Parathyroid hormone for bone regeneration

Tmem119 deficiency delays bone repair in mice

Tmem119 was identified as a bone anabolic factor in osteoblasts, however the roles of Tmem119 on bone repair have remained unknown. Therefore, we herein investigated the roles of Tmem119 on bone repair by examining the bone repair process after a femoral bone defect using Tmem119-deficient mice. In Tmem119-deficient mice, bone repair after a femoral bone defect was significantly delayed 10 and 14 days after bone injury in female and male mice with 3-dimensional micro-computed tomography analyses, respectively. The number of alkaline phosphatase-positive cells at the damaged sites was significantly decreased 7 days after bone injury in Tmem119-deficient mice, although the number of Osterix-positive cells was not significantly different 4 days after bone injury. The number of tartrate-resistant acid phosphatase-positive multinucleated cells as well as the number and luminal area of CD31-positive vessels at the damaged sites were not significantly different between Tmem119-deficient and wild-type mice. The present study first showed that Tmem119 deficiency delayed bone repair partly through a decrease in the osteoblastic bone formation of differentiated osteoblasts.

Jaw osteoporosis: Challenges to oral health and emerging perspectives of treatment

Osteoporosis is a prevalent bone metabolic disease that poses a significant challenge to global human health. Jaw osteoporosis, characterized by microstructural damage of the jaw resulting from various factors, is one of the common manifestations of this condition. Recent studies have demonstrated that jaw osteoporosis has multifaceted effects on oral health and can negatively impact conditions such as periodontitis, oral implantation, orthodontic treatment, and wound healing. However, there are still some limitations in the conventional treatment of osteoporosis. For instance, while bisphosphonates can enhance bone quality, they may also lead to osteonecrosis of the jaw, which poses a potential safety hazard in oral diagnosis and treatment. In recent years, considerable attention has been focused on improving the pathological condition of jaw osteoporosis. Treatment strategies such as gut microbial regulation, extracellular vesicles, molecular targeted therapy, herbal medicine, mechanical stimulation are expected to enhance efficacy and minimize adverse reactions. Therefore, understanding these effects and exploring novel treatments for jaw osteoporosis may provide new insights for oral health maintenance and disease treatment. This article reviews the impact of jaw osteoporosis on oral health and describes the limitations associated with current methods. It also discusses emerging perspectives on treatment, offering a comprehensive overview of the challenges and future directions in managing jaw osteoporosis.

Collagen structures of demineralized bone paper direct mineral metabolism

Bone is a dynamic mineralized tissue that undergoes continuous turnover throughout life. While the general mechanism of bone mineral metabolism is documented, the role of underlying collagen structures in regulating osteoblastic mineral deposition and osteoclastic mineral resorption remains an active research area, partly due to the lack of biomaterial platforms supporting accurate and analytical investigation. The recently introduced osteoid-inspired demineralized bone paper (DBP), prepared by 20-μm thin sectioning of demineralized bovine compact bone, holds promise in addressing this challenge as it preserves the intrinsic bony collagen structure and retains semi-transparency. Here, we report on the impact of collagen structures on modulating osteoblast and osteoclast-driven bone mineral metabolism using vertical and transversal DBPs that exhibit a uniaxially aligned and a concentric ring collagen structure, respectively. Translucent DBP reveals these collagen structures and facilitates longitudinal tracking of mineral deposition and resorption under brightfield microscopy for at least 3 wk. Genetically labeled primary osteogenic cells allow fluorescent monitoring of these cellular processes. Osteoblasts adhere and proliferate following the underlying collagen structures of DBPs. Osteoblastic mineral deposition is significantly higher in vertical DBP than in transversal DBP. Spatiotemporal analysis reveals notably more osteoblast adhesion and faster mineral deposition in vascular regions than in bone regions. Subsequent osteoclastic resorption follows these mineralized collagen structures, directing distinct trench and pit-type resorption patterns. In vertical DBP, trench-type resorption occurs at an 80% frequency, whereas transversal DBP shows 35% trench-type and 65% pit-type resorption. Our studies substantiate the importance of collagen structures in regulating mineral metabolism by osteogenic cells. DBP is expected to serve as an enabling biomaterial platform for studying various aspects of cellular and extracellular bone remodeling biology.

Dental implant considerations in patients with systemic diseases: An updated comprehensive review

BACKGROUND

Various medical conditions and the drugs used to treat them have been shown to impede or complicate dental implant surgery. It is crucial to carefully monitor the medical status and potential post-operative complications of patients with systemic diseases, particularly elderly patients, to minimize the risk of health complications that may arise.

AIM

The purpose of this study was to review the existing evidence on the viability of dental implants in patients with systemic diseases and to provide practical recommendations to achieve the best possible results in the corresponding patient population.

METHODS

The information for our study was compiled using data from PubMed, Scopus, Web of Science and Google Scholar databases and searched separately for each systemic disease included in our work until October 2023. An additional manual search was also performed to increase the search sensitivity. Only English-language publications were included and assessed according to titles, abstracts and full texts.

RESULTS

In total, 6784 studies were found. After checking for duplicates and full-text availability, screening for the inclusion criteria and manually searching reference lists, 570 articles remained to be considered in this study.

CONCLUSION

In treating patients with systemic conditions, the cost-benefit analysis should consider the patient's quality of life and expected lifespan. The success of dental implants depends heavily on ensuring appropriate maintenance therapy, ideal oral hygiene standards, no smoking and avoiding other risk factors. Indications and contraindications for dental implants in cases of systemic diseases are yet to be more understood; broader and hardcore research needs to be done for a guideline foundation.

Bone and Joint-on-Chip Platforms: Construction Strategies and Applications

Organ-on-a-chip, also known as "tissue chip," is an advanced platform based on microfluidic systems for constructing miniature organ models in vitro. They can replicate the complex physiological and pathological responses of human organs. In recent years, the development of bone and joint-on-chip platforms aims to simulate the complex physiological and pathological processes occurring in human bones and joints, including cell-cell interactions, the interplay of various biochemical factors, the effects of mechanical stimuli, and the intricate connections between multiple organs. In the future, bone and joint-on-chip platforms will integrate the advantages of multiple disciplines, bringing more possibilities for exploring disease mechanisms, drug screening, and personalized medicine. This review explores the construction and application of Organ-on-a-chip technology in bone and joint disease research, proposes a modular construction concept, and discusses the new opportunities and future challenges in the construction and application of bone and joint-on-chip platforms.

Pharmaceutical Management of Secondary Hyperparathyroidism and the Role of Surgery: A 5-Year Retrospective Study

Background and Objectives: Secondary hyperparathyroidism (SHPT) poses a common condition among patients with chronic kidney disease (CKD) due to the chronic stimulation of the parathyroid glands as a result of persistently low calcium levels. As a first option for medical treatment, vitamin D receptor analogs (VDRAs) and calcimimetic agents are generally used. Apart from cinacalcet, which is orally taken, in recent years, another calcimimetic agent, etelcalcetide, is being administered intravenously during dialysis. Materials and Methods: In a 5-year retrospective study between 2018 and 2023, 52 patients undergoing dialysis were studied. The aim of this study is to highlight the possible effects and/or benefits that intravenously administered calcimimetic agents have on CKD patients. A total of 34 patients (65.4%) received cinacalcet and etelcalcetide while parathormone (PTH) and calcium serum levels were monitored on a monthly basis. Results: A total of 29 out of 33 patients (87.9%) that received treatment with etelcalcetide showed a significant decrease in PTH levels, which rose up to 57% compared to the initial values. None of the included patients needed to undergo parathyroidectomy (PTx) due to either extremely high and persistent PTH levels or severe side effects of the medications. It is generally strongly advised that parathyroidectomies should be performed by an expert surgical team. In recent years, a significant decrease in parathyroidectomies has been recorded globally, a fact that is mainly linked to the constantly wider use of new calcimimetic agents. This decrease in parathyroidectomies has resulted in an important decrease in complications occurring in cervical surgeries (e.g., perioperative hemorrhage and nerve damage). Conslusions: Despite the fact that these surgical complications cannot be easily compared to the pharmaceutical side effects, the recorded decrease in parathyroidectomies is considered to be notable, especially in cases of relapse where a difficult reoperation would be considered based on previously published guidelines.

Comparative Analysis of Stromal Vascular Fraction and Alternative Mechanisms in Bone Fracture Stimulation to Bridge the Gap between Nature and Technological Advancement: A Systematic Review

BACKGROUND

Various stimulation methods, including electrical, ultrasound, mechanical, and biological interventions, are explored, each leveraging intricate cellular and molecular dynamics to expedite healing. The advent of stromal vascular fraction (SVF) marks a significant stride, offering multifarious benefits in bone healing, from enhanced bone formation to optimal vascular integration, drawing a harmonious balance between innate mechanisms and scientific advancements.

METHODS

This systematic review was conducted focusing on literature from 2016 to 2023 and encompassing various bone healing stimulation mechanisms like SVF, electrical, ultrasound, and mechanical stimulation. The extracted data underwent meticulous synthesis and analysis, emphasizing comparative evaluations of mechanisms, applications, and outcomes of each intervention.

RESULTS

The reviewed studies reveal the potential of SVF in bone fracture healing, with its regenerative and anti-inflammatory effects. The purification of SVF is crucial for safe therapeutic use. Characterization involves flow cytometry and microscopy. Studies show SVF's efficacy in bone regeneration, versatility in various contexts, and potential for clinical use. SVF appears superior to electrical, ultrasound, and mechanical stimulation, with low complications.

CONCLUSIONS

This review compares bone healing methods, including SVF. It provides valuable insights into SVF's potential for bone regeneration. However, due to limited human studies and potential bias, cautious interpretation is necessary. Further research is essential to validate these findings and determine the optimal SVF applications in bone healing.

Active components and mechanisms of total flavonoids from Rhizoma Drynariae in enhancing cranial bone regeneration: An investigation employing serum pharmacochemistry and network pharmacology approaches

ETHNOPHARMACOLOGICAL RELEVANCE

Rhizoma Drynariae, as the dried rhizome of Drynaria fortunei (Kunze ex Mett.) J. Sm., is a traditional Chinese medicine for treating the injury and bone broken of falling and beating. Total flavonoids is considered as the major and effective compounds for the therapeutic efficacy of Rhizoma Drynariae.

AIM OF THE STUDY

To explore the effect of total flavonoids from Rhizoma Drynariae (TFRD) on bone regeneration and the underlying mechanisms.

MATERIALS AND METHODS

The effect of TFRD in various doses on bone reconstruction in cranial bone defect rats was explored in vivo. The active ingredients in TFRD-medicated serum were characterized by serum pharmacochemistry and integrated by network pharmacology analysis and target prediction. To elucidate the underlying mechanism of TFRD on bone regeneration, experimental validation in vitro was executed to assess the influence of different concentrations of TFRD-medicated serum on osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs).

RESULTS

Micro-CT, histological examination, immunohistochemical analysis, and ELSA demonstrated that administration of TFRD could promote bone reconstruction in a rat cranial defect model. We identified 27 active components of TFRD using ultra-high-performance liquid chromatography coupled with tandem mass spectrometry (UHPLC-MS/MS). Results from CCK8, ALP, and Alizarin Red S staining revealed that TFRD-medicated serum notably enhanced BMSCs proliferation and osteogenic differentiation. qRT-PCR and Western blot harvested results consistent with those predicted by network pharmacology, providing further evidence that TFRD activated the TGF-β signaling pathway to benefit bone regeneration.

CONCLUSION

The active components of TFRD modulate the TGF-β signaling pathway to facilitate osteogenesis, thereby repairing cranial bone defects.

Insights into the Mechanism of Osteoporosis and the Available Treatment Options

Osteoporosis, one of the most prevalent bone illnesses, majorly affects postmenopausal women and men over 50 years of age. Osteoporosis is associated with an increased susceptibility to fragility fractures and can result in persistent pain and significant impairment in affected individuals. The primary method for diagnosing osteoporosis involves the assessment of bone mineral density (BMD) through the utilisation of dual energy x-ray absorptiometry (DEXA). The integration of a fracture risk assessment algorithm with bone mineral density (BMD) has led to significant progress in the diagnosis of osteoporosis. Given that osteoporosis is a chronic condition and multiple factors play an important role in maintaining bone mass, comprehending its underlying mechanism is crucial for developing more effective pharmaceutical interventions for the disease. The effective management of osteoporosis involves the utilisation of appropriate pharmacological agents in conjunction with suitable dietary interventions and lifestyle modifications. This review provides a comprehensive understanding of the types of osteoporosis and elucidates the currently available pharmacological treatment options and their related mechanism of action and usage.

Functional and analytical recapitulation of osteoclast biology on demineralized bone paper

Osteoclasts are the primary target for osteoporosis drug development. Recent animal studies revealed the crucial roles of osteoblasts in regulating osteoclastogenesis and the longer lifespans of osteoclasts than previously thought with fission and recycling. However, existing culture platforms are limited to replicating these newly identified cellular processes. We report a demineralized bone paper (DBP)-based osteoblast culture and osteoclast assay platform that replicates osteoclast fusion, fission, resorption, and apoptosis with high fidelity and analytical power. An osteoid-inspired DBP supports rapid and structural mineral deposition by osteoblasts. Coculture osteoblasts and bone marrow monocytes under biochemical stimulation recapitulate osteoclast differentiation and function. The DBP-based bone model allows longitudinal quantitative fluorescent monitoring of osteoclast responses to bisphosphonate drug, substantiating significantly reducing their number and lifespan. Finally, we demonstrate the feasibility of humanizing the bone model. The DBP-based osteo assay platforms are expected to advance bone remodeling-targeting drug development with improved prediction of clinical outcomes.

Parathyroid hormone stimulates bone regeneration in an atrophic non-union model in aged mice

BACKGROUND

Non-union formation still represents a major burden in trauma and orthopedic surgery. Moreover, aged patients are at an increased risk for bone healing failure. Parathyroid hormone (PTH) has been shown to accelerate fracture healing in young adult animals. However, there is no information whether PTH also stimulates bone regeneration in atrophic non-unions in the aged. Therefore, the aim of the present study was to analyze the effect of PTH on bone regeneration in an atrophic non-union model in aged CD-1 mice.

METHODS

After creation of a 1.8 mm segmental defect, mice femora were stabilized by pin-clip fixation. The animals were treated daily with either 200 mg/kg body weight PTH 1-34 (n = 17) or saline (control; n = 17) subcutaneously. Bone regeneration was analyzed by means of X-ray, biomechanics, micro-computed tomography (µCT) imaging as well as histological, immunohistochemical and Western blot analyses.

RESULTS

In PTH-treated animals bone formation was markedly improved when compared to controls. This was associated with an increased bending stiffness as well as a higher number of tartrate-resistant acid phosphatase (TRAP)-positive osteoclasts and CD31-positive microvessels within the callus tissue. Furthermore, PTH-treated aged animals showed a decreased inflammatory response, characterized by a lower number of MPO-positive granulocytes and CD68-positive macrophages within the bone defects when compared to controls. Additional Western blot analyses demonstrated a significantly higher expression of cyclooxygenase (COX)-2 and phosphoinositide 3-kinase (PI3K) in PTH-treated mice.

CONCLUSION

Taken together, these findings indicate that PTH is an effective pharmacological compound for the treatment of non-union formation in aged animals.

The Navicular Cuneiform Joint: Updates on Avoiding and Managing a Nonunion

Naviculocuneiform arthrodesis, while often used to support the medial column during management of primary/post-traumatic arthritis, deformity correction, or in the surgical treatment of progressive collapsing foot deformity, can develop nonunion. Addressing this condition hinges on the assessment of various parameters such as patient/host factors and recognition of the etiology of the nonunion. In this article, methods of optimizing this surgical intervention through anatomic and physiologic considerations are highlighted. Further, information is provided to assist foot and ankle surgeons in performing a comprehensive work-up to allow for successful reconstruction and optimal patient outcomes.

Bioactive Materials for Bone Regeneration: Biomolecules and Delivery Systems

Novel tissue regeneration strategies are constantly being developed worldwide. Research on bone regeneration is noteworthy, as many promising new approaches have been documented with novel strategies currently under investigation. Innovative biomaterials that allow the coordinated and well-controlled repair of bone fractures and bone loss are being designed to reduce the need for autologous or allogeneic bone grafts eventually. The current engineering technologies permit the construction of synthetic, complex, biomimetic biomaterials with properties nearly as good as those of natural bone with good biocompatibility. To ensure that all these requirements meet, bioactive molecules are coupled to structural scaffolding constituents to form a final product with the desired physical, chemical, and biological properties. Bioactive molecules that have been used to promote bone regeneration include protein growth factors, peptides, amino acids, hormones, lipids, and flavonoids. Various strategies have been adapted to investigate the coupling of bioactive molecules with scaffolding materials to sustain activity and allow controlled release. The current manuscript is a thorough survey of the strategies that have been exploited for the delivery of biomolecules for bone regeneration purposes, from choosing the bioactive molecule to selecting the optimal strategy to synthesize the scaffold and assessing the advantages and disadvantages of various delivery strategies.

Phytochemical Compounds Involved in the Bone Regeneration Process and Their Innovative Administration: A Systematic Review

Bone metabolism is a complex process which is influenced by the activity of bone cells (e.g., osteocytes, osteoblasts, osteoclasts); the effect of some specific biomarkers (e.g., parathyroid hormone, vitamin D, alkaline phosphatase, osteocalcin, osteopontin, osteoprotegerin, osterix, RANKL, Runx2); and the characteristic signaling pathways (e.g., RANKL/RANK, Wnt/β, Notch, BMP, SMAD). Some phytochemical compounds-such as flavonoids, tannins, polyphenols, anthocyanins, terpenoids, polysaccharides, alkaloids and others-presented a beneficial and stimulating effect in the bone regeneration process due to the pro-estrogenic activity, the antioxidant and the anti-inflammatory effect and modulation of bone signaling pathways. Lately, nanomedicine has emerged as an innovative concept for new treatments in bone-related pathologies envisaged through the incorporation of medicinal substances in nanometric systems for oral or local administration, as well as in nanostructured scaffolds with huge potential in bone tissue engineering.

Human cells with osteogenic potential in bone tissue research

Bone regeneration after injury or after surgical bone removal due to disease is a serious medical challenge. A variety of materials are being tested to replace a missing bone or tooth. Regeneration requires cells capable of proliferation and differentiation in bone tissue. Although there are many possible human cell types available for use as a model for each phase of this process, no cell type is ideal for each phase. Osteosarcoma cells are preferred for initial adhesion assays due to their easy cultivation and fast proliferation, but they are not suitable for subsequent differentiation testing due to their cancer origin and genetic differences from normal bone tissue. Mesenchymal stem cells are more suitable for biocompatibility testing, because they mimic natural conditions in healthy bone, but they proliferate more slowly, soon undergo senescence, and some subpopulations may exhibit weak osteodifferentiation. Primary human osteoblasts provide relevant results in evaluating the effect of biomaterials on cellular activity; however, their resources are limited for the same reasons, like for mesenchymal stem cells. This review article provides an overview of cell models for biocompatibility testing of materials used in bone tissue research.

Identification of the miRNAome in human fracture callus and nonunion tissues

Background

Nonunions remain a challenging post-traumatic complication that often leads to a financial and health burden that affects the patient's quality of life. Despite a wealth of knowledge about fracture repair, especially gene and more recently miRNA expression, much remains unknown about the molecular differences between normal physiological repair (callus tissue) and a nonunion. To probe this lack of knowledge, we embarked on a study that sought to identify and compare the human miRNAome of normal bone to that present in a normal fracture callus and those from two different classic nonunion types, hypertrophic and oligotrophic.

Methods

Normal bone and callus tissue samples were harvested during revision surgery from patients with physiological fracture repair and nonunions (hypertrophic and oligotrophic) and analyzed using histology. Also, miRNAs were isolated and screened using microarrays followed by bioinformatic analyses, including, differential expression, pathways and biological processes, as well as elucidation of target genes.

Results

Out of 30,424 mature miRNAs (from 203 organisms) screened via microarrays, 635 (∼2.1%) miRNAs were found to be upregulated and 855 (∼2.8%) downregulated in the fracture callus and nonunion tissues as compared to intact bone. As our tissue samples were derived from humans, we focused on the human miRNAs and out of the 4223 human miRNAs, 86 miRNAs (∼2.0%) were upregulated and 51 (∼1.2%) were downregulated. Although there were similarities between the three experimental samples, we also found specific miRNAs that were unique to individual samples. We further identified the predicted target genes from these differentially expressed miRNAs as well as the relevant biological processes, including specific signaling pathways that are activated in all three experimental samples.

Conclusion

Collectively, this is the first comprehensive study reporting on the miRNAome of intact bone as compared to fracture callus and nonunion tissues. Further, we identify specific miRNAs involved in normal physiological fracture repair as well as those of nonunions.

The translational potential of this article

The data generated from this study further increase our molecular understanding of the roles of miRNAs during normal and aberrant fracture repair and this knowledge can be used in the future in the development of miRNA-based therapeutics for skeletal regeneration.

Parathyroid hormones in relation to serum cadmium and lead: the NHANES 2003-2006

The toxic effects of cadmium and lead exposure on parathyroid function have been investigated extensively while the results were conflicting. We aimed to investigate the association of blood cadmium and lead with serum parathyroid hormone (PTH) based on the general population. We analyzed a sample of 9400 adults aged 18 years or older from the US National Health and Nutrition Examination Survey 2003-2004 to 2005-2006. We estimated the association using multivariable linear regression analysis by taking cadmium and lead as a continuous or quartile variable. Restricted cubic splines were utilized to explore the non-linear relationship between cadmium or lead and PTH. The median blood cadmium and lead levels were 0.34 µg/L and 1.43 µg/dL, respectively. Cadmium was significantly associated with PTH when taken as a continuous variable [Odds ratio (OR): 0.97; 95% confidence interval (95% CI): 0.95-0.99] or a quartile variable (fourth vs first quartile, OR: 0.94; 95% CI: 0.91-0.97). Lead was significantly associated with PTH when taken as a continuous variable (OR: 1.04; 95% CI: 1.02-1.07) or a quartile variable (fourth vs first quartile, OR: 1.06; 95% CI: 1.01-1.10). P values for non-linearity were all less than 0.05. The association between cadmium and PTH was not significant in females. Cadmium was negatively associated with PTH, and lead was positively associated with PTH both in a non-linear manner among the general population. However, there was a gender difference in the relationship between cadmium and PTH.

Biosimilarity Assessment of the Biosimilar Teriparatide Candidate and the Reference Drug in Healthy Subjects

SAL001, a recombinant form of parathyroid hormone, is a biosimilar drug to teriparatide and is planned to be used in osteoporosis treatment. A single-dose, randomized, open-label, 2-way crossover trial was conducted in healthy subjects to compare the pharmacokinetics (PK) and safety between SAL001 and the reference drug. Sixty-four subjects were enrolled in the study, and 61 subjects completed the study. In each period, 20 μg of the test or reference formulation was administered subcutaneously. SAL001 was administered by autoinjector pen, whereas the reference drug was administered by a self-matched injection pen. Serial blood samples were obtained for the analyses of PK and serum calcium concentration. Geometric mean ratios with 90%CIs for the maximum plasma concentration (C_max ) and area under the plasma concentration-time curve (AUC) were estimated. The safety of these 2 formulations was also evaluated. Overall, the 90%CIs for the geometric mean ratios of C_max , AUC from time 0 to the last quantifiable time point, and AUC from time 0 extrapolated to infinity of the test or reference product were within 80.0%-125.0% of biosimilarity criteria. Other PK parameters, serum calcium concentration, and safety profiles had no significant differences between the 2 formulations. SAL001 demonstrated PK similarity to the reference drug, and the serum calcium concentration and safety profiles of SAL001 were also considered comparable to the reference drug.

Circ_CUX1/miR-130b-5p/p300 axis for parathyroid hormone-stimulation of Runx2 activity in rat osteoblasts: A combined bioinformatic and experimental approach

Parathyroid hormone (PTH) regulates the expression of bone remodeling genes by enhancing the activity of Runx2 in osteoblasts. p300, a histone acetyltransferase, acetylated Runx2 to activate the expression of its target genes. PTH stimulated the expression of p300 in rat osteoblastic cells. Increasing studies suggested the potential of non-coding RNAs (ncRNAs), such as microRNAs (miRNAs) and circular RNAs (circRNAs), in regulating gene expression under both physiological and pathological conditions. In this study, we hypothesized that PTH regulates Runx2 activity via ncRNAs-mediated p300 expression in rat osteoblastic cells. Bioinformatics and experimental approaches identified PTH-upregulation of miR-130b-5p and circ_CUX1 that putatively target p300 and miR-130b-5p, respectively. An antisense-mediated knockdown of circ_CUX1 was performed to determine the sponging activity of circ_CUX1. Knockdown of circ_CUX1 promoted miR-130b-5p activity and reduced p300 expression, resulting in decreased Runx2 acetylation in rat osteoblastic cells. Further, bioinformatics analysis identified the possible signaling pathways that regulate Runx2 activity and osteoblast differentiation via circ_CUX1/miR-130b-5p/p300 axis. The predicted circ_CUX1/miR-130b-5p/p300 axis might pave the way for better diagnostic and therapeutic approaches for bone-related diseases.

Global cannabinoid receptor 1 deficiency affects disuse-induced bone loss in a site-specific and sex-dependent manner

Bone loss during mechanical unloading increases fracture risk and is a major concern for the general population and astronauts during spaceflight. The endocannabinoid system (ECS) plays an important role in bone metabolism. One of the main ECS receptors, cannabinoid receptor 1 (CB1), has been studied in regards to basic bone metabolism; however, little is known as to how CB1 and the ECS affect bone in different mechanical environments. In this study, we analyzed the influence of global CB1 deficiency and sex on mice during disuse caused by single limb immobilization. Female mice were more sensitive to disuse-induced BV/TV loss than males in both the femoral metaphysis and tibial epiphysis. Genotype also affected bone loss in a sex-dependent manner, with male mice deficient in CB1 receptors (CB1KO) and female wildtype (WT) mice experiencing increased bone loss in both the tibial metaphysis and femoral epiphysis. Genotype affected the response to disuse as CB1KO mice displayed greater changes in femoral ultimate force, along with lower tibial ultimate stress, compared to WT mice. Female mice had a significantly higher femoral, and lower tibial ultimate force compared to male mice. These results reveal that disuse-induced bone loss due to CB1 deficiency is sex-dependent. CB1 deficiency in male mice exacerbated bone loss, while in females CB1 deficiency appeared to protect against disuse-induced bone loss. Regardless of genotype, female mice were more sensitive than males to disuse. These results suggest that CB1 receptors may represent a potential therapeutic target for mitigation of disuse-induced bone loss.

Enhanced bone tissue regeneration with hydrogel-based scaffolds by embedding parathyroid hormone in mesoporous bioactive glass

OBJECTIVES

To evaluate hydrogel-based scaffolds embedded with parathyroid hormone (PTH)-loaded mesoporous bioactive glass (MBG) on the enhancement of bone tissue regeneration in vitro.

MATERIALS AND METHODS

MBG was produced via sol-gel technique followed by PTH solution imbibition. PTH-loaded MBG was blended into the hydrogels and submitted to a lyophilisation process associated with a chemical crosslinking reaction to the production of the scaffolds. Characterisation of the MBG and PTH-loaded MBG scaffolds, including the scanning electron microscope (SEM) connected with an X-ray detector (EDX), Fourier transform infrared (FTIR), compression strength, rheological measurements, swelling and degradation rates, and PTH release analysis, were performed. Also, bioactivity using simulated-body fluid (SBF), biocompatibility (MTT), and osteogenic differentiation analyses (von Kossa and Alizarin Red stainings, and μ-computed tomography, μCT) of the scaffolds were carried out.

RESULTS

SEM images demonstrated MBG particles dispersed into the hydrogel-based scaffold structure, which was homogeneously porous and well interconnected. EDX and FTIR revealed large amounts of carbon, oxygen, sodium, and silica in the scaffold composition. Bioactivity experiments revealed changes on sample surfaces over the analysed period, indicating the formation of carbonated hydroxyapatite; however, the chemical composition remained stable. PTH-loaded hydrogel-based scaffolds were biocompatible for stem cells from human-exfoliated deciduous teeth (SHED). A high quantity of calcium deposits on the extracellular matrix of SHED was found for PTH-loaded hydrogel-based scaffolds. μCT images showed MBG particles dispersed into the scaffolds' structure, and a porous, lamellar, and interconnected hydrogel architecture.

CONCLUSIONS

PTH-loaded hydrogel-based scaffolds demonstrated consistent morphology and physicochemical properties for bone tissue regeneration, as well as bioactivity, biocompatibility, and osteoinductivity in vitro. Thus, the scaffolds presented here are recommended for future studies on 3D printing.

CLINICAL RELEVANCE

Bone tissue regeneration is still a challenge for several approaches to oral and maxillofacial surgeries, though tissue engineering applying SHED, scaffolds, and osteoinductive mediators might help to overcome this clinical issue.

Dynamic Balance between PTH1R-Dependent Signal Cascades Determines Its Pro- or Anti-Osteogenic Effects on MSC

Parathyroid hormone (PTH) is one of the key regulators of calcium and phosphate metabolism in the body, controlling bone metabolism and ion excretion by the kidneys. At present, attempts to use PTH as a therapeutic agent have been associated with side-effects, the nature of which is not always clear and predictable. In addition, it is known that in vivo impairment of PTH post-receptor signaling is associated with atypical differentiation behavior not only of bone cells, but also of connective tissues, including adipose tissue. In this work, we studied the functional responses of multipotent mesenchymal stromal cells (MSCs) to the action of PTH at the level of single cells. We used MSCs isolated from the periosteum and subcutaneous adipose tissue to compare characteristics of cell responses to PTH. We found that the hormone can activate three key responses via its receptor located on the surface of MSCs: single transients of calcium, calcium oscillations, and hormone-activated smooth increase in intracellular calcium. These types of calcium responses led to principally different cellular responses of MSCs. The cAMP-dependent smooth increase of intracellular calcium was associated with pro-osteogenic action of PTH, whereas phospholipase C dependent calcium oscillations led to a decrease in osteogenic differentiation intensity. Different variants of calcium responses are in dynamic equilibrium. Suppression of one type of response leads to increased activation of another type and, accordingly, to a change in the effect of PTH on cell differentiation.

Parathyroid Hormone Secretion and Related Syndromes

In this article, we will get to know about the parathyroid hormone and the parathyroid gland. Its anatomy, physiology, and pathology will be delved into. There will be a brief discussion about its secretion and also about various clinical syndromes related to it. Parathormone, the parathyroid glands, regulate normal calcium and phosphorus levels in the body. An increase in the secretion of parathormone results in increased calcium uptake from the kidney, intestine, and bones, hence elevating the blood calcium level. A few mechanisms of action of this hormone are increased by the presence of vitamin D. The increase in the secretion of this hormone as compared to the normal levels is termed hyperparathyroidism. Incidence is maximum after 60 years of age. The ratio of females to males is 2:1. There are three types of hyperparathyroidism which will be described in this article. Clinical manifestations of hyperparathyroidism include skeletal disease, renal involvement, GI manifestations, psychiatric diseases, decreased neuro-muscular irritability, decreased deep tendon reflexes, muscular weakness, and atrophy. Assessment for hyperparathyroidism can be done by various diagnostic tests which are described further in this article. Medical/surgical management to cure this is also well-established nowadays. The decrease in the secretion of this hormone as compared to normal levels is termed hypoparathyroidism. Serum calcium levels are very low, serum phosphate levels are very high, and tetany can develop. The incidence is that females are more prone than males. Assessment for acute hypoparathyroidism will show positive Chvostek sign and trousseau sign, hyperactive deep tendon reflexes, and paresthesia. Assessment of chronic hypoparathyroidism will show lethargy, weakness, fatigue, cataracts, brittle nails, dry scaly skin, personality changes, and can even cause permanent brain damage. The normal secretion process of this hormone and diseases when its secretion becomes abnormal and why that happens are briefed in this article.

Taohong Siwu Decoction Promotes Osteo-Angiogenesis in Fractures by Regulating the HIF-1α Signaling Pathway

Background

Vascular damage is a major consequence of bone fracture. Taohong Siwu decoction (TSD) can raise the expression of vascular endothelial growth factor (VEGF) in fracture healing. However, its molecular mechanism in promoting angiogenesis is still unknown. The aim of this study was to investigate the potential mechanisms of TSD in the regulation of osteo-angiogenesis in fracture healing.

Methods

A rat tibial fracture model was established. After low- (4.5 g·kg⁻¹), medium- (9 g·kg⁻¹), and high-dose TSD (18 g·kg⁻¹) and panax notoginsenoside (25 mg kg⁻¹) treatment, hematoxylin-eosin staining was employed to visualize pathological changes in bone tissues. The levels of cytokines (interleukin (IL)-2, tumor necrosis factor-α (TNF-α), IL-6, and IL-1β), thromboxane B2 (TXB2), and 6 ketone prostaglandin F1α (6-Keto-PGF1α) were quantified by enzyme-linked immunosorbent assay (ELISA). Immunofluorescence was used to identify the rat aortic endothelial cells (RAECs). Control serum, 10% TSD-containing serum, and 10% TSD-containing serum combined with hypoxia-inducible factor-1α (HIF-1α) inhibitor were used to treat the RAECs and rat osteoblasts. Transwell migration assay was utilized to examine the migration of the RAECs. The Matrigel tubulogenesis assay was used for the assessment of angiogenesis. The expression of angiogenesis- (von Hippel-Lindau tumor suppressor (VHL), HIF-1α, VEGF, angiopoietin-2 (Ang-2), and pVHL) and osteogenesis-related (alkaline phosphatase (ALP), runt-related transcription factor 2 (Runx2), and osteopontin-1 (OPN-1)) protein and gene was detected by western blot and quantitative real-time PCR (qRT-PCR).

Results

Compared with the model group, TSD increased the trabecular bone areas, numbers, and thicknesses in fractured rats. In the plasma, the levels of cytokines and TXB2 in the middle- and high-dose TSD group were significantly lower than those in the model group (P < 0.01). The 6-keto-PGF1α content was increased by middle- and high-dose TSD intervention (P < 0.01). Compared to the control serum group, the angiogenesis and migration of the RAECs were enhanced in the TSD group (P < 0.001). The expression of HIF-1α, VEGF, and Ang-2 in the TSD group upregulated significantly (P < 0.001). VHL and pVHL were inhibited under TSD-containing serum treatment (P < 0.001). ALP, Runx2, and OPN-1 were increased obviously in the TSD group (P < 0.001). Nevertheless, the HIF-1α inhibitor reversed these changes (P < 0.001).

Conclusion

TSD promotes angiogenesis and osteogenesis by regulating the HIF-1α signaling pathway. Meanwhile, it can effectively reduce the risk of inflammation and improve blood circulation.

Hormone and implant osseointegration: Elaboration of the relationship among function, preclinical, and clinical practice

As clusters of peptides or steroids capable of high-efficiency information transmission, hormones have been substantiated to coordinate metabolism, growth, development, and other physiological processes, especially in bone physiology and repair metabolism. In recent years, the application of hormones for implant osseointegration has become a research hotspot. Herein, we provide a comprehensive overview of the relevant reports on endogenous hormones and their corresponding supplementary preparations to explore the association between hormones and the prognosis of implants. We also discuss the effects and mechanisms of insulin, parathyroid hormone, melatonin, vitamin D, and growth hormone on osseointegration at the molecular and body levels to provide a foothold and guide future research on the systemic conditions that affect the implantation process and expand the relative contraindications of the implant, and the pre-and post-operative precautions. This review shows that systemic hormones can regulate the osseointegration of oral implants through endogenous or exogenous drug-delivery methods.

Locally Applied Repositioned Hormones for Oral Bone and Periodontal Tissue Engineering: A Narrative Review

Bone and periodontium are tissues that have a unique capacity to repair from harm. However, replacing or regrowing missing tissues is not always effective, and it becomes more difficult as the defect grows larger. Because of aging and the increased prevalence of debilitating disorders such as diabetes, there is a considerable increase in demand for orthopedic and periodontal surgical operations, and successful techniques for tissue regeneration are still required. Even with significant limitations, such as quantity and the need for a donor area, autogenous bone grafts remain the best solution. Topical administration methods integrate osteoconductive biomaterial and osteoinductive chemicals as hormones as alternative options. This is a promising method for removing the need for autogenous bone transplantation. Furthermore, despite enormous investigation, there is currently no single approach that can reproduce all the physiologic activities of autogenous bone transplants. The localized bioengineering technique uses biomaterials to administer different hormones to capitalize on the host’s regeneration capacity and capability, as well as resemble intrinsic therapy. The current study adds to the comprehension of the principle of hormone redirection and its local administration in both bone and periodontal tissue engineering.

Traditional Chinese Medicine as a Promising Strategy for the Treatment of Alzheimer's Disease Complicated With Osteoporosis

Alzheimer’s disease (AD) and osteoporosis (OP) are progressive degenerative diseases caused by multiple factors, placing a huge burden on the world. Much evidence indicates that OP is a common complication in AD patients. In addition, there is also evidence to show that patients with OP have a higher risk of AD than those without OP. This suggests that the association between the two diseases may be due to a pathophysiological link rather than one disease causing the other. Several in vitro and in vivo studies have also proved their common pathogenesis. Based on the theory of traditional Chinese medicine, some classic and specific natural Chinese medicines are widely used to effectively treat AD and OP. Current evidence also shows that these treatments can ameliorate both brain damage and bone metabolism disorder and further alleviate AD complicated with OP. These valuable therapies might provide effective and safe alternatives to major pharmacological strategies.

Supramolecular Peptide Nanofiber Hydrogels for Bone Tissue Engineering: From Multihierarchical Fabrications to Comprehensive Applications

Bone tissue engineering is becoming an ideal strategy to replace autologous bone grafts for surgical bone repair, but the multihierarchical complexity of natural bone is still difficult to emulate due to the lack of suitable biomaterials. Supramolecular peptide nanofiber hydrogels (SPNHs) are emerging biomaterials because of their inherent biocompatibility, satisfied biodegradability, high purity, facile functionalization, and tunable mechanical properties. This review initially focuses on the multihierarchical fabrications by SPNHs to emulate natural bony extracellular matrix. Structurally, supramolecular peptides based on distinctive building blocks can assemble into nanofiber hydrogels, which can be used as nanomorphology-mimetic scaffolds for tissue engineering. Biochemically, bioactive motifs and bioactive factors can be covalently tethered or physically absorbed to SPNHs to endow various functions depending on physiological and pharmacological requirements. Mechanically, four strategies are summarized to optimize the biophysical microenvironment of SPNHs for bone regeneration. Furthermore, comprehensive applications about SPNHs for bone tissue engineering are reviewed. The biomaterials can be directly used in the form of injectable hydrogels or composite nanoscaffolds, or they can be used to construct engineered bone grafts by bioprinting or bioreactors. Finally, continuing challenges and outlook are discussed.

Advanced Surface Modification for 3D-Printed Titanium Alloy Implant Interface Functionalization

With the development of three-dimensional (3D) printed technology, 3D printed alloy implants, especially titanium alloy, play a critical role in biomedical fields such as orthopedics and dentistry. However, untreated titanium alloy implants always possess a bioinert surface that prevents the interface osseointegration, which is necessary to perform surface modification to enhance its biological functions. In this article, we discuss the principles and processes of chemical, physical, and biological surface modification technologies on 3D printed titanium alloy implants in detail. Furthermore, the challenges on antibacterial, osteogenesis, and mechanical properties of 3D-printed titanium alloy implants by surface modification are summarized. Future research studies, including the combination of multiple modification technologies or the coordination of the structure and composition of the composite coating are also present. This review provides leading-edge functionalization strategies of the 3D printed titanium alloy implants.

Effects of local single dose administration of parathormone on the early stages of osseointegration: A pre-clinical study

The present study aimed to evaluate the effect of parathormone (PTH) administered directly to the implant's surface prior to insertion, using a large translational animal model. Sixty titanium implants were divided into four groups: (i) Collagen, control group, where implants were coated with Type-I Bovine-collagen, and three experimental groups, where implants received varying doses of PTH: (ii) 12.5, (iii) 25, and (iv) 50 μg, prior to placement. Fifteen female sheep (~2 years old, weighing ~65 kg) received four implants in an interpolated fashion in C3, C4 or C5 vertebral bodies. After 3-, 6- and 12-weeks, samples were harvested, histologically processed, qualitatively and quantitatively assessed for bone-to-implant contact (BIC) and bone area fraction occupancy (BAFO). BIC yielded lower values at 6-weeks for 50 μg relative to the control group, with no significant differences, when compared to the 12.5- and 25-μg. No significant differences were detected at 6-weeks between collagen, 12.5- and 25-μg groups. At 3- and 12-weeks, no differences were detected for BIC among PTH groups. With respect to BAFO, no significant differences were observed between the control and experimental groups independent of PTH concentration and time in vivo. Qualitative observations at 3-weeks indicated the presence of a more mature bone near the implant's surface with the application of PTH, however, no significant differences in new bone formation or healing patterns were observed at 6- and 12-weeks. Single local application of different concentrations of PTH on titanium implant's surface did not influence the osseointegration at any time-point evaluation in low-density bone.

Procalcitonin is expressed in osteoblasts and limits bone resorption through inhibition of macrophage migration during intermittent PTH treatment

Intermittent injections of parathyroid hormone (iPTH) are applied clinically to stimulate bone formation by osteoblasts, although continuous elevation of parathyroid hormone (PTH) primarily results in increased bone resorption. Here, we identified Calca, encoding the sepsis biomarker procalcitonin (ProCT), as a novel target gene of PTH in murine osteoblasts that inhibits osteoclast formation. During iPTH treatment, mice lacking ProCT develop increased bone resorption with excessive osteoclast formation in both the long bones and axial skeleton. Mechanistically, ProCT inhibits the expression of key mediators involved in the recruitment of macrophages, representing osteoclast precursors. Accordingly, ProCT arrests macrophage migration and causes inhibition of early but not late osteoclastogenesis. In conclusion, our results reveal a potential role of osteoblast-derived ProCT in the bone microenvironment that is required to limit bone resorption during iPTH.

Possible effects of hyperparathyroidism in the loss of osseointegration of dental implants: A case report

Background: Hyperparathyroidism (HPT) is a common endocrine disorder with potential complications on the skeletal, renal, neurocognitive and cardiovascular systems. Its association with the lack of osseointegration of dental implants has not been described in the medical literature. Case presentation: This case report aims to discuss two cases of dental implant loss in which a high level of parathormone (PTH) was found in the absence of any other systemic or local comorbidity, suggesting the possible correlation between HPT and implant. Both patients were referred to the clinic complaining about prosthetic complications, gingival inflammation and mobility of the dental prosthesis. After a Cone-Beam computed Tomography evaluation, all implants of both patients were removed for rejection arising from periimplantitis and then four implants were inserted in the patient 1 and five implants in the patient 2. For both patients short implants (Bicon LLC, Boston, Massachusetts, USA), featured by 4 mm in diameter and 5 mm in height, were used and the prosthesis substructure was made of Trinia® (Bicon LLC, Boston, Massachusetts, USA). During the fifth year, the patients reported complications and the implant treatment failure. In order to establish the causes of failure, a thorough investigation was performed. Since no causes were detected, the patients were required to perform a blood test to evaluate bone metabolism and specifically to assess parathyroid-hormone levels (PTH), calcium levels and vitamin D. Results: The results of the blood tests showed normal calcemia, vitamin D deficiency and elevated PTH levels in both patients. After an endocrinologist's consultation, secondary hyperparathyroidism was diagnosed. Conclusion: It is reasonable to assume that the loss of osseointegration of dental implants can be correlated with the effects of HPT.

Biomimetic Methacrylated Gelatin Hydrogel Loaded With Bone Marrow Mesenchymal Stem Cells for Bone Tissue Regeneration

Large-segment bone defect caused by trauma or tumor is one of the most challenging problems in orthopedic clinics. Biomimetic materials for bone tissue engineering have developed dramatically in the past few decades. The organic combination of biomimetic materials and stem cells offers new strategies for tissue repair, and the fate of stem cells is closely related to their extracellular matrix (ECM) properties. In this study, a photocrosslinked biomimetic methacrylated gelatin (Bio-GelMA) hydrogel scaffold was prepared to simulate the physical structure and chemical composition of the natural bone extracellular matrix, providing a three-dimensional (3D) template and extracellular matrix microenvironment. Bone marrow mesenchymal stem cells (BMSCS) were encapsulated in Bio-GelMA scaffolds to examine the therapeutic effects of ECM-loaded cells in a 3D environment simulated for segmental bone defects. In vitro results showed that Bio-GelMA had good biocompatibility and sufficient mechanical properties (14.22kPa). A rat segmental bone defect model was constructed in vivo. The GelMA-BMSC suspension was added into the PDMS mold with the size of the bone defect and photocured as a scaffold. BMSC-loaded Bio-GelMA resulted in maximum and robust new bone formation compared with hydrogels alone and stem cell group. In conclusion, the bio-GelMA scaffold can be used as a cell carrier of BMSC to promote the repair of segmental bone defects and has great potential in future clinical applications.

Biophysical Stimuli as the Fourth Pillar of Bone Tissue Engineering

The repair of critical bone defects remains challenging worldwide. Three canonical pillars (biomaterial scaffolds, bioactive molecules, and stem cells) of bone tissue engineering have been widely used for bone regeneration in separate or combined strategies, but the delivery of bioactive molecules has several obvious drawbacks. Biophysical stimuli have great potential to become the fourth pillar of bone tissue engineering, which can be categorized into three groups depending on their physical properties: internal structural stimuli, external mechanical stimuli, and electromagnetic stimuli. In this review, distinctive biophysical stimuli coupled with their osteoinductive windows or parameters are initially presented to induce the osteogenesis of mesenchymal stem cells (MSCs). Then, osteoinductive mechanisms of biophysical transduction (a combination of mechanotransduction and electrocoupling) are reviewed to direct the osteogenic differentiation of MSCs. These mechanisms include biophysical sensing, transmission, and regulation. Furthermore, distinctive application strategies of biophysical stimuli are presented for bone tissue engineering, including predesigned biomaterials, tissue-engineered bone grafts, and postoperative biophysical stimuli loading strategies. Finally, ongoing challenges and future perspectives are discussed.

Research Progress of the Role of Anthocyanins on Bone Regeneration

Bone regeneration in osteoporosis and fragility fractures which are highly associated with age remains a great challenge in the orthopedic field, even though the bone is subjected to a continuous process of remodeling which persists throughout lifelong. Regulation of osteoblast and osteoclast differentiation is recognized as effective therapeutic targets to accelerate bone regeneration in osteopenic conditions. Anthocyanins (ACNs), a class of naturally occurring compounds obtained from colored plants, have received increasing attention recently because of their well-documented biological effects, such as antioxidant, anti-inflammation, and anti-apoptosis in chronic diseases, like osteoporosis. Here, we summarized the detailed research progress on ACNs on bone regeneration and their molecular mechanisms on promoting osteoblast differentiation as well as inhibiting osteoclast formation and differentiation to explore their promising therapeutic application in repressing bone loss and helping fragility fracture healing. Better understanding the role and mechanisms of ACNs on bone regeneration is helpful for the prevention or treatment of osteoporosis and also for the exploration of new bone regenerative medicine.

Systemic Administration of PTH Supports Vascularization in Segmental Bone Defects Filled with Ceramic-Based Bone Graft Substitute

Non-unions continue to present a challenge to trauma surgeons, as current treatment options are limited, duration of treatment is long, and the outcome often unsatisfactory. Additionally, standard treatment with autologous bone grafts is associated with comorbidity at the donor site. Therefore, alternatives to autologous bone grafts and further therapeutic strategies to improve on the outcome and reduce cost for care providers are desirable. In this study in Sprague–Dawley rats we employed a recently established sequential defect model, which provides a platform to test new potential therapeutic strategies on non-unions while gaining mechanistic insight into their actions. The effects of a combinatorial treatment of a bone graft substitute (HACaS+G) implantation and systemic PTH administration was assessed by µ-CT, histological analysis, and bio-mechanical testing and compared to monotreatment and controls. Although neither PTH alone nor the combination of a bone graft substitute and PTH led to the formation of a stable union, our data demonstrate a clear osteoinductive and osteoconductive effect of the bone graft substitute. Additionally, PTH administration was shown to induce vascularization, both as a single adjuvant treatment and in combination with the bone graft substitute. Thus, systemic PTH administration is a potential synergistic co-treatment to bone graft substitutes.

Causal Relationship Between Parathyroid Hormone and the Risk of Osteoarthritis: A Mendelian Randomization Study

Background

Previous studies have demonstrated an inverse association between parathyroid hormone (PTH) and the risk of osteoarthritis (OA). However, it remains unknown whether such association reflects causality. We aimed to apply a Mendelian randomization (MR) approach to investigate the causal association between PTH and OA.

Materials and Methods

We performed a two-sample MR analysis using summary statistics from 13 cohorts (PTH, N = 29,155) and a recent genome-wide association study meta-analysis (OA, N = 455,221) by the UK Biobank and Arthritis Research UK OA Genetics (arcOGEN). MR analyses were carried out mainly using the inverse-variance-weighted method. Sensitivity analyses were performed to test the robustness of the associations using the weighted median method, the MR-Egger method, and "leave-one-out" analysis. Analyses were performed again to test whether the associations remained statistically significant after excluding any outlier variants that were detected using the MR-PRESSO (Mendelian Randomization Pleiotropy RESidual Sum and Outlier) test.

Results

Five single-nucleotide polymorphisms (SNPs) were selected as instrumental variables at the genome-wide significance threshold (p < 5 × 10^-8). The causal effect between PTH and OA was genetically predicted using the inverse-variance-weighted method (odds ratio = 0.67, 95% confidence interval: 0.50-0.90; p = 0.008). This result was borne out using the weighted median method (odds ratio = 0.73, 95% confidence interval: 0.60-0.90; p = 0.004). The causality remained robust after discarding the outlier variants as well as SNPs associated with confounding factors.

Conclusion

MR analysis supported a potential causative relationship between decreased serum circulating PTH and a higher risk of hip and knee OA.

Management of systemic risk factors ahead of dental implant therapy: A beard well lathered is half shaved

As the most successful therapy for missing teeth, dental implant has become increasingly prevalent around the world. A lot of papers have reported diverse local risk factors affecting the success and survival rate of dental implants, either for a short or a long period. However, there are also many types of systemic disorders or relatively administrated medicine that may jeopardize the security and success of dental implant treatment. Additionally, the coronavirus disease 2019 pandemic also poses a challenge to dental implant clinicians. Some of these risk factors are clinically common but to some extent unfamiliar to dentists, thus optimal measurements are often lacking when they occur in dental clinics. In this review, we analyze potential systemic risk factors that may affect the success rate of dental implants. Some of them may affect bone mineral density or enhance the likelihood of local infection, thus impeding osseointegration. Others may even systemically increase the risk of the surgery and threaten patients' life. In order to help novices receive high-risk patients who need to get dental implant treatment in a more reasonable way, we accordingly review recent research results and clinical experiments to discuss promising precautions, such as stopping drugs that impact bone mineral density or the operation, and addressing any perturbations on vital signs.

Parathyroid hormone and its related peptides in bone metabolism

Parathyroid hormone (PTH) is an 84-amino-acid peptide hormone that is secreted by the parathyroid gland. It has different administration modes in bone tissue through which it promotes bone formation (intermittent administration) and bone resorption (continuous administration) and has great potential for application in sbone defect repair. PTH regulates bone metabolism by binding to PTH1R. PTH plays an osteogenic role by acting directly on mesenchymal stem cells, cells with an osteoblastic lineage, osteocytes, and T cells. It also participates as an osteoclast by indirectly acting on osteoclast precursor cells and osteoclasts and directly acting on T cells. In these cells, PTH activates the Wnt signaling, cAMP/PKA, cAMP/PKC, and RANKL/RANK/OPG pathways and other signaling pathways. Although PTH(1-34), also known as teriparatide, has been used clinically, it still has some disadvantages. Developing improved PTH-related peptides is a potential solution to teriparatide's shortcomings. The action mechanism of these PTH-related peptides is not exactly the same as that of PTH. Thus, the mechanisms of PTH and PTH-related peptides in bone metabolism were reviewed in this paper.

Phenanthrenoid Coelogin Isolated from Coelogyne cristata Exerts Osteoprotective Effect Through MAPK-Mitogen-Activated Protein Kinase Signaling Pathway

Osteoporosis is a major health problem in postmenopausal women globally. This study determined the mechanism through which coelogin stimulates osteoblastogenesis and its osteoprotective and bone regenerating potential. Coelogin effect on primary calvarial osteoblast cells was determined by measuring alkaline phosphatase activity, mineralization, osteoblast survival, and apoptosis and protein expression studies. The osteoprotective effect of coelogin was also evaluated on osteopenic adult female Swiss mice. At autopsy, bones were collected for dynamic and histomorphometry studies. Serum samples were also collected for assessment of serum parameters. Coelogin treatment led to increased osteoblast proliferation, survival, differentiation, and mineralization in osteoblast cells. Coelogin supplementation to Ovx mice promoted new bone formation, prevented Ovx-induced deterioration of bone microarchitecture, and enhanced bone regeneration. In addition, signaling studies revealed that coelogin treatment activates the ER-Erk and Akt-dependent signaling pathways which stimulate the osteoblastogenesis in osteoblast cells.

Influence of Intermittent Parathyroid Hormone (PTH) Administration on the Outcomes of Orthodontic Tooth Movement—A Systematic Review

Objective: The aim of this review is to summarize the effects of local and systemic PTH administration on periodontal tissues during orthodontic tooth movement. Materials and methods: An electronic search was conducted on the following databases: PubMed/MEDLINE, Google Scholar, SCOPUS and Embase. On PubMed/MEDLINE, the Medical Subject Headings (MeSH) keywords used were: “orthodontic tooth movement” OR (“tooth” (All Fields) AND “tooth movement” (All Fields)) OR “tooth movement” (All Fields)) AND (“parathyroid hormone”); all studies included using CONSORT. Results: After elimination of duplicates and articles not meeting our inclusion criteria, seven animal studies were included in this review. Although the majority of the studies suggest that PTH may a have a favorable outcome on OTM, most studies were found to have several sources of bias. Conclusion: Animal studies with minimal bias and long-term clinical studies are needed to ascertain the efficacy of intermittent PTH administration in improving the rate and retention of OTM.

DYRK1A Inhibitors as Potential Therapeutics for β-Cell Regeneration for Diabetes

According to the World Health Organization (WHO), 422 million people are suffering from diabetes worldwide. Current diabetes therapies are focused on optimizing blood glucose control to prevent long-term diabetes complications. Unfortunately, current therapies have failed to achieve glycemic targets in the majority of people with diabetes. In this context, regeneration of functional insulin-producing human β-cells in people with diabetes through the use of DYRK1A inhibitor drugs has recently received special attention. Several small molecule DYRK1A inhibitors have been identified that induce human β-cell proliferation in vitro and in vivo. Furthermore, DYRK1A inhibitors have also been shown to synergize β-cell proliferation with other classes of drugs, such as TGFβ inhibitors and GLP-1 receptor agonists. In this perspective, we review the status of DYRK1A as a therapeutic target for β-cell proliferation and provide perspectives on technical and scientific challenges for future translational development.

The role of Zfp467 in mediating the pro-osteogenic and anti-adipogenic effects on bone and bone marrow niche

Conditional deletion of the PTH receptor (Pth1r) in mesenchymal progenitors reduces osteoblast differentiation and bone mass while enhancing adipogenesis and bone marrow adipose tissue. Mechanistically, PTH suppresses the expression of Zfp467, a pro-adipogenic zinc finger transcription factor. Consequently, Pth1r deficiency in mesenchymal progenitors leads to increased Zfp467 expression. Based on these observations, we hypothesized that genetic loss of Zfp467 would lead to a shift in marrow progenitor cell fate towards osteogenesis and increased bone mass. To test this hypothesis, we generated Zfp467-/- mice. Zfp467-/- mice (-/-) were significantly smaller than Zfp467+/+ mice (+/+). μCT showed significantly higher trabecular bone and cortical bone area in -/- vs. +/+, and histomorphometry showed higher structural and dynamic formation parameters in -/- mice vs. +/+. Femoral gene expression including Alpl, Sp7, and Acp5 were increased in -/-mice, whereas Adiponectin, Cebpa, Lepr, and Ppraγ mRNA were lower in -/- mice. Similarly, Fabp4 and Lep in the inguinal depot were also decreased in -/- mice. Moreover, marrow adipocyte numbers were reduced in -/- vs +/+ mice (p<0.007). In vitro, COBs and BMSCs-/- showed more positive ALP and Alizarin Red staining and a decrease in ORO droplets. Pth1r mRNA and protein levels were increased in COBs and BMSCs from -/- mice vs +/+ (p<0.02 for each parameter, -/- vs. +/+). -/- cells also exhibited enhanced endogenous levels of cAMP vs. control cells. Moreover, in an ovariectomy (OVX) mouse model, Zfp467-/- mice had significantly lower fat mass but similar bone mass compared to OVX +/+ mice. In contrast, in a high fat diet (HFD) mouse model, in addition to reduced adipocyte volume and adipogenesis related gene expression in both peripheral and bone marrow fat tissue, greater osteoblast number and higher osteogenesis related gene expression were also observed in -/- HFD mice vs. +/+ HFD mice. Taken together, these results demonstrate that ZFP467 negatively influences skeletal homeostasis and favors adipogenesis. Global deletion of Zfp467 increases PTHR1, cAMP and bone turnover, hence its repression is a component of PTH signaling and its regulation. These data support a critical role for Zfp467 in early lineage allocation and provide a novel potential mechanism by which PTH acts in an anabolic manner on the bone remodeling unit.

Osteogenic potential of the growth factors and bioactive molecules in bone regeneration

The growing need for treatment of the impaired bone tissue has resulted in the quest for the improvement of bone tissue regeneration strategies. Bone tissue engineering is trying to create bio-inspired systems with a coordinated combination of the cells, scaffolds, and bioactive factors to repair the damaged bone tissue. The scaffold provides a supportive matrix for cell growth, migration, and differentiation and also, acts as a delivery system for bioactive factors. Bioactive factors including a large group of cytokines, growth factors (GFs), peptides, and hormonal signals that regulate cellular behaviors. These factors stimulate osteogenic differentiation and proliferation of cells by activating the signaling cascades related to ossification and angiogenesis. GFs and bioactive peptides are significant parts of the bone tissue engineering systems. Besides, the use of the osteogenic potential of hormonal signals has been an attractive topic, particularly in osteoporosis-related bone defects. Due to the unstable nature of protein factors and non-specific effects of hormones, the engineering of scaffolds to the controlled delivery of these bioactive molecules has paramount importance. This review updates the growth factors, engineered peptides, and hormones that are used in bone tissue engineering systems. Also, discusses how these bioactive molecules may be linked to accelerating bone regeneration.

Secreted Protein Acidic and Rich in Cysteine as A Regeneration Factor: Beyond the Tissue Repair

Diverse pathologies (inflammation, tissues injuries, cancer, etc.) and physiological conditions (obesity, physical activity, etc.) induce the expression/secretion of the matricellular protein, secrete protein acidic and rich in cysteine (SPARC). SPARC contributes to the creation of an environment that is suitable for tissue regeneration through a variety of roles, including metabolic homeostasis, inflammation reduction, extracellular matrix remodeling and collagen maturation. Such a homeostatic environment optimizes tissue regeneration and improves tissues’ repair ability. These properties that SPARC has within the regeneration contexts could have a variety of applications, such as in obesity, cancer, sarcopenia, diabetes and bioengineering.

Emerging insights into the comparative effectiveness of anabolic therapies for osteoporosis

Over the past three decades, the mainstay of treatment for osteoporosis has been antiresorptive agents (such as bisphosphonates), which have been effective with continued administration in lowering fracture risk. However, the clinical landscape has changed as adherence to these medications has declined due to perceived adverse effects. As a result, decreases in hip fracture rates that followed the introduction of bisphosphonates have now levelled off, which is coincident with a decline in the use of the antiresorptive agents. In the past two decades, two types of anabolic agents (including three new drugs), which represent a novel approach to improving bone quality by increasing bone formation, have been approved. These therapies are expected to lead to a new clinical paradigm in which anabolic agents will be used either alone or in combination with antiresorptive agents to build new bone and reduce fracture risk. This Review examines the mechanisms of action for these anabolic agents by detailing their receptor-activating properties for key cell types in the bone and marrow niches. Using these advances in bone biology as context, the comparative effectiveness of these anabolic agents is discussed in relation to other therapeutic options for osteoporosis to better guide their clinical application in the future.

Rational design of hydrogels to enhance osteogenic potential

Bone tissue engineering (BTE) encompasses the field of biomaterials, cells, and bioactive molecules to successfully guide the growth and repair of bone tissue. Current BTE strategies rely on delivering osteogenic molecules or cells via scaffolding materials. However, growth factor- and stem cell-based treatments have several limitations, such as source restriction, low stability, difficulties in predicting long-term efficacy, and high costs, among others. These issues have promoted the development of material-based therapy with properties of accessibility, high stability, tunable efficacy, and low-cost production. Hydrogels are widely used in BTE applications because of their unique hydrophilic nature and tunable physicochemical properties to mimic the native bone environment. However, current hydrogel materials are not ideal candidates due to minimal osteogenic capability on their own. Therefore, recent studies of BTE hydrogels attempt to counterbalance these issues by modifying their biophysical properties. In this article, we review recent progress in the design of hydrogels to instruct osteogenic potential, and present strategies developed to precisely control its bone healing properties.

Influence of parathyroid hormone on periodontal healing in animal models: A systematic review

OBJECTIVES

The purpose of this systematic review was to determine the potential interest of parathyroid hormone (PTH) as an adjunct to periodontal treatment based on studies performed in rodents.

MATERIALS & METHODS

Electronic databases (MEDLINE, Web of Science) were searched up to December 2019. Studies assessing the impact of PTH administration in experimental periodontitis in rodents have been identified.

RESULTS

Amongst the 247 identified articles, 10 met the inclusion criteria and were included in this systematic review. Experimental periodontitis was mainly induced by ligature placement or surgically with a dental bur. All studies considered bone healing after PTH administration at different frequencies as primary outcome. Results showed that an intermittent administration of PTH promoted bone healing and neovascularization. Nevertheless, a decrease of soft tissue inflammation was also observed.

CONCLUSION

Intermittent administration of PTH appears to enhance significantly periodontal healing and to promote alveolar bone regeneration. However, due to the risk of side effects, the development of scaffolds allowing its local and time-controlled delivery is of importance.

Impact of Release Kinetics on Efficacy of Locally Delivered Parathyroid Hormone for Bone Regeneration Applications

Characterizing the release profile for materials-directed local delivery of bioactive molecules and its effect on bone regeneration is an important step to improve our understanding of, and ability to optimize, the bone healing response. This study examined the local delivery of parathyroid hormone (PTH) using a thiol-ene hydrogel embedded in a porous poly(propylene fumarate) (PPF) scaffold for bone regeneration applications. The aim of this study was to characterize the degradation-controlled in vitro release kinetics of PTH from the thiol-ene hydrogels, in vivo hydrogel degradation in a subcutaneous implant model, and bone healing in a rat critical size bone defect. Tethering PTH to the hydrogel matrix eliminated the early timepoint burst release that was observed in previous in vitro work where PTH was free to diffuse out of the matrix. Only 8% of the tethered PTH was released from the hydrogel during the first 2 weeks, but by day 21, 80% of the PTH was released, and complete release was achieved by day 28. In vivo implantation revealed that complete degradation of the hydrogel alone occurred by day 21; however, when incorporated in a three-dimensional printed osteoconductive PPF scaffold, the hydrogel persisted for >56 days. Treatment of bone defects with the composite thiol-ene hydrogel-PPF scaffold, delivering either 3 or 10 μg of tethered PTH 1-84, was found to increase bridging of critical size bone defects, whereas treatment with 30 μg of tethered PTH resulted in less bone ingrowth into the defect area. Continued development of this biomaterial delivery system for PTH could lead to improved therapies for treatment of nonunion fractures and critical size bone defects.

Epidemiology, Clinical Assessments, and Current Treatments of Nonunions

PURPOSE OF REVIEW

The failure of bony union following a fracture, termed a fracture nonunion, has severe patient morbidity and economic consequences. This review describes current consensuses and future directions of investigation for determining why, detecting when, and effective treatment if this complication occurs.

RECENT FINDINGS

Current nonunion investigation is emphasizing an expanded understanding of the biology of healing. This has led to assessments of the immune environment, multiple cytokines and morphogenetic factors, and the role of skeletogenic stem cells in the development of nonunion. Detecting biological markers and other objective diagnostic criteria is also a current objective of nonunion research. Treatment approaches in the near future will likely be dominated by the development of specific adjunct therapies to the nonunion surgical management, which will be informed by an expanded mechanistic understanding of nonunion biology. Current consensus among orthopedists is that improved diagnosis and treatment of nonunion hinges first on discoveries at the bench side with later translation to the clinic.