The effects of parathyroid hormone and alendronate alone or in combination in postmenopausal osteoporosis

Treatment of glucocorticoid-induced osteoporosis with concurrent denosumab and romosozumab: a case report

Osteoporosis is a metabolic bone disorder for which treatment options include antiresorptive therapies (e.g., bisphosphonates, denosumab); anabolics (e.g., teriparatide, abaloparatide); and dual mechanisms (e.g., romosozumab). Management of osteoporosis with concurrent antiresorptive and anabolic agents may be superior to monotherapy, as demonstrated in the DATA trial with the combination of denosumab and teriparatide. However, there is limited experience with the combination of denosumab and romosozumab, which may be an alternative antiresorptive/anabolic regimen for individuals who are not candidates for PTH receptor agonists. In this case, we present a young man with glucocorticoid-induced osteoporosis who could not tolerate a daily injectable anabolic and who experienced improvement in bone mineral density with concurrent denosumab and off-label romosozumab administration.

Beyond resorption: osteoclasts as drivers of bone formation

Emerging evidence illustrates that osteoclasts (OCs) play diverse roles beyond bone resorption, contributing significantly to bone formation and regeneration. Despite this, OCs remain mysterious cells, with aspects of their lifespan-from origin, fusion, alterations in cellular characteristics, to functions-remaining incompletely understood. Recent studies have identified that embryonic osteoclastogenesis is primarily driven by osteoclast precursors (OCPs) derived from erythromyeloid progenitors (EMPs). These precursor cells subsequently fuse into OCs essential for normal bone development and repair. Postnatally, hematopoietic stem cells (HSCs) become the primary source of OCs, gradually replacing EMP-derived OCs and assuming functional roles in adulthood. The absence of OCs during bone development results in bone structure malformation, including abnormal bone marrow cavity formation and shorter long bones. Additionally, OCs are reported to have intimate interactions with blood vessels, influencing bone formation and repair through angiogenesis regulation. Upon biomaterial implantation, activation of the innate immune system ensues immediately. OCs, originating from macrophages, closely interact with the immune system. Furthermore, evidence from material-induced bone formation events suggests that OCs are pivotal in these de novo bone formation processes. Nevertheless, achieving a pure OC culture remains challenging, and interpreting OC functions in vivo faces difficulties due to the presence of other multinucleated cells around bone-forming biomaterials. We here describe the fusion characteristics of OCPs and summarize reliable markers and morphological changes in OCs during their fusion process, providing guidance for researchers in identifying OCs both in vitro and in vivo. This review focuses on OC formation, characterization, and the roles of OCs beyond resorption in various bone pathophysiological processes. Finally, therapeutic strategies targeting OCs are discussed.

Effects of daily teriparatide, weekly high-dose teriparatide, or bisphosphonate on cortical and trabecular bone of vertebra and proximal femur in postmenopausal women with fragility fracture: Sub-analysis by quantitative computed tomography from the TERABIT study

PURPOSE

The effects of daily teriparatide (D-PTH, 20 μg/day), weekly high-dose teriparatide (W-PTH, 56.5 μg/week), or bisphosphonate (BP) on the vertebra and proximal femur were investigated using quantitative computed tomography (QCT).

METHODS

A total of 131 postmenopausal women with a history of fragility fractures were randomized to receive D-PTH, W-PTH, or bisphosphonate (oral alendronate or risedronate). QCT were evaluated at baseline and after 18 months of treatment.

RESULTS

A total of 86 participants were evaluated by QCT (Spine: D-PTH: 25, W-PTH: 21, BP: 29. Hip: PTH: 22, W-PTH: 21, BP: 32. Dropout rate: 30.5 %). QCT of the vertebra showed that D-PTH, W-PTH, and BP increased total vBMD (+34.8 %, +18.2 %, +11.1 %), trabecular vBMD (+50.8 %, +20.8 %, +12.2 %), and marginal vBMD (+20.0 %, +14.0 %, +11.5 %). The increase in trabecular vBMD was greater in the D-PTH group than in the W-PTH and BP groups. QCT of the proximal femur showed that D-PTH, W-PTH, and BP increased total vBMD (+2.8 %, +3.6 %, +3.2 %) and trabecular vBMD (+7.7 %, +5.1 %, +3.4 %), while only W-PTH and BP significantly increased cortical vBMD (-0.1 %, +1.5 %, +1.6 %). Although there was no significant increase in cortical vBMD in the D-PTH group, cortical bone volume (BV) increased in all three treatment groups (+2.1 %, +3.6 %, +3.1 %).

CONCLUSIONS

D-PTH had a strong effect on trabecular bone of vertebra. Although D-PTH did not increase cortical BMD of proximal femur, it increased cortical BV. W-PTH had a moderate effect on trabecular bone of vertebra, while it increased both cortical BMD and BV of proximal femur. Although BP had a limited effect on trabecular bone of vertebra compared to teriparatide, it increased both cortical BMD and BV of proximal femur.

Real-life effects of pharmacological osteoporosis treatments on bone mineral density by quantitative computed tomography

INTRODUCTION

Monitoring of bone mineral density (BMD) is used to assess pharmacological osteoporosis therapy. This study examined the real-life effects of antiresorptive and osteoanabolic treatments on volumetric BMD (vBMD) of the spine by quantitative computed tomography (QCT).

MATERIALS AND METHODS

Patients aged ≥ 50 years with a vBMD < 120 mg/ml had ≥ 2 QCT. For analysis of therapy effects, the pharmacological treatment and the duration of each therapy were considered. Identical vertebrae were evaluated in all vBMD measurements for each patient. A linear mixed model with random intercepts was used to estimate the effects of pharmacological treatments on vBMD.

RESULTS

A total of 1145 vBMD measurements from 402 patients were analyzed. Considering potential confounders such as sex, age, and prior treatment, a reduction in trabecular vBMD was estimated for oral bisphosphonates (- 1.01 mg/ml per year; p < 0.001), intravenous bisphosphonates (- 0.93 mg/ml per year; p = 0.015) and drug holiday (- 1.58 mg/ml per year; p < 0.001). Teriparatide was estimated to increase trabecular vBMD by 4.27 mg/ml per year (p = 0.018). Patients receiving denosumab showed a statistically non-significant decrease in trabecular vBMD (- 0.44 mg/ml per year; p = 0.099). Compared to non-treated patients, pharmacological therapy had positive effects on trabecular vBMD (1.35 mg/ml; p = 0.001, 1.43 mg/ml; p = 0.004, 1.91 mg/ml; p < 0.001, and 6.63 mg/ml; p < 0.001 per year for oral bisphosphonates, intravenous bisphosphonates, denosumab, and teriparatide, respectively).

CONCLUSION

An increase in trabecular vBMD by QCT was not detected with antiresorptive agents. Patients treated with teriparatide showed increasing trabecular vBMD. Non-treatment led to a larger decrease in trabecular vBMD than pharmacological therapy.

Hydroxychloroquine and a low antiresorptive activity bisphosphonate conjugate prevent and reverse ovariectomy-induced bone loss in mice through dual antiresorptive and anabolic effects

Osteoporosis remains incurable. The most widely used antiresorptive agents, bisphosphonates (BPs), also inhibit bone formation, while the anabolic agent, teriparatide, does not inhibit bone resorption, and thus they have limited efficacy in preventing osteoporotic fractures and cause some side effects. Thus, there is an unmet need to develop dual antiresorptive and anabolic agents to prevent and treat osteoporosis. Hydroxychloroquine (HCQ), which is used to treat rheumatoid arthritis, prevents the lysosomal degradation of TNF receptor-associated factor 3 (TRAF3), an NF-κB adaptor protein that limits bone resorption and maintains bone formation. We attempted to covalently link HCQ to a hydroxyalklyl BP (HABP) with anticipated low antiresorptive activity, to target delivery of HCQ to bone to test if this targeting increases its efficacy to prevent TRAF3 degradation in the bone microenvironment and thus reduce bone resorption and increase bone formation, while reducing its systemic side effects. Unexpectedly, HABP-HCQ was found to exist as a salt in aqueous solution, composed of a protonated HCQ cation and a deprotonated HABP anion. Nevertheless, it inhibited osteoclastogenesis, stimulated osteoblast differentiation, and increased TRAF3 protein levels in vitro. HABP-HCQ significantly inhibited both osteoclast formation and bone marrow fibrosis in mice given multiple daily PTH injections. In contrast, HCQ inhibited marrow fibrosis, but not osteoclast formation, while the HABP alone inhibited osteoclast formation, but not fibrosis, in the mice. HABP-HCQ, but not HCQ, prevented trabecular bone loss following ovariectomy in mice and, importantly, increased bone volume in ovariectomized mice with established bone loss because HABP-HCQ increased bone formation and decreased bone resorption parameters simultaneously. In contrast, HCQ increased bone formation, but did not decrease bone resorption parameters, while HABP also restored the bone lost in ovariectomized mice, but it inhibited parameters of both bone resorption and formation. Our findings suggest that the combination of HABP and HCQ could have dual antiresorptive and anabolic effects to prevent and treat osteoporosis.

Romosozumab versus parathyroid hormone receptor agonists: which osteoanabolic to choose and when?

Osteoanabolic agents are used as a first line treatment in patients at high fracture risk. The PTH receptor 1 (PTH1R) agonists teriparatide (TPTD) and abaloparatide (ABL) increase bone formation, bone mineral density (BMD), and bone strength by activating PTH receptors on osteoblasts. Romosozumab (ROMO), a humanized monoclonal antibody against sclerostin, dramatically but transiently stimulates bone formation and persistently reduces bone resorption. Osteoanabolic agents increase BMD and bone strength while being more effective than antiresorptives in reducing fracture risk in postmenopausal women. However, direct comparisons of the antifracture benefits of osteoanabolic therapies are limited. In a direct comparison of TPTD and ABL, the latter resulted in greater BMD increases at the hip. While no differences in vertebral or non-vertebral fracture risk were observed between the two drugs, ABL led to a greater reduction of major osteoporotic fractures. Adverse event profiles were similar between the two agents except for hypercalcemia, which occurred more often with TPTD. No direct comparisons of fracture risk reduction between ROMO and the PTH1R agonists exist. Individual studies have shown greater increases in BMD and bone strength with ROMO compared with TPTD in treatment-naive women and in women previously treated with bisphosphonates. Some safety aspects, such as a history of tumor precluding the use of PTH1R agonists, and a history of major cardiovascular events precluding the use of ROMO, should also be considered when choosing between these agents. Finally, convenience of administration, reimbursement by national health systems and length of clinical experience may influence patient choice.

Delayed and significant hypercalcaemia due to teriparatide therapy: a case report and review

INTRODUCTION

Transient hypercalcaemia due to teriparatide occurs in up to 11% of patients though delayed hypercalcaemia (> 24 h post injection) is rare. We report the case of a female who developed significant delayed hypercalcaemia after teriparatide treatment for osteoporosis and review other cases in the literature to date.

CASE REPORT

A 72-year-old female on teriparatide for the treatment of osteoporosis was found to have hypercalcaemia (3.30 mmol/l) on routine testing approximately 3 months after starting therapy. Serum calcium pretreatment was normal at 2.39 mmol/l. She was admitted to the hospital for investigations which identified a serum 25-hydroxyvitamin D of 94 nmol/l, a low parathyroid hormone of 6.0 pg/ml, and normal test results for 1,25 dihydroxyvitamin D (115 pmol/l), parathyroid hormone-related peptide (< 1.4 pmol/ml), serum electrophoresis and angiotensin-converting enzyme (39 IU/l). CT abdomen, pelvis, and thorax revealed no evidence of malignancy and an isotope bone scan ruled out skeletal metastases. Serum calcium normalised (2.34 mmol/l) several days after stopping teriparatide and calcium supplements and administering intravenous fluid. On restarting teriparatide, delayed hypercalcaemia reoccurred and treatment was switched to denosumab.

DISCUSSION

Delayed moderate to severe hypercalcaemia (serum calcium > 3.0 mmol/l) due to teriparatide is rare but may lead to therapy withdrawal. The underlying predisposing risk factors remain unclear and highlight the importance of a routine serum calcium assessment on therapy.

Jiangu formula: A novel osteoclast-osteoblast coupling agent for effective osteoporosis treatment

BACKGROUND

The discovering of an osteoclast (OC) coupling active agent, capable of suppressing OC-mediated bone resorption while concurrently stimulating osteoblast (OB)-mediated bone formation, presents a promising strategy to overcome limitations associated with existing antiresorptive agents. However, there is a lack of research on active OC coupling agents.

PURPOSE

This study aims to investigate the potential of Jiangu Formula (JGF) in inhibiting OCs while maintaining the OCOB coupling function.

METHODS

The anti-osteoporosis efficacy of JGF was evaluated in osteoporosis models induced by ovariectomy in C57BL/6 mouse and SD rats. The effect of JGF on OCs was evaluated by detecting its capacity to inhibit OC differentiation and bone resorption in an in vitro osteoclastogenesis model induced by RANKL. The OCOB coupling activity of JGF was evaluated by measuring the secretion levels of OC-derived coupling factors, OB differentiation activity of MC3T3-E1 interfered with conditioned medium, and the effect of JGF on OC inhibition and OB differentiation in a C3H10T1/2-RAW264.7 co-culture system. The mechanism of JGF was studied by network pharmacology and validated using western blot, immunofluorescence (IF), and ELISA. Following that, the active ingredients of JGF were explored through a chemotype-assembly approach, activity evaluation, and LC-MS/MS analysis.

RESULTS

JGF inhibited bone resorption in murine osteoporosis without compromising the OCOB coupling effect on bone formation. In vitro assays showed that JGF preserved the coupling effect of OC on OB differentiation by maintaining the secretion of OC-derived coupling factors. Network analysis predicted STAT3 as a key regulation point for JGF to exert anti-osteoporosis effect. Further validation assays confirmed that JGF upregulated p-STAT3(Ser727) and its regulatory factors IL-2 in RANKL-induced RAW264.7 cells. Moreover, 23 components in JGF with anti-OC activity identified by chemotype-assembly approach and verification experiments. Notably, six compounds, including ophiopogonin D, ginsenoside Re, ginsenoside Rf, ginsenoside Rg3, ginsenoside Ro, and ononin were identified as OC-coupling compounds.

CONCLUSION

This study first reported JGF as an agent that suppresses bone loss without affecting bone formation. The potential coupling mechanism of JGF involves the upregulation of STAT3 by its regulators IL-2. Additionally, the chemotype-assembly approach elucidated the activity compounds present in JGF, offering a novel strategy for developing an anti-resorption agent that preserves bone formation.

State of the Art Imaging of Osteoporosis

Osteoporosis is a common disease, particularly prevalent in geriatric populations, which causes significant worldwide morbidity due to increased bone fragility and fracture risk. Currently, the gold-standard modality for diagnosis and evaluation of osteoporosis progression and treatment relies on dual-energy x-ray absorptiometry (DXA), which measures bone mineral density (BMD) and calculates a score based upon standard deviation of measured BMD from the mean. However, other imaging modalities can also be used to evaluate osteoporosis. Here, we review historical as well as current research into development of new imaging modalities that can provide more nuanced or opportunistic analyses of bone quality, turnover, and density that can be helpful in triaging severity and determining treatment success in osteoporosis. We discuss the use of opportunistic computed tomography (CT) scans, as well as the use of quantitative CT to help determine fracture risk and perform more detailed bone quality analysis than would be allowed by DXA . Within magnetic resonance imaging (MRI), new developments include the use of advanced MRI techniques such as quantitative susceptibility mapping (QSM), magnetic resonance spectroscopy, and chemical shift encoding-based water-fat MRI (CSE-MRI) to enable clinicians improved assessment of nonmineralized bone compartments as well as a way to longitudinally assess bone quality without the repeated exposure to ionizing radiation. Within ultrasound, development of quantitative ultrasound shows promise particularly in future low-cost, broadly available screening tools. We focus primarily on historical and recent developments within radiotracer use as applicable to osteoporosis, particularly in the use of hybrid methods such as NaF-PET/CT, wherein patients with osteoporosis show reduced uptake of radiotracers such as NaF. Use of radiotracers may provide clinicians with even earlier detection windows for osteoporosis than would traditional biomarkers. Given the metabolic nature of this disease, current investigation into the role molecular imaging can play in the prediction of this disease as well as in replacing invasive diagnostic procedures shows particular promise.

New Horizons: Translational Aspects of Osteomorphs

Osteomorphs are a newly described osteoclast lineage cell in mice, which are suggested to play a significant role in the maintenance of bone resorption. Preclinical investigations revealed that osteomorphs are generated through the fission of multinucleated bone-resorbing osteoclasts and can also re-fuse with existing osteoclasts. Modifications to RANKL signaling have been shown to alter cycles of fission and re-fusion of osteomorphs in mice. These novel findings were also shown to contribute to the rebound phenomenon after cessation of anti-RANKL therapy in mice. Moreover, the absence of osteomorph-specific genes in mice exhibits bone structural and quality phenotypes. Given these insights, it could be speculated that osteomorphs play a significant role in bone homeostasis, bone metabolic diseases, and response to therapeutics. In this review, we discuss these potential translational roles for osteomorphs. Importantly, we highlight the need for future preclinical and clinical studies to verify the presence of osteomorphs in humans and explore further the translational implications of this discovery.

Non-biological Antiresorptive: Bisphosphonates

Background

Bisphosphonates, synthetic analogs of endogenous pyrophosphates, are pivotal in managing various bone disorders, primarily osteoporosis, which affects millions globally. While osteoporosis, especially postmenopausal osteoporosis, significantly benefits from bisphosphonate therapy, considerations arise regarding their administration and potential side effects.

Clinical application of Bisphosphonates

Bisphosphonates, divided into nitrogen-containing and non-nitrogenous groups, exert their influence through distinct mechanisms, with the former being notably more potent. The role of bisphosphonates in other diseases, such as Paget's bone and skeletal metastasis disease is also discussed. Detailed information on the administration routes, dosage regimens, and considerations for drug holidays is provided. The article navigates through the chemical structure, generations, and mechanism of action of bisphosphonates. The article covers administration routes, dosage regimens, and drug holidays, in addition to discussing potential adverse effects and contraindications.

Conclusions

Bisphosphonates hold an unrivaled legacy in the management of osteoporosis. The ubiquitous availability and the cost-effectiveness of these time-tested medications make them an invaluable asset in the osteoporosis treatment landscape, especially in developing nations like India.

Bone Remodeling and Modeling: Cellular Targets for Antiresorptive and Anabolic Treatments, Including Approaches Through the Parathyroid Hormone (PTH)/PTH-Related Protein Pathway

Bone is continuously in a state of building and renewal, though the process of remodeling that takes place at many sites asynchronously throughout the skeleton, with bone formation and resorption equal at these sites (bone multicellular units). Remodeling takes place on bone surfaces, both on trabeculae and in the cortex, and serves the purposes of replacing old bone or that damaged by microfractures throughout the skeleton. The bone loss and consequent osteoporotic fractures that result from excess resorption over formation have mainly been prevented or treated by antiresorptive drugs that inhibit osteoclast formation and/or activity. Virtually all of the evidence leading to acceptance of antiresorptive drugs as treatment has depended upon their prevention of vertebral fractures. In recent decades, new prospects came of anabolic treatments that partly restore bone volume and microstructure restore bone that has been lost. The first of these was parathyroid hormone (PTH), shown by daily injection to increase markers of bone formation and prevent fractures. This field of interest enlarged with the discovery of PTH-related protein (PTHrP), so closely related in structure and action to PTH. The structural relationship between PTH and PTHrP is important in assessing their physiological and pharmacological roles, with the N-terminal domains of the 2 having virtually equal actions on target cells. Abaloparatide, a peptide analogue based on the structures of PTHrP and PTH, has been approved in some countries as a therapy for osteoporosis. Treatment through the PTH receptor activation pathway, and probably with any anabolic therapy, needs to be followed by antiresorptive treatment in order to maintain bone that has been restored. No matter how effective anabolic therapies for the skeleton become, it seems highly likely that there will be a continuing need for antiresorptive drugs.

Combination Therapy of Denosumab and Teriparatide in Osteoporosis

Osteoporosis is a chronic disease that often requires long-term treatment for many years. The clinician should know about all the drugs that are currently being used for treatment in osteoporosis and their mechanism of action, efficacy, safety profile, mode of administration and number of years they can be given safely without causing significant adverse effects. The categories of drugs that are currently being used for osteoporosis are antiresorptives such as oral and intravenous bisphosphonates, denosumab, and anabolics like teriparatide. This article will focus on the combination therapy of denosumab and teriparatide and will discuss how this combination is better than other class of drugs when given alone or in combination in osteoporosis patients especially those who are at high risk of fragility fractures.

Long-term and sequential treatment for osteoporosis

Osteoporosis is a skeletal disorder that causes impairment of bone structure and strength, leading to a progressively increased risk of fragility fractures. The global prevalence of osteoporosis is increasing in the ageing population. Owing to the chronic character of osteoporosis, years or even decades of preventive measures or therapy are required. The long-term use of bone-specific pharmacological treatment options, including antiresorptive and/or osteoanabolic approaches, has raised concerns around adverse effects or potential rebound phenomena after treatment discontinuation. Imaging options, risk scores and the assessment of bone turnover during initiation and monitoring of such therapies could help to inform individualized treatment strategies. Combination therapies are currently used less often than 'sequential' treatments. However, all patients with osteoporosis, including those with secondary and rare causes of osteoporosis, as well as specific patient populations (for example, young adults, men and pregnant women) require new approaches for long-term therapy and disease monitoring. New pathophysiological aspects of bone metabolism might therefore help to inform and revolutionize the diagnosis and treatment of osteoporosis.

Mechanistic advances in osteoporosis and anti-osteoporosis therapies

Osteoporosis is a type of bone loss disease characterized by a reduction in bone mass and microarchitectural deterioration of bone tissue. With the intensification of global aging, this disease is now regarded as one of the major public health problems that often leads to unbearable pain, risk of bone fractures, and even death, causing an enormous burden at both the human and socioeconomic layers. Classic anti-osteoporosis pharmacological options include anti-resorptive and anabolic agents, whose ability to improve bone mineral density and resist bone fracture is being gradually confirmed. However, long-term or high-frequency use of these drugs may bring some side effects and adverse reactions. Therefore, an increasing number of studies are devoted to finding new pathogenesis or potential therapeutic targets of osteoporosis, and it is of great importance to comprehensively recognize osteoporosis and develop viable and efficient therapeutic approaches. In this study, we systematically reviewed literatures and clinical evidences to both mechanistically and clinically demonstrate the state-of-art advances in osteoporosis. This work will endow readers with the mechanistical advances and clinical knowledge of osteoporosis and furthermore present the most updated anti-osteoporosis therapies.

Pharmaceutical treatment of bone loss: From animal models and drug development to future treatment strategies

Animal models are fundamental to advance our knowledge of the underlying pathophysiology of bone loss and to study pharmaceutical countermeasures against it. The animal model of post-menopausal osteoporosis from ovariectomy is the most widely used preclinical approach to study skeletal deterioration. However, several other animal models exist, each with unique characteristics such as bone loss from disuse, lactation, glucocorticoid excess, or exposure to hypobaric hypoxia. The present review aimed to provide a comprehensive overview of these animal models to emphasize the importance and significance of investigating bone loss and pharmaceutical countermeasures from perspectives other than post-menopausal osteoporosis only. Hence, the pathophysiology and underlying cellular mechanisms involved in the various types of bone loss are different, and this might influence which prevention and treatment strategies are the most effective. In addition, the review sought to map the current landscape of pharmaceutical countermeasures against osteoporosis with an emphasis on how drug development has changed from being driven by clinical observations and enhancement or repurposing of existing drugs to today's use of targeted anti-bodies that are the result of advanced insights into the underlying molecular mechanisms of bone formation and resorption. Moreover, new treatment combinations or repurposing opportunities of already approved drugs with a focus on dabigatran, parathyroid hormone and abaloparatide, growth hormone, inhibitors of the activin signaling pathway, acetazolamide, zoledronate, and romosozumab are discussed. Despite the considerable progress in drug development, there is still a clear need to improve treatment strategies and develop new pharmaceuticals against various types of osteoporosis. The review also highlights that new treatment indications should be explored using multiple animal models of bone loss in order to ensure a broad representation of different types of skeletal deterioration instead of mainly focusing on primary osteoporosis from post-menopausal estrogen deficiency.

The Promoting Effect of a Local Pulsatile Parathyroid Hormone Delivery on Healing of the Mandibular Fracture in Rats

Parathyroid hormone (PTH) can promote bone formation and mineralization in mandibular fractures, and is systemically administered through daily injections. In this study, the local delivery of PTH using carboxymethyl chitosan/polyvinyl alcohol and alginate was investigated. Bovine serum albumin was used as a drug substitute, and the delivery system was verified to release drugs in a pulsed rhythm. After the delivery system was subcutaneously implanted in Sprague-Dawley (SD) rats, no rejection reaction was detected, indicating that it has good biocompatibility and biodegradability in vivo. Then, an SD rat model of mandibular fracture was established, and 24 rats were randomly divided into two groups. The control group was reduced and fixed with screws and a microplate, and the experimental group received pulsatile PTH release system (14 μg PTH) + screws and microplate fixation. The animals were euthanized on postoperative weeks 1-4. Observation of gross specimens, digital radiography, and hematoxylin and eosin showed that the local PTH pulsatile release system promoted osteogenesis and accelerated fracture healing. In summary, PTH can be loaded by biomaterials to locally target the fracture and stimulate bone formation. Moreover, the pulsatile PTH release system provides a potential therapeutic protocol for mandibular fracture. Impact statement Our study prepares a drug release system that could impulsively release parathyroid hormone. The system could enhance bone regeneration in rats with mandibular fracture. These data provide a foundation for future studies aimed to understand and optimize the use of bioactive molecule pulsatile delivery for bone regeneration and tissue engineering applications.

Risk factors and management of hyperuricemia after renal transplantation

Hyperuricemia (HUA) is a common complication after renal transplantation. Currently, there is no uniform consensus on factors which increase the risk for and treatment of HUA in renal transplant recipients. The purpose of this review is to summarize current and proposed risk factors and strategies to manage HUA after renal transplantation in order to assist renal function protection and prolong graft survival time.

Effect of Teriparatide on Bone Mineral Density and Bone Markers in Real-Life: Argentine Experience

PURPOSE

To evaluate the effect of teriparatide (TPTD) on bone mineral density (BMD) and bone markers under clinical practice conditions. To assess whether the results in real-life match those published in clinical trials.

METHODS

Cross-sectional study of postmenopausal women treated with TPTD for at least 12 months.

RESULTS

264 patients were included in the study. Main characteristics are as follows: age: 68.7 ± 10.2 years, previous fractures: 57.6%, and previously treated with antiresorptive (AR-prior): 79%. All bone turnover markers studied significantly increased after 6 months. CTX and BGP remained high up to 24 months, but total and bone alkaline phosphatase returned to basal values at month 18. There was a significant increase in lumbar spine (LS) BMD after 6 months (+6.2%), with a maximum peak at 24 months (+13%). Femoral neck (FN) and total hip (TH) BMD showed a significant increase later than LS (just at month 12), reaching a maximum peak at month 24 (FN + 7.9% and TH + 5.5%). A significant increase in LS BMD was found from month 6 to month 24 compared to basal in both AR-naïve, and AR-prior patients (+16.7% and +10.5%, respectively), without significant differences between the two groups. Comparable results were found in FN and TH BMD. Main conclusions. As reported in real-life clinical studies, treatment of osteoporotic postmenopausal women with TPTD induced a significant increase in bone turnover markers from month 6 onward and an increase in BMD from months 6-12 with continuous gain up to month 24. The real-life results of our study matched the results of randomized clinical trials. In addition, TPTD induced an increase in BMD, regardless of the previous use of AR.

Emerging Role of 18F-NaF PET/Computed Tomographic Imaging in Osteoporosis: A Potential Upgrade to the Osteoporosis Toolbox

Osteoporosis is a metabolic bone disorder that leads to a decline in bone microarchitecture, predisposing individuals to catastrophic fractures. The current standard of care relies on detecting bone structural change; however, these methods largely miss the complex biologic forces that drive these structural changes and response to treatment. This review introduces sodium fluoride (18F-NaF) positron emission tomography/computed tomography (PET/CT) as a powerful tool to quantify bone metabolism. Here, we discuss the methods of 18F-NaF PET/CT, with a special focus on dynamic scans to quantify parameters relevant to bone health, and how these markers are relevant to osteoporosis.

Orchestrated delivery of PTH [1-34] followed by zoledronic acid prevents radiotherapy-induced bone loss but does not abrogate marrow damage

Postradiotherapy bone fragility fractures are a frequent late-onset complication in cancer survivors. There is a critical need to develop preventative interventions, and the use of Food and Drug Administration-approved drugs remains an attractive option. Prior data from our lab and others have shown that parathyroid hormone [1-34] mitigates radiotherapy-induced bone loss, but only for the duration of drug delivery. Utilizing a murine hindlimb radiotherapy model, we investigated whether orchestrated delivery of single-dose zoledronic acid could extend these anabolic benefits after cessation of parathyroid hormone delivery. We then explored the potential use of parathyroid hormone as a bone marrow radioprotectant. While the addition of zoledronic acid to parathyroid hormone increased irradiated bone mass, there was no increase in femur bending strength. In this model, the parathyroid hormone was not effective as a marrow radioprotectant, although this could be due to the short course of parathyroid hormone treatment. Marrow repopulation kinetics differed from those in total body irradiation, with hematopoietic stem cell repopulation occurring relatively early at four weeks postirradiation. Furthermore, we found radiation induced a loss of marrow stromal cells and an increase in inflammatory monocytes. Statement of Clinical Significance: Staged delivery of parathyroid hormone and zoledronic acid shows promise as an off-the-shelf intervention to mitigate post-radiotherapy bone damage in cancer patients, but parathyroid hormone is unlikely to function as a broad-spectrum marrow radioprotectant.

The why and how of sequential and combination therapy in osteoporosis. A review of the current evidence

It is now well recognized that over the lifetime of a patient with osteoporosis, more than one medication will be needed to treat the disease and to decrease fracture risk. Though current gaps in osteoporosis therapy can be potentially mitigated with sequential and combination regimens, how to move seamlessly amongst the multiple treatments currently available for osteoporosis for sustained efficacy is still unclear. Data from recent studies show that an anabolic agent such as teriparatide or romosozumab followed by an antiresorptive affords maximal gain in BMD and possibly better and earlier fracture risk reduction compared to a regimen which follows the opposite sequence. Sequentially moving to a bisphosphonate such as alendronate from an anabolic agent such as abaloparatide has also been shown to preserve the fracture reduction benefits seen with the latter. This sequence of an anabolic agent followed by an antiresorptive should especially be considered in the high-risk patient with imminent fracture risk to rapidly reduce the risk of subsequent fractures. The data surrounding optimum timing of initiation of bisphosphonate therapy following denosumab discontinuation is still unclear. Though data suggests that combining a bisphosphonate with teriparatide does not provide substantial BMD gains compared to monotherapy, the concomitant administration of denosumab with teriparatide has been shown to significantly increase areal BMD as well as to increase volumetric BMD and estimated bone strength. This narrative review explores the available evidence regarding the various sequential and combination therapy approaches and the potential role they could play in better managing osteoporosis.

Effect of Teriparatide Versus Zoledronate on Posterior Lumbar Interbody Fusion in Postmenopausal Women with Osteoporosis

OBJECTIVE

We evaluated the efficacy of teriparatide versus zoledronate on spinal fusion in osteoporotic patients after posterior lumbar interbody fusion (PLIF).

METHODS

Postmenopausal women with osteoporosis undergoing PLIF for degenerative spondylolisthesis were randomly assigned to receive either zoledronate or teriparatide. During the 2-year follow-up period, serial radiographs were used to determine fusion status and instrumentation-related sequelae (a composite of adjacent vertebral compressive fracture, instrumentation failure, and fusion failure). The bone mineral density (BMD) and Oswestry disability index (ODI) were also serially measured.

RESULTS

Of the 77 patients, 36 were in the teriparatide group and 41 in the zoledronate group and had completed the 2-year follow-up assessments. Bony union had been achieved more frequently in the teriparatide group than in the zoledronate group at 6 months postoperatively (P < 0.05), although the overall rate of bone union was comparable between the 2 groups. The incidence of instrumentation-related sequelae was also comparable between the 2 groups (teriparatide vs. zoledronate group, 13.9% vs. 22.0%). Regarding antiosteoporosis, the BMD values had significantly improved in both groups at the last follow-up. The teriparatide group had attained more BMD increments at 12 months postoperatively than had the zoledronate group. Furthermore, the ODI had consistently decreased in both groups with a lower ODI in the teriparatide group than in the zoledronate group at 12 months postoperatively.

CONCLUSIONS

Among postmenopausal women with osteoporosis, teriparatide showed superior bone union at 6 months and greater BMD improvement at 12 months after PLIF compared with zoledronate administration, although both resulted in similar overall effects on spinal fusion.

Conditioned medium of amniotic fluid-derived stromal cells exerts a bone anabolic effect by enhancing progenitor population and angiogenesis

A cell-free approach utilizing the paracrine effects of mesenchymal stromal cells is receiving attention in regenerative medicine. In the present study, we evaluated the effects of a conditioned medium of amniotic fluid-derived stromal cells (AFSC-CM) on bone metabolism. In mice, intraperitoneal injections of AFSC-CM increased bone mass and enhanced bone turnover. The precursor populations of myeloid and mesenchymal lineages, as well as endothelial cells in bone marrow, were also augmented by AFSC-CM administration. In an in vitro culture experiment, AFSC-CM increased osteoclast differentiation of bone marrow-derived macrophages, but had no significant effect on the osteogenic differentiation of preosteoblasts. However, AFSC-CM administration dramatically accelerated the migration and tube formation of endothelial cells, and a cytokine array showed that AFSC-CM contained many angiogenic factors. These results indicate that AFSC-CM exerts a bone anabolic effect by changing the bone marrow microenvironment, including angiogenesis and precursor expansion. Therefore, ameliorating marrow angiogenesis is a potential therapeutic strategy for bone regeneration, for which AFSCs can be a good cellular source.

Aminobisphosphonates: Reconsideration 25 years after their approval for the treatment of osteoporosis

Aminobisphosphonates are widely used in the treatment of osteoporosis. They have a high affinity for hydroxyapatite, binding primarily to resorbing surfaces, but also to forming surfaces and to some extent to resting surfaces. They inhibit osteoclasts, thereby decreasing remodelling units. Consequently, they increase bone mass and reduce stress risers. This decreases the risk of fractures. If this decrease is sufficient, they can be temporarily withdrawn (drug holidays), which prevents serious complications (atypical femoral fracture). They probably reduce mortality. Virtually all patients with osteoporosis can benefit from them at some point in the course of their disease (at the beginning of treatment or after the administration of anabolics, selective estrogen receptor modulators or denosumab). If well tolerated orally, alendronate and risedronate are preferable. Otherwise, zoledronate is preferred. Their efficacy vs. cost-safety-convenience ratio makes aminobisphosphonates reference drugs in the field of osteoporosis.

Efficacy of the Combination of Teriparatide and Denosumab in the Treatment of Postmenopausal Osteoporosis: A Meta-Analysis

Aim: Evidence on the efficacy of combination treatment of teriparatide and denosumab for osteoporosis remains controversial. We aim to compare the efficacy between the combination treatment and monotherapy among patients with postmenopausal osteoporosis.

Methods and results: We systematically searched PubMed, EMBASE, the Cochrane Library, and Web of Science up to 26 January 2022, for relevant studies. This meta-analysis reviewed all randomized controlled trials (RCTs) that reported on the combination treatment of teriparatide and denosumab in patients with postmenopausal osteoporosis. The articles were examined individually by two reviewers, and the relevant data was extracted. We combined weighted mean difference (WMD) for bone mineral density (BMD) using random- or fixed- effect models and conducted subgroup analyses. Sensitivity analyses were performed, and possible publication bias was also assessed. Overall, combination treatment enhanced the mean percent change of bone mineral density in lumbar spine than monotherapy (WMD = 2.91, 95%CI: 1.983.83; p = 0.00). And, combination treatment has been beneficial for enhancing the mean percent change of BMD in hip (WMD = 3.19, 95%CI: 2.25∼4.13; p = 0.00). There was no significant difference between combination treatment and monotherapy in terms of the adverse events (RR = 0.81, 95%CI: 0.45∼1.45; p = 0.472).

Conclusion: The meta-analysis indicates that combination treatment led to greater BMD at the lumbar spine and hip in comparison to monotherapy, without an increased incidence of adverse events.

Systematic Review Registration: (https://inplasy.com/), identifier (Inplasy Protocol 2734).

Structural pharmacology of PTH and PTHrP

Parathyroid hormone (PTH) and PTH-related peptide (PTHrP) regulate extracellular phosphate and calcium homeostasis as well as bone remodeling. PTH is a classic endocrine peptide hormone whose synthesis and negative feedback by multiple factors control release from the parathyroid glands. PTHrP is ubiquitously expressed (pre- and postnatally) and acts in an autocrine/paracrine manner. This review considers the structural pharmacology and actions of PTH and PTHrP, biological consequences of inherited mutations, engineered analogs that illuminate similarities and differences in physiologic actions, and targeted therapeutic opportunities.

Unmasking Fracture Risk in Type 2 Diabetes: The Association of Longitudinal Glycemic Hemoglobin Level and Medications

CONTEXT

Fracture risk is underestimated in people with type 2 diabetes (T2D).

OBJECTIVE

To investigate the longitudinal relationship of glycated hemoglobin (HbA1c) and common medications on fracture risk in people with T2D.

METHODS

This retrospective population-based cohort study was conducted using de-identified claims and electronic health record data obtained from the OptumLabs Data Warehouse for the period January 1, 2007, to September 30, 2015. For each individual, the study was conducted within a 2-year HbA1c observation period and a 2-year fracture follow-up period. A cohort of 157 439 individuals with T2D [age ≥ 55 years with mean HbA1c value ≥ 6%] were selected from 4 018 250 US Medicare Advantage/Commercial enrollees with a T2D diagnosis. All fractures and fragility fractures were measured.

RESULTS

With covariates adjusted, poor glycemic control in T2D individuals was associated with an 29% increase of all fracture risk, compared with T2D individuals who had adequate glycemic control (HR: 1.29; 95% CI, 1.22-1.36). Treatment with metformin (HR: 0.88; 95% CI, 0.85-0.92) and DPP4 inhibitors (HR: 0.93; 95% CI, 0.88-0.98) was associated with a reduced all fracture risk, while insulin (HR: 1.26; 95% CI, 1.21-1.32), thiazolidinediones (HR: 1.23; 95% CI, 1.18-1.29), and meglitinides (HR: 1.12; 95% CI, 1.00-1.26) were associated with an increased all fracture risk (All P value < 0.05). Bisphosphonates were associated similarly with increased fracture risk in the T2D and nondiabetic groups.

CONCLUSION

Longitudinal 2-year HbA1c is independently associated with elevated all fracture risk in T2D individuals during a 2-year follow-up period. Metformin and DPP4 inhibitors can be used for management of T2D fracture risk.

Novel insights into the coupling of osteoclasts and resorption to bone formation

Bone remodeling consists of resorption by osteoclasts (OCs) and formation by osteoblasts (OBs). Precise coordination of these activities is required for the resorbed bone to be replaced with an equal amount of new bone in order to maintain skeletal mass throughout the lifespan. This coordination of remodeling processes is referred to as the "coupling" of resorption to bone formation. In this review, we discuss the essential role for OCs in coupling resorption to bone formation, mechanisms for this coupling, and how coupling becomes less efficient or disrupted in conditions of bone loss. Lastly, we provide perspectives on targeting coupling to treat human bone disease.

Comparison of Quantitative Computed Tomography and Dual X-Ray Absorptiometry: Osteoporosis Detection Rates in Diabetic Patients

Introduction Diabetes mellitus (DM) adversely affects the skeletal system and is associated with an increased risk of osteoporosis and fragility fractures. This study aimed to assess the diagnostic accuracy of quantitative computed tomography (QCT) in osteoporosis detection in patients with DM. Methods A cross-sectional diagnostic accuracy study was conducted at the diabetic clinic of a tertiary care teaching hospital in North India. A total of 30 individuals with DM were subjected to spinal QCT and lumbar spine and hip dual x-ray absorptiometry (DXA). Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and positive and negative likelihood ratios of QCT were measured against DXA and the diagnostic discordance between QCT and DXA was investigated. Results QCT, compared to the gold standard DXA, has a sensitivity/specificity of 92.8% (95% CI 92.4%-93.2%)/81.2% (95% CI 80.6%-81.8%). The PPV/NPV of QCT was 81.2% (95% CI 80.6%-81.8%)/92.8% (95% CI 92.4%-93.2%). The positive likelihood ratio/negative likelihood ratio was 4.95 (95% CI 4.79-5.11)/0.087 (95% CI 0.082-0.093). Area under the curve was 0.871 (95% CI 0.731-1.00). Minor diagnostic discordance was present in 36.6% of patients with diabetes. Conclusion  The current study assessed the diagnostic accuracy of QCT in osteoporosis detection in people with diabetes. DXA is the gold standard diagnostic tool; however, its availability is limited. The current study showed that QCT is an excellent diagnostic tool. Based on these results, this study recommends that QCT may serve as a problem-solving investigation tool where DXA is unavailable, or it may be the primary investigation tool for bone mineral density measurement and osteoporosis detection if a dedicated DXA scanner is inaccessible. This study also recommends further investigating the feasibility of opportunistic osteoporosis screening in routine abdominal and chest CT. Finally, considering the silent nature of osteoporosis and the high prevalence of osteoporosis in individuals with diabetes, a proactive approach is required in the screening of osteoporosis.

Romosozumab Enhances Vertebral Bone Structure in Women With Low Bone Density

Romosozumab monoclonal antibody treatment works by binding sclerostin and causing rapid stimulation of bone formation while decreasing bone resorption. The location and local magnitude of vertebral bone accrual by romosozumab and how it compares to teriparatide remains to be investigated. Here we analyzed the data from a study collecting lumbar computed tomography (CT) spine scans at enrollment and 12 months post-treatment with romosozumab (210 mg sc monthly, n = 17), open-label daily teriparatide (20 μg sc, n = 19), or placebo (sc monthly, n = 20). For each of the 56 women, cortical thickness (Ct.Th), endocortical thickness (Ec.Th), cortical bone mineral density (Ct.bone mineral density (BMD)), cancellous BMD (Cn.BMD), and cortical mass surface density (CMSD) were measured across the first lumbar vertebral surface. In addition, color maps of the changes in the lumbar vertebrae structure were statistically analyzed and then visualized on the bone surface. At 12 months, romosozumab improved all parameters significantly over placebo and resulted in a mean vertebral Ct.Th increase of 10.3% versus 4.3% for teriparatide, an Ec.Th increase of 137.6% versus 47.5% for teriparatide, a Ct.BMD increase of 2.1% versus a -0.1% decrease for teriparatide, and a CMSD increase of 12.4% versus 3.8% for teriparatide. For all these measurements, the differences between romosozumab and teriparatide were statistically significant (p < 0.05). There was no significant difference between the romosozumab-associated Cn.BMD gains of 22.2% versus 18.1% for teriparatide, but both were significantly greater compared with the change in the placebo group (-4.6%, p < 0.05). Cortical maps showed the topographical locations of the increase in bone in fracture-prone areas of the vertebral shell, walls, and endplates. This study confirms widespread vertebral bone accrual with romosozumab or teriparatide treatment and provides new insights into how the rapid prevention of vertebral fractures is achieved in women with osteoporosis using these anabolic agents. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Applications of Calcium-Based Nanomaterials in Osteoporosis Treatment

With rapidly aging populations worldwide, osteoporosis has become a serious global public health problem. Caused by disordered systemic bone remodeling, osteoporosis manifests as progressive loss of bone mass and microarchitectural deterioration of bone tissue, increasing the risk of fractures and eventually leading to osteoporotic fragility fractures. As fracture risk increases, antiosteoporosis treatments transition from nonpharmacological management to pharmacological intervention, and finally to the treatment of fragility fractures. Calcium-based nanomaterials (CBNMs) have unique advantages in osteoporosis treatment because of several characteristics including similarity to natural bone, excellent biocompatibility, easy preparation and functionalization, low pH-responsive disaggregation, and inherent pro-osteogenic properties. By combining additional ingredients, CBNMs can play multiple roles to construct antiosteoporotic biomaterials with different forms. This review covers recent advances in CBNMs for osteoporosis treatment. For ease of understanding, CBNMs for antiosteoporosis treatment can be classified as locally applied CBNMs, such as implant coatings and filling materials for osteoporotic bone regeneration, and systemically administered CBNMs for antiosteoporosis treatment. Locally applied CBNMs for osteoporotic bone regeneration develop faster than the systemically administered CBNMs, an important consideration given the serious outcomes of fragility fractures. Nevertheless, many innovations in construction strategies and preparation methods have been applied to build systemically administered CBNMs. Furthermore, with increasing interest in delaying osteoporosis progression and avoiding fragility fracture occurrence, research into systemic administration of CBNMs for antiosteoporosis treatment will have more development prospects. Deep understanding of the CBNM preparation process and optimizing CBNM properties will allow for increased application of CBNMs in osteoporosis treatments in the future.

Additive Effect of Parathyroid Hormone and Zoledronate Acid on Prevention Particle Wears-Induced Implant Loosening by Promoting Periprosthetic Bone Architecture and Strength in an Ovariectomized Rat Model

Implant-generated particle wears are considered as the major cause for the induction of implant loosening, which is more susceptible to patients with osteoporosis. Monotherapy with parathyroid hormone (PTH) or zoledronate acid (ZOL) has been proven efficient for preventing early-stage periprosthetic osteolysis, while the combination therapy with PTH and ZOL has exerted beneficial effects on the treatment of posterior lumbar vertebral fusion and disuse osteopenia. However, PTH and ZOL still have not been licensed for the treatment of implant loosening to date clinically. In this study, we have explored the effect of single or combined administration with PTH and ZOL on implant loosening in a rat model of osteoporosis. After 12 weeks of ovariectomized surgery, a femoral particle-induced periprosthetic osteolysis model was established. Vehicle, PTH (5 days per week), ZOL (100 mg/kg per week), or combination therapy was utilized for another 6 weeks before sacrifice, followed by micro-CT, histology, mechanical testing, and bone turnover examination. PTH monotherapy or combined PTH with ZOL exerted a protective effect on maintaining implant stability by elevating periprosthetic bone mass and inhibiting pseudomembrane formation. Moreover, an additive effect was observed when combining PTH with ZOL, resulting in better fixation strength, higher periprosthetic bone mass, and less pseudomembrane than PTH monotherapy. Taken together, our results suggested that a combination therapy of PTH and ZOL might be a promising approach for the intervention of early-stage implant loosening in patients with osteoporosis.

Regulation of TNF-Induced Osteoclast Differentiation

Increased osteoclast (OC) differentiation and activity is the critical event that results in bone loss and joint destruction in common pathological bone conditions, such as osteoporosis and rheumatoid arthritis (RA). RANKL and its decoy receptor, osteoprotegerin (OPG), control OC differentiation and activity. However, there is a specific concern of a rebound effect of denosumab discontinuation in treating osteoporosis. TNFα can induce OC differentiation that is independent of the RANKL/RANK system. In this review, we discuss the factors that negatively and positively regulate TNFα induction of OC formation, and the mechanisms involved to inform the design of new anti-resorptive agents for the treatment of bone conditions with enhanced OC formation. Similar to, and being independent of, RANKL, TNFα recruits TNF receptor-associated factors (TRAFs) to sequentially activate transcriptional factors NF-κB p50 and p52, followed by c-Fos, and then NFATc1 to induce OC differentiation. However, induction of OC formation by TNFα alone is very limited, since it also induces many inhibitory proteins, such as TRAF3, p100, IRF8, and RBP-j. TNFα induction of OC differentiation is, however, versatile, and Interleukin-1 or TGFβ1 can enhance TNFα-induced OC formation through a mechanism which is independent of RANKL, TRAF6, and/or NF-κB. However, TNFα polarized macrophages also produce anabolic factors, including insulin such as 6 peptide and Jagged1, to slow down bone loss in the pathological conditions. Thus, the development of novel approaches targeting TNFα signaling should focus on its downstream molecules that do not affect its anabolic effect.

Osteoporosis therapies and their mechanisms of action (Review)

Osteoporosis is a common disease that affects millions of patients worldwide and is most common in menopausal women. The main characteristics of osteoporosis are low bone density and increased risk of fractures due to deterioration of the bone architecture. Osteoporosis is a chronic disease that is difficult to treat; thus, investigations into novel effective therapeutic methods are required. A number of studies have focused on determining the most effective treatment options for this disease. There are several treatment options for osteoporosis that differ depending on the characteristics of the disease, and these include both well-established and newly developed drugs. The present review focuses on the various drugs available for osteoporosis, the associated mechanisms of action and the methods of administration.

Advances in bone turnover markers

Bone fragility fractures remain an important worldwide health and economic problem due to increased morbidity and mortality. The current methods for predicting fractures are largely based on the measurement of bone mineral density and the utilization of mathematical risk calculators based on clinical risk factors for bone fragility. Despite these approaches, many bone fractures remain undiagnosed. Therefore, current research is focused on the identification of new factors such as bone turnover markers (BTM) for risk calculation. BTM are a group of proteins and peptides released during bone remodeling that can be found in serum or urine. They derive from bone resorptive and formative processes mediated by osteoclasts and osteoblasts, respectively. Potential use of BTM in monitoring these phenomenon and therefore bone fracture risk is limited by physiologic and pathophysiologic factors that influence BTM. These limitations in predicting fractures explain why their inclusion in clinical guidelines remains limited despite the large number of studies examining BTM.

The Effects of Osteoporotic and Non-osteoporotic Medications on Fracture Risk and Bone Mineral Density

Osteoporosis is a highly prevalent bone disease affecting more than 37.5 million individuals in the European Union (EU) and the  United States of America (USA). It is characterized by low bone mineral density (BMD), impaired bone quality, and loss of structural and biomechanical properties, resulting in reduced bone strength. An increase in morbidity and mortality is seen in patients with osteoporosis, caused by the approximately 3.5 million new osteoporotic fractures occurring every year in the EU. Currently, different medications are available for the treatment of osteoporosis, including anti-resorptive and osteoanabolic medications. Bisphosphonates, which belong to the anti-resorptive medications, are the standard treatment for osteoporosis based on their positive effects on bone, long-term experience, and low costs. However, not only medications used for the treatment of osteoporosis can affect bone: several other medications are suggested to have an effect on bone as well, especially on fracture risk and BMD. Knowledge about the positive and negative effects of different medications on both fracture risk and BMD is important, as it can contribute to an improvement in osteoporosis prevention and treatment in general, and, even more importantly, to the individual's health. In this review, we therefore discuss the effects of both osteoporotic and non-osteoporotic medications on fracture risk and BMD. In addition, we discuss the underlying mechanisms of action.

Myeloid Lineage Ablation of Phlpp1 Regulates M-CSF Signaling and Tempers Bone Resorption in Female Mice

Prior work demonstrated that Phlpp1 deficiency alters trabecular bone mass and enhances M-CSF responsiveness, but the cell types and requirement of Phlpp1 for this effect were unclear. To understand the function of Phlpp1 within myeloid lineage cells, we crossed Phlpp1 floxed mice with mice harboring LysM-Cre. Micro-computed tomography of the distal femur of 12-week-old mice revealed a 30% increase in bone volume per total volume of Phlpp1 female conditional knockouts, but we did not observe significant changes within male Phlpp1 cKOLysM mice. Bone histomorphmetry of the proximal tibia further revealed that Phlpp1 cKOLysM females exhibited elevated osteoclast numbers, but conversely had reduced levels of serum markers of bone resorption as compared to littermate controls. Osteoblast number and serum markers of bone formation were unchanged. In vitro assays confirmed that Phlpp1 ablation enhanced osteoclast number and area, but limited bone resorption. Additionally, reconstitution with exogenous Phlpp1 suppressed osteoclast numbers. Dose response assays demonstrated that Phlpp1-/- cells are more responsive to M-CSF, but reconstitution with Phlpp1 abrogated this effect. Furthermore, small molecule-mediated Phlpp inhibition enhanced osteoclast numbers and size. Enhanced phosphorylation of Phlpp substrates-including Akt, ERK1/2, and PKCζ-accompanied these observations. In contrast, actin cytoskeleton disruption occurred within Phlpp inhibitor treated osteoclasts. Moreover, Phlpp inhibition reduced resorption of cells cultured on bovine bone slices in vitro. Our results demonstrate that Phlpp1 deficiency within myeloid lineage cells enhances bone mass by limiting bone resorption while leaving osteoclast numbers intact; moreover, we show that Phlpp1 represses osteoclastogenesis and controls responses to M-CSF.

Salicylic acid-based nanomedicine with self-immunomodulatory activity facilitates microRNA therapy for metabolic skeletal disorders

Metabolic skeletal disorders remain a major clinical challenge. The complexity of this disease requires a strategy to address the net effects of both inflammation and impaired bone formation. microRNA-based gene therapy provides several therapeutic advantages to tackle these issues. Herein, we describe a microRNA-21 (miR-21) delivery system with an additional therapeutic effect from that of the delivery carrier itself. Poly (salicylic acid) (PSA) is, for the first time, synthesized via polycondensation of salicylic acid (SA), a bioactive ingredient widely used for anti-inflammation in medicine. PSA can self-assemble into nanoparticles (PSA-NPs) and can effectively deliver genes both in vitro and in vivo. The carrier was then attached to repetitive sequences of aspartate, serine, serine (DSS)₆ for delivering miRNAs specifically to bone-formation surfaces. In vitro studies showed that miR-21@PSA-NP could effectively realize the intracellular delivery of miR-21 with low toxicity, while in vivo results indicated that the miR-21@PSA-NP-DSS₆ prolonged blood circulation time, enhanced bone accumulation, and significantly improved the efficacy of miR-21-based bone anabolic therapy in osteoporotic mice. The constructed delivery system (miR-21@PSA-NP-DSS₆) inherited the advantages of both SA and miR-21, which could ameliorate bone-inflamed niche and rescued the impaired bone formation ability. The synergy of anti-inflammatory and pro-osteogenic effects significantly improved trabecular bone microstructure in osteoporotic mice. STATEMENT OF SIGNIFICANCE: The complexity of metabolic skeletal disorders requires a strategy to address the net effects of both inflammation and impaired bone formation. microRNA-based gene therapy provides several therapeutic advantages to tackle these issues. We develop a novel microRNA-21 delivery system with additional therapeutic effect from that of the gene carrier itself. Poly (salicylic acid) (PSA) nanoparticles, for the first time, synthesized via polycondensation of salicylic acid and can effectively deliver genes both in vitro and in vivo. The constructed delivery system (miR-21@PSA-NP-DSS₆) inherited the advantages of both SA (commonly used anti-inflammation drug in medicine) and miR-21 (a pro-osteogenic molecule), which could ameliorate bone-inflamed niche, rescued impaired bone formation ability and significantly improved trabecular bone microstructure in osteoporotic mice.

Osteoporosis Remission and New Bone Formation with Mesoporous Silica Nanoparticles

Nanotechnology changed the concept of treatment for a variety of diseases, producing a huge impact regarding drug and gene delivery. Among the different targeted diseases, osteoporosis has devastating clinical and economic consequences. Since current osteoporosis treatments present several side effects, new treatment approaches are needed. Recently, the application of small interfering RNA (siRNA) has become a promising alternative. Wnt/β-catenin signaling pathway controls bone development and formation. This pathway is negatively regulated by sclerostin, which knock-down through siRNA application would potentially promote bone formation. However, the major bottleneck for siRNA-based treatments is the necessity of a delivery vector, bringing nanotechnology as a potential solution. Among the available nanocarriers, mesoporous silica nanoparticles (MSNs) have attracted great attention for intracellular delivery of siRNAs. The mesoporous structure of MSNs permits the delivery of siRNAs together with another biomolecule, achieving a combination therapy. Here, the effectiveness of a new potential osteoporosis treatment based on MSNs is evaluated. The proposed system is effective in delivering SOST siRNA and osteostatin through systemic injection to bone tissue. The nanoparticle administration produced an increase expression of osteogenic related genes improving the bone microarchitecture. The treated osteoporotic mice recovered values of a healthy situation approaching to osteoporosis remission.

Recent Progresses in the Treatment of Osteoporosis

Osteoporosis (OP) is a chronic bone disease characterized by aberrant microstructure and macrostructure of bone, leading to reduced bone mass and increased risk of fragile fractures. Anti-resorptive drugs, especially, bisphosphonates, are currently the treatment of choice in most developing countries. However, they do have limitations and adverse effects, which, to some extent, helped the development of anabolic drugs such as teriparatide and romosozumab. In patients with high or very high risk for fracture, sequential or combined therapies may be considered with the initial drugs being anabolic agents. Great endeavors have been made to find next generation drugs with maximal efficacy and minimal toxicity, and improved understanding of the role of different signaling pathways and their crosstalk in the pathogenesis of OP may help achieve this goal. Our review focused on recent progress with regards to the drug development by modification of Wnt pathway, while other pathways/molecules were also discussed briefly. In addition, new observations made in recent years in bone biology were summarized and discussed for the treatment of OP.

The V-ATPase a3 Subunit: Structure, Function and Therapeutic Potential of an Essential Biomolecule in Osteoclastic Bone Resorption

This review focuses on one of the 16 proteins composing the V-ATPase complex responsible for resorbing bone: the a3 subunit. The rationale for focusing on this biomolecule is that mutations in this one protein account for over 50% of osteopetrosis cases, highlighting its critical role in bone physiology. Despite its essential role in bone remodeling and its involvement in bone diseases, little is known about the way in which this subunit is targeted and regulated within osteoclasts. To this end, this review is broadened to include the three other mammalian paralogues (a1, a2 and a4) and the two yeast orthologs (Vph1p and Stv1p). By examining the literature on all of the paralogues/orthologs of the V-ATPase a subunit, we hope to provide insight into the molecular mechanisms and future research directions specific to a3. This review starts with an overview on bone, highlighting the role of V-ATPases in osteoclastic bone resorption. We then cover V-ATPases in other location/functions, highlighting the roles which the four mammalian a subunit paralogues might play in differential targeting and/or regulation. We review the ways in which the energy of ATP hydrolysis is converted into proton translocation, and go in depth into the diverse role of the a subunit, not only in proton translocation but also in lipid binding, cell signaling and human diseases. Finally, the therapeutic implication of targeting a3 specifically for bone diseases and cancer is discussed, with concluding remarks on future directions.

Paracrine Kynurenic Pathway Activation in the Bone of Young Uremic Rats Can Antagonize Anabolic Effects of PTH on Bone Turnover and Strength through the Disruption of PTH-Dependent Molecular Signaling

Secondary hyperparathyroidism and abnormalities in tryptophan (TRP) metabolism are commonly observed in chronic kidney disease (CKD). The present study aimed to establish potential interactions between endogenous parathyroid hormone (PTH) and activation of the bone kynurenine (KYN) pathway in relation to bone turnover and strength in young rats after one month (CKD-1) and three months (CKD-3) of experimental CKD. TRP, KYN, KYN/TRP ratio and bone turnover markers (BTMs) were measured in trabecular and cortical bone tissue. Expression of aryl hydrocarbon receptor (AhR) and the genes involved in osteogenesis was determined in femoral bone. Biomechanical testing of femoral diaphysis and femoral neck was also performed. Activation of the KYN pathway in trabecular bone during CKD development intensified the expression of genes related to osteogenesis, which led to a decrease in cyclic adenosine monophosphate (cAMP) and BTMs levels, resulting in a stiffer and mechanically weaker femoral neck. In contrast, reduction of the KYN pathway in cortical bone allowed to unblock the PTH-dependent anabolic activating transcription factor 4/parathyroid hormone 1 receptor (PTH1R/ATF4) axis, led to cAMP accumulation, better bone turnover and strength in the course of CKD development. In summary, the paracrine KYN pathway in bone can interfere with the anabolic effects of PTH on bone through disrupting PTH-dependent molecular signaling.

A pilot study comparing daily teriparatide with monthly cycles of teriparatide and raloxifene

This 6-month pilot study in osteoporotic postmenopausal women evaluated cyclic TPD/RLX compared to daily subcutaneous TPD with the concept of optimizing bone formation. Compared to daily subcutaneous TPD, cyclic therapy showed comparable increase in spine BMD and favorable effects on total proximal femur BMD and cortical thickness.

PURPOSE

There is no cure for osteoporosis; better medications or different approaches with current agents are needed. We hypothesized that monthly cycles of teriparatide (TPD) followed by raloxifene (RLX) might promote ongoing bone formation. Additionally, as TPD might initially adversely affect hip BMD, such effects may be mitigated by a cyclic approach. Therefore, this 6-month pilot study evaluated the effect of cyclic TPD/RLX compared to daily subcutaneous TPD on bone markers, BMD, trabecular bone score (TBS), and hip parameters assessed by 3D modeling.

METHODS

Postmenopausal osteoporotic women (n=26) were randomized to open-label TPD 20 daily or alternating monthly cycles of TPD followed by monthly RLX 60 mg daily. BMD was measured at the lumbar spine (LS), femur, and radius by DXA. To further assess LS BMD, QCT and opportunistic CT (L1 Hounsfield units [HU]) were performed. LS TBS and hip cortical and trabecular parameters were assessed using DXA. Baseline group comparisons were performed by unpaired T-test with change over time evaluated by repeated measures ANOVA.

RESULTS

Participant mean age, BMI, and lowest T-score were 67.0 years, 26.0 kg/m², and -2.7; no between-group differences in serum chemistries, 25(OH)D, or BMD were observed. LS-BMD increased (p<0.001) with TPD or TPD/RLX as measured by DXA (4.8%/5.2%), QCT (13%/9.4%), or HU (15.6%/10.2%) with no between-group difference. TPD/RLX produced beneficial between-group differences in total proximal femur BMD (1.5%, p<0.05) and cortical thickness (1.6%, p<0.05).

CONCLUSION

Compared with daily TPD, cyclic TPD/RLX comparably increased spine BMD and might have favorable effects on proximal femur BMD and cortical thickness.

SLPI is a critical mediator that controls PTH-induced bone formation

Osteoclastic bone resorption and osteoblastic bone formation/replenishment are closely coupled in bone metabolism. Anabolic parathyroid hormone (PTH), which is commonly used for treating osteoporosis, shifts the balance from osteoclastic to osteoblastic, although it is unclear how these cells are coordinately regulated by PTH. Here, we identify a serine protease inhibitor, secretory leukocyte protease inhibitor (SLPI), as a critical mediator that is involved in the PTH-mediated shift to the osteoblastic phase. Slpi is highly upregulated in osteoblasts by PTH, while genetic ablation of Slpi severely impairs PTH-induced bone formation. Slpi induction in osteoblasts enhances its differentiation, and increases osteoblast-osteoclast contact, thereby suppressing osteoclastic function. Intravital bone imaging reveals that the PTH-mediated association between osteoblasts and osteoclasts is disrupted in the absence of SLPI. Collectively, these results demonstrate that SLPI regulates the communication between osteoblasts and osteoclasts to promote PTH-induced bone anabolism.

Review of Current Real-World Experience with Teriparatide as Treatment of Osteoporosis in Different Patient Groups

Teriparatide has proven effective in reducing both vertebral and non-vertebral fractures in clinical trials of post-menopausal and glucocorticoid-induced osteoporosis. Widespread adoption of Teriparatide over the last two decades means that there is now substantial experience of its use in routine clinical practice, which is summarized in this paper. Extensive real-world experience of Teriparatide in post-menopausal osteoporosis confirms the fracture and bone density benefits seen in clinical trials, with similar outcomes identified also in male and glucocorticoid-induced osteoporosis. Conversely, very limited experience has been reported in pre-menopausal osteoporosis or in the use of Teriparatide in combination with other therapies. Surveillance studies have identified no safety signals relating to the possible association of Teriparatide with osteosarcoma. We also review the evidence for predicting response to Teriparatide in order to inform the debate on where best to use Teriparatide in an increasingly crowded therapeutic landscape.

Bisphosphonates impair the onset of bone formation at remodeling sites

Bisphosphonates are widely used anti-osteoporotic drugs targeting osteoclasts. They strongly inhibit bone resorption, but also strongly reduce bone formation. This reduced formation is commonly ascribed to the mechanism maintaining the resorption/formation balance during remodeling. The present study provides evidence for an additional mechanism where bisphosphonates actually impair the onset of bone formation after resorption. The evidence is based on morphometric parameters recently developed to assess the activities reversing resorption to formation. Herein, we compare these parameters in cancellous bone of alendronate- and placebo-treated postmenopausal osteoporotic patients. Alendronate increases the prevalence of eroded surfaces characterized by reversal cells/osteoprogenitors at low cell density and remote from active bone surfaces. This indicates deficient cell expansion on eroded surfaces - an event that is indispensable to start formation. Furthermore, alendronate decreases the coverage of these eroded surfaces by remodeling compartment canopies, a putative source of reversal cells/osteoprogenitors. Finally, alendronate strongly decreases the activation frequency of bone formation, and decreases more the formative compared to the eroded surfaces. All these parameters correlate with each other. These observations lead to a model where bisphosphonates hamper the osteoprogenitor recruitment required to initiate bone formation. This effect results in a larger eroded surface, thereby explaining the well-known paradox that bisphosphonates strongly inhibit bone resorption without strongly decreasing eroded surfaces. The possible mechanism for hampered osteoprogenitor recruitment is discussed: bisphosphonates may decrease the release of osteogenic factors by the osteoclasts, and/or bisphosphonates released by osteoclasts may act directly on neighboring osteoprogenitor cells as reported in preclinical studies.

Severe Idiopathic Osteoporosis in a Premenopausal Woman: A Case for Dual Therapy

Currently available agents improve bone mineral density (BMD) values on their own in monotherapy but may not completely restore microarchitecture and the patient may continue to sustain fragility fractures. Current monotherapies can only address either increased bone resorption or decreased bone formation. In this setting, combination therapy with antiresorptive and anabolic agents appears to be a promising option. A 49-year-old premenopausal woman presented with severe low backache associated with significant height loss. Evaluation elsewhere revealed severe osteoporosis, which prompted treatment with three doses of parenteral zoledronate 4 mg annually, followed by oral alendronate 70 mg once weekly for 7 years. However, her symptoms persisted despite treatment, and investigations done at our center confirmed severe osteoporosis, with multiple vertebral compression fractures. She was initiated on teriparatide therapy but despite 1 year of treatment, there was persistent height loss. In addition, there was a marked elevation of bone resorption, which prompted us to add denosumab which was administered subcutaneously every 6 months. On follow-up, there was marked relief from pain, no further decrease in height, and progressive improvement in BMD, and bone turnover markers were noted. A dual therapy with anabolic agent teriparatide and antiresorptive agent denosumab for osteoporosis may be a viable option in individuals with severe osteoporosis who do not respond well to a single agent.

Association of Hydrogen Sulfide with Femoral Bone Mineral Density in Osteoporosis Patients: A Preliminary Study

Background

Accumulated evidence has suggested that hydrogen sulfide (H₂S) has a role in bone formation and bone tissue regeneration. However, it is unknown whether the H₂S content is associated with bone mineral density (BMD) in patients with osteopenia/osteoporosis.

Material/Methods

In the present study, we aimed to explore the changes of serum H₂S in osteopenia and osteoporosis patients. We analyzed femur expression of cystathionine β synthase (CBS), cystathionine γ lyase (CSE), and 3-mercaptopyruvate sulfurtransferase (3-MST), which are key enzymes for generating H₂S.

Results

Sixteen (16%) patients had osteopenia, 9 (9%) had osteoporosis, and 75 (75%) had normal BMD. In comparison with patients with normal BMD (controls), the serum levels of H₂S were unexpectedly increased in patients with osteopenia and osteoporosis. This increase was much higher in patients with osteoporosis than in those with osteopenia. Serum H₂S levels were negatively correlated with femoral BMD, but not lumbar BMD. Interestingly, the expression of CBS and CSE were downregulated in femur tissues in patients with osteoporosis, whereas the expression of 3-MST remained unchanged. Serum phosphorus levels, alkaline phosphatase, hemoglobin, and triglycerides were found to be closely associated with CBS and CSE scores in femur tissues.

Conclusions

Serum H₂S levels and femur CBS and CSE expression may be involved in osteoporosis pathogenesis.