Autophagy regulates age-related delayed jawbone regeneration and decreased osteoblast osteogenesis by degrading FABP3.

The regenerative ability of limb bones after injury decreases during aging, but whether a similar phenomenon occurs in jawbones and whether autophagy plays a role in this process remain unclear. Through retrospective analysis of clinical data and studies on a mouse model of jawbone defects, we confirmed the presence of delayed or impaired bone regeneration in the jawbones of old individuals and mice. Subsequently, osteoblasts (OBs) derived from mouse jawbones were isolated, showing reduced osteogenesis in senescent osteoblasts (S-OBs). We observed a reduction in autophagy within both aged jawbones and S-OBs. Additionally, pharmacological inhibition of autophagy in normal OBs (N-OBs) led to cell aging and decreased osteogenesis, while autophagic activation reversed the aging phenotype of S-OBs. The activator rapamycin (RAPA) increased the autophagy level and bone regeneration in aged jawbones. Finally, we found that fatty acid-binding protein 3 (FABP3) was degraded by autolysosomes through its interaction with sequestosome 1 (P62/SQSTM1). Autophagy inhibition within senescent jawbones and S-OBs led to the excessive accumulation of FABP3, and FABP3 knockdown partially rescued the decreased osteogenesis in S-OBs and alleviated age-related compromised jawbone regeneration. In summary, we confirmed that autophagy inhibition plays an important role in delaying bone regeneration in aging jawbones. Autophagic activation or FABP3 knockdown can partially rescue the osteogenesis of S-OBs and the regeneration of aging jawbones, providing insight into jawbone aging.

Suppression of the NLRP3 Inflammasome through Activation of the Transient Receptor Potential Channel Melastatin 2 Promotes Osteogenesis in Tooth Extraction Sockets of Periodontitis.

This study explored the role of transient receptor potential channel melastatin 2 (TRPM2)-mediated activation of NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasome in osteogenesis during healing of tooth extraction sockets. Tooth extraction socket tissue samples were collected from patients with or without periodontitis. In a TRPM2 knockout mouse model of socket healing, mice with or without periodontitis and their wild-type littermates were used for comparing the socket healing phenotypes. Micro-computed tomography imaging, three-dimensional reconstruction of the sockets, and hematoxylin and eosin staining for histopathologic analysis were performed. Immunofluorescence, immunohistochemistry, and Western blot analysis were used for evaluation of protein expression; the mRNA levels were evaluated by quantitative RT-PCR. Osteogenic, chondrogenic, and adipogenic differentiation potential of human bone marrow mesenchymal stem cells (BMMSCs) was evaluated. Calcium deposition was evaluated using Alizarin Red S staining. NLRP3 and CASP1 were up-regulated in tooth sockets of periodontitis patients. NLRP3 knockdown promoted the osteogenic differentiation of maxillary BMMSCs under inflammatory conditions. TRPM2 was up-regulated in the tooth extraction socket tissue of periodontitis. Inhibiting TRPM2 expression mitigated the NLRP3 inflammasome and its deleterious effect on osteogenesis. Activation of the TRPM2 ion channel regulated osteogenesis of BMMSCs under inflammatory conditions via Ca2+ influx, the mitochondrial dynamics, and pyroptosis. Targeting the TRPM2/Ca2+/NLRP3 axis could be beneficial in the healing process of the tooth extraction sockets of patients with periodontitis.

Enhanced osteogenesis by addition of cancellous bone chips at xenogenic bone augmentation: In vitro and in vivo experiments.

OBJECTIVES: To investigate and compare the influence of deproteinized bovine bone mineral (DBBM) combined with autologous cortical (CorBC) or cancellous bone chips (CanBC) as bone grafts on guided bone regeneration (GBR) in vivo and in vitro. MATERIALS AND METHODS: Defects were created in the mandibular buccal alveolar ridges in dogs and randomly filled with 3 groups of bone grafts: DBBM, DBBM + CorBC, or DBBM + CanBC. Osteogenesis was evaluated by sequential fluorescent labeling and histological analysis. Moreover, rat bilateral calvaria defects were randomly grafted with DBBM, DBBM + CorBC, or DBBM + CanBC. A blank group was included as control. Defect healing was assessed by histological staining, micro-CT, and quantitative polymerase chain reaction. In vitro migration, proliferation, and osteogenic differentiation assays were performed by stimulating rat bone marrow mesenchymal stem cells (rBMSCs) with cortical (CorBCM) or cancellous bone conditioned medium (CanBCM) to unveil the cellular mechanism. RESULTS: In the canine model, the augmented sites of DBBM + CanBC exhibited higher mineralized tissue proportion than the other two groups (DBBM: 0.61 ± 0.03 versus DBBM + CorBC: 0.69 ± 0.07 versus DBBM + CanBC: 0.86 ± 0.06; p < .05). In the rat model, the BV/TV value of DBBM + CanBC (0.51 ± 0.01) was higher than those of DBBM + CorBC (0.41 ± 0.02), DBBM (0.31 ± 0.01), and Control (0.10 ± 0.01; p < .01). Further radiological, histological and transcriptional results showed similar trends. In vitro experiments revealed that CorBCM and especially CanBCM could enhance rBMSCs migration, proliferation, and osteogenic differentiation. CONCLUSION: In vivo and in vitro experiments verified favorable synergistic effect of mixing autologous bone chips with DBBM on osteogenesis. Furthermore, CanBC presented more powerful osteogenic effect than CorBC.

LAMA5-inspired adhesive dodecapeptide facilitates efficient dentine regeneration: An in vitro and in vivo study.

AIM: The primary goal of this study was to investigate the potential effects of A5G81 in inducing reparative dentine (RD) formation both in vitro and in vivo. METHODOLOGY: Cell adhesion was observed by crystal violet staining and quantified by Sodium Dodecyl Sulphate (SDS) extraction. Cell proliferation was investigated using Cell Counting Kit-8 (CCK-8) assay. Spreading of cytoskeleton was visualized using immunofluorescence staining. Protein expression level of Akt signalling pathway was compared in a human Akt pathway phosphorylation array. Genes that were up or downregulated by A5G81 were identified by RNA sequencing. The mRNA expression of odontoblastic markers was detected by quantitative real-time polymerase chain reaction (qPCR). Moreover, mineralization of human dental pulp cells (hDPCs) was visualized by alizarin red staining and quantified using cetylpyridinium chloride (CPC). A direct pulp-capping model was established in SD rats and the RD formation at 2 weeks after operation was observed using HE staining. RESULTS: A5G81 (optimal coating concentration: 0.5 mg/mL) promoted hDPCs adhesion and proliferation to a level that was similar to Type I collagen (COL-1). Meanwhile, A5G81 activated Akt signalling pathway, albeit to a lesser extent than COL-1. An inhibition test indicated that A5G81 induced hDPCs adhesion by activating PI3K pathway. A5G81 induced the expression of ECM remodelling genes and odontoblastic genes, which were demonstrated by RNA-seq and qPCR, respectively. In addition, A5G81 efficiently accelerated the mineralization of hDPCs in both immobilized and soluble forms, a property that makes it more applicable in dental clinic. Finally, the pulp-capping study in rats suggested that use of A5G81 could successfully induce the formation of RD within 2 weeks. CONCLUSION: Coating of A5G81 to non-tissue culture-treated polystyrene facilitates spreading, proliferation and differentiation of hDPCs, resulting in rapid RD formation in artificially exposed pulp.

Triggering receptor expressed on myeloid cells-2 stimulates osteoclast differentiation and bone loss in periodontitis.

OBJECTIVE: To investigate the expression of triggering receptor expressed on myeloid cells 2 (TREM-2) in the healthy and diseased tissue, including gingivitis or periodontitis, and then to assess whether it has an impact on the development of periodontitis. METHODS AND MATERIALS: The gingival tissues from healthy controls, gingivitis, and periodontitis underwent hematoxylin-eosin and immunohistochemical staining, and the association of TREM-2 expression or TREM-2+ cell counts with clinical parameters was assessed. An anti-TREM-2 antibody was used to block the osteoclastogenesis in vitro and during the experimental periodontitis by injection into the gingiva. The relative gene expression of TREM-2 in different gingival tissues was analyzed by quantitative PCR. RESULTS: In the gingival tissues of periodontitis, TREM-2 expression and TREM-2+ cell counts were significantly higher than those of gingivitis and healthy controls (p<0.05). In the group of periodontitis showing moderate signs, the gingival tissues displayed significantly lower TREM-2 expression, in contrast with the group with advanced periodontal symptoms (p < 0.05). Consistently, blocking TREM-2 significantly decreased osteoclast formation both in vitro and in vivo (p < 0.05). CONCLUSION: Increased TREM-2 expression and TREM-2+ cells were positively associated with the development of periodontitis. Osteoclast differentiation and stimulating alveolar bone loss were partly relied on TREM-2, which could be a target to be blocked for attenuating osteoclastogenesis in periodontitits.

Heterogeneity of fibroblasts from radicular cyst influenced osteoclastogenesis and bone destruction.

AIM: To analyze the heterogeneity of fibroblasts isolated from the fibrous capsules of radicular cysts and explore the effects of fibroblast subsets on bone destruction. METHODOLOGY: Radicular cysts were divided into groups according to varying perilesional sclerosis identified by radiograph. Colony-forming units (CFUs) were isolated from the fibrous capsules of cysts, by which Trap + MNCs were induced, and the expression of osteoclastogenesis-related genes was compared among groups by real-time PCR. The variances in gene profiles of CFUs were identified by principal component analysis, and then, CFUs were divided into subsets using cluster analysis. The induction of Trap + MNCs and related gene expression was compared among subsets, and osteoclastogenic induction was blocked by IST-9 or bevacizumab. The fibroblast subsets in cysts were investigated by retrospective immunostaining with IST-9, VEGF-A, and CD34. A fibroblast subset that underwent gene editing by CRISPR/Cas was injected into the site of bone defects in animal models, and the in vivo effects on osteoclastogenesis were investigated. RESULTS: The fibroblast CFUs isolated from radicular cysts with perilesional unsclerotized cysts induced more Trap + MNCs than those with perilesional sclerotic cysts (p < .05). Most fibroblast CFUs from unsclerotized cysts belonged to Cluster 2, which induced more Trap + MNCs (p < .05) and highly expressed genes facilitating osteoclastogenesis; these results were different from those of Cluster 1 (p < .05), in which most CFUs were isolated from perilesional sclerotic cysts or controls (p < .05). The high expression of EDA + FN and VEGF-A was investigated in both the fibroblasts of Cluster 2 and the fibrous capsules of unsclerotized cysts (p < .05), and the number of Trap + MNCs induced by Cluster 2 was decreased by treatment with IST-9 and bevacizumab (p < .05). Consistently, EDA exon exclusion significantly decreased the osteoclastogenic induction of fibroblasts from Cluster 2 in vivo (p < .05). CONCLUSION: The fibrous capsules of radicular cysts contain heterogeneous fibroblasts that can form subsets exhibiting different effects on osteoclastogenesis. The subset, which depending on the autocrine effects of EDA + FN on VEGF-A, mainly contributes to the osteoclastogenesis and bone destruction of radicular cysts. The regulation of the proportion of subsets is a possible strategy for artificially interfering with osteoclastogenesis.

Bevacizumab or fibronectin gene editing inhibits the osteoclastogenic effects of fibroblasts derived from human radicular cysts.

Fibronectin (FN) is a main component of extracellular matrix (ECM) in most adult tissues. Under pathological conditions, particularly inflammation, wound healing and tumors, an alternatively spliced exon extra domain A (EDA) is included in the FN protein (EDA+FN), which facilitates cellular proliferation, motility, and aggressiveness in different lesions. In this study we investigated the effects of EDA+FN on bone destruction in human radicular cysts and explored the possibility of editing FN gene or blocking the related paracrine signaling pathway to inhibit the osteoclastogenesis. The specimens of radicular cysts were obtained from 20 patients. We showed that the vessel density was positively associated with both the lesion size (R = 0.49, P = 0.001) and EDA+FN staining (R = 0.26, P = 0.022) in the specimens. We isolated fibroblasts from surgical specimens, and used the CRISPR/Cas system to knockout the EDA exon, or used IST-9 antibody and bevacizumab to block EDA+FN and VEGF, respectively. Compared to control fibroblasts, the fibroblasts from radicular cysts exhibited significantly more Trap+MNCs, the relative expression level of VEGF was positively associated with both the ratio of EDA+FN/total FN (R = 0.271, P = 0.019) and with the number of Trap+MNCs (R = 0.331, P = 0.008). The knockout of the EDA exon significantly decreased VEGF expression in the fibroblasts derived from radicular cysts, leading to significantly decreased osteoclastogenesis; similar results were observed using bevacizumab to block VEGF, but block of EDA+FN with IST-9 antibody had no effect. Furthermore, the inhibitory effects of gene editing on Trap+MNC development were restored by exogenous VEGF. These results suggest that EDA+FN facilitates osteoclastogenesis in the fibrous capsule of radicular cysts, through a mechanism mediated by VEGF via an autocrine effect on the fibroblasts. Bevacizumab inhibits osteoclastogenesis in radicular cysts as effectively as the exclusion of the EDA exon by gene editing.

The fibroblast of radicular cyst facilitate osteoclastogenesis via the autocrine of Fibronectin containing extra domain A.

OBJECTIVE: To investigate the alternative spliced isoforms of Fibronectin (FN) in the stroma of radicular cysts and analyze the associations between these isoforms and the osteoclastogenic effects of fibroblasts. METHODS AND MATERIALS: The specimens of radicular cysts were stained with immunohistochemistry, and the associations between each FN isoform and clinical parameters were assessed. The fibroblasts isolated from cysts or jaw bone were cultured to induce the Trap + MNCs. In the conditioned medium, the Fibronectin containing extra domain A (EDA + FN) was neutralized by antibody IST-9, and the EDA exon of fibroblasts was knockout by CRISPR/Cas system, for assessing the osteoclastogenic effects. The mRNA level of FN isoforms and the osteoclastogenesis-related genes were analyzed by quantitive PCR. RESULTS: EDA + FN staining was positively associated with the size of the lesions (p < 0.05). In contrast with the controls, the ratio of EDA + FN/total FN in the fibroblasts from radicular cysts was significantly higher (p < 0.05), and positively associate with Trap + MNCs counting, it was consistent with increased expression of COX-2, IL-6, IL-17, and the RANKL/OPG (p < 0.05). The Trap + MNCs counting and osteoclastogenesis-related genes were decreased by IST-9 blocking and EDA exon knockout in fibroblasts, but the blockage of the interaction between EDA + FN and pre-osteoclasts exhibited little effects on Trap + MNCs formation. CONCLUSION: The microenvironment of the fibrous capsule of radicular cysts facilitates the splicing of EDA exon, it endues EDA + FN with autocrine effects on fibroblast itself, and it increases the expression of osteoclastogenesis-related genes, by which the osteoclastogenesis in radicular cysts could be initiated.

The detection of Gper1 as an important gene promoting jawbone regeneration in the context of estrogen deficiency.

Numerous studies have demonstrated that estrogen deficiency inhibit the proliferation and differentiation of pre-osteoblasts in skeleton by affecting osteogenic signaling, lead to decreased bone mass and impaired regeneration. To explore the mechanisms maintaining bone regeneration under estrogen deficiency, we randomly selected 1102 clinical cases, in which female patients aged between 18 and 75 have underwent tooth extraction in Stomatological Hospital of Tongji University, there is little difference in the healing effect of extraction defects, suggesting that to some extent, the regeneration of jawbone is insensitive to the decreased estrogen level. To illuminate the mechanisms promoting jawbone regeneration under estrogen deficiency, a tooth extraction defect model was established in the maxilla of female rats who underwent ovariectomy (OVX) or sham surgery, and jawbone marrow stromal cells (BMSCs) were isolated for single-cell sequencing. Further quantitative PCR, RNA interference, alizarin red staining, immunohistochemistry and western blotting experiments demonstrated that in the context of ovariectomy, maxillary defects promoted G protein-coupled estrogen receptor 1 (Gper1) expression, stimulate downstream cAMP/PKA/pCREB signaling, and facilitate cell proliferation, and thus provided sufficient progenitors for osteogenesis and enhanced the regeneration capacity of the jawbone. Correspondingly, the heterozygous deletion of the Gper1 gene attenuated the phosphorylation of CREB, led to decreased cell proliferation, and impaired the restoration of maxillary defects. This study demonstrates the importance of Gper1 in maintaining jawbone regeneration, especially in the context of estrogen deficiency.

Paired-Related Homeobox 1-Positive Cells Are Needed for Osseointegration.

PURPOSE: To explore the contribution of paired-related homeobox 1-positive cells to the implant-induced osseointegration process in adult alveolar bone and the potential underlying mechanisms. MATERIALS AND METHODS: Cre recombinase-induced lineage tracing and cell ablation were conducted in a murine dental implant model. Scratch and transwell assays were used to assess MC3T3-E1 cell migration after paired-related homeobox 1 overexpression. Single-cell RNA sequencing were applied to identify potential genes involved in pairedrelated homeobox 1-positive cells-driven osteogenesis. RESULTS: Paired-related homeobox 1- positive cells were observed to accumulate in the peri-implant area in a time-dependent manner. The number of these cells were found to reach its maximum on day 14. Osseointegration in mice were noticeably impaired after ablation of paired-related homeobox 1-positive cells. Further, it was discovered that paired-related homeobox 1 promotes MC3T3- E1 cell migration, a process which is indispensable for sound healing of peri-implant tissue. Finally, Semaphorin 3C was detected exclusively and abundantly expressed by paired-related homeobox 1-positive cells. Knockdown of semaphorin 3C in paired-related homeobox 1- positive cells significantly weakened their osteogenic potential. CONCLUSION: Our data suggest that paired-related homeobox 1-positive cells contribute to the osseointegration process under stress stimulation and semaphorin 3C may play a critical role in paired-related homeobox 1- positive cell-driven osteogenesis. Paired-related homeobox 1 could significantly promote MC3T3-E1 cell migration.

Leptin receptor (+) stromal cells respond to periodontitis and attenuate alveolar bone repair via CCRL2-mediated Wnt inhibition.

The impaired bone healing in tooth extraction sockets due to periodontitis presents a major obstacle to restoring oral health. The mechanisms regulating the osteogenic capacity of jawbone-derived stromal cells in the periodontitis microenvironment remain elusive. Leptin receptor (LepR) expressing stromal cells, which largely overlap with Cxcl12-abundant reticular (CAR) cells in bone tissue, rapidly proliferate and differentiate into bone-forming cells during extraction socket healing to support alveolar bone repair. In this study, we identify that CCRL2 is significantly expressed and inhibits osteogenesis in LepR+/CAR cells of alveolar bones with periodontitis. The Ccrl2-KO mice exhibit significant improvements in bone healing in extraction sockets with periodontitis. Specifically, the binding of CCRL2 to SFRP1 on the surface of LepR+/CAR cells can amplify the suppressive effect of SFRP1 on Wnt signaling under inflammation, thus hindering the osteogenic differentiation of LepR+/CAR cells and resulting in poor bone healing in extraction sockets with periodontitis. Together, we clarify that the CCRL2 receptor of LepR+/CAR cells can respond to periodontitis and crosstalk with Wnt signaling to deteriorate extraction socket healing.

The impaired bone healing in tooth extraction sockets due to periodontitis presents a major obstacle to restoring oral health. Alterations in the cellular activity of LepR+/CAR cells, an essential stromal cell population for extraction socket healing, in the periodontitis microenvironment have yet to be determined. In this study, we identify that CCRL2, as a potent agent of inflammation-bone crosstalk, is significantly expressed and inhibits osteogenesis in LepR+/CAR cells of alveolar bones with periodontitis. Specifically, the binding of CCRL2 to SFRP1 on the surface of LepR+/CAR cells can amplify the suppressive effect of SFRP1 on the Wnt/ß-catenin signaling under inflammation, thus hindering the osteogenic differentiation of LepR+/CAR cells and resulting in poor bone healing in tooth extraction sockets with periodontitis.

Effects of Implant Diameter on Implant Stability and Osseointegration in the Early Stage in a Dog Model.

Purpose: To determine the optimal implant diameter under limited bone width by comparing the effects of implants with different diameters on implant stability, peri-implant bone stability, and osseointegration. In addition, to evaluate the reliability of resonance frequency analysis (RFA) in detecting osseointegration and marginal bone level (MBL). Materials and Methods: Mandibular premolars and first molars of seven beagle dogs were extracted. After 8 weeks, their mandibular models and radiographic information were collected to fabricate implant templates. Implant sites were randomly divided into three groups according to diameter: Ø3.3, Ø4.1, and Ø4.8 mm. Implant stability quotient (ISQ) measurement and radiographic evaluation were performed after surgery (baseline) and at 4, 8, and 12 weeks. Three dogs were euthanized at 4 weeks to observe osteogenesis and implant-tissue interface biology. Four dogs were euthanized at 12 weeks to observe osseointegration. Hard tissue sections were prepared to analyze osteogenesis (fluorescence double labeling) and osseointegration (methylene blue-acid fuchsin staining). Results: At baseline and at 4, 8, and 12 weeks, the ISQ values of Ø4.1- and Ø4.8-mm implants did not differ (P > .05), but both had higher values than the Ø3.3-mm implants (P < .05). The mean marginal bone resorption (MBR) associated with Ø3.3-, Ø4.1-, and Ø4.8-mm implants was 0.65 ± 0.58 mm, 0.37 ± 0.28 mm, and 0.73 ± 0.37 mm, respectively. The buccal MBR of Ø4.8-mm implants was significantly higher than that of Ø4.1-mm implants (P < .05). The bone-to-implant contact (BIC) percentage at 12 weeks did not differ for any group (P > .05). The correlation coefficients between the ISQ and MBL of the Ø3.3-, Ø4.1-, and Ø4.8-mm implants were -0.84 (P < .01), -0.90 (P < .001), and -0.93 (P < .001), respectively, while that between the ISQ and BIC was 0.15 (P > .05). Conclusions: During the early healing stage, the performance of Ø4.1- and Ø4.8-mm implants in terms of implant stability was better than that of Ø3.3-mm implants. Implant diameter may not influence BIC percentage. RFA can be used to evaluate implant stability and MBL but is not suitable to assess the degree of osseointegration.

Interactions of Fibroblast Subtypes Influence Osteoclastogenesis and Alveolar Bone Destruction in Periodontitis.

Background: To analyze the fibroblasts subtypes in the gingival tissues of healthy controls, gingivitis and periodontitis patients, as well as the effects of interaction between subtypes on alveolar bone destruction. Methods: Gingival tissues were divided into three groups according to clinical and radiographic examination, and the immunostaining of EDA+FN was assessed. Fibroblasts from gingiva developed colony formation units (CFUs) and induced Trap+MNCs. The expression of osteoclastogenesis-related genes was assessed by real-time PCR. Variances in the gene profiles of CFUs were identified by principal component analysis, and cluster analysis divided CFUs into subtypes. The induction of Trap+MNCs and gene expression were compared among individual or cocultured subtypes. The fibroblast subtypes exerted critical effect on Trap+MNCs formation were selected and edited by CRISPR/Cas to investigate the influence on osteoclastogenesis in the periodontitis in mice. Results: Most periodontitis samples exhibited intensive EDA+FN staining (P < 0.05), and these fibroblasts also induced most Trap+MNCs among three groups; consistently, fibroblasts from periodontitis highly expressed genes facilitating osteoclastogenesis. According to gene profiles and osteoclastogenic induction, four clusters of CFUs were identified. The proportion of clusters was significantly different (P < 0.05) among three groups, and their interaction influenced osteoclastogenic induction. Although Cluster 4 induced less osteoclasts, it enhanced the effects of Clusters 1 and 3 on Trap+MNCs formation (P < 0.05). EDA knockout in Cluster 4 abrogated this promotion (P < 0.05), and decreased osteoclasts and alveolar bone destruction in experimental periodontitis (P < 0.05). Conclusion: Heterogeneous fibroblast subtypes affect the switch or development of periodontitis. A subtype (Cluster 4) played important role during alveolar bone destruction, by regulating other subtypes via EDA+FN paracrine.

Application of piezoelectric materials in the field of bone: a bibliometric analysis.

In the past 4 decades, many articles have reported on the effects of the piezoelectric effect on bone formation and the research progress of piezoelectric biomaterials in orthopedics. The purpose of this study is to comprehensively evaluate all existing research and latest developments in the field of bone piezoelectricity, and to explore potential research directions in this area. To assess the overall trend in this field over the past 40 years, this study comprehensively collected literature reviews in this field using a literature retrieval program, applied bibliometric methods and visual analysis using CiteSpace and R language, and identified and investigated publications based on publication year (1984-2022), type of literature, language, country, institution, author, journal, keywords, and citation counts. The results show that the most productive countries in this field are China, the United States, and Italy. The journal with the most publications in the field of bone piezoelectricity is the International Journal of Oral & Maxillofacial Implants, followed by Implant Dentistry. The most productive authors are Lanceros-Méndez S, followed by Sohn D.S. Further research on the results obtained leads to the conclusion that the research direction of this field mainly includes piezoelectric surgery, piezoelectric bone tissue engineering scaffold, manufacturing artificial cochleae for hearing loss patients, among which the piezoelectric bone tissue engineering scaffold is the main research direction in this field. The piezoelectric materials involved in this direction mainly include polyhydroxybutyrate valerate, PVDF, and BaTiO3.

A novel lineage of osteoprogenitor cells with dual epithelial and mesenchymal properties govern maxillofacial bone homeostasis and regeneration after MSFL.

Bone regeneration originates from proliferation and differentiation of osteoprogenitors via either endochondral or intramembranous ossification; and the regeneration capacities decline with age and estrogen loss. Maxillary sinus floor lifting (MSFL) is a commonly used surgical procedure for guiding bone regeneration in maxilla. Radiographic analysis of 1210 clinical cases of maxilla bone regeneration after MSFL revealed that the intrasinus osteogenic efficacy was independent of age and gender, however; and this might be related to the Schneiderian membrane that lines the sinus cavity. In view of the particularity of this biological process, our present study aimed to elucidate the underlying mechanism of MSFL-induced bone regeneration. We first established a murine model to simulate the clinical MSFL. By single-cell RNA-sequencing and flow cytometry-based bulk RNA-sequencing, we identified a novel Krt14+Ctsk+ subset of cells that display both epithelial and mesenchymal properties and the transcriptomic feature of osteoprogenitors. Dual recombinases-mediated lineage tracing and loss-of-function analyses showed that these Krt14+Ctsk+ progenitors contribute to both MSFL-induced osteogenesis and physiological bone homeostasis by differentiating into Krt14-Ctsk+ descendants which show robust osteogenic capacity. In addition, we detected a similar population of Krt14+Ctsk+ cells in human samples of Schneiderian membrane, which show a highly similar osteogenic potential and transcriptomic feature to the corresponding cells in mice. The identification of this Krt14+Ctsk+ population, featured by osteoprogenitor characteristics and dual epithelial-mesenchymal properties, provides new insight into the understanding of bone regeneration and may open more possibilities for clinical applications.

Amorphous Precursor-Mediated Calcium Phosphate Coatings with Tunable Microstructures for Customized Bone Implants.

Calcium phosphate (CaP) is frequently used as coating for bone implants to promote osseointegration. However, commercial CaP coatings via plasma spraying display similar microstructures, and thus fail to provide specific implants according to different surgical conditions or skeletal bone sites. Herein, inspired by the formation of natural biominerals with various morphologies mediated by amorphous precursors, CaP coatings with tunable microstructures mediated by an amorphous metastable phase are fabricated. The microstructures of the coatings are precisely controlled by both polyaspartic acid and Mg2+ . The cell biological behaviors, including alkaline phosphatase activity, mineralization, and osteogenesis-related genes expression, on the CaP coatings with different microstructures, exhibit significant differences. Furthermore, in vivo experiments demonstrate the osseointegration in different types of rats and bones indeed favors different CaP coatings. This biomimetic strategy can be used to fabricate customized bone implants that can meet the specific requirements of various surgery conditions.

Macrophage M1/M2 polarization dynamically adapts to changes in microenvironment and modulates alveolar bone remodeling after dental implantation.

As one of the first arriving immune cells after dental implantation, Mϕs own the abilities to polarize into to a spectrum of diverse phenotypes, from "classically activated" M1 Mϕs to "alternatively activated" M2 Mϕs. Herein, it was hypothesized that Mϕ phenotypes dynamically adapt after dental implantation, and the changes ensue a cascade of coordinated interplay with the bone-forming osteoblast and the bone-resorbing osteoclast. Results showed that the remodelling process after dental implantation was similar with the standard response to tissue injury (exampled by tooth extraction models), only with the delay of bone regeneration phases. Additionally, Mϕ activation in both groups underwent a transition from M1 Mϕs dominated to M2-type dominated stage, but the persistence of M1 Mϕs occurred in rat model of dental implantation. Further research in vitro showed that M1 Mϕs are involved in osteoclast activities via secreting the highest levels of TNF-α and IL-1ß, as well as being the potential precursor of osteoclasts. Besides, they also recruited BMSCs by secreting the highest levels of chemoattractants, CCL2 and VEGF. M2 Mϕs accelerated osteogenesis in the subsequent stage via their capability to secrete osteogenesis-related proteins, BMP-2 and TGF-ß1. However, the osteogenic differentiation of BMSCs was inhibited when cultured in a high concentration of conditioned media from each Mϕ phenotype, meaning that the immune strategies should be controlled within the proper ranges. These results suggest that coordinated efforts by both M1 and M2 Mϕs for bone remodelling, which may highlight an optimization strategy for tissue engineering implants.

Trem2 mediated Syk-dependent ROS amplification is essential for osteoclastogenesis in periodontitis microenvironment.

Periodontitis is the sixth most prevalent diseases around the globe, which is closely related to many systemic diseases and affects general health. As the leading cause of tooth loss, periodontitis is characterized by irreversible alveolar bone loss and activated osteoclastogenic process, which might be closely related to the activated intracellular reactive oxygen species (ROS) in osteoclasts. Here, we demonstrated triggering receptor expressed on myeloid cells 2 (Trem2) as a key regulator of osteoclastogenesis with the regulation of intracellular ROS signals in periodontitis. In the present study, the expression of Trem2 was significantly upregulated in human alveolar bones diagnosed with chronic periodontitis, as assessed by RNA-seq. In the mice model of periodontitis, the alveolar bone resorption was impeded in the presence of the conditional knockout of Trem2 in osteoclasts. Furthermore, we identified Trem2/DAP12/Syk-dependent cascade as a vital intracellular signaling for the amplification of reactive oxygen species (ROS) signals in osteoclastogenesis, while the accumulation of soluble Aß42 oligomers (Aßo) in periodontitis microenvironment further strengthened the signals and enhanced osteoclastogenesis through direct interactions with Trem2. Collectively, Trem2 mediated ROS signal amplification cascade was crucial in the process of osteoclastogenesis in periodontitis, suggesting the potential of Trem2 as a target for the prevention and treatment of bone destruction in periodontitis.

Titanium alloy cannulated screws and biodegradable magnesium alloy bionic cannulated screws for treatment of femoral neck fractures: a finite element analysis.

BACKGROUND: Cannulated screws (CS) are one of the most widely used treatments for femoral neck fracture, however, associated with high rate of complications. In this study, we designed a new type of cannulated screws called degradable magnesium alloy bionic cannulated screws (DMBCS) and our aim was to compare the biomechanical properties of DMBCS, the traditionally used titanium alloy bionic cannulated screws (TBCS) and titanium alloy cannulated screws (TTCS). METHODS: A proximal femur model was established based on CT data of a lower extremity from a voluntary healthy man. Garden type III femoral neck fracture was constructed and fixed with DMBCS, TBCS, and TTCS, respectively. Biomechanical effect which three type of CS models have on femoral neck fracture was evaluated and compared using von Mises stress distribution and displacement. RESULTS: In the normal model, the maximum stress value of cortical bone and cancellous bone was 76.18 and 6.82 MPa, and the maximum displacement was 5.52 mm. Under 3 different fracture healing status, the stress peak value of the cortical bone and cancellous bone in the DMBCS fixation model was lower than that in the TTCS and TBCS fixation, while the maximum displacement of DMBCS fixation model was slightly higher than that of TTCS and TBCS fixation models. As the fracture heals, stress peak value of the screws and cortical bone of intact models are decreasing, while stress peak value of cancellous bone is increasing initially and then decreasing. CONCLUSIONS: The DMBCS exhibits the superior biomechanical performance than TTCS and TBCS, whose fixation model is closest to the normal model in stress distribution. DMBCS is expected to reduce the rates of post-operative complications with traditional internal fixation and provide practical guidance for the structural design of CS for clinical applications.

Enhancing the Osteogenic Differentiation and Rapid Osseointegration of 3D Printed Ti6Al4V Implants via Nano-Topographic Modification.

Personalized precision therapy and rapid osseointegration are the main development directions of dental implants. Three-dimensional (3D) printing is the most promising method to fabricate personalized implants with complex design and structure. Rapid osseointegration guarantees the survival of implants especially at early implant time, and the surface modification via nano-technology is considered as the most effective method to promote osseointegration. Herein, the Ti6Al4V implants were fabricated by 3D-printing method then the nano-topographic surface was constructed on them to improve the biological responses. The results showed that the nano-topographic modification favored the adhesion and osteogenic differentiation of bone marrow derived mesenchymal stromal cells (BMSCs), accelerating the rapid osseointegration in vivo in rat condyle of femur model. It is reasonable to predict that 3D-printed implants with nano-topographic surface modification have a promising future in orthopedic applications.