Long-term safety concerns of antiresorptive therapy

Microdroplets Encapsulated with NFATc1-siRNA and Exosomes-Derived from MSCs Onto 3D Porous PLA Scaffold for Regulating Osteoclastogenesis and Promoting Osteogenesis

Introduction

Osteoporotic-related fractures remains a significant public health concern, thus imposing substantial burdens on our society. Excessive activation of osteoclastic activity is one of the main contributing factors for osteoporosis-related fractures. While polylactic acid (PLA) is frequently employed as a biodegradable scaffold in tissue engineering, it lacks sufficient biological activity. Microdroplets (MDs) have been explored as an ultrasound-responsive drug delivery method, and mesenchymal stem cell (MSC)-derived exosomes have shown therapeutic effects in diverse preclinical investigations. Thus, this study aimed to develop a novel bioactive hybrid PLA scaffold by integrating MDs-NFATc1-silencing siRNA to target osteoclast formation and MSCs-exosomes (MSC-Exo) to influence osteogenic differentiation (MDs-NFATc1/PLA-Exo).

Methods

Human bone marrow-derived mesenchymal stromal cells (hBMSCs) were used for exosome isolation. Transmission electron microscopy (TEM) and confocal laser scanning microscopy were used for exosome and MDs morphological characterization, respectively. The MDs-NFATc1/PLA-Exo scaffold was fabricated through poly(dopamine) and fibrin gel coating. Biocompatibility was assessed using RAW 264.7 macrophages and hBMSCs. Osteoclast formations were examined via TRAP staining. Osteogenic differentiation of hBMSCs and cytokine expression modulation were also investigated.

Results

MSC-Exo exhibited a cup-shaped structure and effective internalization into cells, while MDs displayed a spherical morphology with a well-defined core-shell structure. Following ultrasound stimulation, the internalization study demonstrated efficient delivery of bioactive MDs into recipient cells. Biocompatibility studies indicated no cytotoxicity of MDs-NFATc1/PLA-Exo scaffolds in RAW 264.7 macrophages and hBMSCs. Both MDs-NFATc1/PLA and MDs-NFATc1/PLA-Exo treatments significantly reduced osteoclast differentiation and formation. In addition, our results further indicated MDs-NFATc1/PLA-Exo scaffold significantly enhanced osteogenic differentiation of hBMSCs and modulated cytokine expression.

Discussion

These findings suggest that the bioactive MDs-NFATc1/PLA-Exo scaffold holds promise as an innovative structure for bone tissue regeneration. By specifically targeting osteoclast formation and promoting osteogenic differentiation, this hybrid scaffold may address key challenges in osteoporosis-related fractures.

2,4'-Dihydroxybenzophenone Exerts Bone Formation and Antiosteoporotic Activity by Stimulating the β-Catenin Signaling Pathway

2,4'-Dihydroxybenzophenone (DHP) is an organic compound derived from Garcinia xanthochymus, but there have been no reports on its biochemical functions and bioavailability. In this study, we evaluated whether DHP affects osteoblast differentiation and activation in MC3T3-E1 preosteoblast cells, as well as antiosteoporotic activity in zebrafish larvae. Nontoxic concentrations of DHP-treated MC3T3-E1 preosteoblast cells increased alkaline phosphatase (ALP) activation and mineralization in a concentration-dependent manner, accompanied by higher expression of osteoblast-specific markers, including Runt-related transcription factor 2 (RUNX2), osterix, and ALP. Consistent with the data in MC3T3-E1 preosteoblast cells, DHP upregulated osteoblast-specific marker genes in zebrafish larvae and simultaneously enhanced vertebral formation. We also revealed that DHP increased the phosphorylation of glycogen synthase kinase-3β (GSK-3β) at Ser9 and the total expression of β-catenin in the cytosol and markedly increased the localization of β-catenin into the nucleus. Furthermore, DHP restored the prednisolone (PDS)-induced marked decrease in ALP activity and mineralization, as well as osteoblast-specific marker expression. In PDS-treated zebrafish, DHP also alleviated PDS-induced osteoporosis by restoring vertebral formation and osteoblast-related gene expression. Taken together, these results suggest that DHP is a potential osteoanabolic candidate for treating osteoporosis by stimulating osteoblast differentiation.

Role of Actinomyces spp. and related organisms in the development of medication-related osteonecrosis of the jaw (MRONJ): Clinical evidence based on a case series

Medication-related osteonecrosis of the jaw (MRONJ) is an increasingly common consequence of antiresorptive treatment, which often leads to the development of necrotic exposed bone surfaces with inflammatory processes affecting the jawbone. Although the development of MRONJ is often associated with the inflammatory response or infections caused by the colonizing members of the oral microbiota, the exact pathogenesis of MRONJ is still not fully understood. In the present paper, we aimed to provide additional, microbiological culture-supported evidence, supporting the "infection hypothesis" that Actinomyces spp. and related organisms may play an important pathogenic role in the development of MRONJ and the resulting bone necrosis. In our case series, all patients presented with similar underlying conditions and anamnestic data, and have received antiresorptive medications (bisphosphonates or a RANK ligand (RANKL) inhibitor) to prevent the occurrence or progression of bone metastases, secondary to prostate cancer. Nevertheless, a few years into antiresorptive drug therapy, varying stages of MRONJ was identified in the mentioned patients. In all three cases, quantitative microbiological culture of the necrotic bone samples yielded a complex microbiota, dominated by Actinomyces and Schaalia spp. with high colony counts. Additionally, our followed-up case series document the treatment of these patients with a combination of surgical intervention and long-term antibiotic therapy, where favourable clinical responses were seen is all cases. If the "infection hypothesis" is valid, it may have significant consequences in the preventative and therapeutic strategies associated with this disease.

Low-Dose Staphylococcal Enterotoxin C2 Mutant Maintains Bone Homeostasis via Regulating Crosstalk between Bone Formation and Host T-Cell Effector Immunity

Studies in recent years have highlighted an elaborate crosstalk between T cells and bone cells, suggesting that T cells may be alternative therapeutic targets for the maintenance of bone homeostasis. Here, it is reported that systemic administration of low-dose staphylococcal enterotoxin C2 (SEC2) 2M-118, a form of mutant superantigen, dramatically alleviates ovariectomy (OVX)-induced bone loss via modulating T cells. Specially, SEC2 2M-118 treatment increases trabecular bone mass significantly via promoting bone formation in OVX mice. These beneficial effects are largely diminished in T-cell-deficient nude mice and can be rescued by T-cell reconstruction. Neutralizing assays determine interferon gamma (IFN-γ) as the key factor that mediates the beneficial effects of SEC2 2M-118 on bone. Mechanistic studies demonstrate that IFN-γ stimulates Janus kinase/signal transducer and activator of transcription (JAK-STAT) signaling, leading to enhanced production of nitric oxide, which further activates p38 mitogen-activated protein kinase (MAPK) and Runt-related transcription factor 2 (Runx2) signaling and promotes osteogenic differentiation. IFN-γ also directly inhibits osteoclast differentiation, but this effect is counteracted by proabsorptive factors tumor necrosis factor alpha (TNF-α) and interleukin 1 beta (IL-1β) secreted from IFN-γ-stimulated macrophages. Taken together, this work provides clues for developing innovative approaches which target T cells for the prevention and treatment of osteoporosis.

The Effect of Space Travel on Bone Metabolism: Considerations on Today's Major Challenges and Advances in Pharmacology

Microgravity-induced bone loss is currently a significant and unresolved health risk for space travelers, as it raises the likelihood for irreversible changes that weaken skeletal integrity and the incremental onset of fracture injuries and renal stone formation. Another issue related to bone tissue homeostasis in microgravity is its capacity to regenerate following fractures due to weakening of the tissue and accidental events during the accomplishment of particularly dangerous tasks. Today, several pharmacological and non-pharmacological countermeasures to this problem have been proposed, including physical exercise, diet supplements and administration of antiresorptive or anabolic drugs. However, each class of pharmacological agents presents several limitations as their prolonged and repeated employment is not exempt from the onset of serious side effects, which limit their use within a well-defined range of time. In this review, we will focus on the various countermeasures currently in place or proposed to address bone loss in conditions of microgravity, analyzing in detail the advantages and disadvantages of each option from a pharmacological point of view. Finally, we take stock of the situation in the currently available literature concerning bone loss and fracture healing processes. We try to understand which are the critical points and challenges that need to be addressed to reach innovative and targeted therapies to be used both in space missions and on Earth.

Pristimerin Protects Against OVX-Mediated Bone Loss by Attenuating Osteoclast Formation and Activity via Inhibition of RANKL-Mediated Activation of NF-κB and ERK Signaling Pathways

Introduction

Osteoporosis is an osteolytic bone condition characterized by decreased bone strength and increased bone fragility. It is the result of elevated formation or activity of bone-resorbing osteoclasts. Although current therapeutic agents are efficacious against osteoclast-mediated bone loss, detrimental side effects preclude the long-term use of these agents. Pristimerin (PRI) is a naturally occurring quinone-methide triterpenoid that has been revealed to exert anti-inflammatory and anti-tumor effects via regulating various signaling cascades including NF-κB and MAPK activation.

Methods

The bone marrow macrophages were used to confirm the anti-osteoclastic and anti-resorptive functions of PRI in vitro. An in vivo ovariectomy (OVX) model was applied to verify the function of PRI protecting bone loss.

Results

PRI abolished the early activation of NF-κB and ERK MAPK signal cascades thereby thwarting the downstream expression of c-Fos and NFATc1, which prevented the production of mature osteoclasts. In vivo, PRI protects mice against ovariectomy (OVX)-mediated bone loss by diminishing osteoclast formation and bone resorptive activity.

Conclusion

Our study shows that PRI demonstrates therapeutic potential in the effective treatment against osteoclast-induced osteolytic diseases like osteoporosis.

Physicians' Attitudes on Management of Osteopenia in South Korea

Background

Osteopenia patients have a risk of fracture and may develop osteoporosis. We investigated physicians’ management of osteopenia patients in South Korea.

Methods

A survey was conducted using a questionnaire including 6 items: (1) do you think anti-osteoporosis medications are necessary in osteopenia patients?; (2) what is your preference to manage osteopenia patients, except for anti-osteoporosis medications?; (3) what is your indication for the anti-osteoporosis medication in osteopenia patients?; (4) what kind of anti-osteoporosis medication do you prefer to treat osteopenia patients?; (5) do you use bisphosphonates?; and (6) if not, what is the reason for not using?.

Results

Among the 173 participants, 150 (86.7%) replied that anti-osteoporosis medications were necessary in osteopenia patients. Indications for the medication were (1) past medical history of pathologic fracture in 85 (49.1%); (2) T-score <-2.5 on dual energy X-ray absorptiometry in 73 (42.2%); (3) previous history of osteoporosis in 44 (25.4%); (4) risk of fracture according to fracture risk assessment tool in 34 (19.7%); and (5) progressive bone loss in 31 (17.9%). One hundred and sixteen (67.1%) favored bisphosphonates, 93 (53.8%) selective estrogen-receptor modulator, and 24 (13.9%) hormone replacement therapy. Thirty-one (17.9%) replied that they do not use bisphosphonates due to (1) restricted reimbursement by the health insurance in 24 (77.4%); and (2) bisphosphonate-related complications in 19 (61.3%).

Conclusions

Most respondents (86.7%) thought anti-osteoporosis medications were necessary in osteopenia patients, but 17.9% of the respondents did not use bisphosphonates. Restricted reimbursement by the national health insurance was the major obstacle against the use of bisphosphonates.

Osteopenia: debates and dilemmas

Whether or not to use pharmacologic agents for primary prevention of fracture among elderly men and women with osteopenia is debated by clinicians. In this review we provide an update to enable better understanding and characterization of this population, including the prevalence of osteopenia, transitioning from osteopenia to osteoporosis, and clinically applicable tools for fracture risk assessment. We also emphasize the very limited evidence of the benefits and risks of anti-osteoporotic agents for this population for primary fracture prevention, and the need for future studies to guide clinical practice.

Use of pharmacologic agents for the primary prevention of osteoporosis among older women with low bone mass

We examined the use of pharmacologic agents for the primary prevention of osteoporosis among older women with osteopenia. We found that these individuals were not managed in concordance with the National Osteoporosis Foundation (NOF) guidelines and that self-perceived osteoporosis risk and lower bone density were strongly associated with receipt of treatment.

INTRODUCTION

Although osteoporosis medications are used for the primary prevention of osteoporosis among persons with low bone mass (osteopenia), their use may be discordant with clinical practice guidelines.

METHODS

We studied women 55 years and older participating in the Global Longitudinal Study of Osteoporosis in Women (GLOW). Eligible participants had a dual energy x-ray absorptiometry (DXA) test performed at the University of Alabama at Birmingham hospital and had an osteopenia diagnosis based on their DXA test results. Participants' demographics, fracture risk factors, and exposure to osteoporosis medications were determined from the GLOW survey. We examined the proportions of women managed in concordance with the National Osteoporosis Foundation 2008 guidelines, and we assessed factors independently associated with osteoporosis treatment decisions. Women with a prior spine or hip fracture were excluded.

RESULTS

Among 597 eligible women from GLOW, the mean age ± standard deviation (SD) was 70 ± 7 years. Among all subjects, 309 (52%) were treated in concordance with the NOF 2008 guidelines. Greater self-perceived osteoporosis risk and lower bone mineral density were significantly and consistently associated with receipt of osteoporosis treatment, both for those considered appropriate and for those considered inappropriate for treatment based on the NOF guidelines.

CONCLUSIONS

We found significant discordance between NOF 2008 guidelines and pharmacologic management of women with osteopenia. A person's self-perceived osteoporosis risk and bone mineral density were most strongly associated with receipt of osteoporosis medication use among women with low bone mass.

Zinc supplementation improves bone density in patients with thalassemia: a double-blind, randomized, placebo-controlled trial

BACKGROUND

Patients with thalassemia major (Thal) frequently have low plasma zinc, which has been associated with low bone mass.

OBJECTIVE

The objective was to determine the effect of zinc supplementation on bone mass in patients with Thal.

DESIGN

Forty-two subjects (21 females aged 10-30 y) with Thal and low bone mass were randomly assigned to receive 25 mg Zn/d or placebo. Bone mineral content (BMC) and areal bone mineral density (aBMD) were assessed by using dual-energy X-ray absorptiometry, and fasting blood was collected for the measurement of plasma zinc at 0, 12, and 18 mo.

RESULTS

Thirty-two subjects, 81% of whom were transfusion dependent, completed the study (mean ± SD: 17.1 ± 5.2 y). Plasma zinc was ≤70 μg/dL in 11 subjects at baseline and increased significantly with zinc supplementation (P = 0.014). Use of intention-to-treat analysis and linear models for longitudinal data, adjusted for baseline and pubertal stage, showed that the zinc group had significantly greater increases in whole-body BMC (adjusted mean ± SE: 63 ± 15 g; P = 0.02), and aBMD (0.023 ± 0.006 g/cm(2); P = 0.04) than did the placebo group after 18 mo. Furthermore, adjusted spine and hip aBMD z scores each decreased by 0.3 SDs (both P = 0.04) in the placebo compared with the zinc group over the 18-mo study.

CONCLUSIONS

In young patients with Thal, zinc supplementation resulted in greater gains in total-body bone mass than did placebo. Zinc was well tolerated and is worthy of investigation in larger trials in Thal patients across a range of ages and disease severity. This trial was registered at clinicaltrials.gov as NCT00459732.

Functional impairment of bone formation in the pathogenesis of osteoporosis: the bone marrow regenerative competence

The skeleton is a high-renewal organ that undergoes ongoing cycles of remodeling. The regenerative bone formation arm ultimately declines in the aging, postmenopausal skeleton, but current therapies do not adequately address this deficit. Bone marrow is the primary source of the skeletal anabolic response and the mesenchymal stem cells (MSCs), which give rise to bone matrix-producing osteoblasts. The identity of these stem cells is emerging, but it now appears that the term 'MSC' has often been misapplied to the bone marrow stromal cell (BMSC), a progeny of the MSC. Nevertheless, the changes in BMSC phenotype associated with age and estrogen depletion likely contribute to the attenuated regenerative competence of the marrow and may reflect alterations in MSC phenotype. Here we summarize current concepts in bone marrow MSC identity, and within this context, review recent observations on changes in bone marrow population dynamics associated with aging and menopause.

Antiresorptive drugs (bisphosphonates), atypical fractures and rebound effect: new evidence of similitude

BACKGROUND

Homeopathy is based on treatment by similitude ('like cures like') administering to sick individuals substances that cause similar symptoms in healthy individuals, employing the secondary and paradoxical action of the organism as therapeutic response. This vital or homeostatic reaction of the organism can be scientifically explained by the rebound effect of drugs, resulting in worsening of symptoms after suspension of treatment. Bisphosphonates (BPs) reduce 'typical' fractures in patients with osteoporosis, but recent studies report 'atypical' fractures of the femur after stopping the BPs, a rebound effect may be the causal mechanism.

METHOD

Review of the literature concerning the relationship between atypical femoral fractures and antiresorptive drugs (bisphosphonates), identifying the pathogenesis of this adverse event.

RESULTS

Several studies have described multiple cases of 'atypical' low-impact subtrochanteric stress fractures or complete fractures of the femur. These fractures are often bilateral, preceded by pain in the affected thigh, may have a typical X-ray appearance, and may delayed healing. Rebound of osteoclastic activity after suspension of antiresorptive drugs is a plausible mechanism to explain this phenomenon.

CONCLUSION

As for other classes of drugs, the rebound effect of antiresorptive drugs supports Hahnemann's similitude principle (primary action of the drugs followed by secondary and opposite action of the organism), and clarifies this 'unresolved' issue. Unfortunately, the rebound effect is little discussed among health professionals, depriving them of important knowledge ensure safe management of drugs.

Nmp4/CIZ closes the parathyroid hormone anabolic window

Chronic degenerative diseases are increasing with the aging U.S. population. One consequence of this phenomenon is the need for long-term osteoporosis therapies. Parathyroid hormone (PTH), the only FDA-approved treatment that adds bone to the aged skeleton, loses its potency within two years of initial treatment but the mechanism regulating its limited "anabolic window" is unknown. We have discovered that disabling the nucleocytoplasmic shuttling transcription factor nuclear matrix protein 4/cas interacting zinc finger protein (Nmp4/CIZ) in mice extends the PTH bone-forming capacity. Nmp4 was discovered during our search for nuclear matrix transcription factors that couple this hormone's impact on osteoblast cytoskeletal and nuclear organization with its anabolic capacity. CIZ was independently discovered as a protein that associates with the focal adhesion-associated mechanosensor p130Cas. The Nmp4/CIZ-knockout (KO) skeletal phenotype exhibits a modestly enhanced bone mineral density but manifests an exaggerated response to both PTH and to BMP2 and is resistant to disuse-induced bone loss. The cellular basis of the global Nmp4/CIZ-KO skeletal phenotype remains to be elucidated but may involve an expansion of the bone marrow osteoprogenitor population along with modestly enhanced osteoblast and osteoclast activities supporting anabolic bone turnover. As a shuttling Cys(2)His(2) zinc finger protein, Nmp4/CIZ acts as a repressive transcription factor perhaps associated with epigenetic remodeling complexes, but the functional significance of its interaction with p130Cas is not known. Despite numerous remaining questions, Nmp4/CIZ provides insights into how the anabolic window is regulated, and itself may provide an adjuvant therapy target for the treatment of osteoporosis by extending PTH anabolic efficacy.

Inflammatory rheumatic disorders and bone

Inflammatory joint diseases such as rheumatoid arthritis, as well as other rheumatic conditions, such as systemic lupus erythematosus (SLE) and ankylosing spondylitis, comprise a heterogeneous group of joint disorders that are all associated with extra-articular side effects, including bone loss and fractures. The concept of osteoimmunology is based on growing insights into the links between the immune system and bone. The pathogenesis of osteoporosis in these patients is multifactorial. We have, more or less as an example, described this extensively for patients with SLE. High disease activity (inflammation) and immobility are common factors that substantially increase fracture risk in these patients, on top of the background fracture risk based on, among other factors, age, body mass index, and gender. Although no fracture reduction has been shown in intervention studies in patients with inflammatory rheumatic diseases, we present treatment options that might be useful for clinicians who are treating these patients.