Piezo1 contributes to alveolar bone remodeling by activating ß-catenin under compressive stress.

INTRODUCTION: The mechanosensitive ion channel, Piezo1, is responsible for transducing mechanical stimuli into intracellular biochemical signals and has been identified within periodontal ligament cells (PDLCs). Nonetheless, the precise biologic function of Piezo1 in the regulation of alveolar bone remodeling by PDLCs during compressive forces remains unclear. Therefore, this study focused on elucidating the role of the Piezo1 channel in alveolar bone remodeling and uncovering its underlying mechanisms. METHODS: PDLCs were subjected to compressive force and Piezo1 inhibitors. Piezo1 and ß-catenin expressions were quantified by quantitative reverse transcription polymerase chain reaction and Western blot. The intracellular calcium concentration was measured using Fluo-8 AM staining. The osteogenic and osteoclastic activities were assessed using alkaline phosphatase staining, enzyme-linked immunosorbent assay, quantitative reverse transcription polymerase chain reaction, and Western blot. In vivo, orthodontic tooth movement was used to determine the effects of Piezo1 on alveolar bone remodeling. RESULTS: Piezo1 and activated ß-catenin expressions were upregulated under compressive force. Piezo1 inhibition reduced ß-catenin activation, osteogenic differentiation, and osteoclastic activities. ß-catenin knockdown reversed the increased osteogenic differentiation but had little impact on osteoclastic activities. In vivo, Piezo1 inhibition led to decreased tooth movement distance, accompanied by reduced ß-catenin activation and expression of osteogenic and osteoclastic markers on the compression side. CONCLUSIONS: The Piezo1 channel is a key mechanotransduction component of PDLCs that senses compressive force and activates ß-catenin to regulate alveolar bone remodeling.

Quantitative characterizations of the Sharpey's fibers of rat molars.

BACKGROUND AND OBJECTIVE: The Sharpey's fibers of periodontal ligament (PDL) anchor the PDL to alveolar bone and cementum and are essential for the function of PDL. While qualitative analyses of the Sharpey's fibers have been widely explored, a comprehensive quantitative characterization of the Sharpey's fibers is not available. In this work, we selected rat molars as a model and comprehensively characterized the PDL Sharpey's fibers (diameter, density, length, embedding angle, and insertion angle). MATERIALS AND METHODS: A total of 24 rat mandibular molars, eight maxillary first molars, and their surrounding alveolar bone were harvested, fixed, rendered anorganic and observed under scanning electron microscopy (SEM). The mandibles and maxillae (n = 4) were harvested, processed, sectioned, and stained with Sirius red for histological observation. SEM images were used for quantitative analyses of diameters and densities of the Sharpey's fibers, while Sirius red staining images were used to measure lengths and angles. The Sharpey's fibers were comprehensively characterized in terms of positions (cervical, middle, and apical thirds), PDL fiber groups (alveolar crest, horizontal, oblique, apical, and interradicular groups), sides (cementum and bone sides), and teeth (mandibular first, second, third molars, and maxillary first molar). RESULTS: Our results showed that the characteristic parameters of the Sharpey's fibers varied in different positions, fiber groups, sides, and teeth. Specifically, the median diameter of the Sharpey's fibers on the bone side was significantly greater than that on the cementum side, while the median density of the Sharpey's fibers on the bone side was significantly lower than that on the cementum side, regardless of the positions and teeth. For the same tooth, the median length of the embedded Sharpey's fibers on the bone side was more than two times greater than that on the cementum side. Among all fiber groups, the alveolar crest group had the maximum length of the Sharpey's fibers on the bone side and the minimal length of the Sharpey's fibers on the cementum side. There is an approximate 5-15° difference between the embedding angle and the insertion angle in each group. The oblique group had the smallest embedding angles on both the bone and cementum sides. CONCLUSION: This study provides a comprehensive and quantitative characterization of the Sharpey's fibers using rat molars as a model. Overall, these parameters varied according to different vertical positions, fiber groups, teeth, and jawbones. The quantitative information of the Sharpey's fibers presented in this work facilitates our understanding of PDL functions and advances the development of biomimetic materials for periodontal tissue regeneration.

Intermittent parathyroid hormone (PTH) promotes cementogenesis and alleviates the catabolic effects of mechanical strain in cementoblasts.

BACKGROUND: External root resorption, commonly starting from cementum, is a severe side effect of orthodontic treatment. In this pathological process and repairing course followed, cementoblasts play a significant role. Previous studies implicated that parathyroid hormone (PTH) could act on committed osteoblast precursors to promote differentiation, and inhibit apoptosis. But little was known about the role of PTH in cementoblasts. The purpose of this study was to investigate the effects of intermittent PTH on cementoblasts and its influence after mechanical strain treatment. RESULTS: Higher levels of cementogenesis- and differentiation-related biomarkers (bone sialoprotein (BSP), osteocalcin (OCN), Collagen type I (COL1) and Osterix (Osx)) were shown in 1-3 cycles of intermittent PTH treated groups than the control group. Additionally, intermittent PTH increased alkaline phosphatase (ALP) activity and mineralized nodules formation, as measured by ALP staining, quantitative ALP assay, Alizarin red S staining and quantitative calcium assay. The morphology of OCCM-30 cells changed after mechanical strain exertion. Expression of BSP, ALP, OCN, osteopontin (OPN) and Osx was restrained after 18 h mechanical strain. Furthermore, intermittent PTH significantly increased the expression of cementogenesis- and differentiation-related biomarkers in mechanical strain treated OCCM-30 cells. CONCLUSIONS: Taken together, these data suggested that intermittent PTH promoted cementum formation through activating cementogenesis- and differentiation-related biomarkers, and attenuated the catabolic effects of mechanical strain in immortalized cementoblasts OCCM-30.

Combined Use of Facial Osteoplasty and Orthognathic Surgery for Treatment of Dentofacial Deformities.

PURPOSE: Orthognathic surgery is an efficient procedure for cosmetic and functional aims. However, when functional improvement is achieved by mandibular or maxillary operations, additional esthetic corrections may be imperative for some patients. This study aims to introduce our primary practice of simultaneous facial bone contouring and orthognathic surgery for esthetic reasons. PATIENTS AND METHODS: Ten patients with dentofacial deformities as well as a prominent angle, asymmetric deformities, or a high zygoma and zygomatic arch were recruited from West China Hospital of Stomatology, Sichuan University (Chengdu, China), between January 1, 2014, and July 31, 2015. Traditional orthognathic surgical procedures such as bilateral sagittal split osteotomy and Le Fort I osteotomy combined with facial osteoplasty including mandibular angle ostectomy, outer cortex ostectomy of the mandibular angle, and zygoma and zygomatic arch reduction were performed. Radiographs and medical photographs were taken before and after surgery to compare the effectiveness of the combined use of facial osteoplasty and orthognathic surgery. RESULTS: All patients had an uneventful postoperative recovery, with no signs of infection, jaw displacement, or osteonecrosis. Radiographs taken 1 week after surgery and pictures of the facial profile and occlusion taken 6 months after surgery showed satisfactory esthetic outcomes. All patients were satisfied with the functional and cosmetic results. CONCLUSIONS: This study indicated the clinical feasibility of simultaneous facial bone contouring and orthognathic surgery for the treatment of dentofacial deformities. Simultaneous facial bone contouring seems to be an alternative procedure in addition to conventional orthognathic surgery for cosmetic aims in certain patients.

The effect of teeth extraction for orthodontic treatment on the upper airway: a systematic review.

PURPOSE: The purpose of this study was to evaluate the effect of teeth extraction for orthodontic treatment on the upper airway. METHODS: Relevant trials assessing the effect of orthodontic extractions on the upper airway were retrieved electronically through PubMed, Embase, Medline, Web of Knowledge, and the Cochrane Library. The processes of literature search, selection, quality assessment, and data extraction were performed by two authors independently. RESULTS: Seven articles were included in this systematic review. They were categorized into three groups according to their indications for extractions, namely anteroposterior discrepancy (group 1), crowding (group 2), and unspecified indications (group 3). In group 1, enrolled patients were diagnosed with class I bimaxillary protrusion and had four first premolars extracted, with a significant decrease in upper airway dimension. In group 2, increase in the upper airway dimension was reported in patients who were diagnosed with class I crowding and four first premolars extracted. In group 3, all patients were adolescents and no significant change in the upper airway dimension was observed. CONCLUSIONS: Currently, it is difficult to draw evidence-based conclusions because of the exceeding heterogeneity among included studies, and more qualified trials are required to provide reliable evidence. Extractions followed by large retraction of the anterior teeth in adult bimaxillary protrusion cases could possibly lead to narrowing of the upper airway. Mesial movement of the molars appeared to increase the posterior space for the tongue and enlarge the upper airway dimensions. Although the effect of teeth extraction on upper airway dimension seems to be related to indications for extraction, accepted scientific evidence is still insufficient owing to the limited number of included studies. The relationship between the upper airway size and the respiratory function has not been demonstrated. While there may be a decrease in the upper airway volume, there is no evidence that this would turn an airway more collapsible. None of the studies assessed in this review had actual functional assessment of breathing. Additional qualified trials are necessary to verify reliability.

E7-Conjugated Bio-Inspired Microspheres as a Biological Barrier for Guided Tissue Regeneration.

Guided tissue regeneration (GTR), which is based on creating a physical barrier to prevent the downgrowth of epithelial and connective tissues into the defect site, has been widely used in clinical practice for periodontal regeneration for many years. However, its outcomes remain variable due to highly specific indications, the demand for proficient surgical skills, and frequent occurrence of complications. In this study, we developed a new GTR biomaterial that acts as a biological barrier for epithelial cells and fibroblasts while also serving as a scaffold for bone marrow-derived mesenchymal stem cells (BMSCs) and periodontal ligament stem cells (PDLSCs). This innovative GTR biomaterial is bioinspired injectable microspheres that are self-assembled from nanofibers, and their surfaces are conjugated with E7, a short peptide that selectively promotes BMSC and PDLSC adhesion but inhibits the attachment and spreading of epithelial cells and gingival fibroblasts. The selective affinity afforded by E7 on the surfaces of the nanofibrous microspheres facilitated the colonization of BMSCs in the periodontal defect, thereby substantially improving functional periodontal regeneration, as evidenced by enhanced new bone formation, reduced root exposure, and diminished attachment loss. The remarkable superiority of the bioinspired microspheres over conventional GTR materials in promoting periodontal regeneration underscores the potential of this innovative approach to enhance the efficacy of functional periodontal tissue regeneration.

Multifunctional peptide-conjugated nanocarriers for pulp regeneration in a full-length human tooth root.

Dental pulp is a highly vascularized tissue, situated in an inextensible environment surrounded by rigid dentinal walls. The pulp receives its blood supply solely from the small apical foramen of a tooth root. Due to the unique anatomy that controls nutrition supply, regeneration of pulp tissue in a full-length tooth root has long been a challenge in regenerative endodontics. In this study, we designed and synthesized a multifunctional peptide-conjugated, pH-sensitive, non-viral gene vector for fast revascularization and pulp regeneration in a full-length human tooth root. The multifunctional peptide was designed to have distinctive features, including a cell-penetrating peptide to enhance cellular uptake, a nuclear localization signal peptide to assist in the translocation of an angiogenic gene into the nucleus, and a fluorescent tryptophan residue to visualize and quantify the transfection efficiency. Furthermore, a pH-sensitive dimethylmaleic anhydride (DMA) was integrated with the multifunctional peptide to enhance the transfected gene complex to escape from endosomes/lysosomes after internalization. In vitro experiments showed that the multifunctional non-viral gene vector significantly increased internalization and gene transfection efficiency as well as reduced cytotoxicity. After dental pulp stem cells (DPSCs) were transfected with the multifunctional gene vector/pVEGF complexes, the expression of VEGF from the DPSCs was upregulated for more than eight folds, which in turn greatly enhanced endothelial cell migration and vascular-like tube formation. Six weeks after implantation, the VEGF-transfected DPSCs accelerated new blood vessel formation and the regenerated pulp tissue occupied most of the area in the canal of a full-length human tooth root. The multifunctional peptide conjugated non-viral gene delivery is a safe and effective approach for regenerative endodontics. STATEMENT OF SIGNIFICANCE: Pulp regeneration in a full-length tooth root canal has long been a challenge in regenerative endodontics. This is due to the unique root anatomy that allows the blood supply of the tooth root only from a small apical foramen (< 1 mm), leading to a severe barrier for revascularization during pulp regeneration. In this work, we designed a multifunctional peptide-conjugated, pH-sensitive, non-viral gene vector to address this challenge. Our work shows that the peptide-conjugated system was an excellent carrier for fast revascularization and pulp tissue regeneration in a full-length toot root. This study will interest the multidisciplinary readership in gene delivery, biomaterials, and dental/craniofacial tissue engineering community.

Lithium chloride promotes osteogenesis and suppresses apoptosis during orthodontic tooth movement in osteoporotic model via regulating autophagy.

Osteoporosis is a widely distributed disease that may cause complications such as accelerated tooth movement, bone resorption, and tooth loss during orthodontic treatment. Promoting bone formation and reducing bone resorption are strategies for controlling these complications. For several decades, the autophagy inducer lithium chloride (LiCl) has been explored for bipolar . In this study, we investigated the autophagy-promoting effect of LiCl on bone remodeling under osteoporotic conditions during tooth movement. Ovariectomy was used to induce osteoporosis status in vivo. The results showed that LiCl rejuvenated autophagy, decreased apoptosis, and promoted bone formation, thus protecting tooth movement in osteoporotic mice. Furthermore, in vitro experiments showed that LiCl reversed the effects of ovariectomy on bone marrow-derived mesenchymal stem cells (BMSCs) extracted from ovariectomized mice, promoting osteogenesis and suppressing apoptosis by positively regulating autophagy. These findings suggest that LiCl can significantly decrease adverse effects of osteoporosis on bone remodeling, and that it has great potential significance in the field of bone formation during tooth movement in osteoporosis patients.

Mechanosensitive Piezo1 in Periodontal Ligament Cells Promotes Alveolar Bone Remodeling During Orthodontic Tooth Movement.

Orthodontic tooth movement (OTM) is a process depending on the remodeling of periodontal tissues surrounding the roots. Orthodontic forces trigger the conversion of mechanical stimuli into intercellular chemical signals within periodontal ligament (PDL) cells, activating alveolar bone remodeling, and thereby, initiating OTM. Recently, the mechanosensitive ion channel Piezo1 has been found to play pivotal roles in the different types of human cells by transforming external physical stimuli into intercellular chemical signals. However, the function of Piezo1 during the mechanotransduction process of PDL cells has rarely been reported. Herein, we established a rat OTM model to study the potential role of Piezo1 during the mechanotransduction process of PDL cells and investigate its effects on the tension side of alveolar bone remodeling. A total of 60 male Sprague-Dawley rats were randomly assigned into three groups: the OTM + inhibitor (INH) group, the OTM group, and the control (CON) group. Nickel-titanium orthodontic springs were applied to trigger tooth movement. Mice were sacrificed on days 0, 3, 7, and 14 after orthodontic movement for the radiographic, histological, immunohistochemical, and molecular biological analyses. Our results revealed that the Piezo1 channel was activated by orthodontic force and mainly expressed in the PDL cells during the whole tooth movement period. The activation of the Piezo1 channel was essential for maintaining the rate of orthodontic tooth movement and facilitation of new alveolar bone formation on the tension side. Reduced osteogenesis-associated transcription factors such as Runt-related transcription factor 2 (RUNX2), Osterix (OSX), and receptor activator of nuclear factor-kappa B ligand (RANKL)/osteoprotegerin (OPG) ratio were examined when the function of Piezo1 was inhibited. In summary, Piezo1 plays a critical role in mediating both the osteogenesis and osteoclastic activities on the tension side during OTM.

Resveratrol represses tumor necrosis factor α/c-Jun N-terminal kinase signaling via autophagy in human dental pulp stem cells.

OBJECTIVES: To study the effects of polyphenol resveratrol on TNFα-induced inflammatory signaling as well as the underlying mechanism in human dental pulp stem cells (DPSCs). MATERIALS AND METHODS: Human DPSCs were cultured and treated by TNFα in the presence or absence of resveratrol. NF-κB and mitogen-activated protein kinase (MAPK) signaling pathways were analyzed by Western blotting and immunofluorescence staining. Interleukin 6 (IL6) and interleukin 8 (IL8) mRNA levels were analyzed by reverse transcription polymerase chain reaction. For the mechanistic study, autophagy was examined and further manipulated by gene silencing of Atg5 using siRNAs. Statistical analysis was performed by Student's t- test, and values of p < 0.05 were considered significant. RESULTS: Upon TNFα treatments, neither degradation of IκBα nor the phosphorylation and nuclear translocation of p65 NF-κB were inhibited by resveratrol at different concentrations. In contrast, resveratrol dramatically inhibited TNFα-induced phosphorylation of c-Jun N-terminal kinase (JNK) MAPK. Furthermore, resveratrol activated autophagy, as evidenced by the accumulated autophagic puncta formed by lipid bound LC3B in resveratrol-treated cells. Intriguingly, both resveratrol and JNK inhibitor SP600125 suppressed TNFα-induced IL6 and IL8 mRNA expression (P < 0.05). Silencing autophagy gene Atg5 led to the hyper-activation of JNK and augmented TNFα-induced IL6 and IL8 mRNA expression (P < 0.05). CONCLUSIONS: The results suggest that resveratrol suppresses TNFα-induced inflammatory cytokines expressed by DPSCs through regulating the inhibitory autophagy-JNK signaling cascade. Resveratrol might be beneficial to ameliorate pulpal damage during the acute phase of inflammation in vital pulp therapy.

Accuracy of virtual surgical planning in two-jaw orthognathic surgery: comparison of planned and actual results.

OBJECTIVE: This study aims to evaluate the accuracy of virtual surgical planning in two-jaw orthognathic surgery via quantitative comparison of preoperative planned and postoperative actual skull models. STUDY DESIGN: Thirty consecutive patients who required two-jaw orthognathic surgery were included. A composite skull model was reconstructed by using Digital Imaging and Communications in Medicine (DICOM) data from spiral computed tomography (CT) and STL (stereolithography) data from surface scanning of the dental arch. LeFort I osteotomy of the maxilla and bilateral sagittal split ramus osteotomy (of the mandible were simulated by using Dolphin Imaging 11.7 Premium (Dolphin Imaging and Management Solutions, Chatsworth, CA). Genioplasty was performed, if indicated. The virtual plan was then transferred to the operation room by using three-dimensional (3-D)-printed surgical templates. Linear and angular differences between virtually simulated and postoperative skull models were evaluated. RESULTS: The virtual surgical planning was successfully transferred to actual surgery with the help of 3-D-printed surgical templates. All patients were satisfied with the postoperative facial profile and occlusion. The overall mean linear difference was 0.81 mm (0.71 mm for the maxilla and 0.91 mm for the mandible); and the overall mean angular difference was 0.95 degrees. CONCLUSIONS: Virtual surgical planning and 3-D-printed surgical templates facilitated the diagnosis, treatment planning, and accurate repositioning of bony segments in two-jaw orthognathic surgery.