Effect of high-frequency loading and parathyroid hormone administration on peri-implant bone healing and osseointegration

Titanium nanotopography enhances mechano-response of osteocyte three-dimensional network toward osteoblast activation

The bone turnover capability influences the acquisition and maintenance of osseointegration. The architectures of osteocyte three-dimensional (3D) networks determine the direction and activity of bone turnover through osteocyte intercellular crosstalk, which exchanges prostaglandins through gap junctions in response to mechanical loading. Titanium nanosurfaces with anisotropically patterned dense nanospikes promote the development of osteocyte lacunar-canalicular networks. We investigated the effects of titanium nanosurfaces on intercellular network development and regulatory capabilities of bone turnover in osteocytes under cyclic compressive loading. MLO-Y4 mouse osteocyte-like cell lines embedded in type I collagen 3D gels on titanium nanosurfaces promoted the formation of intercellular networks and gap junctions even under static culture conditions, in contrast to the poor intercellular connectivity in machined titanium surfaces. The osteocyte 3D network on the titanium nanosurfaces further enhanced gap junction formation after additional culturing under cyclic compressive loading simulating masticatory loading, beyond the degree observed on machined titanium surfaces. A prostaglandin synthesis inhibitor cancelled the dual effects of titanium nanosurfaces and cyclic compressive loading on the upregulation of gap junction-related genes in the osteocyte 3D culture. Supernatants from osteocyte monolayer culture on titanium nanosurfaces promoted osteocyte maturation and intercellular connections with gap junctions. With cyclic loading, titanium nanosurfaces induced expression of the regulatory factors of bone turnover in osteocyte 3D cultures, toward higher osteoblast activation than that observed on machined surfaces. Titanium nanosurfaces with anisotropically patterned dense nanospikes promoted intercellular 3D network development and regulatory function toward osteoblast activation in osteocytes activated by cyclic compressive loading, through intercellular crosstalk by prostaglandin.

Pre-implantation teriparatide administration improves initial implant stability and accelerates the osseointegration process in osteoporotic rats

PURPOSE

Osteoporotic individuals who have dental implants usually require a prolonged healing time for osseointegration due to the shortage of bone mass and the lack of initial stability. Although studies have shown that intermittent teriparatide administration can promote osseointegration, there is little data to support the idea that pre-implantation administration is necessary and beneficial.

METHODS

Sixty-four titanium implants were placed in the bilateral proximal tibial metaphysis in 32 female SD rats. Bilateral ovariectomy (OVX) was used to induce osteoporosis. Four major groups (n = 8) were created: PRE (OVX + pre-implantation teriparatide administration), POST (OVX + post-implantation administration), OP (OVX + normal saline (NS)) and SHAM (sham rats + NS). Half of rats (n = 4) in each group were euthanized respectively at 4 weeks or 8 weeks after implantation surgery, and four major groups were divided into eight subgroups (PRE4 to SHAM8). Tibiae were collected for micro-CT morphometry, biomechanical test and undecalcified sections analysis.

RESULTS

Compared to OP group, rats in PRE and SHAM groups had a higher value of insertion torque (p < 0.05). The micro-CT analysis, biomechanical test, and histological data showed that peri-implant trabecular growth, implants fixation and bone-implant contact (BIC) were increased after 4 or 8 weeks of teriparatide treatment (p < 0.05). There was no statistically difference in those parameters between PRE4 and POST8 subgroups (p > 0.05).

CONCLUSIONS

In osteoporotic rats, post-implantation administration of teriparatide enhanced peri-implant bone formation and this effect was stronger as the medicine was taken longer. Pre-implantation teriparatide treatment improved primary implant stability and accelerated the osseointegration process.

Zoledronate Promotes Peri-Implant Osteogenesis in Diabetic Osteoporosis by the AMPK Pathway

Together with diabetic osteoporosis (DOP), diabetes patients experience poor peri-implant osteogenesis following implantation for dentition defects. Zoledronate (ZOL) is widely used to treat osteoporosis clinically. To evaluate the mechanism of ZOL for the treatment of DOP, experiments with DOP rats and high glucose-grown MC3T3-E1 cells were used. The DOP rats treated with ZOL and/or ZOL implants underwent a 4-week implant-healing interval, and then microcomputed tomography, biomechanical testing, and immunohistochemical staining were performed to elucidate the mechanism. In addition, MC3T3-E1 cells were maintained in an osteogenic medium with or without ZOL to confirm the mechanism. The cell migration, cellular actin content, and osteogenic differentiation were evaluated by a cell activity assay, a cell migration assay, as well as alkaline phosphatase, alizarin red S, and immunofluorescence staining. The mRNA and protein expression of adenosine monophosphate-activated protein kinase (AMPK), phosphorylated AMPK (p-AMPK), osteoprotegerin (OPG), receptor activator of nuclear factor kappa B ligand (RANKL), bone morphogenetic protein 2 (BMP2), and collagen type I (Col-I) were detected using real-time quantitative PCRs and western blot assays, respectively. In the DOP rats, ZOL markedly improved osteogenesis, enhanced bone strength and increased the expression of AMPK, p-AMPK, and Col-I in peri-implant bones. The in vitro findings showed that ZOL reversed the high glucose-induced inhibition of osteogenesis via the AMPK signaling pathway. In conclusion, the ability of ZOL to promote osteogenesis in DOP by targeting AMPK signaling suggests that therapy with ZOL, particularly simultaneous local and systemic administration, may be a unique approach for future implant repair in diabetes patients.

Genetic architecture in neonatal intensive care unit patients with congenital heart defects: a retrospective study from the China Neonatal Genomes Project

BACKGROUND

Congenital heart defects (CHDs) are the most common type of birth defects. The genetic aetiology of CHD is complex and incompletely understood. The overall distribution of genetic causes in patients with CHD from neonatal intensive care units (NICUs) needs to be studied.

METHODS

CHD cases were extracted from the China Neonatal Genomes Project (2016-2021). Next-generation sequencing results and medical records were retrospectively evaluated to note the frequency of genetic diagnosis and the respective patient outcomes.

RESULTS

In total, 1795 patients were included. The human phenotype ontology term of atrial septal defect, patent ductus arteriosus and ventricular septal defect account for a large portion of the CHD subtype. Co-occurring extracardiac anomalies were observed in 35.1% of patients. 269 of the cases received genetic diagnoses that could explain the phenotype of CHDs, including 172 copy number variations and 97 pathogenic variants. The detection rate of trio-whole-exome sequencing was higher than clinical exome sequencing (21.8% vs 14.5%, p<0.05). Further follow-up analysis showed the genetic diagnostic rate was higher in the deceased group than in the surviving group (29.0% vs 11.9%, p<0.05).

CONCLUSION

This is the largest cohort study to explore the genetic spectrum of patients with CHD in the NICU in China. Our findings may benefit future work on improving genetic screening and counselling for NICU patients with CHD.

Management of Osteoporosis Medication after Osteoporotic Fracture

The aim of this study was to provide helpful information for use in selection of an appropriate medication after osteoporotic fractures through conduct of a literature review. In addition, a review of the recommendations of several societies for prevention of subsequent fractures was performed and the appropriate choice of medication for treatment of atypical femur fractures was examined. Clinical perspective was obtained and an updated search of literature was conducted across PubMed and MEDLINE and relevant articles were selected. The articles were selected manually according to relevance, and the references for identified articles and reviews were also evaluated for relevance. The following areas are reviewed: Commonly prescribed osteoporosis medications: BPs (bisphosphonates), denosumab, and SERMs (selective estrogen receptor modulators) in antiresorptive medications and recombinant human parathyroid hormone teriparatide, recently approved Romosuzumab in anabolic agents, clinical practice guidelines for the management of osteoporosis, osteoporotic fracture, and atypical femur fracture. Most medications for treatment of osteoporosis do not delay fracture healing and the positive effect of teriparatide on fracture healing has been confirmed. In cases where an osteoporotic fracture is diagnosed, risk assessment should be performed for selection of very high-risk patients in order to prevent subsequent fractures, and administration of anabolic agents is recommended.

Investigating the impact of oral health on pregnancy and offspring outcomes: protocol for the Lifetime Impact of ORal heAlth (LIORA) cohort study

INTRODUCTION

Oral health is a fundamental component of well-being, and is closely associated with overall health and quality of life. Oral health may also affect the next generation. The children of mothers with poor oral health are likely to also have poor oral health as they go through life. We aim to investigate associations between maternal oral health and general health, pregnancy outcomes, offspring oral health and offspring general health.

METHODS AND ANALYSIS

The Lifetime Impact of Oral Health study is a prospective, observational cohort study being done at a single centre in Chongqing, China. A total of 1000 pregnant women will be recruited in their first trimester (11-14 weeks gestation). After obtaining informed consent, general and oral health assessments will be undertaken. Maternal lifestyle, demographic data and biospecimens (blood, hair, urine, nail clippings, saliva, dental plaque, buccal, vaginal and anal swabs) will be collected. Pregnancy outcomes will be recorded at the time of delivery. Cord blood and placenta samples will be collected. The offspring will be followed up for general and oral health examinations, neurodevelopmental assessments and biospecimen (dental plaque, saliva, buccal swabs, exfoliated primary dentition, urine, hair, nail clippings) collection until they are 15 years old. Biological samples will undergo comprehensive metabolomic, microbiome and epigenome analyses. Associations between maternal oral health and general health, pregnancy outcomes, offspring oral health and offspring general health will be investigated and the underlying mechanisms explored.

ETHICS AND DISSEMINATION

This project has been approved by the Research Ethics Committee of the Affiliated Hospital of Stomatology of Chongqing Medical University (CQHS-REC-2021 LSNo.23). Participants will be required to provide informed consent to participate in the study. Dissemination of findings will take the form of publications in peer-reviewed journals and presentations at national and international conferences.

TRIAL REGISTRATION NUMBER

ChiCTR2100046898.

The impact of medication on osseointegration and implant anchorage in bone determined using removal torque-A review

Permanently anchored metal implants are frequently used in dental, craniomaxillofacial, and orthopaedic rehabilitation. The success of such therapies is owed to the phenomenon of osseointegration—the direct connection between the living bone and the implant. The extent of biomechanical anchorage (i.e., physical interlocking between the implant and bone) can be assessed with removal torque (RTQ) measurement. Implant anchorage is strongly influenced by underlying bone quality, involving physicochemical and biological properties such as composition and structural organisation of extracellular matrix, extent of micro-damage, and bone turnover. In this review, we evaluated the impact of various pharmacological agents on osseointegration, from animal experiments conducting RTQ measurements. In addition to substances whose antiresorptive and/or anti-catabolic effects on bone are well-documented (e.g., alendronate, zoledronate, ibandronate, raloxifene, human parathyroid hormone, odanacatib, and the sclerostin monoclonal antibody), positive effects on RTQ have been reported for substances that do not primarily target bone (e.g., aminoguanidine, insulin, losartan, simvastatin, bone morphogenetic protein, alpha-tocopherol, and the combination of silk fibroin powder and platelet-rich fibrin). On the contrary, several substances (e.g., prednisolone, cyclosporin A, cisplatin, and enamel matrix derivative) tend to adversely impact RTQ. While morphometric parameters such as bone-implant contact appear to influence the biomechanical anchorage, increased or decreased RTQ is not always accompanied by corresponding fluctuations in bone-implant contact. This further confirms that factors such as bone quality underpin biomechanical anchorage of metal implants. Several fundamental questions on drug metabolism and bioavailability, drug dosage, animal-to-human translation, and the consequences of treatment interruption remain yet unanswered.

•

Effects of pharmacological agents on osseointegration of metal implants are reviewed.

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Removal torque is considered as an objective measure of osseointegration.

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Most investigated anabolic agents are alendronate, zoledronate, and ibandronate.

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hPTH has a positive effect while cyclosporin A and cisplatin have negative effects.

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Correction of underlying systemic disorders leads to improved osseointegration.

Effects of Drugs and Chemotherapeutic Agents on Dental Implant Osseointegration: Narrative Review

BACKGROUND

Dental implants have been one of the most popular treatments for rehabilitating individuals with single missing teeth or fully edentulous jaws since their introduction. As more implant patients are well-aged and take several medications due to various systemic conditions, clinicians should be mindful of possible drug implications on bone remodeling and osseointegration.

OBJECTIVE

The present study aims to study and review some desirable and some unwelcomed implications of medicine on osseointegration.

METHODS

A broad search for proper relevant studies were conducted in four databases, including Web of Science, Pubmed, Scopus, and Google Scholar.

RESULTS

Some commonly prescribed medicines such as nonsteroidal anti-inflammatory drugs (NSAIDs), glucocorticoids, proton pump inhibitors (PPIs), selective serotonin reuptake inhibitors (SSRIs), anticoagulants, metformin, and chemotherapeutic agents may jeopardize osseointegration. On the contrary, some therapeutic agents such as anabolic, anti-catabolic, or dual anabolic and anti-catabolic agents may enhance osseointegration and increase the treatment's success rate.

CONCLUSION

Systemic medications that enhance osseointegration include mineralization promoters and bone resorption inhibitors. On the other hand, medications often given to the elderly with systemic problems might interfere with osseointegration, leading to implant failure. However, to validate the provided research, more human studies with a higher level of evidence are required.

Parathyroid Hormone 1 Receptor Signaling in Dental Mesenchymal Stem Cells: Basic and Clinical Implications

Parathyroid hormone (PTH) and parathyroid hormone-related protein (PTHrP) are two peptides that regulate mineral ion homeostasis, skeletal development, and bone turnover by activating parathyroid hormone 1 receptor (PTH1R). PTH1R signaling is of profound clinical interest for its potential to stimulate bone formation and regeneration. Recent pre-clinical animal studies and clinical trials have investigated the effects of PTH and PTHrP analogs in the orofacial region. Dental mesenchymal stem cells (MSCs) are targets of PTH1R signaling and have long been known as major factors in tissue repair and regeneration. Previous studies have begun to reveal important roles for PTH1R signaling in modulating the proliferation and differentiation of MSCs in the orofacial region. A better understanding of the molecular networks and underlying mechanisms for modulating MSCs in dental diseases will pave the way for the therapeutic applications of PTH and PTHrP in the future. Here we review recent studies involving dental MSCs, focusing on relationships with PTH1R. We also summarize recent basic and clinical observations of PTH and PTHrP treatment to help understand their use in MSCs-based dental and bone regeneration.

Anabolic Bone Stimulus Requires a Pre-Exercise Meal and 45-Minute Walking Impulse of Suprathreshold Speed-Enhanced Momentum to Prevent or Mitigate Postmenopausal Osteoporosis within Circadian Constraints

Osteoporosis currently afflicts 8 million postmenopausal women in the US, increasing the risk of bone fractures and morbidity, and reducing overall quality of life. We sought to define moderate exercise protocols that can prevent postmenopausal osteoporosis. Our previous findings singled out higher walking speed and pre-exercise meals as necessary for suppression of bone resorption and increasing of markers of bone formation. Since both studies were amenable to alternate biomechanical, nutritional, and circadian interpretations, we sought to determine the relative importance of higher speed, momentum, speed-enhanced load, duration of impulse, and meal timing on osteogenic response. We hypothesized that: (1) 20 min of exercise one hour after eating is sufficient to suppress bone resorption as much as a 40-min impulse and that two 20 min exercise bouts separated by 7 h would double the anabolic effect; (2) early morning exercise performed after eating will be as effective as mid-day exercise for anabolic outcome; and (3) the 08:00 h 40-min. exercise uphill would be as osteogenic as the 40-min exercise downhill. Healthy postmenopausal women, 8 each, were assigned to a no-exercise condition (SED) or to 40- or 20-min exercise bouts, spaced 7 h apart, for walking uphill (40 Up and 20 Up) or downhill (40 Down and 20 Down) to produce differences in biomechanical variables. Exercise was initiated at 08:00 h one hour after eating in 40-min groups, and also 7 h later, two hours after the midday meal, in 20-min groups. Measurements were made of CICP (c-terminal peptide of type I collagen), osteocalcin (OC), and bone-specific alkaline phosphatase (BALP), markers of bone formation, and of the bone resorptive marker CTX (c-terminal telopeptide of type 1 collagen). The osteogenic ratios CICP/CTX, OC/CTX, and BALP/CTX were calculated. Only the 40-min downhill exercise of suprathreshold speed-enhanced momentum, increased the three osteogenic ratios, demonstrating the necessity of a 40-min, and inadequacy of a 20-min, exercise impulse. The failure of anabolic outcome in 40-min uphill exercise was attributed to a sustained elevation of PTH concentration, as its high morning elevation enhances the CTX circadian rhythm. We conclude that postmenopausal osteoporosis can be prevented or mitigated in sedentary women by 45 min of morning exercise of suprathreshold speed-enhanced increased momentum performed shortly after a meal while walking on level ground, or by 40-min downhill, but not 40-min uphill, exercise to avoid circadian PTH oversecretion. The principal stimulus for the anabolic effect is exercise, but the prerequisite for a pre-exercise meal demonstrates the requirement for nutrient facilitation.

Feeding intervention potentiates the effect of mechanical loading to induce new bone formation in mice

The benefits of increased human lifespan depend upon duration of healthy, independent living; the healthspan. Bone-wasting disorders contribute significantly to loss of independence, frailty, and morbidity in older people. Therefore, there is an unmet need globally for lifestyle interventions to reduce the likelihood of bone fractures with age. Although many mechanisms are involved in disorders of bone loss, there is no single regulatory pathway and, therefore, there is no single treatment available to prevent their occurrence. Our aim in these studies was to determine whether fasting/feeding interventions alter the effect of mechanical loading on bone anabolic activities and increase bone mass. In young 17-week-old mice, 16-hour fasting period followed by reintroduction of food for 2 hours increased markedly the potency of mechanical loading, that mimics the effect of exercise, to induce new cortical bone formation. Consistent with this finding, fasting and re-feeding increased the response of bone to a loading stimulus that, alone, does not stimulate new bone formation in ad-lib fed mice. Older mice (20 months) experienced no potentiation of loading-induced bone formation with the same timing of feeding interventions. Interestingly, the pre-, prandial, and postprandial endocrine responses in older mice were different from those in young animals. The hormones that change in response to timing of feeding have osteogenic effects that interact with loading-mediated effects. Our findings indicate associations between timing of food ingestion and bone adaptation to loading. If translated to humans, such non-pharmacological lifestyle interventions may benefit skeletal health of humans throughout life-course and in older age.

Does Low-Magnitude High-Frequency Vibration (LMHFV) Worth for Clinical Trial on Dental Implant? A Systematic Review and Meta-Analysis on Animal Studies

Being as a non-pharmacological medical intervention, low-magnitude high-frequency vibration (LMHFV) has shown a positive effect on bone induction and remodeling for various muscle diseases in animal studies, among which dental implants osteointegration were reported to be improved as well. However, whether LMHFV can be clinically used in dental implant is still unknown. In this study, efficacy, parameters and side effects of LMHFV were analyzed via data before 15th July 2020, collecting from MEDLINE/PubMed, Embase, Ovid and Cochrane Library databases. In the screened 1,742 abstracts and 45 articles, 15 animal studies involving 972 implants were included. SYRCLE's tool was performed to assess the possible risk of bias for each study. The GRADE approach was applied to evaluate the quality of evidence. Random effects meta-analysis detected statistically significant in total BIC (P < 0.0001) and BV/TV (P = 0.001) upon loading LMHFV on implants. To conclude, LMHFV played an active role on BIC and BV/TV data according to the GRADE analysis results (medium and low quality of evidence). This might illustrate LMHFV to be a worthy way in improving osseointegration clinically, especially for osteoporosis.

Systematic Review Registration:https://www.crd.york.ac.uk/PROSPERO, identifier: NCT02612389

Osteogenic effect of low-intensity pulsed ultrasound and whole-body vibration on peri-implant bone. An experimental in vivo study

OBJECTIVES

The aims of this study were (i) to compare the osteogenic impact of low-intensity pulsed ultrasound (LIPUS) and low-magnitude high-frequency (LMHF) loading achieved with whole-body vibration (WBV) on peri-implant bone healing and implant osseointegration in rat tibiae, and (ii) to examine their combined effect on these processes.

MATERIAL AND METHODS

Titanium implants were inserted in the bilateral tibiae of 28 Wistar rats. Rats were randomly divided into four groups: LIPUS + WBV, LIPUS, WBV, and control. LIPUS was applied to the implant placement site for 20 min/day on 5 days/week (1.5 MHz and 30 mW/cm² ). WBV was applied for 15 min/day on 5 days/week (50 Hz and 0.5 g). In the LIPUS + WBV group, both stimuli were applied under the same stimulation conditions as in the LIPUS and WBV groups. After 4 weeks of treatment, peri-implant bone healing and implant osseointegration were assessed using removal torque (RT) tests, micro-CT analyses of relative gray (RG) value, and histomorphometrical analyses of bone-to-implant contact (BIC) and peri-implant bone formation (BV/TV).

RESULTS

The LIPUS + WBV group had significantly greater BIC than the WBV and control groups. Although there were no significant intergroup differences in RT, RG value, and BV/TV, these variables tended to be greater in the LIPUS + WBV group than the other groups.

CONCLUSIONS

The combination of LIPUS and LMHF loading may promote osteogenic activity around the implant. However, further study of the stimulation conditions of LIPUS and LMHF loading is necessary to better understand the osteogenic effects and the relationship between the two stimuli.

Parathyroid hormone increases alveolar bone homoeostasis during orthodontic tooth movement in rats with periodontitis via crosstalk between STAT3 and β-catenin

Periodontitis patients are at risk of alveolar bone loss during orthodontic treatment. The aim of this study was to investigate whether intermittent parathyroid hormone (1–34) treatment (iPTH) could reduce alveolar bone loss during orthodontic tooth movement (OTM) in individuals with periodontitis and the underlying mechanism. A rat model of OTM in the context of periodontitis was established and alveolar bone loss was observed. The control, iPTH and iPTH + stattic groups received injections of vehicle, PTH and vehicle, or PTH and the signal transducer and activator of transcription 3 (STAT3) inhibitor stattic, respectively. iPTH prevented alveolar bone loss by enhancing osteogenesis and suppressing bone resorption in the alveolar bone during OTM in rats with periodontitis. This effect of iPTH was along with STAT3 activation and reduced by a local injection of stattic. iPTH promoted osteoblastic differentiation and might further regulate the Wnt/β-catenin pathway in a STAT3-dependent manner. The findings of this study suggest that iPTH might reduce alveolar bone loss during OTM in rats with periodontitis through STAT3/β-catenin crosstalk.

Bone and Cartilage Interfaces With Orthopedic Implants: A Literature Review

The interface between a surgical implant and tissue consists of a complex and dynamic environment characterized by mechanical and biological interactions between the implant and surrounding tissue. The implantation process leads to injury which needs to heal over time and the rapidity of this process as well as the property of restored tissue impact directly the strength of the interface. Bleeding is the first and most relevant step of the healing process because blood provides growth factors and cellular material necessary for tissue repair. Integration of the implants placed in poorly vascularized tissue such as articular cartilage is, therefore, more challenging than compared with the implants placed in well-vascularized tissues such as bone. Bleeding is followed by the establishment of a provisional matrix that is gradually transformed into the native tissue. The ultimate goal of implantation is to obtain a complete integration between the implant and tissue resulting in long-term stability. The stability of the implant has been defined as primary (mechanical) and secondary (biological integration) stability. Successful integration of an implant within the tissue depends on both stabilities and is vital for short- and long-term surgical outcomes. Advances in research aim to improve implant integration resulting in enhanced implant and tissue interface. Numerous methods have been employed to improve the process of modifying both stability types. This review provides a comprehensive discussion of current knowledge regarding implant-tissue interfaces within bone and cartilage as well as novel approaches to strengthen the implant-tissue interface. Furthermore, it gives an insight into the current state-of-art biomechanical testing of the stability of the implants. Current knowledge reveals that the design of the implants closely mimicking the native structure is more likely to become well integrated. The literature provides however several other techniques such as coating with a bioactive compound that will stimulate the integration and successful outcome for the patient.

Shear Stress Modulates Osteoblast Cell and Nucleus Morphology and Volume

Mechanical loading preserves bone mass and function—yet, little is known about the cell biological basis behind this preservation. For example, cell and nucleus morphology are critically important for cell function, but how these morphological characteristics are affected by the physiological mechanical loading of bone cells is under-investigated. This study aims to determine the effects of fluid shear stress on cell and nucleus morphology and volume of osteoblasts, and how these effects relate to changes in actin cytoskeleton and focal adhesion formation. Mouse calvaria 3T3-E1 (MC3T3-E1) osteoblasts were treated with or without 1 h pulsating fluid flow (PFF). Live-cell imaging was performed every 10 min during PFF and immediately after PFF. Cytoskeletal organization and focal adhesions were visualized, and gene and protein expression quantified. Two-dimensional (2D) and three-dimensional (3D) morphometric analyses were made using MeasureStack and medical imaging interaction toolkit (MITK) software. 2D-images revealed that 1 h PFF changed cell morphology from polygonal to triangular, and nucleus morphology from round to ellipsoid. PFF also reduced cell surface area (0.3-fold), cell volume (0.3-fold), and nucleus volume (0.2-fold). During PFF, the live-cell volume gradually decreased from 6000 to 3000 µm³. After PFF, α-tubulin orientation was more disorganized, but F-actin fluorescence intensity was enhanced, particularly around the nucleus. 3D-images obtained from Z-stacks indicated that PFF increased F-actin fluorescence signal distribution around the nucleus in the XZ and YZ direction (2.3-fold). PFF increased protein expression of phospho-paxillin (2.0-fold) and integrin-α5 (2.8-fold), but did not increase mRNA expression of paxillin-a (PXNA), paxillin-b (PXNB), integrin-α5 (ITGA51), or α-tubulin protein expression. In conclusion, PFF induced substantial changes in osteoblast cytoskeleton, as well as cell and nucleus morphology and volume, which was accompanied by elevated gene and protein expression of adhesion and structural proteins. More insights into the mechanisms whereby mechanical cues drive morphological changes in bone cells, and thereby, possibly in bone cell behavior, will aid the guidance of clinical treatment, particularly in the field of orthodontics, (oral) implantology, and orthopedics.

Influence of Low-Magnitude High-Frequency Vibration on Bone Cells and Bone Regeneration

Bone is a mechanosensitive tissue for which mechanical stimuli are crucial in maintaining its structure and function. Bone cells react to their biomechanical environment by activating molecular signaling pathways, which regulate their proliferation, differentiation, and matrix production. Bone implants influence the mechanical conditions in the adjacent bone tissue. Optimizing their mechanical properties can support bone regeneration. Furthermore, external biomechanical stimulation can be applied to improve implant osseointegration and accelerate bone regeneration. One promising anabolic therapy is vertical whole-body low-magnitude high-frequency vibration (LMHFV). This form of vibration is currently extensively investigated to serve as an easy-to-apply, cost-effective, and efficient treatment for bone disorders and regeneration. This review aims to provide an overview of LMHFV effects on bone cells in vitro and on implant integration and bone fracture healing in vivo. In particular, we review the current knowledge on cellular signaling pathways which are influenced by LMHFV within bone tissue. Most of the in vitro experiments showed that LMHFV is able to enhance mesenchymal stem cell (MSC) and osteoblast proliferation. Furthermore, osteogenic differentiation of MSCs and osteoblasts was shown to be accelerated by LMHFV, whereas osteoclastogenic differentiation was inhibited. Furthermore, LMHFV increased bone regeneration during osteoporotic fracture healing and osseointegration of orthopedic implants. Important mechanosensitive pathways mediating the effects of LMHFV might be the Wnt/beta-catenin signaling pathway, the estrogen receptor (ER) signaling pathway, and cytoskeletal remodeling.

Osteocyte apoptosis: the roles and key molecular mechanisms in resorption-related bone diseases

Vital osteocytes have been well known to function as an important orchestrator in the preservation of robustness and fidelity of the bone remodeling process. Nevertheless, some key pathological factors, such as sex steroid deficiency and excess glucocorticoids, and so on, are implicated in inducing a bulk of apoptotic osteocytes, subsequently resulting in resorption-related bone loss. As much, osteocyte apoptosis, under homeostatic conditions, is in an optimal state of balance tightly controlled by pro- and anti-apoptotic mechanism pathways. Importantly, there exist many essential signaling proteins in the process of osteocyte apoptosis, which has a crucial role in maintaining a homeostatic environment. While increasing in vitro and in vivo studies have established, in part, key signaling pathways and cross-talk mechanism on osteocyte apoptosis, intrinsic and complex mechanism underlying osteocyte apoptosis occurs in various states of pathologies remains ill-defined. In this review, we discuss not only essential pro- and anti-apoptotic signaling pathways and key biomarkers involved in these key mechanisms under different pathological agents, but also the pivotal role of apoptotic osteocytes in osteoclastogenesis-triggered bone loss, hopefully shedding new light on the attractive and proper actions of pharmacotherapeutics of targeting apoptosis and ensuing resorption-related bone diseases such as osteoporosis and fragility fractures.

High shear stress amplitude in combination with prolonged stimulus duration determine induction of osteoclast formation by hematopoietic progenitor cells

To date, it is unclear how fluid dynamics stimulate mechanosensory cells to induce an osteoprotective or osteodestructive response. We investigated how murine hematopoietic progenitor cells respond to 2 minutes of dynamic fluid flow stimulation with a precisely controlled sequence of fluid shear stresses. The response was quantified by measuring extracellular adenosine triphosphate (ATP), immunocytochemistry of Piezo1, and sarcoplasmic/endoplasmic Ca²⁺ reticulum ATPase 2 (SERCA2), and by the ability of soluble factors produced by mechanically stimulated cells to modulate osteoclast differentiation. We rejected our initial hypothesis that peak wall shear stress rate determines the response of hematopoietic progenitor cells to dynamic fluid shear stress, as it had only a minor correlation with the abovementioned parameters. Low stimulus amplitudes corresponded to activation of Piezo1, SERCA2, low concentrations of extracellular ATP, and inhibition of osteoclastogenesis and resorption area, while high amplitudes generally corresponded to osteodestructive responses. At a given amplitude (3 Pa) and waveform (square), the duration of individual stimuli (duty cycle) showed a strong correlation with the release of ATP and osteoclast number and resorption area. Collectively, our data suggest that hematopoietic progenitor cells respond in a viscoelastic manner to loading, since a combination of high shear stress amplitude and prolonged duty cycle is needed to trigger an osteodestructive response. PLAIN LANGUAGE SUMMARY: In case of painful joints or missing teeth, the current intervention is to replace them with an implant to keep a high-quality lifestyle. When exercising or chewing, the cells in the bone around the implant experience mechanical loading. This loading generally supports bone formation to strengthen the bone and prevent breaking, but can also stimulate bone loss when the mechanical loading becomes too high around orthopedic and dental implants. We still do not fully understand how cells in the bone can distinguish between mechanical loading that strengthens or weakens the bone. We cultured cells derived from the bone marrow in the laboratory to test whether the bone loss response depends on (i) how fast a mechanical load is applied (rate), (ii) how intense the mechanical load is (amplitude), or (iii) how long each individual loading stimulus is applied (duration). We mimicked mechanical loading as it occurs in the body, by applying very precisely controlled flow of fluid over the cells. We found that a mechanosensitive receptor Piezo1 was activated by a low amplitude stimulus, which usually strengthens the bone. The potential inhibitor of Piezo1, namely SERCA2, was only activated by a low amplitude stimulus. This happened regardless of the rate of application. At a constant high amplitude, a longer duration of the stimulus enhanced the bone-weakening response. Based on these results we deduce that a high loading amplitude tends to be bone weakening, and the longer this high amplitude persists, the worse it is for the bone.

Formulating injectable pastes of porous calcium phosphate glass microspheres for bone regeneration applications

Current trends in regenerative medicine treatments for bone repair applications focus on cell-based therapies. These aim to deliver the treatment via a minimally invasive injection to reduce patient trauma and to improve efficacy. This paper describes the injectability of porous calcium phosphate glass microspheres to be used for bone repair based on their formulation, rheology and flow behavior. The use of excipients (xanthan gum, methyl cellulose and carboxyl methyl cellulose) were investigated to improve flow performance. Based on our results, the flow characteristics of the glass microsphere pastes vary according to particle size, surface area, and solid to liquid ratio, as well as the concentration of viscosity modifiers used. The optimal flow characteristics of calcium phosphate glass microsphere pastes was found to contain 40 mg/mL of xanthan gum which increased viscosity whilst providing elastic properties (∼29,000 Pa) at shear rates that mirror the injection process and the resting period post injection, preventing the glass microspheres from both damage and dispersion. It was established that a base formulation must contain 1 g of glass microspheres (60-125 μm in size) per 1 mL of cell culture media, or 0.48 g of glass microspheres of sizes between 125 and 200 μm. Furthermore, the glass microsphere formulations with xanthan gum were readily injectable via a syringe-needle system (3-20 mL, 18G and 14G needles), and have the potential to be utilized as a cell (or other biologics) delivery vehicle for bone regeneration applications.

The combined effect of Parathyroid hormone (1-34) and whole-body Vibration exercise in the treatment of postmenopausal OSteoporosis (PaVOS study): a randomized controlled trial

Treatment effects of combining teriparatide and whole-body vibration exercise (WBV) vs teriparatide alone in twelve months were compared using bone mineral density (BMD), bone microarchitecture, and bone turnover markers. We found an increased effect in lumbar spine BMD by adding WBV to teriparatide in postmenopausal osteoporotic women.

INTRODUCTION

The parathyroid hormone (PTH) analogue teriparatide is an effective but expensive anabolic treatment for osteoporosis. Whole-body vibration exercise (WBV) has been found to stimulate muscle and bone strength in some studies. Animal data demonstrate a beneficial effect on bone when combining PTH with mechanical loading. The aim of this study was to investigate if combining WBV exercise and teriparatide treatment gives additional beneficial effects on bone compared to teriparatide alone in postmenopausal women with osteoporosis.

METHODS

The PaVOS study is a randomized controlled trial where postmenopausal osteoporotic women starting teriparatide 20 μg/day were randomized to WBV + teriparatide or teriparatide alone. WBV consisted of three sessions a week (12 min, including 1:1 ratio of exercise:rest). Bone mineral density (BMD) and bone microarchitecture, bone turnover markers, and sclerostin measurements were obtained. Data were analyzed using a linear mixed regression model with adjustment for baseline values or robust cluster regression in an intention-to-treat (ITT) analysis.

RESULTS

Thirty-five women were randomized (17 in teriparatide + WBV group and 18 in teriparatide group). At 12 months, both groups increased significantly in BMD at the lumbar spine. The teriparatide + WBV group increased by (mean ± SD) 8.90% ± 5.47 and the teriparatide group by 6.65% ± 5.51. The adjusted treatment effect of adding WBV to teriparatide was statistically significant at 2.95% [95% CI = 0.14-5.77; P = 0.040]. Markers of bone turnover increased significantly in both groups at three and six months with no significant difference between groups. No other treatment effects were observed in hip BMD, bone microarchitecture parameters, or sclerostin levels in either group.

CONCLUSION

Twelve months of WBV and teriparatide had a significant clinically relevant treatment effect in lumbar spine BMD compared to teriparatide alone in postmenopausal osteoporotic women. ClinicalTrials.gov :(NCT02563353).

Intermittent parathyroid hormone 1-34 induces oxidation and deterioration of mineral and collagen quality in newly formed mandibular bone

Intermittent parathyroid hormone (PTH) administration is known to promote bone healing after surgical procedures. However, the mechanism and influence of PTH on the mineral and collagen quality of the jaw are not well understood. Most studies have focused on analyzing the bone density and microstructure of the mandible, and have insufficiently investigated its mineral and collagen quality. Oxidative stress activates osteoclasts, produces advanced glycation end products, and worsens mineral and collagen quality. We hypothesized that PTH induces oxidation and affects the mineral and collagen quality of newly formed mandibular bone. To test this, we examined the mineral and collagen quality of newly formed mandibular bone in rats administered PTH, and analyzed serum after intermittent PTH administration to examine the degree of oxidation. PTH administration reduced mineralization and worsened mineral and collagen quality in newly formed bone. In addition, total anti-oxidant capacity in serum was significantly decreased and the oxidative-INDEX was increased among PTH-treated compared to vehicle-treated rats, indicating serum oxidation. In conclusion, intermittent administration of PTH reduced mineral and collagen quality in newly formed mandibular bone. This effect may have been induced by oxidation.

Targeted Drug Delivery from Titanium Implants: A Review of Challenges and Approaches

Titanium implants are considered the gold standard of treatment for dental and orthopedic applications. Biocompatibility, low elasticity, and corrosion resistance are some of the key properties of these metallic implants. Nonetheless, a long-term clinical failure of implants may occur due to inadequate osseointegration. Poor osseointegration induces mobility, inflammation, increased bone resorption, and osteolysis; hence, it may result in painful revision surgeries. Topographical modifications, improvement in hydrophilicity, and the development of controlled-release drug-loading systems have shown to improve cellular adhesion, proliferation, and differentiation. Surface modifications, along with drug coating, undoubtedly demonstrate better osseointegration, especially in challenged degenerative conditions, such as osteoporosis, osteoarthritis, and osteogenesis imperfecta. Anabolic bone-acting drugs, such as parathyroid hormone peptides, simvastatin, prostaglandin-EP4-receptor antagonist, vitamin D, strontium ranelate, and anti-catabolic bone-acting drugs, such as calcitonin, bisphosphonates, and selective estrogen receptor modulators, expedite the process of osseointegration. In addition, various proteins, peptides, and growth factors may accessorize the idea of localized therapy. Loading these substances on modified titanium surfaces is achieved commonly by mechanisms such as direct coating, adsorption, and incorporating in biodegradable polymers. The primary approach toward the optimum drug loading is a critical trade-off between factors preventing release of a drug immediately and those allowing slow and sustained release. Recent advances broaden the understanding of the efficacy of adsorption, hydrogel coating, and electrospinning layer-by-layer coating facilitated by differential charge on metallic surface. This review discusses the existing approaches and challenges for the development of stable and sustained drug delivery systems on titanium implants, which would promote faster and superior osseointegration.

The effect of low-magnitude high-frequency loading on peri-implant bone healing and implant osseointegration in Beagle dogs

PURPOSE

Low-magnitude, high-frequency (LMHF) loading plays an important role in bone healing. The present study aimed to evaluate the effect of LMHF loading applied directly to titanium dental implants on peri-implant bone healing and implant osseointegration.

METHODS

The mandibular premolars and molars were extracted from six male Beagle dogs. Three months post-extraction, each of the six dogs had three titanium implants (Aadva Standard Implant Narrow, Φ3.3×8mm) inserted into the mandibular premolar and molar area (three implants per side). In each animal, one side was randomly selected to undergo daily LMHF loading (treatment group), while the other side had no further intervention (control). The loading was applied directly to the implant abutment using an individual jig and a custom-made loading device (8μm, 100Hz). The implant stability quotient (ISQ) was tested every week. Three dogs were euthanized after 2 weeks, and three were euthanized after 8 weeks. Tissue samples were fixed and stained for micro-computed tomography (micro-CT) and histomorphometric analyses. Data were analyzed statistically, with significance set at p<0.05.

RESULTS

The treatment group had significantly increased peri-implant bone volume relative to tissue volume in region of interest 2 (100-500μm) compared with the control group after 2 weeks of loading (p<0.05); however, there was no significant difference between groups after 8 weeks. The ISQ value and the micro-CT results did not differ between groups during the study period.

CONCLUSIONS

LMHF loading positively influenced peri-implant bone healing in the early healing period.