Insights into the bisphosphonate holiday: a preliminary FTIRI study

Low turnover renal osteodystrophy with abnormal bone quality and vascular calcification in patients with mild to moderate CKD

Introduction

Limited information is available on renal osteodystrophy (ROD) and vascular calcification (VC) during early chronic kidney disease (CKD). This study was designed to evaluate ROD and VC in 32 patients with CKD stages II to IV.

Methods

Patients underwent dual-energy X-ray absorptiometry (DXA) for assessment of bone mineral density (BMD) and trabecular bone score (TBS), thoracic computed tomography for VC scoring using the Agatston method, and anterior iliac crest bone biopsy for mineralized bone histology, histomorphometry, and Fourier transform infrared spectroscopy (FTIR). Classical and novel bone markers were determined in the blood.

Results

Mean estimated glomerular filtration rate (eGFR) was 44 ± 16 ml/min per 1.73 m². Of the patients, 84% had low bone turnover. In Whites, eGFR correlated negatively with the turnover parameter activation frequency (Ac.f) (r −0.48, P = 0.019) and with parameters of bone formation. Most patients had VC (>80%) which correlated positively with levels of phosphorus, c-terminal fibroblast growth factor-23, and activin. Aortic calcifications (ACs) correlated negatively with bone formation rate (BFR) and Ac.f (rho −0.62, −0.61, P < 0.001). TBS correlated negatively with coronary calcification (rho −0.42, P = 0.019) and AC (rho −0.57, P = 0.001). These relationships remained after adjustment of age. The mineral-to-matrix ratio, an FTIR metric reflecting bone quality, was negatively related to Ac.f and positively related to AC.

Conclusion

Low bone turnover and VC are predominant in early stages of CKD. This is the first study demonstrating mineral abnormalities indicating reduced bone quality in these stages of CKD.

Graphene-Oxide Porous Biopolymer Hybrids Enhance In Vitro Osteogenic Differentiation and Promote Ectopic Osteogenesis In Vivo

Over the years, natural-based scaffolds have presented impressive results for bone tissue engineering (BTE) application. Further, outstanding interactions have been observed during the interaction of graphene oxide (GO)-reinforced biomaterials with both specific cell cultures and injured bone during in vivo experimental conditions. This research hereby addresses the potential of fish gelatin/chitosan (GCs) hybrids reinforced with GO to support in vitro osteogenic differentiation and, further, to investigate its behavior when implanted ectopically. Standard GCs formulation was referenced against genipin (Gp) crosslinked blend and 0.5 wt.% additivated GO composite (GCsGp/GO 0.5 wt.%). Pre-osteoblasts were put in contact with these composites and induced to differentiate in vitro towards mature osteoblasts for 28 days. Specific bone makers were investigated by qPCR and immunolabeling. Next, CD1 mice models were used to assess de novo osteogenic potential by ectopic implantation in the subcutaneous dorsum pocket of the animals. After 4 weeks, alkaline phosphate (ALP) and calcium deposits together with collagen synthesis were investigated by biochemical analysis and histology, respectively. Further, ex vivo materials were studied after surgery regarding biomineralization and morphological changes by means of qualitative and quantitative methods. Furthermore, X-ray diffraction and Fourier-transform infrared spectroscopy underlined the newly fashioned material structuration by virtue of mineralized extracellular matrix. Specific bone markers determination stressed the osteogenic phenotype of the cells populating the material in vitro and successfully differentiated towards mature bone cells. In vivo results of specific histological staining assays highlighted collagen formation and calcium deposits, which were further validated by micro-CT. It was observed that the addition of 0.5 wt.% GO had an overall significant positive effect on both in vitro differentiation and in vivo bone cell recruitment in the subcutaneous region. These data support the GO bioactivity in osteogenesis mechanisms as being self-sufficient to elevate osteoblast differentiation and bone formation in ectopic sites while lacking the most common osteoinductive agents.

Bone Quality and Fractures in Women With Osteoporosis Treated With Bisphosphonates for 1 to 14 Years

Oral bisphosphonates are the primary medication for osteoporosis, but concerns exist regarding potential bone-quality changes or low-energy fractures. This cross-sectional study used artificial intelligence methods to analyze relationships among bisphosphonate treatment duration, a wide variety of bone-quality parameters, and low-energy fractures. Fourier transform infrared spectroscopy and histomorphometry quantified bone-quality parameters in 67 osteoporotic women treated with oral bisphosphonates for 1 to 14 years. Artificial intelligence methods established two models relating bisphosphonate treatment duration to bone-quality changes and to low-energy clinical fractures. The model relating bisphosphonate treatment duration to bone quality demonstrated optimal performance when treatment durations of 1 to 8 years were separated from treatment durations of 9 to 14 years. This may be due to a change in relationship of bone-quality parameters with treatment duration. This model also showed that the effects of bisphosphonate treatment duration were most highly correlated with changes in means and standard deviations of infrared spectroscopically derived mineral and matrix parameters and histomorphometric bone turnover parameters. A second model related treatment duration to bone fracture in all 22 patients who fractured while on treatment with bisphosphonates for more than 8 years. This second model showed that bisphosphonate treatment duration, not hip bone mineral density (BMD), was the most strongly correlated parameter to these low-energy bone fractures. Application of artificial intelligence enabled analysis of large quantities of structural, cellular, mineral, and matrix bone-quality parameters to determine relationships with long-term oral bisphosphonate treatment and fracture. Infrared spectroscopy provides clinically relevant bone-quality information of which bone mineral purity is among the most relevant. Nine or more years of bisphosphonate treatment was associated with abnormal bone mineral purity, matrix abnormalities, and low-energy fractures. These data justify limiting bisphosphonate treatment duration to 8 years. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

A Bisphosphonate With a Low Hydroxyapatite Binding Affinity Prevents Bone Loss in Mice After Ovariectomy and Reverses Rapidly With Treatment Cessation

Bisphosphonates (BPs) are a mainstay of osteoporosis treatment; however, concerns about bone health based on oversuppression of remodeling remain. Long‐term bone remodeling suppression adversely affects bone material properties with microdamage accumulation and reduced fracture toughness in animals and increases in matrix mineralization and atypical femur fractures in patients. Although a “drug holiday” from BPs to restore remodeling and improve bone quality seems reasonable, clinical BPs have long functional half‐lives because of their high hydroxyapatite (HAP) binding affinities. This places a practical limit on the reversibility and effectiveness of a drug holiday. BPs with low HAP affinity and strong osteoclast inhibition potentially offer an alternative approach; their antiresorptive effect should reverse rapidly when dosing is discontinued. This study tested this concept using NE‐58025, a BP with low HAP affinity and moderate osteoclast inhibition potential. Young adult female C57Bl/6 mice were ovariectomized (OVX) and treated with NE‐58025, risedronate, or PBS vehicle for 3 months to test effectiveness in preventing long‐term bone loss. Bone microarchitecture, histomorphometry, and whole‐bone mechanical properties were assessed. To test reversibility, OVX mice were similarly treated for 3 months, treatment was stopped, and bone was assessed up to 3 months post‐treatment. NE‐58025 and RIS inhibited long‐term OVX‐induced bone loss, but NE‐58025 antiresorptive effects were more pronounced. Withdrawing NE‐58025 treatment led to the rapid onset of trabecular resorption with a 200% increase in osteoclast surface and bone loss within 1 month. Cessation of risedronate treatment did not lead to increases in resorption indices or bone loss. These results show that NE‐58025 prevents OVX‐induced bone loss, and its effects reverse quickly following cessation treatment in vivo. Low‐HAP affinity BPs may have use as reversible, antiresorptive agents with a rapid on/off profile, which may be useful for maintaining bone health with long‐term BP treatment. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Osteoporosis: Mechanism, Molecular Target and Current Status on Drug Development

CDATA[Osteoporosis is a pathological loss of bone mass due to an imbalance in bone remodeling where osteoclast-mediated bone resorption exceeds osteoblast-mediated bone formation resulting in skeletal fragility and fractures. Anti-resorptive agents, such as bisphosphonates and SERMs, and anabolic drugs that stimulate bone formation, including PTH analogues and sclerostin inhibitors, are current treatments for osteoporosis. Despite their efficacy, severe side effects and loss of potency may limit the long term usage of a single drug. Sequential and combinational use of current drugs, such as switching from an anabolic to an anti-resorptive agent, may provide an alternative approach. Moreover, there are novel drugs being developed against emerging new targets such as Cathepsin K and 17β-HSD2 that may have less side effects. This review will summarize the molecular mechanisms of osteoporosis, current drugs for osteoporosis treatment, and new drug development strategies.

Bisphosphonate drug holidays: Risk of fractures and mortality in a prospective cohort study

PURPOSE

This study examined osteoporotic fractures and mortality in patients pretreated with bisphosphonates (BPs) during BP holidays and ongoing BP use.

METHODS

Interview-based prospective observational study in a cohort of 1973 patients with BP treatment for at least 80% of the total time of the preceding 4 years. Patients were recruited from 146 primarily endocrinological, orthopedic and rheumatological practices and clinics across Germany between May 2013 and June 2015. Outcomes were analyzed by Cox proportional hazards regression in relation to treatment status at the time of the first interview (model 1) or using time-dependent treatment variables (model 2). Temporal changes in fracture risk during BP holidays were evaluated by comparisons among 3 incremental levels of simple moving averages of BP treatment during the preceding 12 months (BP-SMA levels 0%, >0% to <50%, and ≥50%).

RESULTS

For an observation period of up to 25 months, the adjusted hazard ratios (HRs) in model 1 for BP holidays compared to ongoing BP use were 0.87 (95% confidence interval [CI] 0.59-1.28) for major osteoporotic fractures (MOFs), 0.95 (95% CI 0.70-1.28) for any clinical osteoporotic fracture, 0.96 (95% CI 0.55-1.68) for clinical vertebral fractures, and 0.86 (95% CI 0.50-1.48) for mortality. The risk of MOFs was higher for the BP-SMA level 0%, corresponding to a time >12 months since the start of a BP holiday, than for the BP-SMA level >0% to <50%, corresponding mainly to a time >6 to ≤12 months since the start of a BP holiday (adjusted HR 2.28, 95% CI 1.07-4.86). We found an interaction between prevalent vertebral fractures (PVFs) and BP-SMA-related time to first MOF for BP-SMA as a continuous variable (p for interaction 0.046 in the adjusted model). The adjusted HR for MOFs for the BP-SMA level 0% compared to the BP-SMA level >0% to <50% was 3.53 (95% CI 1.19-10.51) with a PVF but was 1.44 (95% CI 0.49-4.22) without a PVF.

CONCLUSIONS

Fracture risk and mortality in patients with preceding BP treatment did not significantly differ between BP holidays and ongoing BP use for an observation period up to 25 months when outcomes were analyzed in relation to treatment at the time of the first interview. However, in the presence of a PVF, the risk of MOFs was higher for a BP-SMA level corresponding to a time >12 months since the start of a BP holiday than for a BP-SMA level corresponding mainly to a time >6 to ≤12 months since the start of a BP holiday. The presence of a PVF may increase the relative risk of MOFs associated with a longer BP holiday.

Sustained delivery of alendronate by engineered collagen scaffold for the repair of osteoporotic bone defects and resistance to bone loss

Researches of biomaterials for osteoporotic bone defects focus on the improvement of its anti-osteoporosis ability, due to osteoporosis is a kind of systemic and long-range bone metabolism disorder. Nevertheless, how to steadily deliver anti-osteoporosis drugs in osteoporotic bone defects is rarely studied. Reported evidences have shown that alendronate (Aln) is known to not only restrain osteoclasts from mediating bone resorption but also stimulate osteoblasts to regenerate bone tissue. Here, we developed an engineered implantable scaffold that could sustainably release Aln for osteoporotic bone defects. Briefly, Aln was added into 2% collagen (Col) solution to form a 5 mg/ml mixture. Then the mixture was filled into pre-designed round models (diameter: 5 mm, height: 2 mm) and crosslinked to obtain engineered Col-Aln scaffolds. The release kinetics showed that Aln was released at an average rate of 2.99 μg/d in the initial 8 days and could sustainably release for 1 month. To detect the repair effects of the Col-Aln scaffolds for osteoporotic defects, the Col and Col-Aln scaffolds were implanted into 5 mm cranial defects in ovariectomized rats. After 3 months, the cranial defects implanted with Col-Aln scaffolds achieved more bone regeneration in defect area (11.74 ± 3.82%) than Col scaffold (5.12 ± 1.15%) (p < .05). Moreover, ovariectomized rats in Col-Aln scaffold group possessed more trabecular bone in femur metaphysis than Col scaffold group as analyzed by Micro-CT. This study demonstrated the engineered Col-Aln scaffold has the potential to repair osteoporotic bone defects and resist bone loss in osteoporosis.

Bisphosphonate drug holidays: One size does not fit all

Bisphosphonates have been safely used to treat osteoporosis, effectively reducing fracture risk after 3 to 5 years of treatment. Recent concerns about long-term safety coupled with posttreatment fracture risk reduction have increased support for drug holidays. The decision to start low-risk patients on drug holidays must be based on current fracture risk assessment.

Osteoporosis Therapeutics 2020

Numerous safe and efficient drug therapies are currently available to decrease risk of low trauma fractures in patients with osteoporosis including postmenopausal, male, and secondary osteoporosis. In this chapter, we give first an overview of the most important outcomes regarding fracture risk reduction, change in bone mineral density (BMD by DXA) and/or bone markers of the phase III clinical studies of well-established therapies (such as Bisphosphonates, Denosumab or Teriparatide) and also novel therapies (such as Romosozumab or Abaloparatide) and highlight their mechanisms of action at bone tissue/material level. The latter understanding is not only essential for the choice of drug, duration and discontinuation of treatment but also for the interpretation of the clinical outcomes (in particular of eventual changes in BMD) after drug administration. In the second part of this chapter, we focus on the management of different forms of osteoporosis and give a review of the respective current guidelines for treatment. Adverse effects of treatment such as atypical femoral fractures, osteonecrosis of the jaw or influence of fracture healing are considered also in this context.

Medical Treatment for Osteoporosis: From Molecular to Clinical Opinions

Osteoporosis is a major concern all over the world. With aging, a gradual loss of bone mass results in osteopenia and osteoporosis. Heritable factors account for 60–80% of optimal bone mineralization. Modifiable factors, such as weight-bearing exercise, nutrition, body mass, and hormonal milieu, play an important role in the development of osteopenia and osteoporosis in adulthood. Currently, anti-resorptive agents, including estrogen, bisphosphonates, and selective estrogen receptor modulators (SERMs), are the drugs of choice for osteoporosis. Other treatments include parathyroid hormone (PTH) as well as the nutritional support of calcium and vitamin D. New treatments such as tissue-selective estrogen receptor complexes (TSECs) are currently in use too. This review, which is based on a systematic appraisal of the current literature, provides current molecular and genetic opinions on osteoporosis and its medical treatment. It offers evidence-based information to help researchers and clinicians with osteoporosis assessment. However, many issues regarding osteoporosis and its treatment remain unknown or controversial and warrant future investigation.

The GLP-1 Receptor Agonist Exenatide Ameliorates Bone Composition and Tissue Material Properties in High Fat Fed Diabetic Mice

Type 2 diabetes mellitus (T2DM) has recently been recognized as a significant risk factor for bone fragility. Careful investigations of bone mechanical properties in human studies suggested possible alterations of bone composition, although this axis has poorly been investigated. The main aim of this study was to evaluate the impact of high fat diet-induced diabetes and therapy using the clinically approved GLP-1 receptor agonist, exenatide, on tissue bone mechanical properties and compositional parameters. Male mice had free access to high fat diet for 16 weeks to induce diabetes prior to commencement of the study. Exenatide was administered twice daily by i.p. injection at a dose of 25 nmol/kg for 52 days. Normal and high fat diet fed (HFD) mice injected with saline were used as controls. Bone mechanical properties was assessed at the organ level by 3-point bending and at the tissue level by nanoindentation. Bone microarchitecture was investigated by microcomputed tomography and bone composition was evaluated by Fourier transform infrared imaging. HFD mice exhibited profound alterations of bone mechanical properties at both the organ and tissue level. Collagen maturity as well as trabecular and cortical bone microarchitectures were abnormal. Administration of exenatide, led to clear ameliorations in bone mechanical properties at the organ and tissue levels by modifications of both cortical microarchitecture and bone compositional parameters (collagen maturity, mineral crystallinity, carbonate/phosphate ratio, acid phosphate content). These results bring new light on the mode of action of exenatide in bone physiology and demonstrate the value of GLP-1 mimetics in the treatment of fragility fractures in diabetes.