Treatment with human parathyroid hormone (1-34) for 18 months increases cancellous bone volume and improves trabecular architecture in ovariectomized cynomolgus monkeys (Macaca fascicularis)

[The recombinant human parathyroid hormone, teriparatide as an alternative remedy for the medication-related osteonecrosis of the jaw]

In developed countries, osteoporosis is one of the most common debilitating conditions in the population over the age of 50. Unfortunately, the pathomechanism of the disease is still not fully understood. Nowadays, the administration of antiresorptive drugs blocking osteoclastic activity is the most commonly used medication to slow down the speed of the bone loss. One of the uncommon side effects of such drugs is the medication-related osteonecrosis of the jaw (MRONJ). Recently, a number of alternative therapeutic approaches has been tested and published, amongst them the recombinant human parathyroid hormone (rhPTH, teriparatide) use, which is turning into a promising treatment modality. According to certain meta-analyses, its pharmacological effect on increasing bone mineral density and controlling pathological vertebral fractures is superior to antiresorptive drugs; however, the so-called "off-label" application of teriparatide remains controversial. As intermittent administration of teriparatide stimulates bone formation, several animal and clinical studies indicated that systemic application of teriparatide shortened fracture healing time and improved quality of the callus and the newly formed bone. Furthermore, recently several clinical studies showed the beneficial effect of the intermittent rhPTH administration in the management of MRONJ. This article reviews the history of the anabolic effect of the low-dose rhPTH discovery, provides evidence-based data from animal and human studies, summarizes its biological mechanisms and the clinical benefits of the anabolic therapy and also their possible role in the management of MRONJ. The majority of the clinical data indicates that, in the case of therapy-resistant osteonecrosis, it may be worthwhile to apply short-term intermittent teriparatide therapy. Notwithstanding, more randomized clinical trials are necessary in order to confirm the efficacy and the safety of the use of teriparatide in the treatment of MRONJ. Orv Hetil. 2023; 164(36): 1406-1415.

Optimal timing for intermittent administration of parathyroid hormone (1-34) for distraction osteogenesis in rabbits

Background

To date, the usefulness of parathyroid hormone [PTH (1–34)] in distraction osteogenesis has been reported in several studies. We aimed to determine the optimal timing of PTH (1–34) administration in a rabbit distraction osteogenesis model.

Methods

The lower hind leg of a Japanese white rabbit was externally fixed, and tibial osteotomy was performed. One week after the osteotomy, bone lengthening was carried out at 0.375 mm/12 h for 2 weeks. After 5 weeks, the lower leg bone was collected. Bone mineral density (BMD), peripheral quantitative computed tomography (pQCT), micro-computed tomography (micro-CT), and mechanical tests were performed on the distracted callus. The rabbits were divided into three groups according to the timing of PTH (1–34) administration: 4 weeks during the distraction and consolidation phases (group D + C), 2 weeks of the distraction phase (group D), and the first 2 weeks of the consolidation phase (group C). A control group (group N) was administered saline for 4 weeks during the distraction and consolidation phases. Furthermore, to obtain histological findings, lower leg bones were collected from each rabbit at 2, 3, and 4 weeks after osteotomy, and tissue sections of the distracted callus were examined histologically.

Results

The BMD was highest in group C and was significantly higher than group D. In pQCT, the total cross-sectional area was significantly higher in groups D + C, D, and C than group N, and the cortical bone area was highest in group C and was significantly higher than group D. In micro-CT, group C had the highest bone mass and number of trabeculae. Regarding the mechanical test, group C had the highest callus failure strength, and this value was significantly higher compared to group N. There was no significant difference between groups D and N. The histological findings revealed that the distracted callus mainly consisted of endochondral ossification in the distraction phase. In the consolidation phase, the chondrocytes were almost absent, and intramembranous ossification was the main type of ossification.

Conclusion

We found that the optimal timing of PTH (1–34) administration is during the consolidation phase, which is mainly characterized by intramembranous ossification.

New Generation of Meso and Antiprogestins (SPRMs) into the Osteoporosis Approach

Receptor activator of nuclear factor κB (RANK) and its ligand (RANKL) play key roles in bone metabolism and the immune system. The RANK/RANKL complex has also been shown to be critical in the formation of mammary epithelia cells. The female hormones estradiol and progesterone closely control the action of RANKL with RANK. Blood concentration of these sex hormones in the postmenopausal period leads to an increase in RANK/RANKL signaling and are a major cause of women's osteoporosis, characterized by altered bone mineralization. Knowledge of the biochemical relationships between hormones and RANK/RANKL signaling provides the opportunity to design novel therapeutic agents to inhibit bone loss, based on the anti-RANKL treatment and inhibition of its interaction with the RANK receptor. The new generation of both anti- and mesoprogestins that inhibit the NF-κB-cyclin D1 axis and blocks the binding of RANKL to RANK can be considered as a potential source of new RANK receptor ligands with anti-RANKL function, which may provide a new perspective into osteoporosis treatment itself as well as limit the osteoporosis rise during breast cancer metastasis to the bone.

Dose-dependent effects of pharmaceutical treatments on bone matrix properties in ovariectomized rats

As both anabolic and anti-catabolic osteoporosis drugs affect bone formation and resorption processes, they may contribute to bone's overall mechanical behavior by altering the quality of the bone matrix. We used an ovariectomized rat model and a novel fracture mechanics approach to investigate whether treatment with an anabolic (parathyroid hormone) or anti-catabolic (alendronate) osteoporosis drugs will alter the organic and mineral matrix components and consequently cortical bone fracture toughness. Ovariectomized (at 5 months age) rats were treated with either parathyroid hormone or alendronate at low and high doses for 6 months (age 6–12 months). Specifically, treatment groups included untreated ovariectomized controls (n = 9), high-dose alendronate (n = 10), low-dose alendronate (n = 9), high-dose parathyroid hormone (n = 10), and low-dose parathyroid hormone (n = 9). After euthanasia, cortical microbeams from the lateral quadrant were extracted, notched, and tested in 3-point bending to measure fracture toughness. Portions of the bone were used to measure changes in the 1) organic matrix through quantification of advanced glycation end-products (AGEs) and non-collagenous proteins, and 2) mineral matrix through assessment of mineral crystallinity. Compared to the ovariectomized group, rats treated with high doses of parathyroid hormone and alendronate had significantly increased cortical bone fracture toughness, which corresponded primarily to increased non-collagenous proteins while there was no change in AGEs. Additionally, low-dose PTH treatment increased matrix crystallinity and decreased AGE levels. In summary, ovariectomized rats treated with pharmaceutical drugs had increased non-collagenous matrix proteins and improved fracture toughness compared to controls. Further investigation is required for different doses and longer treatment periods.

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Alendronate increases non-collagenous proteins and improves fracture toughness.

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Parathyroid hormone also increases collagen maturity and mineral crystallinity.

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Both treatments minimize accumulation of advanced glycation end-products.

Bone quality in hypoparathyroidism

Hypoparathyroidism is a rare disorder characterized by hypocalcemia and deficient or absent levels of parathyroid hormone. The consequences of chronic hypoparathyroidism involve classic target organs of parathyroid hormone, namely the skeleton and the kidneys. In this article, we focus on the abnormalities in bone quality that are associated with hypoparathyroidism. As assessed by several modalities, bone quality is compromised. The evidence for abnormal bone quality includes findings from bone histomorphometry, bone material properties, and high-resolution peripheral computed tomography. These abnormalities include low bone turnover, altered skeletal microarchitecture and bone material properties. How these abnormalities relate to fracture risk are under investigation. In this study, we also reviewed the therapeutic effects of parathyroid hormone as replacement therapy in this disease.

Effects of Combination Denosumab and High-Dose Teriparatide Administration on Bone Microarchitecture and Estimated Strength: The DATA-HD HR-pQCT Study

In postmenopausal women at high risk of fracture, we previously reported that combined denosumab and high-dose (HD; 40 μg) teriparatide increased spine and hip bone mineral density (BMD) more than combination with standard-dose teriparatide (SD; 20 μg). To assess the effects of these combinations on bone microarchitecture and estimated bone strength, we performed high-resolution peripheral quantitative computed tomography (HR-pQCT) at the distal radius and distal tibia in these women, who were randomized to receive either teriparatide 20 μg (n = 39) or 40 μg (n = 37) during months 0 to 9 overlapped with denosumab 60 mg s.c. given at months 3 and 9, for a 15-month study duration. The 69 women who completed at least one study visit after baseline are included in this analysis. Over 15 months, increases in total BMD were higher in the HD-group than the SD-group at the distal tibia (5.3% versus 3.4%, p = 0.01) with a similar trend at the distal radius (2.6% versus 1.0%, p = 0.06). At 15 months, cortical porosity remained similar to baseline, with absolute differences of -0.1% and -0.7% at the distal tibia and -0.4% and -0.1% at the distal radius in the HD-group and SD-group, respectively; p = NS for all comparisons. Tibial cortical tissue mineral density increased similarly in both treatment groups (1.3% [p < 0.0001 versus baseline] and 1.5% [p < 0.0001 versus baseline] in the HD-group and SD-group, respectively; p = 0.75 for overall group difference). Improvements in trabecular microarchitecture at the distal tibia and estimated strength by micro-finite element analysis at both sites were numerically greater in the HD-group compared with SD-group but not significantly so. Together, these findings suggest that short-term treatment combining denosumab with either high- or standard-dose teriparatide improves HR-pQCT measures of bone density, microstructure, and estimated strength, with greater gains in total bone density observed in the HD-group, which may be of benefit in postmenopausal women with severe osteoporosis. © 2020 American Society for Bone and Mineral Research (ASBMR).

Emerging insights into the comparative effectiveness of anabolic therapies for osteoporosis

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

Cortical Bone Porosity in Rabbit Models of Osteoporosis

Cortical bone porosity is intimately linked with remodeling, is of growing clinical interest, and is increasingly accessible by imaging. Thus, the potential of animal models of osteoporosis (OP) to provide a platform for studying how porosity develops and responds to interventions is tremendous. To date, rabbit models of OP have largely focused on trabecular microarchitecture or bone density; some such as ovariectomy (OVX) have uncertain efficacy and cortical porosity has not been extensively reported. Our primary objective was to characterize tibial cortical porosity in rabbit-based models of OP, including OVX, glucocorticoids (GC), and OVX + GC relative to controls (SHAM). We sought to: (i) test the hypothesis that intracortical remodeling is elevated in these models; (ii) contrast cortical remodeling and porosity in these models with that induced by parathyroid hormone (1-34; PTH); and (iii) contrast trabecular morphology in the proximal tibia across all groups. Evidence that an increase in cortical porosity occurred in all groups was observed, although this was the least robust for GC. Histomorphometric measures supported the hypothesis that remodeling rate was elevated in all groups and also revealed evidence of uncoupling of bone resorption and formation in the GC and OVX + GC groups. For trabecular bone, a pattern of loss was observed for OVX, GC, and OVX + GC groups, whereas the opposite was observed for PTH. Change in trabecular number best explained these patterns. Taken together, the findings indicated rabbit models provide a viable and varied platform for the study of OP and associated changes in cortical remodeling and porosity. Intriguingly, the evidence revealed differing effects on the cortical and trabecular envelopes for the PTH model. © 2020 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR)..

PTH(1-34) treatment and/or mechanical loading have different osteogenic effects on the trabecular and cortical bone in the ovariectomized C57BL/6 mouse

In preclinical mouse models, a synergistic anabolic response to PTH(1–34) and tibia loading was shown. Whether combined treatment improves bone properties with oestrogen deficiency, a cardinal feature of osteoporosis, remains unknown. This study quantified the individual and combined longitudinal effects of PTH(1–34) and loading on the bone morphometric and densitometric properties in ovariectomised mice. C57BL/6 mice were ovariectomised at 14-weeks-old and treated either with injections of PTH(1–34); compressive loading of the right tibia; both interventions concurrently; or both interventions on alternating weeks. Right tibiae were microCT-scanned from 14 until 24-weeks-old. Trabecular metaphyseal and cortical midshaft morphometric properties, and bone mineral content (BMC) in 40 different regions of the tibia were measured. Mice treated only with loading showed the highest trabecular bone volume fraction at week 22. Cortical thickness was higher with co-treatment than in the mice treated with PTH alone. In the mid-diaphysis, increases in BMC were significantly higher with loading than PTH. In ovariectomised mice, the osteogenic benefits of co-treatment on the trabecular bone were lower than loading alone. However, combined interventions had increased, albeit regionally-dependent, benefits to cortical bone. Increased benefits were largest in the mid-diaphysis and postero-laterally, regions subjected to higher strains under compressive loads.

New Targets and Emergent Therapies for Osteoporosis

The 11 existing FDA-approved osteoporosis drug treatments include hormone replacement therapy, 2 SERMs (raloxifene and bazedoxifene), 5 inhibitors of bone-resorbing osteoclasts (4 bisphosphonates and anti-RANKL denosumab), 2 parathyroid hormone analogues (teriparatide and abaloparatide), and 1 WNT signaling enhancer (romosozumab). These therapies are effective and provide multiple options for patients and physicians. As the genomic revolution continues, potential novel targets for future drug development are identified. This review takes a wide perspective to describe potentially rewarding topics to explore, including knowledge of genes and pathways involved in bone cell metabolism, the utility of animal models, targeting drugs to bone, and ongoing advances in drug design and delivery.

Implantable multireservoir device with stimulus-responsive membrane for on-demand and pulsatile delivery of growth hormone

Implantable devices for on-demand and pulsatile drug delivery have attracted considerable attention; however, many devices in clinical use are embedded with the electronic units and battery inside, hence making them large and heavy for implantation. Therefore, we propose an implantable device with multiple drug reservoirs capped with a stimulus-responsive membrane (SRM) for on-demand and pulsatile drug delivery. The SRM is made of thermosensitive POSS(MEO₂MA-co-OEGMA) and photothermal nanoparticles of reduced graphene oxide (rGO), and each of the drug reservoirs is filled with the same amount of human growth hormone (hGH). Therefore, with noninvasive near-infrared (NIR) irradiation from the outside skin, the rGO nanoparticles generate heat to rupture the SRM in the implanted device, which can open a single selected drug reservoir to release hGH. Therefore, the device herein is shown to release hGH reproducibly only at the times of NIR irradiation without drug leakage during no irradiation. When implanted in rats with growth hormone deficiency and irradiated with an NIR light from the outside skin, the device exhibits profiles of hGH and IGF1 plasma concentrations, as well as body weight change, similar to those in animals treated with conventional s.c. hGH injections.

Once-Weekly Teriparatide Treatment Prevents Microdamage Accumulation in the Lumbar Vertebral Trabecular Bone of Ovariectomized Cynomolgus Monkeys

The effect of teriparatide treatment on microdamage accumulation has yet to be examined in animal studies. The purpose of this study was to investigate the effect of once-weekly teriparatide treatment on bone microdamage accumulation and the relationship between microdamage parameters and bone mass, architecture, turnover, and collagen cross-linking in the lumbar vertebral trabecular bone of ovariectomized (OVX) cynomolgus monkeys. Female monkeys were divided into four groups (n = 18-20 per group): (1) SHAM group, (2) OVX group, (3) OVX with 1.2 µg/kg once-weekly teriparatide group (LOW group), (4) OVX with 6.0 µg/kg once-weekly teriparatide group (HIGH group). After 18 months, all animals were double-labeled with calcein for histomorphometry. L3 and L7 lumbar vertebrae were harvested and analyzed for differences in histomorphometry, microdamage, and collagen cross-linking. The iliac crest was also analyzed for differences in bone turnover. In the OVX group, cancellous bone mass was reduced and microdamage accumulation was increased as compared with the SHAM control. Once-weekly teriparatide at both doses prevented the decrease in bone mass and increase in microdamage accumulation, and improved the distribution of collagen cross-linkage types. Regression analyses indicated that decreased microdamage accumulation was associated with reduced non-enzymatic cross-link pentosidine rather than increased cancellous bone mass or enzymatic cross-links. These findings suggest that once-weekly teriparatide treatment decreases microdamage accumulation by recovering the balance in collagen cross-links.

Parathyroid hormone for bone regeneration

Delayed healing and/or non-union occur in approximately 5-10% of the fractures that occur annually in the United States. Segmental bone loss increases the probability of non-union. Though grafting can be an effective treatment for segmental bone loss, autografting is limited for large defects since a limited amount of bone is available for harvest. Parathyroid hormone (PTH) is a key regulator of calcium homeostasis in the body and plays an important role in bone metabolism. Presently PTH is FDA approved for use as an anabolic treatment for osteoporosis. The anabolic effect PTH has on bone has led to research on its use for bone regeneration applications. Numerous studies in animal models have indicated enhanced fracture healing as a result of once daily injections of PTH. Similarly, in a human case study, non-union persisted despite treatment attempts with internal fixation, external fixation, and autograft in combination with BMP-7, until off label use of PTH1-84 was utilized. Use of a biomaterial scaffold to locally deliver PTH to a defect site has also been shown to improve bone formation and healing around dental implants in dogs and drill defects in sheep. Thus, PTH may be used to promote bone regeneration and provide an alternative to autograft and BMP for the treatment of large segmental defects and non-unions. This review briefly summarizes the unmet clinical need for improved bone regeneration techniques and how PTH may help fill that void by both systemically and locally delivered PTH for bone regeneration applications. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2586-2594, 2018.

The Biological Enhancement of Spinal Fusion for Spinal Degenerative Disease

In this era of aging societies, the number of elderly individuals who undergo spinal arthrodesis for various degenerative diseases is increasing. Poor bone quality and osteogenic ability in older patients, due to osteoporosis, often interfere with achieving bone fusion after spinal arthrodesis. Enhancement of bone fusion requires shifting bone homeostasis toward increased bone formation and reduced resorption. Several biological enhancement strategies of bone formation have been conducted in animal models of spinal arthrodesis and human clinical trials. Pharmacological agents for osteoporosis have also been shown to be effective in enhancing bone fusion. Cytokines, which activate bone formation, such as bone morphogenetic proteins, have already been clinically used to enhance bone fusion for spinal arthrodesis. Recently, stem cells have attracted considerable attention as a cell source of osteoblasts, promising effects in enhancing bone fusion. Drug delivery systems will also need to be further developed to assure the safe delivery of bone-enhancing agents to the site of spinal arthrodesis. Our aim in this review is to appraise the current state of knowledge and evidence regarding bone enhancement strategies for spinal fusion for degenerative spinal disorders, and to identify future directions for biological bone enhancement strategies, including pharmacological, cell and gene therapy approaches.

Bone grafts and biomaterials substitutes for bone defect repair: A review

Bone grafts have been predominated used to treat bone defects, delayed union or non-union, and spinal fusion in orthopaedic clinically for a period of time, despite the emergency of synthetic bone graft substitutes. Nevertheless, the integration of allogeneic grafts and synthetic substitutes with host bone was found jeopardized in long-term follow-up studies. Hence, the enhancement of osteointegration of these grafts and substitutes with host bone is considerably important. To address this problem, addition of various growth factors, such as bone morphogenetic proteins (BMPs), parathyroid hormone (PTH) and platelet rich plasma (PRP), into structural allografts and synthetic substitutes have been considered. Although clinical applications of these factors have exhibited good bone formation, their further application was limited due to high cost and potential adverse side effects. Alternatively, bioinorganic ions such as magnesium, strontium and zinc are considered as alternative of osteogenic biological factors. Hence, this paper aims to review the currently available bone grafts and bone substitutes as well as the biological and bio-inorganic factors for the treatments of bone defect.

Kinetic reconstruction reveals time-dependent effects of romosozumab on bone formation and osteoblast function in vertebral cancellous and cortical bone in cynomolgus monkeys

Romosozumab, a humanized monoclonal sclerostin antibody under development for the treatment of osteoporosis, has a unique mechanism of action on bone-increasing bone formation and decreasing bone resorption. The effects on bone formation are transient, eliciting a rapid increase in bone formation that attenuates with continued treatment. Although bone formation attenuates, bone mineral density (BMD) continues to increase. To explore potential tissue-level mechanisms that could contribute to a progressive increase in spine BMD, we used kinetic reconstruction techniques to examine the effects of romosozumab on modeling and remodeling units in vertebral cancellous bone from adult cynomolgus monkeys administered romosozumab for 10 and 28weeks. The 10-week study duration captured a period of high modeling-based bone formation, and the 28-week study duration followed the self-regulation or attenuation of bone formation in cancellous bone that occurs with long-term treatment. Sequential fluorochrome labels applied for the kinetic reconstruction were also used to evaluate treatment effects on osteoblast function as early as 3weeks, and on bone formation and bone accrual in the vertebral cortex over 28weeks. Kinetic reconstruction of remodeling and modeling formation sites in vertebral cancellous bone revealed that romosozumab effected significant transient increases in mineral apposition rate in remodeling sites at week 3 that was not sustained with continued treatment. However, romosozumab treatment caused sustained improvement in fractional labeling of osteoid, an index of osteoblast efficiency, at remodeling formative sites at both weeks 10 and 28 that was the major contributor to significant increases in final wall thickness (W.Th) of remodeling packets. Remodeling W.Th matched the final W.Th of modeling packets at week 10. At both weeks 10 and 28, romosozumab significantly decreased eroded surface (ES/BS). At week 28, romosozumab also significantly reduced resorption period (Rs.P) and final resorption depth (Rs.De). The reduced final Rs.De combined with the increased W.Th resulted in a significant increase in bone balance (BB) at the level of the remodeling unit. Assessment of bone formation on the vertebral periosteal and endocortical surfaces following 28weeks of treatment revealed that romosozumab significantly increased bone formation on these surfaces, which had attenuated by week 28, resulting in significant increases in new periosteal and endocortical bone by week 28. These data suggest that multiple factors potentially contribute to the increase in spine BMD with romosozumab treatment. In the early period of treatment, increased modeling-based bone formation, increased W.Th at remodeling sites, a decrease in remodeling space secondary to decreased ES/BS in vertebral cancellous bone, and increased periosteal and endocortical bone formation in the vertebral cortex contribute to the early increase in spine BMD. Following the self-regulation of bone formation when modeling-based bone formation has attenuated, a decrease in remodeling space secondary to reduced ES/BS and a positive BB secondary to decreased final Rs.De and increased W.Th contribute to the progressive increase in spine BMD with long-term treatment.

Influence of Dosing Interval and Administration on the Bone Metabolism, Skeletal Effects, and Clinical Efficacy of Parathyroid Hormone in Treating Osteoporosis: A Narrative Review

Recombinant human parathyroid hormone (PTH) is the key anabolic agent used for preventing fracture in postmenopausal women with osteoporosis. In bone metabolism, PTH signaling is mediated through a G protein–coupled receptor that affects various post‐receptor signaling pathways. Results of preclinical and clinical studies have shown that PTH improves both the structure and strength of bone tissue. Once daily subcutaneous injection of the PTH fragment, teriparatide (PTH [1‐34]), is the most commonly recommended formulation and dosing strategy in clinical practice. However, other dosing intervals, formulations, and routes have been investigated in preclinical and clinical studies. In particular, once‐weekly and cyclical administration have been investigated mainly as a means of reducing the high direct costs of treatment. In preclinical studies, bone formation/resorption markers, bone mineral density measurements, and histomorphometric parameters improved with both once‐daily and once‐weekly administration. However, the magnitude and duration of such improvements were generally greater with once‐daily PTH administration. In clinical studies, reductions in fracture incidence were also noted with both once‐daily and once‐weekly PTH administration, although improvements in nonvertebral fractures are less evident with once‐weekly administration. This narrative review details the differences between PTH formulation and dosing strategies in relation to preclinical and clinical efficacy/safety parameters, although it should be stressed that no head‐to‐head studies allow direct comparisons. This review also seeks to outline practical considerations involved with PTH prescribing and new directions in research regarding routes of administration. © 2017 The Authors. JBMR Plus is published by Wiley Periodicals, Inc. on behalf of the American Society for Bone and Mineral Research.

Positioning novel biologicals in CKD-mineral and bone disorders

Renal osteodystrophy (ROD), the histologic bone lesions of chronic kidney disease (CKD), is now included in a wider syndrome with laboratory abnormalities of mineral metabolism and extra-skeletal calcifications or CKD-mineral and bone disorders (CKD-MBD), to highlight the increased burden of mortality. Aging people, frequently identified as early CKD, could suffer from either the classical age-related osteoporosis (OP) or ROD. Distinguishing between these two bone diseases may not be easy without bone biopsy. In any case, besides classical therapies for ROD, nephrologists are now challenged by the possibility of using new drugs developed for OP. Importantly, while therapies for ROD mostly aim at controlling parathyroid secretion with bone effects regarded as indirect, new drugs for OP directly modulate bone cells activity. Thus, their action could be useful in specific types of ROD. Parathyroid hormone therapy, which is anabolic in OP, could be useful in renal patients with low turnover bone disease. Denosumab, the monoclonal antibody against receptor activator of NF-κB ligand (RANK-L) that inhibits osteoclast activity and proliferation, could be beneficial in cases with high turnover bone. Use of romosozumab, the monoclonal antibody against sclerostin, which both stimulates osteoblasts and inhibits osteoclasts, could allow both anabolic and anti-resorptive effects. However, we should not forget the systemic role now attributed to CKD-MBD. In fact, therapies targeting bone cells activity could also result in unpredicted extra-bone effects and affect cardiovascular outcomes. In conclusion, the new biologicals established for OP could be useful in renal patients with either OP or ROD. In addition, their potential non-bone effects warrant investigation.

Acute development of cortical porosity and endosteal naïve bone formation from the daily but not weekly short-term administration of PTH in rabbit

Teriparatide [human parathyroid hormone (1–34)], which exerts an anabolic effect on bone, is used for the treatment of osteoporosis in patients who are at a high risk for fracture. That the once-daily administration of teriparatide causes an increase in cortical porosity in animal models and clinical studies has been a matter of concern. However, it is not well documented that the frequency of administration and/or the total dose of teriparatide affect the cortical porosity. The present study developed 4 teriparatide regimens [20 μg/kg/day (D20), 40 μg/kg/day (D40), 140 μg/kg/week (W140) and 280 μg/kg/week (W280)] in the rabbit as a model animal with a well-developed Haversian system and osteons. The total weekly doses were equivalent in the low-dose groups (D20 and W140) and in the high-dose groups (D40 and W280). After the short-term (1 month) administration of TPDT, micro-CT, histomorphometry and three-dimensional second harmonic generation (3D-SHG) imaging to visualize the bone collagen demonstrated that daily regimens but not weekly regimens were associated with the significant development of cortical porosity and endosteal naïve bone formation by marrow fibrosis. We concomitantly monitored the pharmacokinetics of the plasma teriparatide levels as well as the temporal changes in markers of bone formation and resorption. The analyses in the present study suggested that the daily repeated administration of teriparatide causes more deleterious changes in the cortical microarchitecture than the less frequent administration of higher doses. The findings of the present study may have some implications for use of teriparatide in clinical treatment.

Romosozumab Improves Bone Mass and Strength While Maintaining Bone Quality in Ovariectomized Cynomolgus Monkeys

Romosozumab (Romo), a humanized sclerostin antibody, is a bone-forming agent under development for treatment of osteoporosis. To examine the effects of Romo on bone quality, mature cynomolgus monkeys (cynos) were treated 4 months post- ovariectomy (OVX) with vehicle, 3 mg/kg, or 30 mg/kg Romo for 12 months, or with 30 mg/kg Romo for 6 months followed by vehicle for 6 months (30/0). Serum bone formation markers were increased by Romo during the first 6 months, corresponding to increased cancellous, endocortical, and periosteal bone formation in rib and iliac biopsies at months 3 and 6. Dual-energy X-ray absorptiometry (DXA) bone mineral density (BMD) was increased by 14% to 26% at the lumbar spine and proximal femur at month 12, corresponding to significant increases in bone strength at 3 and 30 mg/kg in lumbar vertebral bodies and cancellous cores, and at 30 mg/kg in the femur diaphysis and neck. Bone mass remained positively correlated with strength at these sites, with no changes in calculated material properties at cortical sites. These bone-quality measures were also maintained in the 30/0 group, despite a gradual loss of accrued bone mass. Normal bone mineralization was confirmed by histomorphometry and ash analyses. At the radial diaphysis, a transient, reversible 2% reduction in cortical BMD was observed with Romo at month 6, despite relative improvements in bone mineral content (BMC). High-resolution pQCT confirmed this decline in cortical BMD at the radial diaphysis and metaphysis in a second set of OVX cynos administered 3 mg/kg Romo for 6 months. Radial diaphyseal strength was maintained and metaphyseal strength improved with Romo as estimated by finite element modeling. Decreased radial cortical BMD was a consequence of increased intracortical remodeling, with no increase in cortical porosity. Romo resulted in marked improvements in bone mass, architecture, and bone strength, while maintaining bone quality in OVX cynos, supporting its bone efficacy and safety profile. © 2016 American Society for Bone and Mineral Research.

Preparation and in vivo evaluation of an orally available enteric-microencapsulated parathyroid hormone (1-34)-deoxycholic acid nanocomplex

The N-terminal 34-amino-acid peptide fragment of human parathyroid hormone PTH (1-34), is used clinically to treat osteoporosis; however, it is currently administered by a once-daily subcutaneous injection, resulting in poor patient compliance. We have developed enteric microcapsules containing an ionic nanocomplex between PTH (1-34) and lysine-linked deoxycholic acid (LysDOCA) for the oral delivery of PTH (1-34). We measured the particle size of the PTH/LysDOCA complex and assessed its biological activity by determining the cAMP content in MC3T3-E1 cells. We also assessed its permeability across a Caco-2 cell monolayer and the bioavailability of the intrajejunally administered PTH/LysDOCA complex compared with PTH (1-34) in rats. In addition, the antiosteoporotic activity of the PTH/LysDOCA complex, encapsulated in an enteric carrier by coaxial ultrasonic atomization, was evaluated after it was orally administered to ovariectomized (OVX) rats. The formation of an ionic complex between PTH (1-34) and LysDOCA produced nanoparticles of diameter 33.0±3.36 nm, and the bioactivity of the complex was comparable with that of PTH (1-34). The Caco-2 cell permeability and AUClast value of the PTH/LysDOCA (1:10) nanocomplex increased by 2.87- and 16.3-fold, respectively, compared with PTH (1-34) alone. Furthermore, the OVX rats treated with oral PTH/LysDOCA-loaded enteric microcapsules showed an increase in bone mineral density (159%), bone volume fraction (175%), and trabecular number (174%) compared with those in the OVX control group. Therefore, the PTH/LysDOCA nanocomplex oral delivery system is a promising treatment modality for osteoporosis because it improves osteogenesis and trabecular connectivity.

Comparative study of the effect of PTH (1-84) and strontium ranelate in an experimental model of atrophic nonunion

This study aimed to set up an experimental model of long bone atrophic nonunion and to explore the potential role of PTH-1-84 (PTH 1-84) and strontium ranelate (SrR). A model of atrophic nonunion was created in Sprague-Dawley rats at the femoral midshaft level. The animals were randomised into four groups. Group A1: control rodents, fracture without bone gap; Group A2: rodents with subtraction osteotomy (non-union model control) treated with saline; Group B: rodents with subtraction osteotomy treated with human-PTH (PTH 1-84); and Group C: rodents with subtraction osteotomy treated with strontium ranelate (SrR). The groups were followed for 12 weeks. X-rays were be obtained at weeks 1, 6 and 12. After sacrificing the animals, we proceeded to the biomechanical study and four point bending tests to evaluate the resistance of the callus and histological study. In second phase, the expression of genes related to osteoblast function was analysed by reverse transcription-quantitative PCR in rats subjected to substraction osteotomy and treated for 2 weeks. The animals were randomised into three groups: Group A2: rodents treated with saline; Group B: rodents treated with PTH 1-84 and Group C: rodents treated with SrR.

RESULTS

No significant histological differences were found between animals subjected to subtraction osteotomy and treated with either saline or PTH (p=0.628), but significant difference existed between animals receiving saline or SrR (p=0.005). There were no significant differences in X-ray score between the saline and PTH groups at either 6 or 12 weeks (p=0.33 and 0.36, respectively). On the other hand, better X-ray scores were found in the SrR group (p=0.047 and 0.006 in comparison with saline, at 6 and 12 weeks, respectively). In line with this, biomechanical tests revealed improved results in the SrR group. Gene expression analysis revealed a slightly decreased levels of DKK1, a Wnt pathway inhibitor, in rats treated with SrR.

CONCLUSIONS

SrR increases has a beneficial effect in this atrophic non-union model in rats. This suggests that it might have a role may have important implications for the potential clinical role in the treatment of fracture nonunion.

Individual and combined effects of noise-like whole-body vibration and parathyroid hormone treatment on bone defect repair in ovariectomized mice

The effectiveness of intermittent administration of parathyroid hormone and exposure to whole-body vibration on osteoporotic fracture healing has been previously investigated, but data on their concurrent use are lacking. Thus, we evaluated the effects of intermittent administration of parathyroid hormone, whole-body vibration, and their combination on bone repair in osteoporotic mice. Noise-like whole-body vibration with a broad frequency range was used instead of conventional sine-wave whole-body vibration at a specific frequency. Mice were ovariectomized at 9 weeks of age and subjected to drill-hole surgery in the right tibial diaphysis at 11 weeks. The animals were divided into four groups (n = 12 each): a control group, and groups treated with intermittent administration of parathyroid hormone, noise-like whole-body vibration, and both. From postoperative day 2, the groups treated with intermittent administration of parathyroid hormone and groups treated with both intermittent administration of parathyroid hormone and noise-like whole-body vibration were subcutaneously administered parathyroid hormone at a dose of 30 µg/kg/day. The groups treated with noise-like whole-body vibration and groups treated with both intermittent administration of parathyroid hormone and noise-like whole-body vibration were exposed to noise-like whole-body vibration at a root mean squared acceleration of 0.3g and frequency components of 45–100 Hz for 20 min/day. Following 18 days of interventions, the right tibiae were harvested, and the regenerated bone was analyzed by micro-computed tomography and nanoindentation testing. Compared with the control group, callus volume fraction was 40% higher in groups treated with intermittent administration of parathyroid hormone and 73% higher in groups treated with both intermittent administration of parathyroid hormone and noise-like whole-body vibration, and callus thickness was 35% wider in groups treated with both intermittent administration of parathyroid hormone and noise-like whole-body vibration. Indentation modulus was 46% higher in groups treated with noise-like whole-body vibration and 43% higher in groups treated with both intermittent administration of parathyroid hormone and noise-like whole-body vibration, and hardness was 31% higher in groups treated with both intermittent administration of parathyroid hormone and noise-like whole-body vibration compared with the control group. There was no interaction between the two treatments for both structure and mechanical indexes. The main effects of intermittent administration of parathyroid hormone and noise-like whole-body vibration on bone repair included increased bone formation and enhanced mechanical function of regenerated bone, respectively. The combined treatment resulted in further regeneration of bone with high indentation modulus and hardness, suggesting the therapeutic potential of the combined use of noise-like whole-body vibration and intermittent administration of parathyroid hormone for enhancing osteoporotic bone healing.

Effect exerted by Teriparatide upon Repair Function of β-tricalcium phosphate to ovariectomised rat's femoral metaphysis defect caused by osteoporosis

In this study, we tested the effect of Teriparatide (PTH) in combination with β-tricalcium phosphate (β-TCP) as a bone void filler in an ovariectomised rat distal femoral metaphysis model.β-TCP is a completely resorbable synthetic calcium phosphate and the Teriparatide is a drug that can promote bone formation in the condition of osteoporosis. A critical size defect of 3mm in diameter, a through-hole bone defect, was drilled into each distal femur of the ovariectomised rats. The hole was filled with β-TCP and the rat was injected PTH Teriparatide (30μg/kg) in peritoneum 5 times per week. After 4and 8 weeks the animals were killed and the degree of bone healing analysed. In total, 60 animals were investigated. When the β-TCP and PTH were used, histological, biochemistry and histomor-phometric evaluations revealed significantly better bone healing in terms of quantity and quality of the newly formed bone. The Ovariectomised rats which suffer from femur metaphysis defect are cured by embedding β-tricalcuim phosphate and intermittently cured by parathyroid hormone (PTH).

Emerging therapeutic concepts for muscle and bone preservation/building

Loss of muscle or bone mass occurs with ageing, immobility and in association with a variety of systemic diseases. The interaction of these two processes is most evident in the major contribution of falls to the risk of fractures in the elderly population. Exercise and nutrition are key common physiological variables that allow for preservation or formation of greater muscle or bone mass. However, although several pharmacological approaches have the potential to benefit both muscle and bone health, for example vitamin D, selective androgen receptor modulators and ghrelin mimetics, clinical trials with appropriate primary outcomes are lacking. Conventional approaches to address muscle loss are being extended to include stem cell biology and conserved molecular mechanisms of atrophy/hypertrophy. Pharmacological interventions to reduce fracture risk are exploring new mechanisms of action, in particular the uncoupling of bone resorption and formation. Emerging key issues for clinical trial design include adequate phenotyping of patients (personalised medicine), optimisation of the physiological background (multimodal approach) and the use of meaningful and robust outcomes relevant to daily clinical practice. At present, effective treatments that combine beneficial effects on both muscle and bone are lacking, although this is an important target for the future. This review therefore considers current and developing strategies to improve muscle function and bone strength in separate sections.

Engraftment and bone mass are enhanced by PTHrP 1-34 in ectopically transplanted vertebrae (vossicle model) and can be non-invasively monitored with bioluminescence and fluorescence imaging

Evidence exists that parathyroid hormone-related protein (PTHrP) 1-34 may be more anabolic in bone than parathyroid hormone 1-34. While optical imaging is growing in popularity, scant information exists on the relationships between traditional bone imaging and histology and bioluminescence (BLI) and fluorescence (FLI) imaging. We aimed to evaluate the effects of PTHrP 1-34 on bone mass and determine if relationships existed between radiographic and histologic findings in bone and BLI and FLI indices. Vertebrae (vossicles) from mice coexpressing luciferase and green fluorescent protein were implanted subcutaneously into allogenic nude mice. Transplant recipients were treated daily with saline or PTHrP 1-34 for 4 weeks. BLI, FLI, radiography, histology, and µCT of the vossicles were performed over time. PTHrP 1-34 increased bioluminescence the most after 2 weeks, fluorescence at all time points, and decreased the time to peak bioluminescence at 4 weeks (P ≤ 0.027), the latter of which suggesting enhanced engraftment. PTHrP 1-34 maximized vertebral body volume at 4 weeks (P < 0.0001). The total amount of bone observed histologically increased in both groups at 2 and 4 weeks (P ≤ 0.002); however, PTHrP 1-34 exceeded time-matched controls (P ≤ 0.044). A positive linear relationship existed between the percentage of trabecular bone and (1) total bioluminescence (r = 0.595; P = 0.019); (2) total fluorescence (r = 0.474; P = 0.074); and (3) max fluorescence (r = 0.587; P = 0.021). In conclusion, PTHrP 1-34 enhances engraftment and bone mass, which can be monitored non-invasively by BLI and FLI.

Parathyroid hormone and its receptor gene polymorphisms: implications in osteoporosis and in fracture healing

Parathyroid glands secrete parathyroid hormone (PTH) which plays multiple roles in calcium homeostasis and in bone remodeling. Secretion of PTH is regulated by extracellular calcium levels and other humoral factors including 1α,25(OH)2D3. PTH regulates gene expression and induces biological effects directly and indirectly. The human gene encoding PTH is located on chromosome 11. In this review, we study the diverse PTH along with its receptor gene polymorphisms and their association with osteoporosis and fracture healing. Genetic factors are associated with osteoporosis by influencing bone mineral density (BMD), bone turnover, calcium homeostasis, and susceptibility to osteoporotic fractures. Polymorphisms in genes encoding PTH may contribute to genetic regulation of BMD and thus susceptibility to fracture risk. PTH stimulates the proliferation of osteoprogenitor cells, production of alkaline phosphatise, and bone matrix proteins that contribute to hard callus formation and increases strength at the site of fractured bone. During remodeling, PTH promotes osteoclastogenesis restoring the original shape, structure, and mechanical strength of the bone. Some PTH polymorphisms have shown an association with fracture risk. Further research is needed to elucidate the relative importance of PTH genetics and the mechanisms of genetic contributions to gene-gene interactions in the pathogenesis of osteoporosis and in fracture healing.

Wireless implantable chip with integrated nitinol-based pump for radio-controlled local drug delivery

We demonstrate an active, implantable drug delivery device embedded with a microfluidic pump that is driven by a radio-controlled actuator for temporal drug delivery. The polyimide-packaged 10 × 10 × 2 mm(3) chip contains a micromachined pump chamber and check valves of Parylene C to force the release of the drug from a 76 μL reservoir by wirelessly activating the actuator using external radio-frequency (RF) electromagnetic fields. The rectangular-shaped spiral-coil actuator based on nitinol, a biocompatible shape-memory alloy, is developed to perform cantilever-like actuation for pumping operation. The nitinol-coil actuator itself forms a passive 185 MHz resonant circuit that serves as a self-heat source activated via RF power transfer to enable frequency-selective actuation and pumping. Experimental wireless operation of fabricated prototypes shows successful release of test agents from the devices placed in liquid and excited by radiating tuned RF fields with an output power of 1.1 W. These tests reveal a single release volume of 219 nL, suggesting a device's capacity of ~350 individual ejections of drug from its reservoir. The thermal behavior of the activated device is also reported in detail. This proof-of-concept prototype validates the effectiveness of wireless RF pumping for fully controlled, long-lasting drug delivery, a key step towards enabling patient-tailored, targeted local drug delivery through highly miniaturized implants.

Acting on black box warnings requires a GRADE evidence table and an implementation guide: the case of teriparatide

OBJECTIVES

To assess how well do the black box warnings present and communicate evidence in a way that is consistent with evidence-based patient-centered practice, through evaluating the boxed warning on teriparatide-induced osteosarcoma.

STUDY DESIGN AND SETTING

We critically appraised teriparatide black box warning for osteosarcoma by reviewing human and animal studies that were used as basis for the warning. We also evaluated the quality of the evidence using the Grading of Recommendations Assessment, Development and Evaluation framework.

RESULTS

We found that this warning was based on very low-quality evidence that was derived primarily from animal studies. The quality of evidence was rated down because of high risk of bias in addition to inconsistency, indirectness, and imprecision of the estimates. The warning does not provide sufficient guidance for practice like an implementation tool or an evidence profile to clarify the limitations of the evidence.

CONCLUSION

Black box warning for teriparatide-associated osteosarcoma does not explicitly present the quality of evidence, and therefore, it could be of limited use in evidence-based practice. We propose that black box warnings should include an evidence profile and an implementation guide to be more useful in evidence-based patient-centered practice.

Teriparatide increases the insertional torque of pedicle screws during fusion surgery in patients with postmenopausal osteoporosis

Object

The object of this study was to examine the efficacy of preoperative teriparatide treatment for increasing the insertional torque of pedicle screws during fusion surgery in postmenopausal women with osteoporosis.

Methods

Fusion surgery for the thoracic and/or lumbar spine was performed in 29 postmenopausal women with osteoporosis aged 65–82 years (mean 72.2 years). The patients were divided into 2 groups based on whether they were treated with teriparatide (n = 13) or not (n = 16) before the surgery. In the teriparatide-treated group, patients received preoperative teriparatide therapy as either a daily (20 μg/day, n = 7) or a weekly (56.5 μg/week, n = 6) injection for a mean of 61.4 days and a minimum of 31 days. During surgery, the insertional torque was measured in 212 screws inserted from T-7 to L-5 and compared between the 2 groups. The correlation between the insertional torque and the duration of preoperative teriparatide treatment was also investigated.

Results

The mean insertional torque value in the teriparatide group was 1.28 ± 0.42 Nm, which was significantly higher than in the control group (1.08 ± 0.52 Nm, p < 0.01). There was no significant difference between the daily and the weekly teriparatide groups with respect to mean insertional torque value (1.34 ± 0.50 Nm and 1.18 ± 0.43 Nm, respectively, p = 0.07). There was negligible correlation between insertional torque and duration of preoperative teriparatide treatment (r2 = 0.05, p < 0.01).

Conclusions

Teriparatide injections beginning at least 1 month prior to surgery were effective in increasing the insertional torque of pedicle screws during surgery in patients with postmenopausal osteoporosis. Preoperative teriparatide treatment might be an option for maximizing the purchase of the pedicle screws to the bone at the time of fusion surgery.

Inhibition of cathepsin K increases modeling-based bone formation, and improves cortical dimension and strength in adult ovariectomized monkeys

Treatment with the cathepsin K (CatK) inhibitor odanacatib (ODN) protects against bone loss and maintains normal biomechanical properties in the spine and hip of ovariectomized (OVX) preclinical models. Here, we characterized the effects of ODN on the dynamics of cortical modeling and remodeling, and dimension and strength of the central femur in adult OVX-rhesus monkeys. Animals were treated with vehicle or ODN (6 or 30 mg/kg, once per day [q.d., p.o.]) in prevention mode for 21 months. Calcein and tetracycline double-labeling were given at 12 and 21 months, and the femoral cross-sections were subjected to dynamic histomorphometric and cement line analyses. ODN treatment significantly increased periosteal and endocortical bone formation (BFR/BS), accompanied with an increase in endocortical mineralizing surface (102%, p < 0.01) with the 6 mg/kg dose. ODN at both doses reduced remodeling hemiosteon numbers by 51% and 66% (p < 0.05), respectively, and ODN 30 mg/kg numerically reduced activation frequency without affecting wall thickness. On the same endocortical surface, ODN increased all modeling-based parameters, while reducing intracortical remodeling, consistent with the observed no treatment effects on cortical porosity. ODN 30 mg/kg markedly increased cortical thickness (CtTh, p < 0.001) and reduced marrow area (p < 0.01). Lastly, ODN treatment increased femoral structural strength (p < 0.001). Peak load was positively correlated with the increases in bone mineral content (BMC) (r(2)  = 0.9057, p < 0.0001) and CtTh (r2  = 0.6866, p < 0.0001). Taken together, by reducing cortical remodeling-based and stimulating modeling-based bone formation, ODN significantly improved cortical dimension and strength in OVX monkeys. This novel mechanism of CatK inhibition in stimulating cortical formation suggests that ODN represents a novel therapeutic approach for the treatment of osteoporosis.

Total water, phosphorus relaxation and inter-atomic organic to inorganic interface are new determinants of trabecular bone integrity

Bone is the living composite biomaterial having unique structural property. Presently, there is a considerable gap in our understanding of bone structure and composition in the native state, particularly with respect to the trabecular bone, which is metabolically more active than cortical bones, and is readily lost in post-menopausal osteoporosis. We used solid-state nuclear magnetic resonance (NMR) to compare trabecular bone structure and composition in the native state between normal, bone loss and bone restoration conditions in rat. Trabecular osteopenia was induced by lactation as well as prolonged estrogen deficiency (bilateral ovariectomy, Ovx). Ovx rats with established osteopenia were administered with PTH (parathyroid hormone, trabecular restoration group), and restoration was allowed to become comparable to sham Ovx (control) group using bone mineral density (BMD) and µCT determinants. We used a technique combining (1)H NMR spectroscopy with (31)P and (13)C to measure various NMR parameters described below. Our results revealed that trabecular bones had diminished total water content, inorganic phosphorus NMR relaxation time (T1) and space between the collagen and inorganic phosphorus in the osteopenic groups compared to control, and these changes were significantly reversed in the bone restoration group. Remarkably, bound water was decreased in both osteopenic and bone restoration groups compared to control. Total water and T1 correlated strongly with trabecular bone density, volume, thickness, connectivity, spacing and resistance to compression. Bound water did not correlate with any of the microarchitectural and compression parameters. We conclude that total water, T1 and atomic space between the crystal and organic surface are altered in the trabecular bones of osteopenic rats, and PTH reverses these parameters. Furthermore, from these data, it appears that total water and T1 could serve as trabecular surrogates of micro-architecture and compression strength.

The effect of PTH(1-34) on fracture healing during different loading conditions

Parathyroid hormone (PTH) and PTH(1-34) have been shown to promote bone healing in several animal studies. It is known that the mechanical environment is important in fracture healing. Furthermore, PTH and mechanical loading has been suggested to have synergistic effects on intact bone. The aim of the present study was to investigate whether the effect of PTH(1-34) on fracture healing in rats was influenced by reduced mechanical loading. For this purpose, we used female, 25-week-old ovariectomized rats. Animals were subjected to closed midshaft fracture of the right tibia 10 weeks after ovariectomy. Five days before fracture, half of the animals received Botulinum Toxin A injections in the muscles of the fractured leg to induce muscle paralysis (unloaded group), whereas the other half received saline injections (control group). For the following 8 weeks, half of the animals in each group received injections of hPTH(1-34) (20 µg/kg/day) and the other half received vehicle treatment. Fracture healing was assessed by radiology, dual-energy X-ray absorptiometry (DXA), histology, and bone strength analysis. We found that unloading reduced callus area significantly, whereas no effects of PTH(1-34) on callus area were seen in neither normally nor unloaded animals. PTH(1-34) increased callus bone mineral density (BMD) and bone mineral content (BMC) significantly, whereas unloading decreased callus BMD and BMC significantly. PTH(1-34) treatment increased bone volume of the callus in both unloaded and control animals. PTH(1-34) treatment increased ultimate force of the fracture by 63% in both control and unloaded animals and no interaction of the two interventions could be detected. PTH(1-34) was able to stimulate bone formation in normally loaded as well as unloaded intact bone. In conclusion, the study confirms the stimulatory effect of PTH(1-34) on fracture healing, and our data suggest that PTH(1-34) is able to promote fracture healing, as well as intact bone formation during conditions of reduced mechanical loading.

Comparative genomic analysis and evolution of family-B G protein-coupled receptors from six model insect species

Family-B G protein-coupled receptors (GPCR-Bs) play vital roles in many biological processes, including growth, development and reproduction. However, the evolution and function of GPCR-Bs have been poorly understood in insects. We have identified 87 GPCR-Bs from six model insect species, 20 from Tribolium castaneum, 9 from Apis mellifera, 11 from Bombyx mori, 9 from Acyrthosiphon pisum, 14 from Anopheles gambiae and 24 from Drosophila melanogaster. 22 of them were reported in this study for the first time. Phylogenetic analysis revealed that there are three kinds of evolutionary patterns that occurred among GPCR-Bs during insect evolution: one-to-one orthologous relationships, species-specific expansion and episodic duplication or loss in certain insect lineages. A striking finding was the discovery of a parathyroid hormone receptor like gene (pthrl) in invertebrates, which was independently duplicated in vertebrates and invertebrates, whereas this gene was lost at least twice during insect evolution. These results indicate that PTHRL is possibly divergent in the functions between mammals and insects. The information of family-B GPCRs in nondrosophiline insects has been established, and will promote the further study on the function of these GPCRs and deorphanization of them. On the other hand, this study provides us with multiple function of GPCR-Bs in differential organisms, which will be also the potential attacking targets for new pesticides and drugs.

Teriparatide in the treatment of non-unions: scientific and clinical evidences

INTRODUCTION

Each fracture has a failing risk which can lead to a non-union. Among the non-invasive strategies proposed to improve bone healing, also in non-union, the use of teriparatide, a drug for the treatment of the osteoporosis, has increasing supporting data.

EXPERIMENTAL DATA

Many studies mainly on rats, but also on primates, demonstrate the positive effect on fracture healing of teriparatide, both in physiological and pathological conditions, with a more rapid evolution of the reparative callus.

CLINICAL DATA

A double blinded randomized controlled study on wrist fractures demonstrated a positive effect, in term of healing speed, of teriparatide at the dose of 20 μg/day, but not at the higher dose of 40 μg/day. A prospectic randomized study on pelvic fractures showed a faster healing in teriparatide treated patients. The use of teriparatide in non-unions is reported as effective in numerous case report. The effect of teriparatide seems very useful in the non-unions consequent to an atypical femoral fracture after long-term administration of bisphosphonates.

CONCLUSIONS

A conceivable positive effect of teriparatide on fracture healing is well-documented on animals, and very likely on humans, however further studies are needed to confirm these hopeful hypotheses.

Systemic intermittent parathyroid hormone treatment improves osseointegration of press-fit inserted implants in cancellous bone

BACKGROUND AND PURPOSE

Intermittent administration of parathyroid hormone (PTH) has an anabolic effect on bone, as confirmed in human osteoporosis studies, distraction osteogenesis, and fracture healing. PTH in rat models leads to improved fixation of implants in low-density bone or screw insertion transcortically.

MATERIAL AND METHODS

We examined the effect of human PTH (1-34) on the cancellous osseointegration of unloaded implants inserted press-fit in intact bone of higher animal species. 20 dogs were randomized to treatment with human PTH (1-34), 5 μg/kg/day subcutaneously, or placebo for 4 weeks starting on the day after insertion of a cylindrical porous coated plasma-sprayed titanium alloy implant in the proximal metaphyseal cancellous bone of tibia. Osseointegration was evaluated by histomorphometry and fixation by push-out test to failure.

RESULTS

Surface fraction of woven bone at the implant interface was statistically significantly higher in the PTH group by 1.4 fold with (median (interquartile range) 15% (13-18)) in the PTH group and 11% (7-13) in control. The fraction of lamellar bone was unaltered. No significant difference in bone or fibrous tissue was observed in the circumferential regions of 0-500, 500-1,000, and 1,000-2,000 μm around the implant. Mechanically, the implants treated with PTH showed no significant differences in total energy absorption, maximum shear stiffness, or maximum shear strength.

INTERPRETATION

Intermittent treatment with PTH (1-34) improved histological osseointegration of a prosthesis inserted press-fit at surgery in cancellous bone, with no additional improvement of the initial mechanical fixation at this time point.

Changes in 3-dimensional bone structure indices in hypoparathyroid patients treated with PTH(1-84): a randomized controlled study

Hypoparathyroidism (hypoPT) is characterized by a state of low bone turnover and high bone mineral density (BMD) despite conventional treatment with calcium supplements and active vitamin D analogues. To assess effects of PTH substitution therapy on 3-dimensional bone structure, we randomized 62 patients with hypoPT into 24 weeks of treatment with either PTH(1-84) 100 µg/day subcutaneously or similar placebo as an add-on therapy. Micro-computed tomography was performed on 44 iliac crest bone biopsies (23 on PTH treatment) obtained after 24 weeks of treatment. Compared with placebo, PTH caused a 27% lower trabecular thickness (p < 0.01) and 4% lower trabecular bone tissue density (p < 0.01), whereas connectivity density was 34% higher (p < 0.05). Trabecular tunneling was evident in 11 (48%) of the biopsies from the PTH group. Patients with tunneling had significantly higher levels of biochemical markers of bone resorption and formation. At cortical bone, number of Haversian canals per area was 139% higher (p = 0.01) in the PTH group, causing a tendency toward an increased cortical porosity (p = 0.09). At different subregions of the hip, areal BMD (aBMD) and volumetric BMD (vBMD), as assessed by dual-energy X-ray absorptiometry (DXA) and quantitative computed tomography (QCT), decreased significantly by 1% to 4% in the PTH group. However, at the lumbar spine, aBMD decreased by 1.8% (p < 0.05), whereas vBMD increased by 12.8% (p = 0.02) in the PTH compared with the placebo group.

First-in-human testing of a wirelessly controlled drug delivery microchip

The first clinical trial of an implantable microchip-based drug delivery device is discussed. Human parathyroid hormone fragment (1-34) [hPTH(1-34)] was delivered from the device in vivo. hPTH(1-34) is the only approved anabolic osteoporosis treatment, but requires daily injections, making patient compliance an obstacle to effective treatment. Furthermore, a net increase in bone mineral density requires intermittent or pulsatile hPTH(1-34) delivery, a challenge for implantable drug delivery products. The microchip-based devices, containing discrete doses of lyophilized hPTH(1-34), were implanted in eight osteoporotic postmenopausal women for 4 months and wirelessly programmed to release doses from the device once daily for up to 20 days. A computer-based programmer, operating in the Medical Implant Communications Service band, established a bidirectional wireless communication link with the implant to program the dosing schedule and receive implant status confirming proper operation. Each woman subsequently received hPTH(1-34) injections in escalating doses. The pharmacokinetics, safety, tolerability, and bioequivalence of hPTH(1-34) were assessed. Device dosing produced similar pharmacokinetics to multiple injections and had lower coefficients of variation. Bone marker evaluation indicated that daily release from the device increased bone formation. There were no toxic or adverse events due to the device or drug, and patients stated that the implant did not affect quality of life.

Balicatib, a cathepsin K inhibitor, stimulates periosteal bone formation in monkeys

Balicatib, an inhibitor of the osteoclastic enzyme cathepsin K, was tested in ovariectomized monkeys, a model for osteoporosis. As expected, ovariectomy-induced bone mass changes were partially prevented by balicatib treatment. Bone turnover was significantly decreased at most sites, but unlike most bone resorption inhibitors, periosteal bone formation rates were increased.

INTRODUCTION

Selective inhibitors of the osteoclastic enzyme cathepsin K have potential in osteoporosis treatment. This study evaluated the efficacy of balicatib (AAE581), a novel inhibitor of human cathepsin K, on bone mass and dynamic histomorphometric endpoints in ovariectomized monkeys.

METHODS

Eighty adult female Macaca fascicularis underwent bilateral ovariectomies and were dosed twice daily by oral gavage with balicatib at 0, 3, 10, and 50 mg/kg for 18 months (groups O, L, M, H, respectively). Approximately 1 month after treatment initiation, the 50 mg/kg dose was decreased to 30 mg/kg. Twenty animals underwent sham-ovariectomies (group S). Bone mass was measured at 3-6 month intervals. At 18 months, vertebra and femur were collected for histomorphometry.

RESULTS

In both spine and femur, group O animals lost BMD and all other groups gained BMD between 0 and 18 months. In balicatib-treated animals, BMD change in the spine was intermediate between group S and O, with groups L and M significantly different from group O. In femur, all three doses of balicatib significantly increased BMD gain relative to group O and group mean values were also higher than group S. Most histomorphometric indices of bone turnover in vertebra and femoral neck were significantly lower than group O with balicatib treatment, except that periosteal bone formation rates (Ps.BFR) were significantly higher. Ps.BFR in mid-femur was also significantly increased by treatment.

CONCLUSIONS

Balicatib partially prevented ovariectomy-induced changes in bone mass, inhibited bone turnover at most sites, and had an unexpected stimulatory effect on periosteal bone formation.

Balicatib, a cathepsin K inhibitor, stimulates periosteal bone formation in monkeys

Balicatib, an inhibitor of the osteoclastic enzyme cathepsin K, was tested in ovariectomized monkeys, a model for osteoporosis. As expected, ovariectomy-induced bone mass changes were partially prevented by balicatib treatment. Bone turnover was significantly decreased at most sites, but unlike most bone resorption inhibitors, periosteal bone formation rates were increased.

INTRODUCTION

Selective inhibitors of the osteoclastic enzyme cathepsin K have potential in osteoporosis treatment. This study evaluated the efficacy of balicatib (AAE581), a novel inhibitor of human cathepsin K, on bone mass and dynamic histomorphometric endpoints in ovariectomized monkeys.

METHODS

Eighty adult female Macaca fascicularis underwent bilateral ovariectomies and were dosed twice daily by oral gavage with balicatib at 0, 3, 10, and 50 mg/kg for 18 months (groups O, L, M, H, respectively). Approximately 1 month after treatment initiation, the 50 mg/kg dose was decreased to 30 mg/kg. Twenty animals underwent sham-ovariectomies (group S). Bone mass was measured at 3-6 month intervals. At 18 months, vertebra and femur were collected for histomorphometry.

RESULTS

In both spine and femur, group O animals lost bone mineral density (BMD), and all other groups gained BMD between 0 and 18 months. In balicatib-treated animals, BMD change in the spine was intermediate between group S and O, with groups L and M significantly different from group O. In femur, all three doses of balicatib significantly increased BMD gain relative to group O, and group mean values were also higher than group S. Most histomorphometric indices of bone turnover in vertebra and femoral neck were significantly lower than group O with balicatib treatment, except that periosteal bone formation rates (Ps.BFR) were significantly higher. Ps.BFR in mid-femur was also significantly increased by treatment.

CONCLUSIONS

Balicatib partially prevented ovariectomy-induced changes in bone mass, inhibited bone turnover at most sites, and had an unexpected stimulatory effect on periosteal bone formation.

The pathogenesis, diagnosis, investigation and management of osteoporosis

With an increasingly ageing population, osteoporosis and osteoporosis-related fractures is fast becoming an important public health problem placing a considerable economic burden on health service resources. This does not account for the substantial pain, disability and indeed mortality incurred after a fracture, particularly a hip fracture. Osteoporosis is a systemic skeletal disorder which results from an imbalance in bone remodeling. This leads to a reduction in bone strength and increased susceptibility to fracture. It affects up to 1 in 2 women and 1 in 5 men. In the past 2 decades, there have been significant advances in bone biology which have helped in the understanding of the pathogenesis of osteoporosis and have led to improved therapies. In developing strategies for fracture prevention, it is important to identify those individuals with the highest fracture risk who will require pharmacological intervention. Treatment is aimed at fracture prevention and includes modification of general lifestyle factors which have been linked to fractures in epidemiological studies and ensuring optimum calcium and vitamin D intake as adjunct to active anti-fracture therapy. A number of drugs are now approved for the treatment of osteoporosis. This review article will describe the pathogenesis of osteoporosis and focus on the methods currently in use for the identification of patients at high fracture risk and will highlight their usefulness and limitations. The existing anti-fracture pharmacotherapies and those in development will be reviewed. Assessment of their effectiveness including the use of biochemical markers of bone turnover in this clinical context will be reviewed.

Effects of anti-osteoporosis medications on fracture healing

A number of fractures are complicated by impaired healing. This is prevalent in certain risk groups such as elderly, osteoporotics, postmenopausal women, and in people with malnutrition. At present, no pharmacologic treatments are available. Thus, there is an unmet need for medications that can stimulate bone healing. Parathyroid hormone (PTH) is the first bone anabolic drug approved for the treatment of osteoporosis and, intriguingly, a number of animal studies prove the ability of PTH to induce fracture healing. PTH may therefore be a potential novel treatment option in humans with impaired healing. However, more randomized clinical trials documenting the clinical efficacy of PTH as a promoter of fracture healing in the clinical setting are warranted. Also, strontium ranelate seems to have beneficial effects on fracture healing under conditions with impaired healing. However, no clinical studies are available so far, and such studies are warranted before any conclusions can be drawn. In contrast, bisphosphonates-which are the most widely used drug for treating osteoporosis-delay the healing process slightly, although apparently not clinically relevant. Finally, a number of newer antiresorptive agents are available, but very few studies have addressed their effects on bone healing.

The bone architecture is enhanced with combined PTH and alendronate treatment compared to monotherapy while maintaining the state of surface mineralization in the OVX rat

This study examined the effect of PTH and alendronate alone and in combination on the bone architecture, mineralization, and estimated mechanics in the OVX rat. Female Wistar rats aged 7-9months were assigned to one of five groups: (1) sham+vehicle, (2) OVX+vehicle, (3) OVX+PTH, (4) OVX+alendronate, and (5) OVX+PTH and alendronate. Surgery was performed at baseline (week 0), and biweekly treatment (15μg/kg of alendronate and/or daily (5days/week) 40μg/kg hPTH(1-34)) was administered from week 6 to week 14. Micro-CT scans of the right proximal tibial metaphysis were made in vivo at weeks 0, 6, 8, 10, 12 and 14 and measurements of bone microarchitecture and estimated mechanical parameters (finite element analysis) were made from the images. Synchrotron radiation micro-CT scans of the proximal tibia and fourth lumbar vertebrae were conducted ex vivo at the study endpoint to determine the degree and spatial distribution of the bone mineralization. Alendronate preserved the microarchitecture after OVX, and increased cortical (9%, p<0.05) and trabecular thickness (5%, p<0.05). PTH mono- and combined therapy induced increases in cortical (25-35%, p<0.05) and trabecular thicknesses (46-48%, p<0.05), resulting in a full restoration of bone volume in the PTH group, and an increase beyond baseline in the combined group. Improvements in estimated mechanical outcomes were observed in all treatment groups by the end of the study, with the combined group experiencing the greatest increase in predicted stiffness (63%, p<0.05). Alendronate treatment increased the peak mineral content above the other treatment groups at the trabecular (tibia: 6% above PTH, 6% above combined, L4: 4% above PTH, 4% above combined) and endocortical (tibia: 4% above PTH, 3% above combined, L4: 1% above PTH, 2% above combined) surfaces, while no differences in mineralization between the PTH and combined groups were observed. Combined treatment resulted in more pronounced improvements of the bone architecture than PTH monotherapy, while maintaining the state of mineralization observed with PTH treatment.

Changes in the contents of enzymatic immature, mature, and non-enzymatic senescent cross-links of collagen after once-weekly treatment with human parathyroid hormone (1-34) for 18 months contribute to improvement of bone strength in ovariectomized monkeys

Improvements in total content of enzymatic cross-linking, the ratio of hydroxylysine-derived enzymatic cross-links, and non-enzymatic advanced glycation end product cross-link formation from once-weekly administration of hPTH(1-34) for 18 months in OVX cynomolgus monkeys contributed to the improvement of bone strength.

INTRODUCTION

Parathyroid hormone (PTH) is used for the treatment of osteoporosis. To elucidate the contribution of material properties to bone strength after once-weekly treatment with hPTH(1-34) in an ovariectomized (OVX) primate model, the content of collagen and enzymatic immature, mature, and non-enzymatic cross-links, collagen maturity, trabecular architecture, and mineralization in vertebrae were simultaneously estimated.

METHODS

Adult female cynomolgus monkeys were divided into four groups (n = 18-20 each) as follows: SHAM group, OVX group, and OVX monkeys given once-weekly subcutaneous injections of hPTH(1-34) either at 1.2 or 6.0 μg/kg (low- or high-PTH groups) for 18 months. The content of collagen, enzymatic and non-enzymatic cross-linking pentosidine, collagen maturity, trabecular architecture, mineralization, and cancellous bone strength of vertebrae were analyzed.

RESULTS

Low-PTH and high-hPTH treatments increased the content of enzymatic immature and mature cross-links, bone volume (BV/TV), and trabecular thickness, and decreased pentosidine, compared with the OVX group. Stepwise logistic regression analysis revealed that BV/TV, the content of total enzymatic cross-links, and calcium content independently affected ultimate load (model R (2) = 0.748, p < 0.001) and breaking energy (model R (2) = 0.702, p < 0.001). BV/TV was the most powerful and enzymatic cross-link content was the second powerful determinant of both ultimate load and breaking energy. The most powerful determinant of stiffness was the enzymatic cross-link content (model R (2) = 0.270, p < 0.001).

CONCLUSION

Once-weekly preventive administration of hPTH(1-34) increased the total contents of immature and mature enzymatic cross-links, which contributed significantly to vertebral cancellous bone strength.

JTT-305, an orally active calcium-sensing receptor antagonist, stimulates transient parathyroid hormone release and bone formation in ovariectomized rats

Intermittent administration of parathyroid hormone (PTH) has a potent anabolic effect on bone in humans and animals. Calcium-sensing receptor (CaSR) antagonists stimulate endogenous PTH secretion through CaSR on the surface of parathyroid cells and thereby may be anabolic agents for osteoporosis. JTT-305 is a potent oral short-acting CaSR antagonist and transiently stimulates endogenous PTH secretion. The objective of the present study was to investigate the effects of JTT-305 on PTH secretion and bone in ovariectomized rats. Female rats, immediately after ovariectomy (OVX), were orally administered vehicle or JTT-305 (0.3, 1, or 3 mg/kg) for 12 weeks. The serum PTH concentrations were transiently elevated with increasing doses of JTT-305. In the proximal tibia, JTT-305 prevented OVX-induced decreases in both the cancellous and total bone mineral density (BMD) except for the 0.3mg/kg dose. At the 3mg/kg dose, JTT-305 increased the mineralizing surface and bone formation rate in histomorphometry. The efficacy of JTT-305 at the 3mg/kg dose on the BMD corresponded to that of exogenous rat PTH1-84 injection at doses between 3 and 10 μg/kg. In conclusion, JTT-305 stimulated endogenous transient PTH secretion and bone formation, and consequently prevented bone loss in OVX rats. These results suggest that JTT-305 is orally active and has the potential to be an anabolic agent for the treatment of osteoporosis.

Parathyroid hormone treatment increases fixation of orthopedic implants with gap healing: a biomechanical and histomorphometric canine study of porous coated titanium alloy implants in cancellous bone

Parathyroid hormone (PTH) administered intermittently is a bone-building peptide. In joint replacements, implants are unavoidably surrounded by gaps despite meticulous surgical technique and osseointegration is challenging. We examined the effect of human PTH(1-34) on implant fixation in an experimental gap model. We inserted cylindrical (10 × 6 mm) porous coated titanium alloy implants in a concentric 1-mm gap in normal cancellous bone of proximal tibia in 20 canines. Animals were randomized to treatment with PTH(1-34) 5 μg/kg daily. After 4 weeks, fixation was evaluated by histomorphometry and push-out test. Bone volume was increased significantly in the gap. In the outer gap (500 μm), the bone volume fraction median (interquartile range) was 27% (20-37%) for PTH and 10% (6-14%) for control. In the inner gap, the bone volume fraction was 33% (26-36%) for PTH and 13% (11-18%) for control. At the implant interface, the bone fraction improved with 16% (11-20%) for PTH and 10% (7-12%) (P = 0.07) for control. Mechanical implant fixation was improved for implants exposed to PTH. For PTH, median (interquartile range) shear stiffness was significantly higher (PTH 17.4 [12.7-39.7] MPa/mm and control 8.8 [3.3-12.4] MPa/mm) (P < 0.05). Energy absorption was significantly enhanced for PTH (PTH 781 [595-1,198.5] J/m(2) and control 470 [189-596] J/m(2)). Increased shear strength was observed but was not significant (PTH 3.0 [2.6-4.9] and control 2.0 [0.9-3.0] MPa) (P = 0.08). Results show that PTH has a positive effect on implant fixation in regions where gaps exist in the surrounding bone. With further studies, PTH may potentially be used clinically to enhance tissue integration in these challenging environments.