Current perspectives on parathyroid hormone (PTH) and PTH-related protein (PTHrP) as bone anabolic therapies

Leveraging the Recent Advancements in GelMA Scaffolds for Bone Tissue Engineering: An Assessment of Challenges and Opportunities

The field of bone tissue engineering has seen significant advancements in recent years. Each year, over two million bone transplants are performed globally, and conventional treatments, such as bone grafts and metallic implants, have their limitations. Tissue engineering offers a new level of treatment, allowing for the creation of living tissue within a biomaterial framework. Recent advances in biomaterials have provided innovative approaches to rebuilding bone tissue function after damage. Among them, gelatin methacryloyl (GelMA) hydrogel is emerging as a promising biomaterial for supporting cell proliferation and tissue regeneration, and GelMA has exhibited exceptional physicochemical and biological properties, making it a viable option for clinical translation. Various methods and classes of additives have been used in the application of GelMA for bone regeneration, with the incorporation of nanofillers or other polymers enhancing its resilience and functional performance. Despite promising results, the fabrication of complex structures that mimic the bone architecture and the provision of balanced physical properties for both cell and vasculature growth and proper stiffness for load bearing remain as challenges. In terms of utilizing osteogenic additives, the priority should be on versatile components that promote angiogenesis and osteogenesis while reinforcing the structure for bone tissue engineering applications. This review focuses on recent efforts and advantages of GelMA-based composite biomaterials for bone tissue engineering, covering the literature from the last five years.

Cutaneous Calcified Mass of Foot in Pseudohypoparathyoidism: Case Report

Soft tissue calcifications frequently appear on imaging studies, representing a prevalent but non-specific discovery, varying from a local reaction without clear cause to suggesting an underlying systemic condition. Because calcifications like these can arise from various causes, an accurate differential diagnosis is crucial. Differential diagnosis entails a methodical assessment of the patient, encompassing clinical presentation, medical history, radiological and pathological findings, and other pertinent factors. Through scrutiny of the patient's medical and trauma history, we can refine potential causes of calcification to vascular, metabolic, autoimmune, neoplastic, or traumatic origins. Furthermore, routine laboratory assessments, including serum levels of calcium, phosphorus, ionized calcium, vitamin D metabolites, and parathyroid hormone (PTH), aid in identifying metabolic etiologies. We describe a rare occurrence of osteoma cutis in a 15-year-old female patient with a history of pseudohypoparathyroidism (PHP) and Albright's hereditary osteodystrophy (AHO). The patient presented with a painful mass on the lateral side of her left foot. The diagnosis was based on medical history, laboratory tests, and imaging, leading to an excisional biopsy and complete pain relief post-surgery. Understanding such rare occurrences and related conditions is crucial for accurate diagnosis and management.

A well plate-based GelMA photo-crosslinking system with tunable hydrogel mechanical properties to regulate the PTH-mediated osteogenic fate

Versatile and efficient regulation of the mechanical properties of the extracellular matrix is crucial not only for understanding the dynamic changes in biological systems, but also for obtaining precise and effective cellular responses in drug testing. In this study, we developed a well plate-based hydrogel photo-crosslinking system to effectively control the mechanical properties of hydrogels and perform high-throughput assays. We improved cell biocompatibility by using gelatin methacryloyl (GelMA) with a visible light photo-crosslinking method. Multiple cell-laden GelMA hydrogels were simultaneously and uniformly created using multi-arrayed 520 nm light-emitting diodes in a well plate format. The elastic modulus of the hydrogels can be widely adjusted (0.5-30 kPa) using a photo-crosslinking system capable of independently controlling the light intensity or exposure time for multiple samples. We demonstrate the feasibility of our system by observing enhanced bone differentiation of human mesenchymal stem cells (hMSCs) cultured on stiffer hydrogels. Additionally, we observed that the osteogenic fate of hMSCs, affected by the different mechanical properties of the gel, was regulated by parathyroid hormone (PTH). Notably, in response to PTH, hMSCs in a high-stiffness microenvironment upregulate osteogenic differentiation while exhibiting increased proliferation in a low-stiffness microenvironment. Overall, the developed system enables the generation of multiple cell-laden three-dimensional cell culture models with diverse mechanical properties and holds significant potential for expansion into drug testing.

PTH and the Regulation of Mesenchymal Cells within the Bone Marrow Niche

Parathyroid hormone (PTH) plays a pivotal role in maintaining calcium homeostasis, largely by modulating bone remodeling processes. Its effects on bone are notably dependent on the duration and frequency of exposure. Specifically, PTH can initiate both bone formation and resorption, with the outcome being influenced by the manner of PTH administration: continuous or intermittent. In continuous administration, PTH tends to promote bone resorption, possibly by regulating certain genes within bone cells. Conversely, intermittent exposure generally favors bone formation, possibly through transient gene activation. PTH's role extends to various aspects of bone cell activity. It directly influences skeletal stem cells, osteoblastic lineage cells, osteocytes, and T cells, playing a critical role in bone generation. Simultaneously, it indirectly affects osteoclast precursor cells and osteoclasts, and has a direct impact on T cells, contributing to its role in bone resorption. Despite these insights, the intricate mechanisms through which PTH acts within the bone marrow niche are not entirely understood. This article reviews the dual roles of PTH-catabolic and anabolic-on bone cells, highlighting the cellular and molecular pathways involved in these processes. The complex interplay of these factors in bone remodeling underscores the need for further investigation to fully comprehend PTH's multifaceted influence on bone health.

The emerging studies on mesenchymal progenitors in the long bone

Mesenchymal progenitors (MPs) are considered to play vital roles in bone development, growth, bone turnover, and repair. In recent years, benefiting from advanced approaches such as single-cell sequence, lineage tracing, flow cytometry, and transplantation, multiple MPs are identified and characterized in several locations of bone, including perichondrium, growth plate, periosteum, endosteum, trabecular bone, and stromal compartment. However, although great discoveries about skeletal stem cells (SSCs) and progenitors are present, it is still largely obscure how the varied landscape of MPs from different residing sites diversely contribute to the further differentiation of osteoblasts, osteocytes, chondrocytes, and other stromal cells in their respective destiny sites during development and regeneration. Here we discuss recent findings on MPs' origin, differentiation, and maintenance during long bone development and homeostasis, providing clues and models of how the MPs contribute to bone development and repair.

Schnurri-3 inhibition suppresses bone and joint damage in models of rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory disease that leads to systemic and articular bone loss by activating bone resorption and suppressing bone formation. Despite current therapeutic agents, inflammation-induced bone loss in RA continues to be a significant clinical problem due to joint deformity and lack of articular and systemic bone repair. Here, we identify the suppressor of bone formation, Schnurri-3 (SHN3), as a potential target to prevent bone loss in RA. SHN3 expression in osteoblast-lineage cells is induced by proinflammatory cytokines. Germline deletion or conditional deletion of Shn3 in osteoblasts limits articular bone erosion and systemic bone loss in mouse models of RA. Similarly, silencing of SHN3 expression in these RA models using systemic delivery of a bone-targeting recombinant adenoassociated virus protects against inflammation-induced bone loss. In osteoblasts, TNF activates SHN3 via ERK MAPK-mediated phosphorylation and, in turn, phosphorylated SHN3 inhibits WNT/β-catenin signaling and up-regulates RANKL expression. Accordingly, knock-in of a mutation in Shn3 that fails to bind ERK MAPK promotes bone formation in mice overexpressing human TNF due to augmented WNT/β-catenin signaling. Remarkably, Shn3-deficient osteoblasts are not only resistant to TNF-induced suppression of osteogenesis, but also down-regulate osteoclast development. Collectively, these findings demonstrate SHN3 inhibition as a promising approach to limit bone loss and promote bone repair in RA.

Pleiotrophin-Loaded Mesoporous Silica Nanoparticles as a Possible Treatment for Osteoporosis

Osteoporosis is the most common type of bone disease. Conventional treatments are based on the use of antiresorptive drugs and/or anabolic agents. However, these treatments have certain limitations, such as a lack of bioavailability or toxicity in non-specific tissues. In this regard, pleiotrophin (PTN) is a protein with potent mitogenic, angiogenic, and chemotactic activity, with implications in tissue repair. On the other hand, mesoporous silica nanoparticles (MSNs) have proven to be an effective inorganic drug-delivery system for biomedical applications. In addition, the surface anchoring of cationic polymers, such as polyethylenimine (PEI), allows for greater cell internalization, increasing treatment efficacy. In order to load and release the PTN to improve its effectiveness, MSNs were successfully internalized in MC3T3-E1 mouse pre-osteoblastic cells and human mesenchymal stem cells. PTN-loaded MSNs significantly increased the viability, mineralization, and gene expression of alkaline phosphatase and Runx2 in comparison with the PTN alone in both cell lines, evidencing its positive effect on osteogenesis and osteoblast differentiation. This proof of concept demonstrates that MSN can take up and release PTN, developing a potent osteogenic and differentiating action in vitro in the absence of an osteogenic differentiation-promoting medium, presenting itself as a possible treatment to improve bone-regeneration and osteoporosis scenarios.

A novel biologically hierarchical hydrogel with osteoblast precursor-targeting extracellular vesicles ameliorates bone loss in vivo via the sequential action of antagomiR-200b-3p and antagomiR-130b-3p

Osteoporotic fracture is a major health problem plaguing the ageing society, and improving its treatment is an urgent challenge. How to ameliorate bone loss determines the recovery of such fractures. Extracellular vesicle (EV)-loaded hydrogel has the capacity to treat osteoporotic fractures due to its pro-osteogenic property. And balancing proliferation and maturation of osteoblast precursors (OBPs) is of great significance to avoid OBP depletion, which is lacking in current treatment. Based on osteoblastogenic miRNAs, this study aimed to explore the efficacies of the combination of hierarchical hydrogel and EVs altering functional miRNAs level in bone loss. Through bioinformatics analyses, we screened out proliferative gene-targeting miR-200b-3p and osteogenic gene-targeting miR-130b-3p. And antagomiR-200b-3p (ant-200b) enhanced OBP proliferation, and antagomiR-130b-3p (ant-130b) promoted OBP differentiation. After confirming the directional effect of Fibronectin (Fn1) on OBPs, we prepared OBP-targeting EVs. Furthermore, encapsulation of two antagomiRNAs in EVs enhanced the respective effect of ant-200b and ant-130b. Notably, hierarchically injectable hydrogel exerted an effective function in promoting the sequential delivery of EVs-200b and EVs-130b. Importantly, hierarchical hydrogel containing dual EVs effectively ameliorated bone loss. Overall, hierarchical hydrogel based on two antagomiRNAs effectively improves bone loss in vivo due to its role in promoting OBP proliferation and maturation sequentially.

WNT-modulating gene silencers as a gene therapy for osteoporosis, bone fracture, and critical-sized bone defects

Treating osteoporosis and associated bone fractures remains challenging for drug development in part due to potential off-target side effects and the requirement for long-term treatment. Here, we identify recombinant adeno-associated virus (rAAV)-mediated gene therapy as a complementary approach to existing osteoporosis therapies, offering long-lasting targeting of multiple targets and/or previously undruggable intracellular non-enzymatic targets. Treatment with a bone-targeted rAAV carrying artificial microRNAs (miRNAs) silenced the expression of WNT antagonists, schnurri-3 (SHN3), and sclerostin (SOST), and enhanced WNT/β-catenin signaling, osteoblast function, and bone formation. A single systemic administration of rAAVs effectively reversed bone loss in both postmenopausal and senile osteoporosis. Moreover, the healing of bone fracture and critical-sized bone defects was also markedly improved by systemic injection or transplantation of AAV-bound allograft bone to the osteotomy sites. Collectively, our data demonstrate the clinical potential of bone-specific gene silencers to treat skeletal disorders of low bone mass and impaired fracture repair.

A brief review and clinical evidences of teriparatide therapy for atypical femoral fractures associated with long-term bisphosphonate treatment

The risk of bisphosphonate (BP)-associated atypical femur fracture (AFF) has markedly increased over recent decades due to suppression of bone turnover, accumulation of structural micro-damage and reduction of bone remodeling consequent to long-term BP treatment. These medications further delay bone union and result in challenging clinical management. Teriparatide (TPTD), a synthetic human parathyroid hormone, exhibits unique anabolic effects and can increase bone remodeling and improve bone microarchitecture, further promoting fracture healing and reducing the rate of bone non-union. In this study, we briefly define AFF as well as the effects of BPs on AFFs, detailed the role of TPTD in AFF management and the latest clinical therapeutic findings. We have confirmed that TPTD positively promotes the healing of AFFs by reducing the time to bone union and likelihood of non-union. Thus, teriparatide therapy could be considered as an alternative treatment for AFFs, however, further research is required for the establishment of effective clinical guidelines of TPTD use in the management of AFF.

Functional Heterogeneity of Bone Marrow Mesenchymal Stem Cell Subpopulations in Physiology and Pathology

Bone marrow mesenchymal stem cells (BMSCs) are multi-potent cell populations and are capable of maintaining bone and body homeostasis. The stemness and potential therapeutic effect of BMSCs have been explored extensively in recent years. However, diverse cell surface antigens and complex gene expression of BMSCs have indicated that BMSCs represent heterogeneous populations, and the natural characteristics of BMSCs make it difficult to identify the specific subpopulations in pathological processes which are often obscured by bulk analysis of the total BMSCs. Meanwhile, the therapeutic effect of total BMSCs is often less effective partly due to their heterogeneity. Therefore, understanding the functional heterogeneity of the BMSC subpopulations under different physiological and pathological conditions could have major ramifications for global health. Here, we summarize the recent progress of functional heterogeneity of BMSC subpopulations in physiology and pathology. Targeting tissue-resident single BMSC subpopulation offers a potentially innovative therapeutic strategy and improves BMSC effectiveness in clinical application.

PTHrP promotes subchondral bone formation in TMJ-OA

PTH-related peptide (PTHrP) improves the bone marrow micro-environment to activate the bone-remodelling, but the coordinated regulation of PTHrP and transforming growth factor-β (TGFβ) signalling in TMJ-OA remains incompletely understood. We used disordered occlusion to establish model animals that recapitulate the ordinary clinical aetiology of TMJ-OA. Immunohistochemical and histological analyses revealed condylar fibrocartilage degeneration in model animals following disordered occlusion. TMJ-OA model animals administered intermittent PTHrP (iPTH) exhibited significantly decreased condylar cartilage degeneration. Micro-CT, histomorphometry, and Western Blot analyses disclosed that iPTH promoted subchondral bone formation in the TMJ-OA model animals. In addition, iPTH increased the number of osterix (OSX)-positive cells and osteocalcin (OCN)-positive cells in the subchondral bone marrow cavity. However, the number of osteoclasts was also increased by iPTH, indicating that subchondral bone volume increase was mainly due to the iPTH-mediated increase in the bone-formation ability of condylar subchondral bone. In vitro, PTHrP treatment increased condylar subchondral bone marrow-derived mesenchymal stem cell (SMSC) osteoblastic differentiation potential and upregulated the gene and protein expression of key regulators of osteogenesis. Furthermore, we found that PTHrP-PTH1R signalling inhibits TGFβ signalling during osteoblastic differentiation. Collectively, these data suggested that iPTH improves OA lesions by enhancing osteoblastic differentiation in subchondral bone and suppressing aberrant active TGFβ signalling. These findings indicated that PTHrP, which targets the TGFβ signalling pathway, may be an effective biological reagent to prevent and treat TMJ-OA in the clinic.

Engineering mesoporous silica nanoparticles for drug delivery: where are we after two decades?

The present review details a chronological description of the events that took place during the development of mesoporous materials, their different synthetic routes and their use as drug delivery systems. The outstanding textural properties of these materials quickly inspired their translation to the nanoscale dimension leading to mesoporous silica nanoparticles (MSNs). The different aspects of introducing pharmaceutical agents into the pores of these nanocarriers, together with their possible biodistribution and clearance routes, would be described here. The development of smart nanocarriers that are able to release a high local concentration of the therapeutic cargo on-demand after the application of certain stimuli would be reviewed here, together with their ability to deliver the therapeutic cargo to precise locations in the body. The huge progress in the design and development of MSNs for biomedical applications, including the potential treatment of different diseases, during the last 20 years will be collated here, together with the required work that still needs to be done to achieve the clinical translation of these materials. This review was conceived to stand out from past reports since it aims to tell the story of the development of mesoporous materials and their use as drug delivery systems by some of the story makers, who could be considered to be among the pioneers in this area.

Involvement of parathyroid hormone-related peptide in the aggressive phenotype of colorectal cancer cells

Colorectal cancer (CRC) remains one of the leading causes of mortality from malignant diseases worldwide. In general terms, CRC presents high heterogeneity due to the influence of different genetic and environmental factors; also, the neoplastic cells are strongly influenced by the extracellular matrix and several surrounding cells, known together as the tumor microenvironment (TME). Bidirectional communication takes place between the tumor and the TME through the release of autocrine and paracrine factors. Parathyroid hormone-related peptide (PTHrP) is a cytokine secreted by a wide variety of tissues and is able to regulate several cellular functions both in physiological as well as in pathological processes. It exerts its effects as a paracrine/autocrine factor, although its mode of action is mainly paracrine. It has been shown that this peptide is expressed by several tumors and that the tumor secretion of PTHrP is responsible for the malignant humoral hypercalcemia. Eight years ago, when our research group started studying PTHrP effects in the experimental models derived from intestinal tumors, the literature available at the time addressing the effects of PTHrP on colorectal tumors was limited, and no articles had been published regarding to the paracrine action of PTHrP in CRC cells. Based on this and on our previous findings regarding the role of PTH in CRC cells, our purpose in recent years has been to explore the role of PTHrP in CRC. We analyzed the behavior of CRC cells treated with exogenous PTHrP, focalizing in the study of the following events: Survival, cell cycle progression and proliferation, migration, chemoresistance, tumor-associated angiogenesis, epithelial to mesenchymal transition program and other events also associated with invasion, such us the induction of cancer stem cells features. This work summarizes the major findings obtained by our investigation group using in vitro and in vivo CRC models that evidence the participation of PTHrP in the acquisition of an aggressive phenotype of CRC cells and the molecular mechanisms involved in these processes. Recently, we found that this cytokine induces this malignant behavior not only by its direct action on these intestinal cells but also through its influence on cells derived from TME, promoting a communication between CRC cells and surrounding cells that contributes to the molecular and morphological changes observed in CRC cells. These investigations establish the basis for our next studies in order to address the clinical applicability of our findings. Recognizing the factors and mechanisms that promote invasion in CRC cells, evasion to the cytotoxic effects of current CRC therapies and thus metastasis is decisive for the identification of new markers with the potential to improve early diagnosis and/or to predict prognosis, to predetermine drug resistance and to provide treatment guidelines that include targeted therapies for this disease.

Role of Calcium Homeostasis in Modulating EMT in Cancer

Calcium is essential for cells to perform numerous physiological processes. In cancer, the augmentation of calcium signaling supports the more proliferative and migratory cells, which is a characteristic of the epithelial-to-mesenchymal transition (EMT). By genetically and epigenetically modifying genes, channels, and entire signaling pathways, cancer cells have adapted to survive with an extreme imbalance of calcium that allows them to grow and metastasize in an abnormal manner. This cellular remodeling also allows for the evasion of immune surveillance and the development of drug resistance, which lead to poor prognosis in patients. Understanding the role calcium flux plays in driving the phenotypes associated with invasion, immune suppression, metastasis, and drug resistance remains critical for determining treatments to optimize clinical outcomes and future drug discovery.

γ-Aminobutyric Acid Promotes Osteogenic Differentiation of Mesenchymal Stem Cells by Inducing TNFAIP3

BACKGROUND

Osteoporosis is the most common metabolic bone disease. There is still an unmet need for novel therapeutic agents that could be beneficial as osteoporosis treatments. It has been reported that the neurotransmitter γ-aminobutyric acid (GABA) might be associated with human bone formation. However, the precise mechanism remains unclear.

OBJECTIVE

To investigate the effect of GABA on bone metabolism and explore the possible role of TNFAIP3 in this process.

METHODS

GABA had little effect on the proliferation of human mesenchymal stem cells (hMSCs) and RAW 264.7 cells, as indicated by the cell counting kit-8 (CCK-8) assay. The results showed that GABA enhanced the intensity of ALP staining, ALP activity, and accumulation of Ca2+ mineralized nodules in hMSCs during osteogenic induction.

RESULTS

The qRT-PCR results indicated that GABA treatment significantly increased the mRNA expression of osteogenic genes in hMSCs. In RAW 264.7 cells, TRAP staining showed that GABA did not alter the number or size of osteoclasts or the expression of osteoclastic genes, which suggests that GABA does not affect osteoclastic differentiation. Mechanistically, GABA treatment significantly induced the sustained expression of TNFAIP3. Furthermore, by knocking down TNFAIP3, the osteogenic effect of GABA was antagonized, which suggests that TNFAIP3 mediates the effects of GABA in hMSCs.

CONCLUSION

Our results suggested that GABA treatment positively regulated osteogenic differentiation by upregulating TNFAIP3, while no obvious effect on osteoclastic differentiation was detected. Therefore, our results provide a potential gene therapy for the treatment of osteoporosis and low bone mineral density.

Restoration of the intravertebral stability in Kümmell's disease following the treatment of severe postmenopausal osteoporosis by 1-34PTH-a retrospective study

Following the 1-34PTH application for conservative treatment of Kümmell's disease, the intravertebral cleft was filled or bridged by the osseous tissue; the radiological evidence of further collapsing was absent. Pain and the neurological disorder were relieved; bone turnover markers, BMD as well as the health-related quality of life were improved.

INTRODUCTION

Kümmell's disease (KD) patients with severe osteoporosis were applied by the 1-34PTH; the fracture union and the increased bone mineral density (BMD) following this treatment were retrospectively reviewed.

METHODS

Twenty-one postmenopausal osteoporosis (PMOP) patients with KD received at least 6 months of 1-34PTH treatment. The medical records, including clinical evaluation symptoms, radiological evaluation for bone union and the stability of intravertebral vacuum cleft (IVC), BMD, and laboratory examination for osteoporosis recovery and health-related quality of life (HRQOL), were reviewed.

RESULTS

From baseline to month 12, visual analog scale decreased from 8.24 ± 0.54 to 1.71 ± 0.56 (P < 0.001) and the modified Japanese Orthopedic Association scores increased from 6.86 ± 1.77 to 10.43 ± 1.29 (P < 0.001). Sagittal CT demonstrated that the IVC was filled or bridged by the osseous tissue in all patients. Within the vertebra, the IVC area (IVCA) decreased from 4.50 ± 2.50 to 0 mm² (P = 0.001) and the mineralized bone area (MBA) increased from 170.91 ± 102.23 to 259.56 ± 98.60 mm² (P < 0.001). The area ratio of IVC to vertebra decreased from 0.97 ± 0.46 to 0% (P < 0.001), and the area ratio of mineral bone to vertebra was increased from 32.85 ± 14.51 to 54.97 ± 14.01% (P < 0.001). The kyphosis angle increment was 3.43 ± 1.80°, and the loss rate of anterior border height was 11.14 ± 4.82%. No differences were found in posterior border height and spinal canal diameter. The PINP, β-CTx, BMD, and Short Form-36 Health Survey scores markedly increased.

CONCLUSIONS

In KD patients with severe PMOP, 1-34PTH treatment could alleviate the clinical evaluation symptoms, facilitate the recovery of the intravertebral stability, ameliorate the BMD, and improve the HRQoL.

The effects of vitamin D supplementation on types of falls

BACKGROUND/OBJECTIVES

To assess whether vitamin D supplementation prevents specific fall subtypes and sequelae (e.g., fracture).

DESIGN

Secondary analyses of STURDY (Study to Understand Fall Reduction and Vitamin D in You)-a response-adaptive, randomized clinical trial.

SETTING

Two community-based research units.

PARTICIPANTS

Six hundred and eighty-eight participants ≥70 years old with elevated fall risk and baseline serum 25-hydroxyvitamin D levels of 10-29 ng/ml.

INTERVENTION

200 IU/day (control), 1000 IU/day, 2000 IU/day, or 4000 IU/day of vitamin D3.

MEASUREMENTS

Outcomes included repeat falls and falls that were consequential, were injurious, resulted in emergency care, resulted in fracture, and occurred either indoors or outdoors.

RESULTS

After adjustment for multiple comparisons, the risk of fall-related fracture was greater in the pooled higher doses (≥1000 IU/day) group compared with the control (hazard ratio [HR] = 2.66; 95% confidence interval [CI]:1.18-6.00). Although not statistically significant after multiple comparisons adjustment, time to first outdoor fall appeared to differ between the four dose groups (unadjusted p for overall difference = 0.013; adjusted p = 0.222), with risk of a first-time outdoor fall 39% lower in the 1000 IU/day group (HR = 0.61; 95% CI: 0.38-0.97; unadjusted p = 0.036; adjusted p = 0.222) and 40% lower in the 2000 IU/day group (HR = 0.60; 95%CI 0.38-0.97; p = 0.037; adjusted p = 0.222), each versus control.

CONCLUSION

Vitamin D supplementation doses ≥1000 IU/day might have differential effects on fall risk based on fall location and fracture risk, with the most robust finding that vitamin D doses between 1000 and 4000 IU/day might increase the risk of first time falls with fractures. Replication is warranted, given the possibility of type 1 error.

Parathyroid hormone-related protein inhibits nitrogen-containing bisphosphonate-induced apoptosis of human periodontal ligament fibroblasts by activating MKP1 phosphatase

Massive production of reactive oxygen species (ROS) in human periodontal ligament fibroblasts (HPdLFs) by nitrogen-containing bisphosphonates (BPs) is the main factor causing BP-related osteonecrosis of the jaw. Further, oxidative stress and apoptosis of fibroblasts induced by ROS are closely associated with the activation of MAPK. Parathyroid hormone-related protein (PTHrP) can block the activity of MAPK by regulating the levels of MAPK phosphatase 1 (MKP1). Therefore, it is speculated that PTHrP can inhibit the apoptosis of HPdLFs caused by nitrogen-containing BP via regulating the expression levels of MKP1. Herein, alendronate sodium salt trihydrate (nitrogen-containing BP, FOS) and HPdLFs were co-cultured for 24 h, 48 h, and 72 h, and the levels of ROS and apoptosis were determined, respectively. After 48 h co-culture, FOS significantly increased the levels of ROS and apoptosis, and high phosphorylation levels of p38, ERK1/2 and p66^Shc were found in this study. However, the inhibitors of p38 and ERK1/2 significantly reduced the apoptosis of HPdLFs. Interestingly, PTHrP pre-treatment significantly reduced the phosphorylation levels of p38, ERK1/2, and p66^Shc. More importantly, MKP1 inhibitor sanguinarine inhibited the dephosphorylation levels of p38, ERK1/2, and p66^Shc caused by PTHrP. Altogether, PTHrP can inhibit nitrogen-containing BP-induced apoptosis of HPdLFs by activating MKP1 phosphatase.

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.

ZnO-mesoporous glass scaffolds loaded with osteostatin and mesenchymal cells improve bone healing in a rabbit bone defect

The use of 3D scaffolds based on mesoporous bioactive glasses (MBG) enhanced with therapeutic ions, biomolecules and cells is emerging as a strategy to improve bone healing. In this paper, the osteogenic capability of ZnO-enriched MBG scaffolds loaded or not with osteostatin (OST) and human mesenchymal stem cells (MSC) was evaluated after implantation in New Zealand rabbits. Cylindrical meso-macroporous scaffolds with composition (mol %) 82.2SiO₂-10.3CaO-3.3P₂O₅-4.2ZnO (4ZN) were obtained by rapid prototyping and then, coated with gelatin for easy handling and potentiating the release of inorganic ions and OST. Bone defects (7.5 mm diameter, 12 mm depth) were drilled in the distal femoral epiphysis and filled with 4ZN, 4ZN + MSC, 4ZN + OST or 4ZN + MSC + OST materials to evaluate and compare their osteogenic features. Rabbits were sacrificed at 3 months extracting the distal third of bone specimens for necropsy, histological, and microtomography (µCT) evaluations. Systems investigated exhibited bone regeneration capability. Thus, trabecular bone volume density (BV/TV) values obtained from µCT showed that the good bone healing capability of 4ZN was significantly improved by the scaffolds coated with OST and MSC. Our findings in vivo suggest the interest of these MBG complete systems to improve bone repair in the clinical practice.

Effect of cAMP Signaling Regulation in Osteogenic Differentiation of Adipose-Derived Mesenchymal Stem Cells

The successful implementation of adipose-derived mesenchymal stem cells (ADSCs) in bone regeneration depends on efficient osteogenic differentiation. However, a literature survey and our own experience demonstrated that current differentiation methods are not effective enough. Since the differentiation of mesenchymal stem cells (MSCs) into osteoblasts and adipocytes can be regulated by cyclic adenosine monophosphate (cAMP) signaling, we investigated the effects of cAMP activator, forskolin, and inhibitor, SQ 22,536, on the early and late osteogenic differentiation of ADSCs cultured in spheroids or in a monolayer. Intracellular cAMP concentration, protein kinase A (PKA) activity, and inhibitor of DNA binding 2 (ID2) expression examination confirmed cAMP up- and downregulation. cAMP upregulation inhibited the cell cycle and protected ADSCs from osteogenic medium (OM)-induced apoptosis. Surprisingly, the upregulation of cAMP level at the early stages of osteogenic differentiation downregulated the expression of osteogenic markers RUNX2, Osterix, and IBSP, which was more significant in spheroids, and it is used for the more efficient commitment of ADSCs into preosteoblasts, according to the previously reported protocol. However, cAMP upregulation in a culture of ADSCs in spheroids resulted in significantly increased osteocalcin production and mineralization. Thus, undifferentiated and predifferentiated ADSCs respond differently to cAMP pathway stimulation in terms of osteogenesis, which might explain the ambiguous results from the literature.

Mesoporous Silica Nanoparticles for the Treatment of Complex Bone Diseases: Bone Cancer, Bone Infection and Osteoporosis

Bone diseases, such as bone cancer, bone infection and osteoporosis, constitute a major issue for modern societies as a consequence of their progressive ageing. Even though these pathologies can be currently treated in the clinic, some of those treatments present drawbacks that may lead to severe complications. For instance, chemotherapy lacks great tumor tissue selectivity, affecting healthy and diseased tissues. In addition, the inappropriate use of antimicrobials is leading to the appearance of drug-resistant bacteria and persistent biofilms, rendering current antibiotics useless. Furthermore, current antiosteoporotic treatments present many side effects as a consequence of their poor bioavailability and the need to use higher doses. In view of the existing evidence, the encapsulation and selective delivery to the diseased tissues of the different therapeutic compounds seem highly convenient. In this sense, silica-based mesoporous nanoparticles offer great loading capacity within their pores, the possibility of modifying the surface to target the particles to the malignant areas and great biocompatibility. This manuscript is intended to be a comprehensive review of the available literature on complex bone diseases treated with silica-based mesoporous nanoparticles-the further development of which and eventual translation into the clinic could bring significant benefits for our future society.

Bone-targeting AAV-mediated silencing of Schnurri-3 prevents bone loss in osteoporosis

RNAi-based bone anabolic gene therapy has demonstrated initial success, but many practical challenges are still unmet. Here, we demonstrate that a recombinant adeno-associated virus 9 (rAAV9) is highly effective for transducing osteoblast lineage cells in the bone. The adaptor protein Schnurri-3 (SHN3) is a promising therapeutic target for osteoporosis, as deletion of shn3 prevents bone loss in osteoporotic mice and short-term inhibition of shn3 in adult mice increases bone mass. Accordingly, systemic and direct joint administration of an rAAV9 vector carrying an artificial-microRNA that targets shn3 (rAAV9-amiR-shn3) in mice markedly enhanced bone formation via augmented osteoblast activity. Additionally, systemic delivery of rAAV9-amiR-shn3 in osteoporotic mice counteracted bone loss and enhanced bone mechanical properties. Finally, we rationally designed a capsid that exhibits improved specificity to bone by grafting the bone-targeting peptide motif (AspSerSer)6 onto the AAV9-VP2 capsid protein. Collectively, our results identify a bone-targeting rAAV-mediated gene therapy for osteoporosis.

Effects of sequential treatment with intermittent parathyroid hormone and zoledronic acid on particle-induced implant loosening: Evidence from a rat model

Particle-induced implant loosening is a major challenge to long-term survival of joint prostheses. Administration of intermittent parathyroid hormone (PTH) has shown potential in the treatment of cases of early-stage periprosthetic osteolysis, while sequential administration of intermittent PTH (iPTH) and bisphosphonates (Bps) has achieved significant effects on treatment of postmenopausal osteoporosis. The objective of this study was to determine whether sequential treatment could preserve bone mass and implant fixation during a pathological course of peri-implant osteolysis in a rat model. Ninety male Sprague Dawley rats were randomly divided into nine groups, four of which were used for confirmation of establishment of the peri-implant osteolysis model at two time points, while the other five were used to determine the efficiency of the sequential treatment on peri-implant osteolysis. Implant fixation and peri-implant bone mass were evaluated using biomechanical testing, micro-CT analysis, and histology at 6 and 12 weeks postoperative. The biomechanical test demonstrated that the maximum loading force during a push-out test was significantly elevated in the sequential treatment group compared to the osteolysis group and iPTH withdrawal group at 12 weeks. Peri-implant bone morphology also indicated a robust increase in bone volume in the sequential treatment group. Sequential administration of iPTH and Bps was effective in preventing experimental peri-implant osteolysis, resulting in improved implant fixation and increased peri-implant bone volume. Clinical significance: The innovative application of sequential treatment in peri-implant osteolysis could be used clinically to improve the prognosis of patients with early-stage periprosthetic osteolysis. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1489-1497, 2019.

Long-term effects on PTH and mineral metabolism of 1.25 versus 1.75 mmol/L dialysate calcium in peritoneal dialysis patients: a meta-analysis

Background

This study aimed to compare 1.25 and 1.75 mmol/L dialysate calcium for their effects on parathyroid hormone (PTH) and mineral metabolism in peritoneal dialysis (PD).

Methods

The PubMed, Cochrane Library, and EmBase databases were searched from inception to October 2016. Methodological quality assessment of the included studies was performed using the risk of bias tool of the Review Manager software. The meta-analysis was carried out with the Stata12.0 software. Subgroup analysis was performed by study design [randomized controlled trial (RCT) and non-RCT]. Odds ratios or standardized mean differences were used to assess the outcome measures, including intact parathyroid hormone (i-PTH) levels, serum total calcium amounts, ionized calcium levels, phosphate concentrations, and peritonitis episodes.

Results

Seven studies were enrolled in the synthesized analysis, including 4 RCTs and 3 non-RCTs. All studies compared 1.25 mmol/L and 1.75 mmol/L dialysate calcium for PD. Pooled analysis revealed that 1.75 mmol/L dialysate calcium significantly reduced i-PTH levels compared with the 1.25 mmol/L dose in PD patients. However, 1.25 mmol/L dialysate calcium was superior to the 1.75 mmol/L dose in decreasing the levels of serum total calcium and ionized calcium in PD patients. No significant differences in phosphate amounts and peritonitis episodes were observed between the two groups.

Conclusion

These findings indicated that 1.75 mmol/L dialysate calcium is more appropriate for PD patients with secondary hyperparathyroidism. Meanwhile, 1.25 mmol/L dialysate calcium is more favorable to PD patients with secondary hypercalcemia. However, further well-designed and high-quality studies are required to validate these findings.

Sustained-release of sclerostin single-chain antibody fragments using poly(lactic-co-glycolic acid) microspheres for osteoporotic fracture repair

Osteoporotic fracture is one of the most common bone diseases in middle and old age, as the most serious consequence of osteoporosis. Sclerostin single‐chain antibody fragments (SCL‐scFv) have been proven to promote bone formation by binding to scleroprotein, a natural antagonist of the Wnt pathway, but it is difficult to rule alone due to the weak permeability and immunogenicity. Herein, we prepared poly(lactic‐co‐glycolic acid) microspheres as a sustained‐release vehicle to prolong the activity of SCL‐scFv. The morphology of microspheres were uniform and nearly sphere, loading efficiency and encapsulation efficiency of SCL‐scFv microspheres were 6.28 ± 1.04% and 48.37 ± 8.11%, respectively. Approximately 90% of the SCL‐scFvs were released from the microspheres over 28 days with initial burst releasing (38%) in the first 4 days. Sustained‐release of active SCL‐scFv from microspheres promoted bone marrow mesenchymal stem cells osteogenic differentiation in vitro and enhanced fracture healing in ovariectomized rats by improving bone mass and bone formation in the fracture region. All these findings demonstrate that the microspheres are able to simultaneously achieve localized long‐term SCL‐scFv controlled release and effectively promote bone formation, which provides a promising approach for osteoporotic fracture.

Osteostatin potentiates the bioactivity of mesoporous glass scaffolds containing Zn2+ ions in human mesenchymal stem cells

There is an urgent need of biosynthetic bone grafts with enhanced osteogenic capacity. In this study, we describe the design of hierarchical meso-macroporous 3D-scaffolds based on mesoporous bioactive glasses (MBGs), enriched with the peptide osteostatin and Zn2+ ions, and their osteogenic effect on human mesenchymal stem cells (hMSCs) as a preclinical strategy in bone regeneration. The MBG compositions investigated were 80%SiO2-15%CaO-5%P2O5 (in mol-%) Blank (BL), and two analogous glasses containing 4% ZnO (4ZN) and 5% ZnO (5ZN). By using additive fabrication techniques, scaffolds exhibiting hierarchical porosity: mesopores (around 4 nm), macropores (1-600 μm) and big channels (∼1000 μm), were prepared. These MBG scaffolds with or without osteostatin were evaluated in hMCSs cultures. Zinc promoted hMSCs colonization (both the surface and inside) of MBG scaffolds. Moreover, Zn2+ ions and osteostatin together, but not independently, in the scaffolds were found to induce the osteoblast differentiation genes runt related transcription factor-2 (RUNX2) and alkaline phosphatase (ALP) in hMSCs after 7 d of culture in the absence of an osteogenic differentiation-promoting medium. These results add credence to the combined use of zinc and osteostatin as an effective strategy for bone regeneration applications. STATEMENT OF SIGNIFICANCE: Mesoporous bioactive glasses (MBGs) are bioceramics whose unique properties make them excellent materials for bone tissue engineering. Physico-chemical characterization of MBGs as scaffolds made by rapid prototyping, doped with zinc (potential osteogenic, angiogenic and bactericidal ion) and loaded with osteostatin (osteogenic peptide) are described. These Zn-MBGs scaffolds showed 3D hierarchical meso-macroporous structure that enables to host and release osteostatin. When decorated with human mesenchymal stem cells (hMSCs), MBGs scaffoldsenriched with both zinc and osteostatin exhibited a synergistic effect to enhance hMSCs growth, and also hMSCs osteogenic differentiationwithout addition of other osteoblastic differentiation factors to the culture medium. This novel strategy has a great potential for use in bone tissue engineering.

Stem and progenitor cells in skeletal development

Accumulating evidence supports the idea that stem and progenitor cells play important roles in skeletal development. Over the last decade, the definition of skeletal stem and progenitor cells has evolved from cells simply defined by their in vitro behaviors to cells fully defined by a combination of sophisticated approaches, including serial transplantation assays and in vivo lineage-tracing experiments. These approaches have led to better identification of the characteristics of skeletal stem cells residing in multiple sites, including the perichondrium of the fetal bone, the resting zone of the postnatal growth plate, the bone marrow space and the periosteum in adulthood. These diverse groups of skeletal stem cells appear to closely collaborate and achieve a number of important biological functions of bones, including not only bone development and growth, but also bone maintenance and repair. Although these are important findings, we are only beginning to understand the diversity and the nature of skeletal stem and progenitor cells, and how they actually behave in vivo.

Effects of Intermittent Parathyroid Hormone 1-34 Administration on Circulating Mesenchymal Stem Cells in Postmenopausal Osteoporotic Women

BACKGROUND Intermittent parathyroid hormone (PTH) 1-34 administration stimulates osteogenesis and increases bone marrow mesenchymal stem cell (MSC) density; however, its effect on the circulating MSCs is unknown. This study aimed to examine the effect of intermittent PTH 1-34 administration on circulating MSCs in the peripheral blood of postmenopausal osteoporotic women. MATERIAL AND METHODS Fifty-four postmenopausal osteoporotic women at high risk of fracture were enrolled and administered either teriparatide (PTH 1-34) or alendronate for 12 months. Whole blood samples were obtained at baseline, 1, 3, 6, and 12 months after initiation of treatment. Flow cytometry analyses were performed to identify circulating MSCs (CD73+, CD90+, CD105+, CD34-, and CD45-). Serum markers of bone formation, bone resorption, as well as bone mineral density (BMD) were serially measured. Circulating MSCs were isolated from peripheral blood of teriparatide treated women and cultured in osteogenic medium to examine their osteogenic differentiation potential. RESULTS Teriparatide treatment increased circulating MSCs to 141±96% (P<0.001) by month 1, persisting until month 12; this increase was positively associated with increases in bone formation and bone resorption biomarkers (at month 6) and spine BMD (at month 12). Furthermore, intermittent PTH 1-34 administration promoted in vitro osteogenic differentiation of circulating MSCs, evident from increased alkaline phosphatase (ALP) activity, ALP-expressing cell density, calcium deposition, and Runx-2, OSX, COL 1a1, and osteocalcin mRNA upregulation. CONCLUSIONS Intermittent PTH 1-34 administration increased circulating MSC density in women with postmenopausal osteoporosis and enhanced in vitro osteogenic differentiation potential of these cells.

Withdrawal of parathyroid hormone after prolonged administration leads to adipogenic differentiation of mesenchymal precursors in vivo

Intermittent PTH-like drugs are the only approved so-called anabolic agent that increases bone mass in both mice and humans. It is well documented that PTH targets mature cells of the osteoblast lineage, with only indirect evidence of its actions on early cells of the osteoblast lineage. Using a triple transgenic mouse model that allowed labeling of very early cells of the osteoblast lineage, we traced the progeny of these into osteoblast lineage in adult mice. These early cells expressed PTH1R and multiplied when PTH (1-34) was administered daily. We also showed that the early mesenchymal cells showed accelerated differentiation into mature osteocalcin-positive osteoblasts and osteocytes. Rather surprisingly, when teriparatide administration was stopped, these early mesenchymal precursors differentiated into adipocytes. We showed that the adipogenic differentiation is accompanied by a decrease in wnt signaling in osteoblast precursors. In this review, we discuss the possible clinical relevance of this finding and the possible molecular mechanisms that contribute to this phenotype in vivo.

Parathyroid hormone-stimulation of Runx2 during osteoblast differentiation via the regulation of lnc-SUPT3H-1:16 (RUNX2-AS1:32) and miR-6797-5p

Parathyroid hormone (PTH) acts as a regulator of calcium homeostasis and bone remodeling. Runx2, an essential transcription factor in bone, is required for osteoblast differentiation. Noncoding RNAs such as long noncoding RNAs (lncRNAs) and microRNAs (miRNAs) play crucial roles in regulating gene expression in osteoblasts. In this study, we investigated the effects of PTH on osteoblast differentiation via Runx2, lncRNA, and miRNA expression in human bone marrow stromal cells (hBMSCs) and human osteoblastic cells (MG63). PTH-treatment of hBMSCs for 24 h, 7 days, and 14 days stimulated Runx2 mRNA expression. Using bioinformatics tools, we identified 17 lncRNAs originating from human Runx2 gene. Among these, lnc-SUPT3H-1:16 (RUNX2-AS1:32) expression was highly up-regulated by the 7 d PTH-treatment in hBMSCs. We also identified miR-6797-5p as the putative target of lnc-SUPT3H-1:16 and Runx2 using bioinformatics tools. PTH-treatment increased the expression of miR-6797-5p in hBMSCs, and overexpression of miR-6797-5p decreased osteoblast differentiation in MG63 cells, suggesting a role for lnc-SUPT3H-1:16 as sponge molecule. A luciferase gene reporter assay identified direct targeting of miR-6797-5p with lnc-SUPT3H-1:16 and 3'UTR Runx2 in MG63 cells. Thus, PTH stimulated the expression of lnc-SUPT3H-1:16, miR-6797-5p and Runx2, and due to the sponging mechanism of lnc- SUPT3H-1:16 towards miR-6797-5p, Runx2 was protected, resulting in the promotion of osteoblast differentiation.

Pulsed electromagnetic fields prevented the decrease of bone formation in hindlimb-suspended rats by activating sAC/cAMP/PKA/CREB signaling pathway

Microgravity is one of the main threats to the health of astronauts. Pulsed electromagnetic fields (PEMFs) have been considered as one of the potential countermeasures for bone loss induced by space flight. However, the optimal therapeutic parameters of PEMFs have not been obtained and the action mechanism is still largely unknown. In this study, a set of optimal therapeutic parameters for PEMFs (50 Hz, 0.6 mT 50% duty cycle and 90 min/day) selected based on high-throughput screening with cultured osteoblasts was used to prevent bone loss in rats induced by hindlimb suspension, a commonly accepted animal model to simulate the space environment. It was found that hindlimb suspension for 4 weeks led to significant decreases in femoral and vertebral bone mineral density (BMD) and their maximal loads, severe deterioration in bone micro-structure, and decreases in levels of bone formation markers and increases in bone resorption markers. PEMF treatment prevented about 50% of the decreased BMD and maximal loads, preserved the microstructure of cancellous bone and thickness of cortical bone, and inhibited decreases in bone formation markers. Histological analyses revealed that PEMFs significantly alleviated the reduction in osteoblast number and inhibited the increase in adipocyte number in the bone marrow. PEMFs also blocked decreases in serum levels of parathyroid hormone and its downstream signal molecule cAMP, and maintained the phosphorylation levels of protein kinase A (PKA) and cAMP response element-binding protein (CREB). The expression level of soluble adenylyl cyclases (sAC) was also maintained. It therefore can be concluded that PEMFs partially prevented the bone loss induced by weightless environment by maintaining bone formation through signaling of the sAC/cAMP/PKA/CREB pathway. Bioelectromagnetics. 39:569-584, 2018. © 2018 Wiley Periodicals, Inc.

Osteogenic Effect of ZnO-Mesoporous Glasses Loaded with Osteostatin

Mesoporous Bioactive Glasses (MBGs) are a family of bioceramics widely investigated for their putative clinical use as scaffolds for bone regeneration. Their outstanding textural properties allow for high bioactivity when compared with other bioactive materials. Moreover, their great pore volumes allow these glasses to be loaded with a wide range of biomolecules to stimulate new bone formation. In this study, an MBG with a composition, in mol%, of 80% SiO₂⁻15% CaO⁻5% P₂O₅ (Blank, BL) was compared with two analogous glasses containing 4% and 5% of ZnO (4ZN and 5ZN) before and after impregnation with osteostatin, a C-terminal peptide from a parathyroid hormone-related protein (PTHrP107-111). Zn2+ ions were included in the glass for their bone growth stimulator properties, whereas osteostatin was added for its osteogenic properties. Glasses were characterized, and their cytocompatibility investigated, in pre-osteoblastic MC3T3-E1 cell cultures. The simultaneous additions of osteostatin and Zn2+ ions provoked enhanced MC3T3-E1 cell viability and a higher differentiation capacity, compared with either raw BL or MBGs supplemented only with osteostatin or Zn2+. These in vitro results show that osteostatin enhances the osteogenic effect of Zn2+-enriched glasses, suggesting the potential of this combined approach in bone tissue engineering applications.

Bone-targeting liposome formulation of Salvianic acid A accelerates the healing of delayed fracture Union in Mice

Delayed fracture union is a significant clinical challenge in orthopedic practice. There are few non-surgical therapeutic options for this pathology. To address this challenge, we have developed a bone-targeting liposome (BTL) formulation of salvianic acid A (SAA), a potent bone anabolic agent, for improved treatment of delayed fracture union. Using pyrophosphorylated cholesterol as the targeting ligand, the liposome formulation (SAA-BTL) has demonstrated strong affinity to hydroxyapatite in vitro, and to bones in vivo. Locally administered SAA-BTL was found to significantly improve fracture callus formation and micro-architecture with accelerated mineralization rate in callus when compared to the dose equivalent SAA, non-targeting SAA liposome (SAA-NTL) or no treatment on a prednisone-induced delayed fracture union mouse model. Biomechanical analyses further validated the potent therapeutic efficacy of SAA-BTL. These results support SAA-BTL formulation, as a promising therapeutic candidate, to be further developed into an effective and safe clinical treatment for delayed bone fracture union.

Parathyroid hormone-related protein exhibits antioxidant features in osteoblastic cells through its N-terminal and osteostatin domains

Objectives

Oxidative stress plays a major role in the onset and progression of involutional osteoporosis. However, classical antioxidants fail to restore osteoblast function. Interestingly, the bone anabolism of parathyroid hormone (PTH) has been shown to be associated with its ability to counteract oxidative stress in osteoblasts. The PTH counterpart in bone, which is the PTH-related protein (PTHrP), displays osteogenic actions through both its N-terminal PTH-like region and the C-terminal domain.

Methods

We examined and compared the antioxidant capacity of PTHrP (1-37) with the C-terminal PTHrP domain comprising the 107-111 epitope (osteostatin) in both murine osteoblastic MC3T3-E1 cells and primary human osteoblastic cells.

Results

We showed that both N- and C-terminal PTHrP peptides at 100 nM decreased reactive oxygen species production and forkhead box protein O activation following hydrogen peroxide (H₂O₂)-induced oxidation, which was related to decreased lipid oxidative damage and caspase-3 activation in these cells. This was associated with their ability to restore the deleterious effects of H₂O₂ on cell growth and alkaline phosphatase activity, as well as on the expression of various osteoblast differentiation genes. The addition of Rp-cyclic 3′,5′-hydrogen phosphorothioate adenosine triethylammonium salt (a cyclic 3',5'-adenosine monophosphate antagonist) and calphostin C (a protein kinase C inhibitor), or a PTH type 1 receptor antagonist, abrogated the effects of N-terminal PTHrP, whereas protein phosphatase 1 (an Src kinase activity inhibitor), SU1498 (a vascular endothelial growth factor receptor 2 inhibitor), or an anti osteostatin antiserum, inhibited the effects of C-terminal PTHrP.

Conclusion

These findings indicate that the antioxidant properties of PTHrP act through its N- and C-terminal domains and provide novel insights into the osteogenic action of PTHrP.

Cite this article: S. Portal-Núñez, J. A. Ardura, D. Lozano, I. Martínez de Toda, M. De la Fuente, G. Herrero-Beaumont, R. Largo, P. Esbrit. Parathyroid hormone-related protein exhibits antioxidant features in osteoblastic cells through its N-terminal and osteostatin domains. Bone Joint Res 2018;7:58–68. DOI: 10.1302/2046-3758.71.BJR-2016-0242.R2.

Parathyroid hormone-related peptide (1-34) reduces alveolar bone loss in type 1 diabetic rats

OBJECTIVE

To investigate the role of parathyroid hormone related protein (PTHrP) in diabetic periodontitis.

METHODS

After injected with 55mg/kg streptozotocin, diabetic rats were treated subcutaneously with low-dose (40μg/kg, once daily for 5days per week), middle-dose (80μg/kg) or high-dose (160μg/kg) PTHrP(1-34) peptide. Treatment continued for 12 weeks. Changes in periodontal tissues were confirmed by micro-computerized tomography assay and H&E analysis. We used tartrate resistant acid phosphatase (TRAP) staining to identify osteoclast cells. The expression of TNF-α, IL-1β and IL-6 was assessed by immunohistochemistry and Western blot.

RESULTS

Tooth-supporting structure loss was observed in periodontal tissues of diabetic rats. PTHrP (1-34) attenuated alveolar bone loss, especially in the middle-dose and high-dose group. Whereas TNF-α, IL-1β and IL-6 protein levels were increased in the diabetic gingival tissues, PTHrP (1-34) treatment inhibited the increase of IL-1β and IL-6, but had no effect on TNF-α.

CONCLUSION

Type 1 diabetes increased the susceptibility to periodontal disease. Intermittent administration of PTHrP (1-34) exhibited an inhibitory effect on alveolar bone resorption and the gingival inflammation in periodontal tissues of diabetic rats.

Matrix metalloproteinase processing of PTHrP yields a selective regulator of osteogenesis, PTHrP1-17

Parathyroid hormone-related protein (PTHrP) is a critical regulator of bone resorption and augments osteolysis in skeletal malignancies. Here we report that the mature PTHrP_1-36 hormone is processed by matrix metalloproteinases to yield a stable product, PTHrP_1-17. PTHrP_1-17 retains the ability to signal through PTH1R to induce calcium flux and ERK phosphorylation but not cyclic AMP production or CREB phosphorylation. Notably, PTHrP_1-17 promotes osteoblast migration and mineralization in vitro, and systemic administration of PTHrP_1-17 augments ectopic bone formation in vivo. Further, in contrast to PTHrP_1-36, PTHrP_1-17 does not affect osteoclast formation/function in vitro or in vivo. Finally, immunoprecipitation-mass spectrometry analyses using PTHrP_1-17-specific antibodies establish that PTHrP_1-17 is indeed generated by cancer cells. Thus, matrix metalloproteinase-directed processing of PTHrP disables the osteolytic functions of the mature hormone to promote osteogenesis, indicating important roles for this circuit in bone remodelling in normal and disease contexts.

Dose-dependence of PTH-related peptide-1 on the osteogenic induction of MC3T3-E1 cells in vitro

Parathyroid hormone (PTH), an 84-amino acid peptide, is an endocrine hormone that is secreted by parathyroid glands. PTH performs important functions in calcium regulation and bone remodeling. The PTH (1-34) named teriparatide, a 34-amino acid peptide derived from the N-terminus of PTH, conserves most of the functions of PTH, specifically the osteogenic capability. However, teriparatide is only used by injection and exhibits short duration. In addition, this PTH could not thoroughly expose active sites. In this study, a novel PTH-related peptide (designated PTHrP-1) derived from the N-terminus of PTH was added into the complete medium at different concentrations of PTHrP-1 (0, 50, 100, and 200 ng/mL) to induce the MC3T3-E1 cells. PTHrP-1 was detected by high-performance liquid chromatography and matrix-assisted laser desorption/ionization-time-of-flight mass spectroscopy. Cell morphology, cell proliferation, alkaline phosphatase (ALP), and ALP activity, osteocalcin concentration, and collagen type I (Col-I), osteopontin (OPN), and osteocalcin (OCN) mRNA expression by RT-PCR and protein expression by western blotting were observed and detected. The purity of the PTHrP-1 was 95.14%, and the PTHrP-1 can induce MC3T3-E1 cells into osteoblasts, thus improving ALP activity and OCN concentration, and increasing Col-I, OPN, and OCN mRNA expression and protein expression in MC3T3-E1 cell cultures. The PTHrP-1 proved to be an ideal active peptide. In addition, the osteogenic ability of PTHrP-1 at 200 and 100 ng/mL concentrations was not significantly different but significantly higher than 50 and 0 ng/mL groups. Results indicate that PTHrP-1 is a kind of active peptides that exhibits good biocompatibility with MC3T3-E1 cells and could improve cell proliferation and osteogenic differentiation. Moreover, PTHrP-1, at the preferable concentration of 100 ng/mL, could effectively promote MC3T3-E1 cells into osteoblasts.

Osteogenesis Is Improved by Low Tumor Necrosis Factor Alpha Concentration through the Modulation of Gs-Coupled Receptor Signals

In the early phase of bone damage, low concentrations of the cytokine tumor necrosis factor alpha (TNF-α) favor osteoblast differentiation. In contrast, chronic high doses of the same cytokine contribute to bone loss, demonstrating opposite effects depending on its concentration and on the time of exposure. In the bone microenvironment, TNF-α modulates the expression/function of different G protein-coupled receptors (GPCRs) and of their regulatory proteins, GPCR-regulated kinases (GRKs), thus dictating their final biological outcome in controlling bone anabolic processes. Here, the effects of TNF-α were investigated on the expression/responsiveness of the A_2B adenosine receptor (A_2BAR), a Gs-coupled receptor that promotes mesenchymal stem cell (MSC) differentiation into osteoblasts. Low TNF-α concentrations exerted a prodifferentiating effect on MSCs, pushing them toward an osteoblast phenotype. By regulating GRK2 turnover and expression, the cytokine impaired A_2BAR desensitization, accelerating receptor-mediated osteoblast differentiation. These data supported the anabolic effect of TNF-α submaximal concentration and demonstrated that the cytokine regulates GPCR responses by interfering with the receptor desensitization machinery, thereby enhancing the anabolic responses evoked by A_2BAR ligands. Overall, these results indicated that GPCR desensitization plays a pivotal role in osteogenesis and that its manipulation is an effective strategy to favor bone remodeling.

PTHrP-Derived Peptides Restore Bone Mass and Strength in Diabetic Mice: Additive Effect of Mechanical Loading

There is an unmet need to understand the mechanisms underlying skeletal deterioration in diabetes mellitus (DM) and to develop therapeutic approaches to treat bone fragility in diabetic patients. We demonstrate herein that mice with type 1 DM induced by streptozotocin exhibited low bone mass, inferior mechanical and material properties, increased bone resorption, decreased bone formation, increased apoptosis of osteocytes, and increased expression of the osteocyte-derived bone formation inhibitor Sost/sclerostin. Further, short treatment of diabetic mice with parathyroid hormone related protein (PTHrP)-derived peptides corrected these changes to levels undistinguishable from non-diabetic mice. In addition, diabetic mice exhibited reduced bone formation in response to mechanical stimulation, which was corrected by treatment with the PTHrP peptides, and higher prevalence of apoptotic osteocytes, which was reduced by loading or by the PTHrP peptides alone and reversed by a combination of loading and PTHrP peptide treatment. In vitro experiments demonstrated that the PTHrP peptides or mechanical stimulation by fluid flow activated the survival kinases ERKs and induced nuclear translocation of the canonical Wnt signaling mediator β-catenin, and prevented the increase in osteocytic cell apoptosis induced by high glucose. Thus, PTHrP-derived peptides cross-talk with mechanical signaling pathways to reverse skeletal deterioration induced by DM in mice. These findings suggest a crucial role of osteocytes in the harmful effects of diabetes on bone and raise the possibility of targeting these cells as a novel approach to treat skeletal deterioration in diabetes. Moreover, our study suggests the potential therapeutic efficacy of combined pharmacological and mechanical stimuli to promote bone accrual and maintenance in diabetic subjects. © 2016 American Society for Bone and Mineral Research.

The Potential Use of Pharmacological Agents to Modulate Orthodontic Tooth Movement (OTM)

The biological processes that come into play during orthodontic tooth movement (OTM) have been shown to be influenced by a variety of pharmacological agents. The effects of such agents are of particular relevance to the clinician as the rate of tooth movement can be accelerated or reduced as a result. This review aims to provide an overview of recent insights into drug-mediated effects and the potential use of drugs to influence the rate of tooth movement during orthodontic treatment. The limitations of current experimental models and the need for well-designed clinical and pre-clinical studies are also discussed.

Abaloparatide

Abaloparatide is an investigational analog of human PTHrP (1-34) being developed for the treatment of osteoporosis. The amino-acid sequence of abaloparatide is identical to that of PTHrP in the first 20 amino-acids, while over half of the remaining amino-acids are different. Some studies in animals and in humans reported that abaloparatide presented a potent anabolic activity with reduced effects on bone resorption as compared to that observed with teriparatide. This may be due to a more transient signaling response of abaloparatide related to differing affinities of the two drugs to the specific conformations of the PTH1 receptor. In the ACTIVE study, a phase 3 fracture prevention trial, 2460 postmenopausal osteoporotic women at high risk for fracture were randomized to receive 18-months of either daily abaloparatide 80 μg s.c., placebo or teriparatide 20 μg s.c. The reduction in vertebral fracture rate with respect to placebo was 86% in the abaloparatide group and 80% in the teriparatide group. Abaloparatide also produced a significant 43% reduction in the rate of nonvertebral fractures (2.7 vs 4.0% with placebo, p=0.04) whereas teriparatide determined a 28% reduction (2.9 vs 4.0% with placebo, p=NS). Abaloparatide or teriparatide showed similar increases in BMD at lumbar spine, while the patients of the abaloparatide group showed significantly greater increases in BMD at both total hip (4.18 vs 3.26%) and femoral neck (3.60 vs 2.66%). Therefore, if the preliminary data of the ACTIVE study is confirmed, abaloparatide may become an important option for the anabolic treatment of postmenopausal osteoporosis.

Signalling pathways in trophic skeletal development and morphogenesis: Insights from studies on teleost fish

During the development of the vertebrate feeding apparatus, a variety of complicated cellular and molecular processes participate in the formation and integration of individual skeletal elements. The molecular mechanisms regulating the formation of skeletal primordia and their development into specific morphological structures are tightly controlled by a set of interconnected signalling pathways. Some of these pathways, such as Bmp, Hedgehog, Notch and Wnt, are long known for their pivotal roles in craniofacial skeletogenesis. Studies addressing the functional details of their components and downstream targets, the mechanisms of their interactions with other signals as well as their potential roles in adaptive morphological divergence, are currently attracting considerable attention. An increasing number of signalling pathways that had previously been described in different biological contexts have been shown to be important in the regulation of jaw skeletal development and morphogenesis. In this review, I provide an overview of signalling pathways involved in trophic skeletogenesis emphasizing studies of the most species-rich group of vertebrates, the teleost fish, which through their evolutionary history have undergone repeated episodes of spectacular trophic diversification.