[Research Progress in the Regulatory Role of circRNA-miRNA Network in Bone Remodeling]. / circRNA-miRNAç½‘ç»œè°ƒæŽ§éª¨é‡å¡‘çš„ç ”ç©¶è¿›å±•.

The dynamic balance between bone formation and bone resorption is a critical process of bone remodeling. The imbalance of bone formation and bone resorption is closely associated with the occurrence and development of various bone-related diseases. Under both physiological and pathological conditions, non-coding RNAs (ncRNAs) play a crucial regulatory role in protein expression through either inhibiting mRNAs translation or promoting mRNAs degradation. Circular RNAs (circRNAs) are a type of non-linear ncRNAs that can resist the degradation of RNA exonucleases. There is accumulating evidence suggesting that circRNAs and microRNAs (miRNAs) serve as critical regulators of bone remodeling through their direct or indirect regulation of the expression of osteogenesis-related genes. Additionally, recent studies have revealed the involvement of the circRNAs-miRNAs regulatory network in the process by which mesenchymal stem cells (MSCs) differentiate towards the osteoblasts (OB) lineage and the process by which bone marrow-derived macrophages (BMDM) differentiate towards osteoclasts (OC). The circRNA-miRNA network plays an important regulatory role in the osteoblastic-osteoclastic balance of bone remodeling. Therefore, a thorough understanding of the circRNA-miRNA regulatory mechanisms will contribute to a better understanding of the regulatory mechanisms of the balance between osteoblastic and osteoclastic activities in the process of bone remodeling and the diagnosis and treatment of related diseases. Herein, we reviewed the functions of circRNA and microRNA. We also reviewed their roles in and the mechanisms of the circRNA-miRNA regulatory network in the process of bone remodeling. This review provides references and ideas for further research on the regulation of bone remodeling and the prevention and treatment of bone-related diseases.

Assessment of Biochemical Bone Turnover Markers in Polish Healthy Children and Adolescents.

BACKGROUND: Assessing bone turnover in paediatric populations is crucial for understanding the physiological changes occurring during skeletal development and identifying potential abnormalities. The objective of this study was to assess osteocalcin (OC), bone alkaline phosphatase (BALP), and C-terminal telopeptide of type I collagen (CTX-I) levels reflecting bone formation and resorption for age and sex in Polish healthy children and adolescents. MATERIALS AND METHODS: A total of 355 healthy normal-weight children and adolescents (46.5% girls) aged 1-18 years old were recruited. Total body less head (TBLH) and spine L1-L4 were used in children to assess bone mineral density (BMD) by dual-energy X-ray absorptiometry (DXA). Bone marker concentrations were determined by immunoenzymatic methods. RESULTS: Bone marker levels in girls and boys started with higher values in the first year of life and subsequently decreased until reaching a nadir during the prepubertal period. The pubertal peak values of bone markers were reached at 11-13 years old in boys and at 9-11 years old in girls. After puberty, the adolescents showed a gradual decline in bone marker concentrations to the values observed in adults. We found positive correlations between OC level and TBLH-BMD (r = 0.329, p = 0.002), TBLH-BMD Z-score (r = 0.245, p = 0.023), and L1-L4 BMD (r = 0.280, p = 0.009) in the prepubertal group. CONCLUSIONS: We showed serum levels of bone turnover markers-BALP, OC, and CTX-I-in relation to age and sex in healthy Polish children and adolescents. The age intervals of these markers for girls and boys aged 1-18 years old may be clinically useful in the assessment of bone metabolism in individuals with skeletal disorders.

The role of neuropilin in bone/cartilage diseases.

Bone remodeling is the balance between osteoblasts and osteoclasts. Bone diseases such as osteoporosis and osteoarthritis are associated with imbalanced bone remodeling. Skeletal injury leads to limited motor function and pain. Neurophilin was initially identified in axons, and its various ligands and roles in bone remodeling, angiogenesis, neuropathic pain and immune regulation were later discovered. Neurophilin promotes osteoblast mineralization and inhibits osteoclast differentiation and its function. Neuropolin-1 provides channels for immune cell chemotaxis and cytokine diffusion and leads to pain. Neuropolin-1 regulates the proportion of T helper type 17 (Th17) and regulatory T cells (Treg cells), and affects bone immunity. Vascular endothelial growth factors (VEGF) combine with neuropilin and promote angiogenesis. Class 3 semaphorins (Sema3a) compete with VEGF to bind neuropilin, which reduces angiogenesis and rejects sympathetic nerves. This review elaborates on the structure and general physiological functions of neuropilin and summarizes the role of neuropilin and its ligands in bone and cartilage diseases. Finally, treatment strategies and future research directions based on neuropilin are proposed.

Subchondral osteoclasts and osteoarthritis: new insights and potential therapeutic avenues.

Osteoarthritis (OA) is the most common joint disease, and good therapeutic results are often difficult to obtain due to its complex pathogenesis and diverse causative factors. After decades of research and exploration of OA, it has been progressively found that subchondral bone is essential for its pathogenesis, and pathological changes in subchondral bone can be observed even before cartilage lesions develop. Osteoclasts, the main cells regulating bone resorption, play a crucial role in the pathogenesis of subchondral bone. Subchondral osteoclasts regulate the homeostasis of subchondral bone through the secretion of degradative enzymes, immunomodulation, and cell signaling pathways. In OA, osteoclasts are overactivated by autophagy, ncRNAs, and Rankl/Rank/OPG signaling pathways. Excessive bone resorption disrupts the balance of bone remodeling, leading to increased subchondral bone loss, decreased bone mineral density and consequent structural damage to articular cartilage and joint pain. With increased understanding of bone biology and targeted therapies, researchers have found that the activity and function of subchondral osteoclasts are affected by multiple pathways. In this review, we summarize the roles and mechanisms of subchondral osteoclasts in OA, enumerate the latest advances in subchondral osteoclast-targeted therapy for OA, and look forward to the future trends of subchondral osteoclast-targeted therapies in clinical applications to fill the gaps in the current knowledge of OA treatment and to develop new therapeutic strategies.

Proteomics study of bone tissue around ameloblastoma and the potential mechanism of CD36 in bone remodelling.

Ameloblastoma (AM) is characterised by local aggressiveness and bone resorption. To our knowledge, the proteomic profile of bone adjacent to AM has not previously been explored. We therefore looked at the differential proteins in cancellous bone (CB) adjacent to AM and normal CB from the mandible. CB proteins were extracted, purified, quantified, and analysed by liquid chromatography-mass spectrometry (LC-MS) using samples from five patients with AM. These proteins were further investigated using gene ontology for additional functional annotation and enrichment. Proteins that met the screening requirements of expression difference ploidy > 1.5-fold (upregulation and downregulation) and p < 0.05 were subsequently deemed differential proteins. Immunohistochemical staining was performed to confirm the above findings. Compared with normal mandibular CB, 151 differential proteins were identified in CB adjacent to the mandibular AM. These were mainly linked to cellular catabolic processes, lipid metabolism, and fatty acids (FA) metabolism. LC-MS and immunohistochemistry showed that CD36 was one of the notably decreased proteins in CB bordering the AM compared with normal mandibular CB (p = 0.0066 and p = 0.0095, respectively). CD36 expression in CB correlates with bone remodelling in AM, making CD36 a viable target for therapeutic approaches.

Mechanobiochemical bone remodelling around an uncemented acetabular component: influence of bone orthotropy.

Mechanical loosening of an implant is often caused by bone resorption, owing to stress/strain shielding. Adaptive bone remodelling elucidates the response of bone tissue to alterations in mechanical and biochemical environments. This study aims to propose a novel framework of bone remodelling based on the combined effects of bone orthotropy and mechanobiochemical stimulus. The proposed remodelling framework was employed in the finite element model of an implanted hemipelvis to predict evolutionary changes in bone density and associated orthotropic bone material properties. In order to account for variations in load transfer during common daily activities, several musculoskeletal loading conditions of hip joint corresponding to sitting down/up, stairs ascend/descend and normal walking were considered. The bone remodelling predictions were compared with those of isotropic strain energy density (SED)-based, isotropic mechanobiochemical and orthotropic strain-based bone remodelling formulations. Although similar trends of bone resorption were predicted by orthotropic mechanobiochemical (MBC) and orthotropic strain-based models across implanted acetabulum, more volume (10-20%) of bone elements was subjected to bone resorption for the orthotropic MBC model. Higher bone resorption (75-85%) was predicted by the orthotropic strain-based and orthotropic MBC models compared to the isotropic MBC and SED-based models. Higher bone apposition (35-160%) across the implanted acetabulum was predicted by the isotropic MBC model, compared to the SED-based model. The remodelling predictions indicated that a reduction in estrogen level might lead to an increase in bone resorption. The study highlighted the importance of including mechanobiochemical stimulus and bone anisotropy to predict bone remodelling adequately.

Aging impairs the osteocytic regulation of collagen integrity and bone quality.

Poor bone quality is a major factor in skeletal fragility in elderly individuals. The molecular mechanisms that establish and maintain bone quality, independent of bone mass, are unknown but are thought to be primarily determined by osteocytes. We hypothesize that the age-related decline in bone quality results from the suppression of osteocyte perilacunar/canalicular remodeling (PLR), which maintains bone material properties. We examined bones from young and aged mice with osteocyte-intrinsic repression of TGFß signaling (TßRIIocy-/-) that suppresses PLR. The control aged bone displayed decreased TGFß signaling and PLR, but aging did not worsen the existing PLR suppression in male TßRIIocy-/- bone. This relationship impacted the behavior of collagen material at the nanoscale and tissue scale in macromechanical tests. The effects of age on bone mass, density, and mineral material behavior were independent of osteocytic TGFß. We determined that the decline in bone quality with age arises from the loss of osteocyte function and the loss of TGFß-dependent maintenance of collagen integrity.

Assessment of bone turnover markers and DXA parameters to predict bone metastasis progression during zoledronate treatment: a single-center experience.

Bone metastases (BM) are a serious cancer complication, potentially causing substantial morbidity. Among the clinical issues related to BM, there is the lack of specific tools for early diagnosis and prognosis. We explored whether combining bone turnover markers (BTM) with dual-energy X-ray absorptiometry (DXA) assessment could identify early BM progression and risk of skeletal-related events (SREs) during zoledronate treatment. Before the initiation of zoledronate (T0) and after six months of treatment (T1), serum levels of five BTM were measured, and patients (N = 47) underwent DXA evaluation. Standard radiological imaging was performed to assess bone tumor response to medical anti-cancer treatment. High tumor burden in bone correlated with higher serum CTX (p = 0.007) and NTX (p = 0.005) at baseline. Low concentrations of OPG at T0 predicted BM progression with a sensitivity and specificity of 63% and 77%, respectively, when a cutoff of 5.2 pmol/l was used; such a predictive meaning was stronger in patients with lytic BM (sensitivity: 88%, specificity: 80%; p = 0.0006). As for the risk of SREs, we observed an association between low baseline OC (p = 0.04) and OPG (p = 0.08) and the onset of any-time SREs, whereas an increase in OPG over time was associated with reduced risk of on-study events (p = 0.03). Moreover, a statistically significant correlation emerged between low baseline lumbar T-score and femur BMD and on-study SREs (p < 0.001 in both instances). These findings suggest that addition of DXA to BTM dosage could help stratifying the risk of SREs at the time of BM diagnosis but does not enhance our capability of detecting bone progression, during zoledronate treatment.

The role of cannabinoid receptor 2 in bone remodeling during orthodontic tooth movement.

BACKGROUND: The purpose of this study is to explore the effects of CB2 on bone regulation during orthodontic tooth movement. METHODS: Thirty male mice were allocated into 2 groups (n = 15 in each group): wild type (WT) group and CB2 knockout (CB2-/-) group. Orthodontic tooth movement (OTM) was induced by applying a nickel-titanium coil spring between the maxillary first molar and the central incisors. There are three subgroups within the WT groups (0, 7 and 14 days) and the CB2-/- groups (0, 7 and 14 days). 0-day groups without force application. Tooth displacement, alveolar bone mass and alveolar bone volume were assessed by micro-CT on 0, 7 and 14 days, and the number of osteoclasts was quantified by tartrate-resistant acid phosphatase (TRAP) staining. Moreover, the expression levels of RANKL and OPG in the compression area were measured histomorphometrically. RESULTS: The WT group exhibited the typical pattern of OTM, characterized by narrowed periodontal space and bone resorption on the compression area. In contrast, the accelerated tooth displacement, increased osteoclast number (P < 0.0001) and bone resorption on the compression area in CB2-/- group. Additionally, the expression of RANKL was significantly upregulated, while OPG showed low levels in the compression area of the CB2 - / - group (P < 0.0001). CONCLUSIONS: CB2 modulated OTM and bone remodeling through regulating osteoclast activity and RANKL/OPG balance.

Force-induced Caspase-1-dependent pyroptosis regulates orthodontic tooth movement.

Pyroptosis, an inflammatory caspase-dependent programmed cell death, plays a vital role in maintaining tissue homeostasis and activating inflammatory responses. Orthodontic tooth movement (OTM) is an aseptic force-induced inflammatory bone remodeling process mediated by the activation of periodontal ligament (PDL) progenitor cells. However, whether and how force induces PDL progenitor cell pyroptosis, thereby influencing OTM and alveolar bone remodeling remains unknown. In this study, we found that mechanical force induced the expression of pyroptosis-related markers in rat OTM and alveolar bone remodeling process. Blocking or enhancing pyroptosis level could suppress or promote OTM and alveolar bone remodeling respectively. Using Caspase-1-/- mice, we further demonstrated that the functional role of the force-induced pyroptosis in PDL progenitor cells depended on Caspase-1. Moreover, mechanical force could also induce pyroptosis in human ex-vivo force-treated PDL progenitor cells and in compressive force-loaded PDL progenitor cells in vitro, which influenced osteoclastogenesis. Mechanistically, transient receptor potential subfamily V member 4 signaling was involved in force-induced Caspase-1-dependent pyroptosis in PDL progenitor cells. Overall, this study suggested a novel mechanism contributing to the modulation of osteoclastogenesis and alveolar bone remodeling under mechanical stimuli, indicating a promising approach to accelerate OTM by targeting Caspase-1.

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.

Comparison of disc position stability and condylar bone remodelling between two open disc repositioning surgeries: a retrospective single-centre cohort study.

BACKGROUND AND OBJECTIVE: Open suturing (OSu) and mini-screw anchor (MsA) are two commonly used open disc repositioning surgeries for anterior disc displacement (ADD) of the temporomandibular joint (TMJ). This study assesses the differences in disc position stability (DPS) and condylar bone remodelling (CBR) between these two surgical procedures in a single centre. METHODS: A retrospective cohort study using MRI scans (pre-operation, 1 week and 12 months post-operation) of all patients who had open TMJ disc repositioning surgery from January 2016 to June 2021 at one centre through two surgical techniques (OSu and MsA) was performed. The predictor variable was technique (OSu and MsA). Outcome variables were DPS and CBR. During follow-up, DPS was rated as good, acceptable and poor, and CBR was graded as improved, unchanged, and degenerated. Multivariate analysis was used to compare the DPS and CBR at 12 months after adjusting five factors including age, sex, Wilkes stage, preoperative bone status (normal, mild/moderate abnormal) and the degree of disc repositioning (normal, overcorrected, and posteriorly repositioned). Relative risk (RR) for DPS and CBR was calculated by multivariate logistic regression. RESULTS: Three hundred eighty-five patients with 583 joints were included in the study. MRIs at 12 months showed that 514 joints (93.5%) had good DPS, and 344 joints (62.5%) had improved CBR. Multivariate analysis revealed that OSu had higher DPS (RR=2.95; 95% CI, 1.27-6.85) and better CBR (RR=1.58; 95% CI, 1.02-2.46) than MsA. Among the factors affecting DPS, females had better results than males (RR=2.63; 95% CI, 1.11-6.26) and overcorrected or posteriorly repositioned discs were more stable than normally repositioned discs (RR=5.84; 95% CI, 2.58-13.20). The improvement in CBR decreased with age increasing (RR=0.91; 95% CI, 0.89-0.93). Preoperative mild/moderate abnormal bone status had a higher probability of improved CBR compared to normal preoperative bone status (RR=2.60; 95% CI, 1.76-3.83). CONCLUSION: OSu had better DPS and CBR than MsA. Sex and the degree of disc repositioning impacted DPS, while age and preoperative bone status affected CBR.

Protective Effect of Bovine Milk Extracellular Vesicles on Alveolar Bone Loss.

SCOPE: Bovine milk extracellular vesicles (MEVs) have demonstrated therapeutic potential in regulating bone cell activity. However, the outcome of their use on alveolar bone loss has not yet been demonstrated. METHODS AND RESULTS: This study evaluates the effect of oral administration of MEVs on ovariectomized (OVX) mice. There is a reduced height of the alveolar bone crest in OVX mice by MEVs treatment, but the alveolar bone parameters are not altered. OVX mice are then submitted to a force-induced bone remodeling model by orthodontic tooth movement (OTM). MEVs-treated mice have markedly less bone remodeling movement, unlike the untreated OVX mice. Also, OVX mice treated with MEVs show an increased number of osteoblasts and osteocytes associated with higher sclerostin expression and reduce osteoclasts in the alveolar bone. Although the treatment with MEVs in OVX mice does not show differences in root structure in OTM, few odontoclasts are observed in the dental roots of OVX-treated mice. Compared to untreated mice, maxillary and systemic RANKL/OPG ratios are reduced in OVX mice treated with MEVs. CONCLUSION: Treatment with MEVs results in positive bone cell balance in the alveolar bone and dental roots, indicating its beneficial potential in treating alveolar bone loss in the nutritional context.

Chemotherapy and adjuvant therapies' impact on the internal remodeling process of bone and its mechanical behavior for breast cancer patients.

Breast cancer is a significant public health issue affecting women worldwide. While advancements in treatment options have led to improved survival rates, the impact of breast cancer and its treatments on bone health cannot be overlooked. Bone remodeling is a complex process regulated by the delicate balance between bone formation and resorption. Any disruption to this balance can lead to decreased bone density, increased fracture risk, and compromised physical function. To investigate the effects of breast cancer and its treatments on bone remodeling, a finite element model was developed in this study. This model incorporated bone remodeling equations to simulate the mechanical behavior of bone under different conditions. The ABAQUS/UMAT software was used to simulate the behavior of bone tissue under the influence of breast cancer and treatments. Our findings suggest that bone loss is more pronounced after secondary breast cancer and treatment, leading to bone loss (6%-19% decrease in BV/TV), reduced bone stimulation, and decreased effectiveness of physical activity on recovery. These results highlight the importance of early intervention and management of bone health in breast cancer patients to mitigate the negative impact of cancer and treatment on bone remodeling.

Pre-treatment bone turnover does not influence the level of the response to alendronate in postmenopausal osteoporosis at the bone tissue level.

PURPOSE: The main effect of anti-resorptive agents such as bisphosphonates is a reduction of bone resorption, with a consequent marked decrease of bone turnover. This post-hoc analysis investigated the changes of histomorphometric parameters of bone turnover after alendronate (ALN), according to the baseline turnover. METHODS: Ninety postmenopausal women underwent a transiliac bone biopsy before and after 6 (n = 44) or 12 (n = 46) months of treatment with ALN (70 mg/week). The dynamic parameters reflecting the bone formation and bone turnover were mineralizing surface (MS/BS; %), bone formation rate (BFR/BS; µm3/µm2/d), and activation frequency (Ac.f; /yr). Biochemical markers sPINP and the sCTX were assessed before treatment and after 3, 6, and 12 months. Subjects were divided into quartiles based on the baseline values of BFR/BS. RESULTS: At baseline, MS/BS and Ac.f were significantly different (p < 0.0001) among the BFR quartiles. sCTX and sP1NP were not significantly different among quartiles. After ALN treatment, MS/BS was not significantly different among quartiles but Ac.f remained significantly lower in the first quartile compared to the third and fourth ones (p < 0.03). The absolute value of the difference between pre- and post-treatment significantly correlated with the baseline BFR/BS but when expressed in percent of the baseline value, the magnitude of the diminutions of MS/BS, Ac.f, sCTX, and sP1NP was similar in the four baseline BFR quartiles. CONCLUSION: The percentage response to ALN appeared independent of the baseline level of bone turnover. After treatment, the bone turnover tended to be similar in all BFR quartiles. This analysis investigated the influence of baseline turnover measured by bone histomorphometry on the effect of alendronate. When expressed in percent of pre-treatment values, the decreases of histomorphometric parameters and biochemical markers of bone turnover were independent of the baseline turnover.

Osteocyte Mechanotransduction in Orthodontic Tooth Movement.

PURPOSE OF REVIEW: Orthodontic tooth movement is characterized by periodontal tissue responses to mechanical loading, leading to clinically relevant functional adaptation of jaw bone. Since osteocytes are significant in mechanotransduction and orchestrate osteoclast and osteoblast activity, they likely play a central role in orthodontic tooth movement. In this review, we attempt to shed light on the impact and role of osteocyte mechanotransduction during orthodontic tooth movement. RECENT FINDINGS: Mechanically loaded osteocytes produce signaling molecules, e.g., bone morphogenetic proteins, Wnts, prostaglandins, osteopontin, nitric oxide, sclerostin, and RANKL, which modulate the recruitment, differentiation, and activity of osteoblasts and osteoclasts. The major signaling pathways activated by mechanical loading in osteocytes are the wingless-related integration site (Wnt)/ß-catenin and RANKL pathways, which are key regulators of bone metabolism. Moreover, osteocytes are capable of orchestrating bone adaptation during orthodontic tooth movement. A better understanding of the role of osteocyte mechanotransduction is crucial to advance orthodontic treatment. The optimal force level on the periodontal tissues for orthodontic tooth movement producing an adequate biological response, is debated. This review emphasizes that both mechanoresponses and inflammation are essential for achieving tooth movement clinically. To fully comprehend the role of osteocyte mechanotransduction in orthodontic tooth movement, more knowledge is needed of the biological pathways involved. This will contribute to optimization of orthodontic treatment and enhance patient outcomes.

The effect of osteocyte-derived RANKL on bone graft remodeling: An in vivo experimental study.

OBJECTIVES: Autologous bone is considered the gold standard for grafting, yet it suffers from a tendency to undergo resorption over time. While the exact mechanisms of this resorption remain elusive, osteocytes have been shown to play an important role in stimulating osteoclastic activity through their expression of receptor activator of NF-κB (RANK) ligand (RANKL). The aim of this study was to assess the function of osteocyte-derived RANKL in bone graft remodeling. MATERIALS AND METHODS: In Tnfsf11fl/fl ;Dmp1-Cre mice without osteocyte-specific RANKL as well as in Dmp1-Cre control mice, 2.6 mm calvarial bone disks were harvested and transplanted into mice with matching genetic backgrounds either subcutaneously or subperiosteally, creating 4 groups in total. Histology and micro-computed tomography of the grafts and the donor regions were performed 28 days after grafting. RESULTS: Histology revealed marked resorption of subcutaneous control Dmp1-Cre grafts and new bone formation around subperiosteal Dmp1-Cre grafts. In contrast, Tnfsf11fl/fl ;Dmp1-Cre grafts showed effectively neither signs of bone resorption nor formation. Quantitative micro-computed tomography revealed a significant difference in residual graft area between subcutaneous and subperiosteal Dmp1-Cre grafts (p < .01). This difference was not observed between subcutaneous and subperiosteal Tnfsf11fl/fl ;Dmp1-Cre grafts (p = .17). Residual graft volume (p = .08) and thickness (p = .13) did not differ significantly among the groups. Donor area regeneration was comparable between Tnfsf11fl/fl ;Dmp1-Cre and Dmp1-Cre mice and restricted to the defect margins. CONCLUSIONS: The results suggest an active function of osteocyte-derived RANKL in bone graft remodeling.

An orthotropic continuum model with substructure evolution for describing bone remodeling: an interpretation of the primary mechanism behind Wolff's law.

We propose a variational approach that employs a generalized principle of virtual work to estimate both the mechanical response and the changes in living bone tissue during the remodeling process. This approach provides an explanation for the adaptive regulation of the bone substructure in the context of orthotropic material symmetry. We specifically focus upon the crucial gradual adjustment of bone tissue as a structural material that adapts its mechanical features, such as materials stiffnesses and microstructure, in response to the evolving loading conditions. We postulate that the evolution process relies on a feedback mechanism involving multiple stimulus signals. The mechanical and remodeling behavior of bone tissue is clearly a complex process that is difficult to describe within the framework of classical continuum theories. For this reason, a generalized continuum elastic theory is employed as a proper mathematical context for an adequate description of the examined phenomenon. To simplify the investigation, we considered a two-dimensional problem. Numerical simulations have been performed to illustrate bone evolution in a few significant cases: the bending of a rectangular cantilever plate and a three-point flexure test. The results are encouraging because they can replicate the optimization process observed in bone remodeling. The proposed model provides a likely distribution of stiffnesses and accurately represents the arrangement of trabeculae macroscopically described by the orthotropic symmetry directions, as supported by experimental evidence from the trajectorial theory.

Role of mechanosensitive ion channel Piezo1 in tension-side orthodontic alveolar bone remodeling in rats.

OBJECTIVE: Orthodontic tooth movement (OTM) is based on alveolar bone remodeling under mechanical force. In 2010, Piezo1 was identified as a mechanosensitive ion channel that is involved in various physiological functions. We aimed to determine the role of Piezo1 in alveolar bone remodeling during OTM. DESIGN: Twenty-five six-week-old male Sprague-Dawley rats were selected to establish OTM models and sacrificed in groups of five on days 0, 1, 3, 7, and 14. Stereomicroscopy measurements, hematoxylin and eosin staining, tartrate-resistant acid phosphatase staining, and immunohistochemical staining were performed to examine the tooth movement distance, periodontal tissue morphology, and number of multinucleated osteoclasts, and explore the levels of Piezo1, bone-related factors, and Wnt/Ca2+ signaling pathway at different time points in tension-side periodontal tissues during OTM. Furthermore, we injected equivalent grammostola mechanotoxin 4 (GsMTx4; GsMTx4 group, 25 rats) or saline (control group, 25 rats) to OTM rats and recorded the aforementioned measurement indices. RESULTS: Piezo1, bone-related factors and Wnt/Ca2+ signaling pathway levels were elevated on the tension side by orthodontic force in the OTM model. GsMTX4 administration downregulated the aforementioned factors and reduced the tooth movement rate. CONCLUSIONS: Piezo1 is essential for alveolar bone remodeling during OTM. The Wnt/Ca2+ signaling pathway might participate in Piezo1-mediated bone remodeling.

Uso de microvibración e inhibidores de la catepsina K en tratamientos de regeneración ósea dental / Use of micro-vibration and cathepsin K inhibitors in dental bone regeneration treatments

Introducción: el hueso está en remodelación constante para mantener la estructura del esqueleto, tener un ciclo de resorción por los osteoclastos y formación de hueso nuevo a cargo de los osteoblastos; el hueso también es susceptible a enfermedades sistémicas, traumas, edad y trastornos genéticos que afectarán el remodelado óseo, produciendo una pérdida masiva de masa ósea regulado por hormonas, citocinas, enzimas, etcétera. El objetivo es realizar una revisión sistemática de artículos que muestren cambio o alteración al utilizar tratamientos con microvibraciones y farmacológicos sobre la catepsina K en el hueso alveolar. Material y métodos: para realizar una comparación entre la efectividad del tratamiento a base de microvibraciones y con inhibidores de la catepsina K, se realizó una revisión sistemática en nueve bases de datos (Wiley Online Library, PubMed, Google Academic, Scopus, ScienceDirect, SciELO, Medline, EBSCO y Springer Link). La población de estudio fueron ratas y ratones. Resultados: en este estudio se incluyeron 20 artículos cuya investigación se realizó en estudios clínicos. En los resultados podemos observar cómo todos los tratamientos de alguna forma mejoran el proceso de remodelado óseo. Es difícil comparar cuál de los tratamientos dentro de cada grupo es mejor que otro, debido a que los resultados expresados son cualitativos. Conclusión: acorde a los resultados expresados se opta por realizar un tratamiento con microvibraciones debido a que el uso de inhibidores de la catepsina K aún no se encuentra completamente desarrollado y no se comprenden sus consecuencias debido a su manera sistémica de actuar (AU)

Introduction: the bone is in constant remodeling to maintain the skeletal structure, having a cycle of resorption by osteoclasts and formation of new bone by osteoblasts, the bone is also susceptible to systemic diseases, trauma, age and genetic disorders that affect bone remodeling, producing a massive loss of bone mass regulated by hormones, cytokines, enzymes, etcetera. The objective is to perform a systematic review of articles that show a change or alteration when using micro-vibration and pharmacological treatments on cathepsin K in the alveolar bone. Material and methods: in order to make a comparison between the effectiveness of micro-vibration and cathepsin K inhibitor treatments, a systemic review was carried out in nine databases (Wiley Online Library, PubMed, Google Academic, Scopus, ScienceDirect, SciELO, Medline, EBSCO and Springer Link). The study population was rats and mice. Results: this study included 20 articles whose research was carried out in clinical studies. In the results we can see how all the treatments in some way improve the bone remodeling process, it is difficult to compare which treatment within each group is better than the other, because the results expressed are qualitative. Conclusion: according to the results expressed, it is decided that it is better to perform a treatment with micro vibrations because the use of cathepsin K inhibitors are not yet fully developed and their consequences are not understood due to their systemic way of acting (AU)