. Recent research has demonstrated that mechanical forces applied to tissues can induce deformation of cell membranes, leading to conformational changes in Piezo channels that facilitate cation influx, thereby regulating cellular activities. The influx of Ca2+, the most discussed outcome of Piezo channel activation, initiates diverse signaling pathways that regulate dentin hypersensitivity, alveolar bone remodeling, and temporomandibular joint (TMJ) osteoarthritis. The chemical inhibition of Piezo channels has been shown to alleviate dentinal hypersensitivity, reduce the rate of orthodontic tooth movement, and slow the progression of TMJ osteoarthritis in rat models. Mice deficient in piezo channels exhibit impaired reactive dentin formation, reduced alveolar bone volume, and developmental deformities of the jawbone. Considering their roles in decoding the functional effects of mechanical forces, this review summarizes the involvement of Piezo channels in dentistry, organized by anatomical sites, to provide comprehensive knowledge of Piezo channels and their mediated signal crosstalk, which offers promising therapeutic prospects for the treatment of various force-related oral diseases.

IL6-Dependent PIEZO1 Activation Promotes M1-Mediated Orthodontic Root Resorption via CXCL12/CXCR4

Orthodontic root resorption (ORR) is a common yet significant complication of orthodontic treatment, largely driven by interactions between periodontal ligament cells (PDLCs) and M1 macrophages. Despite the clinical relevance of ORR, the role of mechanosensitive ion channels in PDLC-mediated ORR and the underlying mechanisms regulating inflammatory cell recruitment remain poorly understood. Here, we identified PIEZO1 as a critical mechanosensitive ion channel that modulates monocyte recruitment and ORR. Using in vivo models treated with the PIEZO1 activator Yoda1 and inhibitor AAV-shPiezo1, we demonstrated that PIEZO1 activation promoted the recruitment of Ly6Chi inflammatory monocytes and exacerbated ORR. In contrast, PIEZO1 inhibition attenuated ORR and the accumulation of M1 macrophages. Mechanistically, PIEZO1 positively regulated the C-X-C motif chemokine 12 (CXCL12) and its receptor, C-X-C chemokine receptor type 4 (CXCR4). Blocking the CXCL12/CXCR4 axis using the CXCR4 antagonist AMD3100 significantly alleviated ORR, reversed M1 macrophage accumulation, and mitigated the recruitment of CD11b+Ly6Chi monocytes. Transwell migration assays with application of the PIEZO1 activator Yoda1 and PIEZO1 inhibitor GsMTX4 consistently confirmed the PIEZO1/CXCL12/CXCR4 axis as a key driver of PDLC-monocyte interactions. Notably, PIEZO1 overactivation was linked to excessive IL-6 production, and IL-6 deficiency inhibited the activation of PIEZO1 induced by Yoda1, leading to attenuation of ORR, M1 macrophage accumulation, and CXCL12/CXCR4 axis activation. Collectively, these findings reveal PIEZO1 in PDLCs as a pivotal modulator of inflammatory monocyte recruitment via the CXCL12/CXCR4 axis in ORR, with IL-6 playing an essential role in PIEZO1 activation. This study provides new insights into the molecular crosstalk between PDLCs and macrophages, offering potential therapeutic targets for mitigating ORR in orthodontic patients.

Nociceptor Neurons Facilitate Orthodontic Tooth Movement via Piezo2 in Mice

Multiple sensory afferents, including mechanosensitive and nociceptive nerves, are projected to the periodontium. Peptidergic afferents expressing transient receptor potential vanilloid 1 (TRPV1), a receptor for capsaicin, mediate pain caused by orthodontic forces. However, their role in orthodontic force-induced alveolar bone remodeling is poorly understood as is the contribution of mechanosensitive ion channels such as Piezo2 in nociceptive nerves. To investigate this role, we studied orthodontic tooth movement and alveolar bone remodeling using neural manipulations and genetic mouse models. Chemical ablation of TRPV1-expressing afferents localized to the trigeminal ganglia decreased orthodontic force-induced tooth movement and the number of osteoclasts in alveolar bone on the compression side. The extent of the force-induced increase in the ratio of receptor activator of nuclear factor kappa-B ligand/osteoprotegerin in the periodontium was modestly decreased in the chemical ablation group. Furthermore, chemogenetic silencing of TRPV1-lineage afferents reduced orthodontic tooth movement and the number of osteoclasts. Piezo2 was expressed in most periodontal afferents, and chemogenetic inhibition of Piezo2-expressing neurons decreased orthodontic tooth movement and the number of osteoclasts. In addition, the conditional knockout of Piezo2 in TRPV1-lineage afferents decreased orthodontic tooth movement and the number of osteoclasts. Overall, these results suggest that nociceptor neurons play critical roles in orthodontic force-induced alveolar bone remodeling and that the mechanical activation of neuronal Piezo2 in nociceptive nerves facilitates orthodontic tooth movement and associated alveolar bone remodeling.

Piezo1 Regulates Odontogenesis via a FAM83G-Mediated Mechanism in Dental Papilla Cells In Vitro and In Vivo

This study explored the role of Piezo1 in the odontogenic differentiation of dental papilla cells (DPCs) and tissue, focusing on a mechanism involving family with sequence similarity 83, member G (FAM83G). Here, we found Piezo1, a mechanosensitive cation channel, was upregulated during odontogenesis in DPCs and dental papilla tissues. Knockdown of Piezo1 impaired odontogenic differentiation, while its activation by Yoda1 enhanced the process. Using a 3D culture model and an ectopic transplantation model, we confirmed Piezo1's role in vivo. RNA sequencing (RNA-seq) analysis revealed that FAM83G was upregulated in Piezo1-knockdown cells, and FAM83G silencing enhanced odontogenesis in DPCs. These findings indicate that Piezo1 positively regulates odontogenesis by inhibiting FAM83G in DPCs both in vitro and in vivo, with Piezo1 representing a potential target for dental tissue regeneration.

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.

Piezo1 and Piezo2 collectively regulate jawbone development

Piezo1 and Piezo2 are recently reported mechanosensory ion channels that transduce mechanical stimuli from the environment into intracellular biochemical signals in various tissues and organ systems. Here, we show that Piezo1 and Piezo2 display a robust expression during jawbone development. Deletion of Piezo1 in neural crest cells causes jawbone malformations in a small but significant number of mice. We further demonstrate that disruption of Piezo1 and Piezo2 in neural crest cells causes more striking defects in jawbone development than any single knockout, suggesting essential but partially redundant roles of Piezo1 and Piezo2. In addition, we observe defects in other neural crest derivatives such as malformation of the vascular smooth muscle in double knockout mice. Moreover, TUNEL examinations reveal excessive cell death in osteogenic cells of the maxillary and mandibular arches of the double knockout mice, suggesting that Piezo1 and Piezo2 together regulate cell survival during jawbone development. We further demonstrate that Yoda1, a Piezo1 agonist, promotes mineralization in the mandibular arches. Altogether, these data firmly establish that Piezo channels play important roles in regulating jawbone formation and maintenance.

Nociceptor mechanisms underlying pain and bone remodeling via orthodontic forces: toward no pain, big gain

Orthodontic forces are strongly associated with pain, the primary complaint among patients wearing orthodontic braces. Compared to other side effects of orthodontic treatment, orthodontic pain is often overlooked, with limited clinical management. Orthodontic forces lead to inflammatory responses in the periodontium, which triggers bone remodeling and eventually induces tooth movement. Mechanical forces and subsequent inflammation in the periodontium activate and sensitize periodontal nociceptors and produce orthodontic pain. Nociceptive afferents expressing transient receptor potential vanilloid subtype 1 (TRPV1) play central roles in transducing nociceptive signals, leading to transcriptional changes in the trigeminal ganglia. Nociceptive molecules, such as TRPV1, transient receptor potential ankyrin subtype 1, acid-sensing ion channel 3, and the P2X3 receptor, are believed to mediate orthodontic pain. Neuropeptides such as calcitonin gene-related peptides and substance P can also regulate orthodontic pain. While periodontal nociceptors transmit nociceptive signals to the brain, they are also known to modulate alveolar bone remodeling in periodontitis. Therefore, periodontal nociceptors and nociceptive molecules may contribute to the modulation of orthodontic tooth movement, which currently remains undetermined. Future studies are needed to better understand the fundamental mechanisms underlying neuroskeletal interactions in orthodontics to improve orthodontic treatment by developing novel methods to reduce pain and accelerate orthodontic tooth movement-thereby achieving "big gains with no pain" in clinical orthodontics.

The role of mechanically sensitive ion channel Piezo1 in bone remodeling

Piezo1 (2010) was identified as a mechanically activated cation channel capable of sensing various physical forces, such as tension, osmotic pressure, and shear force. Piezo1 mediates mechanosensory transduction in different organs and tissues, including its role in maintaining bone homeostasis. This review aimed to summarize the function and possible mechanism of Piezo1 in the mechanical receptor cells in bone tissue. We found that it is a potential therapeutic target for the treatment of bone diseases.