Effects of teriparatide on cortical histomorphometric variables in postmenopausal women with or without prior alendronate treatment

Transitory Activation and Improved Transition from Erosion to Formation within Intracortical Bone Remodeling in Hypoparathyroid Patients Treated with rhPTH(1-84)

In hypoparathyroidism, lack of parathyroid hormone (PTH) leads to low calcium levels and decreased bone remodeling. Treatment with recombinant human PTH (rhPTH) may normalize bone turnover. This study aimed to investigate whether rhPTH(1-84) continued to activate intracortical bone remodeling after 30 months and promoted the transition from erosion to formation and whether this effect was transitory when rhPTH(1-84) was discontinued. Cortical histomorphometry was performed on 60 bone biopsies from patients (aged 31 to 78 years) with chronic hypoparathyroidism randomized to either 100 μg rhPTH(1-84) a day (n = 21) (PTH) or similar placebo (n = 21) (PLB) for 6 months as add-on to conventional therapy. This was followed by an open-label extension, where patients extended their rhPTH(1-84) (PTH) (n = 5), continued conventional treatment (CON) (n = 5), or withdrew from rhPTH(1-84) and resumed conventional therapy (PTHw) for an additional 24 months (n = 8). Bone biopsies were collected at months 6 (n = 42) and 30 (n = 18). After 6 and 30 months, the overall cortical microarchitecture (cortical porosity, thickness, pore density, and mean pore diameter) in the PTH group did not differ from that of the PLB/CON and PTHw groups. Still, the PTH group had a significantly and persistently higher percentage of pores undergoing remodeling than the PLB/CON groups. A significantly higher percentage of these pores was undergoing bone formation in the PTH compared with the PLB/CON groups, whereas the percentage of pores with erosion only was not different. This resulted in a shift in the ratio between formative and eroded pores, reflecting a faster transition from erosion to formation in the PTH-treated patients. In the rhPTH(1-84) withdrawal group PTHw, the latter effects of PTH were completely reversed in comparison to those of the PLB/CON groups. In conclusion, rhPTH(1-84) replacement therapy in hypoparathyroidism patients promotes intracortical remodeling and its transition from erosion to formation without affecting the overall cortical microstructure. The effect persists for at least 30 months and is reversible when treatment is withdrawn. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Daily administration of parathyroid hormone slows the progression of basic multicellular units in the cortical bone of the rabbit distal tibia

Basic Multicellular Units (BMUs) conduct bone remodeling, a critical process of tissue turnover which, if imbalanced, can lead to disease, including osteoporosis. Parathyroid hormone (PTH 1-34; Teriparatide) is an osteoanabolic treatment for osteoporosis; however, it elevates the rate of intra-cortical remodeling (activation frequency) leading, at least transiently, to increased porosity. The purpose of this study was to test the hypothesis that PTH not only increases the rate at which cortical BMUs are initiated but also increases their progression (Longitudinal Erosion Rate; LER). Two groups (n = 7 each) of six-month old female New Zealand white rabbits were both administered 30 μg/kg of PTH once daily for a period of two weeks to induce remodeling. Their distal right tibiae were then imaged in vivo by in-line phase contrast micro-CT at the Canadian Light Source synchrotron. Over the following two weeks the first group (PTH) received continued daily PTH while the second withdrawal group (PTHW) was administrated 0.9 % saline. At four weeks all animals were euthanized, their distal tibiae were imaged by conventional micro-CT ex vivo and histomorphometry was performed. Matching micro-CT datasets (in vivo and ex vivo) were co-registered in 3D and LER was measured from 612 BMUs. Counter to our hypothesis, mean LER was lower (p < 0.001) in the PTH group (30.19 ± 3.01 μm/day) versus the PTHW group (37.20 ± 2.77 μm/day). Despite the difference in LER, osteonal mineral apposition rate (On.MAR) did not differ between groups indicating the anabolic effect of PTH was sustained after withdrawal. The slowing of BMU progression by PTH warrants further investigation; slowed resorption combined with elevated bone formation rate, may play an important role in how PTH enhances coupling between resorption and formation within the BMU. Finally, the prolonged anabolic response following withdrawal may have utility in terms of optimizing clinical dosing regimens.

Clinical efficacy of denosumab, teriparatide, and oral bisphosphonates in the prevention of glucocorticoid-induced osteoporosis: a systematic review and meta-analysis

BACKGROUND

Continuous use of glucocorticoids (GCs) has become the primary cause of secondary osteoporosis. Bisphosphonate drugs were given priority over denosumab and teriparatide in the 2017 American College of Rheumatology (ACR) guidelines but have a series of shortcomings. This study aims to explore the efficacy and safety of teriparatide and denosumab compared with those of oral bisphosphonate drugs.

METHODS

We systematically searched studies included in the PubMed, Web of Science, Embase, and Cochrane library databases and included randomized controlled trials that compared denosumab or teriparatide with oral bisphosphonates. Risk estimates were pooled using both fixed and random effects models.

RESULTS

We included 10 studies involving 2923 patients who received GCs for meta-analysis, including two drug base analyses and four sensitivity analyses. Teriparatide and denosumab were superior to bisphosphonates in increasing the bone mineral density (BMD) of the lumbar vertebrae [teriparatide: mean difference [MD] 3.98%, 95% confidence interval [CI] 3.61-4.175%, P = 0.00001; denosumab: MD 2.07%, 95% CI 0.97-3.17%, P = 0.0002]. Teriparatide was superior to bisphosphonates in preventing vertebral fractures and increasing hip BMD [MD 2.39%, 95% CI 1.47-3.32, P < 0.00001]. There was no statistically significant difference between serious adverse events, adverse events, and nonvertebral fracture prevention drugs.

CONCLUSIONS

Teriparatide and denosumab exhibited similar or even superior characteristics to bisphosphonates in our study, and we believe that they have the potential to become first-line GC-induced osteoporosis treatments, especially for patients who have previously received other anti-osteoporotic drugs with poor efficacy.

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

PURPOSE

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

METHODS

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

RESULTS

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

Expansion of the osteocytic lacunar-canalicular system involved in pharmacological action of PTH revealed by AI-driven fluorescence morphometry in female rabbits

Osteoporosis is an age-related disorder that is characterized by reduced bone mass. Its prevention and treatment are important healthcare issues for maintaining social activity in aged societies. Although bone fractures mostly occur at sites of weakened cortical bone, pathophysiological and pharmacological evaluations of bone mass have tended to be predominantly assessed in trabecular bone. To statistically characterize cortical bone remodeling, we originally established multimode fluorescence imaging and artificial intelligence (AI)-driven morphometric analyses in six-month-old female rabbits with well-defined cortical remodeling, similar to that in humans. We evaluated three distinct administration frequencies of teriparatide [TPTD; human parathyroid hormone, hPTH (1–34)]: once (1/w), twice (2/w), and seven times (7/w) a week, with the same total dose (140 μg/kg/week). Our analyses revealed significant expansions of the osteocytic lacunar-canalicular system and Haversian canals accompanied by the development of cortical porosity and endosteal naïve bone formation induced by a frequent administration regimen (7/w) of TPTD; however, once-weekly (1/w) and twice-weekly (2/w) administration of TPTD showed little effect. These findings demonstrate a clear contrast between the effects of frequent and infrequent administration of TPTD on cortical bone metabolism and suggest that osteocytic bone remodeling is involved in the pharmacological action of PTH.

Osteoporosis and Fragility Fractures: currently available pharmacological options and future directions

Osteoporosis is a systemic skeletal disease characterized by low bone mass and microarchitectural deterioration of bone tissue, with a consequent increase in bone fragility and susceptibility to fracture. The average lifetime risk of a 50-year-old woman to suffer a fracture of the spine, hip, proximal humerus, or distal forearm has been estimated at close to 50%. In general, pharmacological treatment is recommended in patients who suffered a fragility fracture because their risk of suffering a subsequent fracture is increased dramatically. Therefore, many guidelines recommend pharmacological treatment in patients without a prevalent fracture if their fracture probability is comparable to or higher than that of a person of the same age with a prevalent fracture. The present review aims to highlight currently available pharmacological treatment options and their antifracture efficacy including safety aspects. Drug classes discussed comprise bisphosphonates, selective estrogen receptor modulators, parathyroid hormone peptides and derivatives, humanized monoclonal antibodies, and estrogens and gestagens and their combinations. Furthermore, a brief glimpse is provided into a potentially promising treatment option that involves mesenchymal stem cells.

Management of patients at very high risk of osteoporotic fractures through sequential treatments

Osteoporosis care has evolved markedly over the last 50 years, such that there are now an established clinical definition, validated methods of fracture risk assessment and a range of effective pharmacological agents. Currently, bone-forming (anabolic) agents, in many countries, are used in those patients who have continued to lose bone mineral density (BMD), patients with multiple subsequent fractures or those who have fractured despite treatment with antiresorptive agents. However, head-to-head data suggest that anabolic agents have greater rapidity and efficacy for fracture risk reduction than do antiresorptive therapies. The European Society for Clinical and Economic Aspects of Osteoporosis, Osteoarthritis and Musculoskeletal Diseases (ESCEO) convened an expert working group to discuss the tools available to identify patients at high risk of fracture, review the evidence for the use of anabolic agents as the initial intervention in patients at highest risk of fracture and consider the sequence of therapy following their use. This position paper sets out the findings of the group and the consequent recommendations. The key conclusion is that the current evidence base supports an "anabolic first" approach in patients found to be at very high risk of fracture, followed by maintenance therapy using an antiresorptive agent, and with the subsequent need for antiosteoporosis therapy addressed over a lifetime horizon.

Effective ancillary role and long-term course of daily or weekly teriparatide treatment on refractory medication-related osteonecrosis of the jaw: a clinical case series

Medication-related osteonecrosis of the jaw (MRONJ) is a potentially severe adverse side effect of antiresorptive agents. However, withdrawal of such agents in patients with osteoporosis may increase the risk of fracture. The treatment of MRONJ is challenging, and standard treatment guidelines have yet to be established. In this study, the aim was to find out whether adjuvant daily or weekly teriparatide (TPTD) injections were beneficial for exposed bony MRONJ lesions compared with standard conservative management. We also studied the complications and the patients' response to TPTD therapy. We enrolled 27 patients (January 2012 - December 2016) with chronic and refractory MRONJ. There were four men and 23 women (85% female). Nine patients who did not select TPTD therapy for several reasons formed the non-TPTD group; the remaining 18 were randomly assigned to the daily (n=9) or weekly (n=9) groups. All patients in both groups continued standard conservative therapy in addition to their daily or weekly subcutaneous injection of TPTD (20 μg or 56.5 μg, respectively). We evaluated the complications of TPTD and its benefits. Three patients in the daily group did not complete the study, resulting in six patients in the daily group, nine in the weekly group, and nine in the non-TPTD group in the final analysis. The exposed bone was completely covered with normal mucosa in all patients in the TPTD groups, and the healing period was shorter than that in the non-TPTD group. No patient had complications of atypical fractures of the femoral head. Daily and weekly TPTD treatment resulted in a shortened treatment period compared with standard conservative therapy, with no increase in the rate of complications or worsening of osteoporosis.

The Effect of Teriparatide on the Hip: A Literature Review

Teriparatide (TPTD) is a bone-forming agent used to treat postmenopausal osteoporosis. Since hip fractures are related to higher morbidity and mortality rates than other fractures, efficacious osteoporosis drugs for the hip are critical. We reviewed research articles reporting the efficacy of TPTD in terms of bone mineral density (BMD), fractures prevention, changes in the outer diameter, cortical thickness and porosity, post-operative periprosthetic BMD loss, and healing of typical and atypical fractures of the hip. Data meta-analyses indicated that TPTD not only increased the BMD of the proximal femur but also decreased the risk of hip fractures. Even though TPTD increases the cortical bone porosity of the proximal femur, the bone strength does not decrease as the majority of the porosity is located at the endocortex; further, it increases the outer diameter and thickens the cortical bone. TPTD stimulates bone remodeling and facilitates callus maturity and fracture healing. There have been many reports on improving the effect of TPTD on the healing of atypical fractures; therefore it is advisable to use TPTD considering the increase benefit compared to the risk.

Role of bone-forming agents in the management of osteoporosis

Recent evidence confirms the superiority of osteoanabolic therapy compared to anti-remodeling drugs for rapid improvement in bone density and fracture risk reduction, providing strong justification for the use of these anabolic agents as the initial therapy in high-risk patients, to be followed by anti-remodeling therapy. This review will highlight the results of recent studies and define the current status of osteoanabolic therapy for osteoporosis.

Combination Therapy of PTH and Antiresorptive Drugs on Osteoporosis: A Review of Treatment Alternatives

Antiresorptive drugs have been widely used for osteoporosis. Intermittent parathyroid hormone (PTH), an anabolic agent, increases osteoblast production rate and inhibits apoptosis of osteoblasts, thus increasing skeletal mass besides improving bone microarchitecture and strength. Combination therapy for osteoporosis produced great interests and controversies. Therefore, we performed a systematic literature search from PubMed, EMBASE, Scopus, Web of Science, CINDHL, and the Cochrane Database of Systematic Reviews using the search terms PTH or teriparatide combined with bisphosphonate, alendronate, ibandronate, risedronate, raloxifene, denosumab, and zoledronic acid with the limit osteoporosis. At last, 36 related articles were included for further analysis. Findings from previous studies revealed that combination therapy in different conditions of naive or previous bisphosphonate treatment might have different outcomes. The use of combination therapy, however, may be an alternative option among osteoporotic patients with a history of bisphosphonate use. Combined teriparatide with denosumab appear to show the most substantial and clinically relevant skeletal benefits to osteoporotic patients. Additional research is necessary to define optimal methods of developing sequential and/or cyclical combinations of PTH and antiresorptive agents.

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)..

Intermittent Parathyroid Hormone Accelerates Stress Fracture Healing More Effectively Following Cessation of Bisphosphonate Treatment

Parathyroid hormone (PTH) and bisphosphonates (BPs), including alendronate (ALN), have opposing effects on bone dynamics. The extent to which PTH remains effective in the treatment of stress fracture (SFx) in the presence of an ongoing BP treatment has not been tested. SFx was induced in 150 female Wistar rats, divided into five equal groups (n = 30). All rats were pretreated with ALN (1 μg/kg^-1/day^-1) for 14 days prior to SFx induction, followed by ALN cessation or continuation for the duration of the experiment; this was combined with daily PTH (8 μg/100 g^-1/day^-1) on SFx induction for 14 days, followed by cessation or continuation of ALN after SFx induction or an equivalent vehicle as a control. Ulnas were examined 2 weeks or 6 weeks following SFx. Two toluidine blue- and two tartrate-resistant acid phosphatase-stained sections were examined for histomorphometric analysis using Osteomeasure software. There was a significant interaction between the effects of time and treatment type on the woven bone width and apposition rate, as well as an improvement in the woven bone architecture. However, woven bone variables remained unaffected by the cessation or continuation of ALN. Cessation of ALN increased osteoclast number when compared with the ALN-PTH continuation group (p = 0.006), and vehicle (p = 0.024) after 2 weeks. There was a significant interaction between the effects of time and treatment type on the number of osteoclasts per unit BMU area and length. The number of osteoclasts per unit BMU area and length was significantly greater in ALN cessation groups. It was concluded that intermittent short-duration iPTH treatment effectively increased remodeling of SFx with a concurrent BP treatment, provided that BP was ceased at the time of SFx. Our results could help develop shorter iPTH treatment protocols for the clinical management of SFxs and guide clinical decision-making to cease BP treatment in cases of SFx. © 2020 The Authors. JBMR Plus published by Wiley Periodicals LLC. on behalf of American Society for Bone and Mineral Research.

Loading modality and age influence teriparatide-induced bone formation in the human femoral neck

Teriparatide (TPTD) reduces risk of both vertebral and nonvertebral fracture, but increases bone mineral density (BMD) much more at the spine than the hip. TPTD and mechanical loading may have a synergistic anabolic effect on BMD, which may help explain these site-specific differences. Under normal daily activity, the femoral neck (FN) is under bending, placing one side under tension and the other under compression. We sought to further understand the relationship between mechanical loading and TPTD at the hip by investigating the effect of tensile versus compressive loading on TPTD stimulated bone formation indices in the human FN. Thirty-eight patients receiving total hip replacements for osteoarthritis were randomized to receive placebo (PBO) or TPTD for a mean treatment duration of 6 weeks prior to surgery, and double tetracycline labeling was administered to allow assessment of bone formation. The FN was harvested during surgery and analyzed for dynamic bone formation indices in the compressive and tensile regions of the endocortical and periosteal envelopes. Regression models relating outcome measures to patient characteristics including sex, age, body weight, and FN geometry were also analyzed. Overall, bone formation was higher with TPTD versus placebo on the endocortical surface, but not the periosteal surface. The level of bone formation in both TPTD and placebo groups was greater on the tensile endocortical surface and the compressive periosteal surface. There was a trend toward decreased endocortical eroded surface with TPTD in the compressive but not the tensile region. Patient age and sex explained the greatest variability in endocortical bone formation, and patient body mass and sex explained the greatest variability in periosteal bone formation. Our data represent the first dynamic comparison of teriparatide treatment under two loading modalities in human FN samples. Future work could determine whether specific hip loading intervention could amplify the benefits of teriparatide on the hip in clinical settings.

Relationship between P1NP, a biochemical marker of bone turnover, and bone mineral density in patients transitioned from alendronate to romosozumab or teriparatide: a post hoc analysis of the STRUCTURE trial

INTRODUCTION

Procollagen type I N-terminal propeptide (P1NP), a bone formation marker, reportedly predicts bone mineral density (BMD) response to teriparatide treatment in treatment-naive patients with osteoporosis. Results from a randomized, phase 3, open-label, active-controlled trial- STRUCTURE-showed that in patients previously treated with bisphosphonates, romosozumab led to gains in hip BMD, which were not observed with teriparatide. This post hoc analysis investigated the comparative utility of early changes in P1NP in predicting BMD response in patients who participated in the STRUCTURE trial, which enrolled patients who switched treatment from bisphosphonates to romosozumab/teriparatide.

MATERIALS AND METHODS

Postmenopausal women (aged 55-90 years) with osteoporosis who had previously taken bisphosphonates were randomized to receive open-label subcutaneous romosozumab (210 mg once monthly; n = 218) or teriparatide (20 µg once daily; n = 218) for 12 months. BMD was assessed by dual-energy X-ray absorptiometry at the proximal femur and lumbar spine (LS) at baseline and months 6 and 12. To assess the utility of P1NP, the positive predictive value of increase from baseline in P1NP of > 10 µg/L at month 1 and achievement of various thresholds of percent change from baseline in BMD at month 12 were evaluated.

RESULTS

Overall, 95% (191/202) of patients in the romosozumab group and 91% (183/201) in the teriparatide group demonstrated an increase in P1NP of > 10 µg/L from baseline at month 1. Among these patients, 18% and 3% of romosozumab-treated patients versus 60% and 12% of teriparatide-treated patients showed no increase from baseline (i.e., ≤ 0%) in total hip and LS BMD, respectively, at month 12. These data indicate that in patients switching from bisphosphonates to a bone-forming therapy, increases in P1NP do not help predict the hip BMD response. Although most patients treated with either teriparatide or romosozumab showed an increase in P1NP, the majority of patients on romosozumab showed an increase in hip BMD, while more than half of the patients on teriparatide did not. Teriparatide therapy did not increase total hip BMD in the majority of patients who transitioned from bisphosphonates to teriparatide.

CONCLUSIONS

Thus, increases in P1NP were not predictive of BMD response in the teriparatide group because in approximately 60% of the patients who were administered teriparatide, the hip BMD decreased independent of the change in P1NP levels.

Pretreatment with Pamidronate Decreases Bone Formation but Increases Callus Bone Volume in a Rat Closed Fracture Model

Clinical concerns have been raised over prior exposure to bisphosphonates impairing fracture healing. To model this, groups of male Wistar rats were assigned to saline control or treatment groups receiving 0.15 mg/kg (low dose), 0.5 mg/kg (medium dose), and 5 mg/kg (high dose) Pamidronate (PAM) twice weekly for 4 weeks. At this point, closed fractures were made using an Einhorn apparatus, and bisphosphonate dosing was continued until the experimental endpoint. Specimens were analyzed at 2 and 6 weeks (N = 8 per group per time point). Twice weekly PAM dosing was found to have no effect on early soft callus remodeling at 2 weeks post fracture. At this time point, the highest dose PAM group gave significant increases in bone volume (+ 10%, p < 0.05), bone mineral content (+ 30%, p < 0.01), and bone mineral density (+ 10%, p < 0.01). This PAM dosing regimen showed more substantive effects on hard callus at 6 weeks post fracture, with PAM treatment groups showing + 46-79% increased bone volume. Dynamic bone labeling showed reduced calcein signal in the PAM-treated calluses (38-63%, p < 0.01) and reduced MAR (32-49%, p < 0.01), suggesting a compensatory reduction in bone anabolism. These data support the concept that bisphosphonates lead to profound decreases in bone turnover in fracture repair, however, this does not affect soft callus remodeling.

Standard Versus Cyclic Teriparatide and Denosumab Treatment for Osteoporosis: A Randomized Trial

In the absence of an intervening antiresorptive agent, cyclic administration of teriparatide does not increase bone mineral density (BMD) more than standard daily therapy. Because denosumab is a potent antiresorptive agent with a rapid off-effect, we hypothesized that it might be the optimal agent to help maximize bone gains with cyclic teriparatide. In this 3-year protocol, 70 postmenopausal women with osteoporosis were randomized to 18 months of teriparatide followed by 18 months of denosumab (standard) or three separate 12-month cycles of 6 months of teriparatide followed by 6 months of denosumab (cyclic). BMD (dual-energy X-ray absorptiometry [DXA]) measurements of lumbar spine (LS), total hip (TH), femoral neck (FN), and 1/3 radius (RAD) were performed every 6 months and total body bone mineral (TBBM) at 18 and 36 months. Baseline descriptive characteristics did not differ between groups except for a minimal difference in LS BMD but not T-score (mean age 65 years, mean LS T-score - 2.7). In the standard group, BMD increments at 36 months were: LS 16%, TH 4%, FN 3%, and TBBM 4.8% (all p < 0.001 versus baseline). In the cyclic group, 36-month BMD increments were similar: LS 12%, TH 4%, FN 4%, and TBBM 4.1% (all p < 0.001 versus baseline). At 36 months, the LS BMD increase with standard was slightly larger than with cyclic (p = 0.04), but at 18 months, in the cyclic group, there was no decline in RAD or TBBM (p = 0.007 and < 0.001, respectively, versus standard). Although the cyclic regimen did not improve BMD compared with standard at 36 months, there appeared to be a benefit at 18 months, especially in the highly cortical skeletal sites. This could be clinically relevant in patients at high imminent risk of fracture, particularly at nonvertebral sites. © 2019 American Society for Bone and Mineral Research. © 2019 American Society for Bone and Mineral Research.

Combination and sequential treatment in women with postmenopausal osteoporosis

Introduction: Since postmenopausal osteoporosis is a chronic, potentially disabling condition requiring long-term treatment, the physician is expected to decide the optimal treatment strategy, e.g. how to use the available osteoanabolic and antiresorptive agents, sequentially or in combination, in the most effective and safe way, based on personalized patient care.Areas covered: Herein, the authors outline clinical data regarding the efficacy and safety of various sequential treatment strategies. More specifically, they compare the efficacy of osteoanabolic agents when they precede or follow antiresorptive treatment, as well as the efficacy of antiresorptives following other antiresorptives. Finally, the authors quote and discuss available evidence regarding the efficacy and safety of the co-administration of osteoanabolics and antiresorptives in comparison with monotherapies.Expert opinion: Initiation with an osteoanabolic agent followed by an antiresorptive seems to be the optimal treatment sequence, at least in patients with severe osteoporosis. Osteoanabolic treatment following antiresorptives seems to lead in more modest responses in bone mineral density (BMD) and bone turnover markers. Combination therapy with teriparatide and denosumab or zoledronate has achieved higher BMD gains compared to each agent alone; however, due to the high cost, combination therapy is rarely compensated. On the contrary, the combination of teriparatide with alendronate results in smaller BMD increases than TPTD monotherapy.

Reduced Bone Modeling and Unbalanced Bone Remodeling: Targets for Antiresorptive and Anabolic Therapy

Bone loss during advancing age is the net result of reduced modeling-based bone formation upon the outer (periosteal) envelope and unbalanced remodeling by basic multicellular units (BMUs) upon the three (intracortical, endocortical, and trabecular) components of the inner (endosteal) bone envelope. Each BMU deposits less bone than resorbed, reducing total bone volume and deteriorating the microstructure of the diminished residual bone volume.Antiresorptive agents like bisphosphonates reduce, but do not abolish, the rate of bone remodeling - fewer BMUs remodel, "turn over," the volume of bone. Residual unbalanced remodeling continues to slowly reduce total bone volume and deteriorate bone microstructure. By contrast, denosumab virtually abolishes remodeling so the decrease in bone volume and the deterioration in microstructure cease. The less remodeled matrix remains, leaving more time to complete the slow process of secondary mineralization which reduces the heterogeneity of matrix mineralization and allows it to become glycosylated, changes that may make the smaller and microstructurally deteriorated bone volume more brittle. Neither class of antiresorptive restores bone volume or its microstructure, despite increases in bone mineral density misleadingly suggesting otherwise. Nevertheless, these agents reduce vertebral and hip fractures by 50-60% but only reduce nonvertebral fractures by 20-30%.Restoring bone volume, microstructure, and material composition, "curing" bone fragility, may be partly achieved using anabolic therapy. Teriparatide, and probably abaloparatide, produce mainly remodeling-based bone formation by acting on BMUs existing in their resorption, reversal, or formation phase at the time of treatment and by promoting bone formation in newly initiated BMUs. Romosozumab produces modeling-based bone formation almost exclusively and decreases the surface extent of bone resorption. All three anabolic agents reduce vertebral fracture risk relative to untreated controls; parathyroid hormone 1-34 and romosozumab reduce vertebral fracture risk more greatly than risedronate or alendronate, respectively. Evidence for nonvertebral or hip fracture risk reduction relative to untreated or antiresorptive-treated controls is lacking or inconsistent. Only one study suggests sequential romosozumab followed by alendronate reduces vertebral, nonvertebral, and hip fracture risk compared to continuous alendronate alone. Whether combined antiresorptive and anabolic therapy result in superior fracture risk reduction than monotherapy is untested.

Mapping theme trends and recognizing hot spots in postmenopausal osteoporosis research: a bibliometric analysis

Background

This study aimed to draw a series of scientific maps to quantitatively and qualitatively evaluate hot spots and trends in postmenopausal osteoporosis research using bibliometric analysis.

Methods

Scientific papers published on postmenopausal osteoporosis were extracted from the Web of Science Core Collection and PubMed database. Extracted information was analyzed quantitatively with bibliometric analysis by CiteSpace, the Online Analysis Platform of Literature Metrology and Bibliographic Item Co-Occurrence Matrix Builder (BICOMB). To explore the hot spots in this field, co-word biclustering analysis was conducted by gCLUTO based on the major MeSH terms/MeSH subheading terms-source literatures matrix.

Results

We identified that a total of 5,247 publications related to postmenopausal osteoporosis were published between 2013 and 2017. The overall trend decreased from 1,071 literatures in 2013 to 1,048 literatures in 2017. Osteoporosis International is the leading journal in the field of postmenopausal osteoporosis research, both in terms of impact factor score (3.819) and H-index value (157). The United States has retained a top position and has exerted a pivotal influence in this field. The University of California, San Francisco was identified as a leading institution for research collaboration, and Professors Reginster and Kanis have made great achievements in this area. Eight research hot spots were identified.

Conclusions

Our study found that in the past few years, the etiology and drug treatment of postmenopausal osteoporosis have been research hot spots. They provide a basis for the study of the pathogenesis of osteoporosis and guidelines for the drug treatment of osteoporosis.

Effects of Intermittent Administration of Parathyroid Hormone and Parathyroid Hormone-Related Protein on Fracture Healing: A Narrative Review of Animal and Human Studies

Intermittent administration of parathyroid hormone (PTH) stimulates skeletal remodeling and is a potent anabolic agent in bone. PTH‐related protein (PTHrP) is anabolic acting on the same PTH1 receptor and is in therapeutic use for osteoporosis. The body of literature for PTH actions in fracture healing is emerging with promising yet not entirely consistent results. The objective of this review was to perform a literature analysis to extract up‐to‐date knowledge on the effects of intermittent PTH and PTHrP therapy in bone fracture healing. A literature search of the PubMed database was performed. Clinical case studies and articles related to “regeneration,” “implant,” and “distraction osteogenesis” were excluded. A narrative review was performed to deliberate the therapeutic potential of intermittent PTH administration on fracture healing. A smaller number of studies centered on the use of PTHrP or a PTHrP analog were also reviewed. Animal studies clearly show that intermittent PTH therapy promotes fracture healing and revealed the strong therapeutic potential of PTH. Human subject studies were fewer and not as consistent as the animal studies yet provide insight into the potential of intermittent PTH administration on fracture healing. Differences in outcomes for animal and human studies appear to be attributed partly to variable doses, fracture sites, age, remodeling patterns, and bone architectures, although other factors are involved. Future studies to examine the dose, timing, and duration of PTH administration will be necessary to further delineate the therapeutic potential of PTH for fracture healing in humans. © 2019 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Treatment of Osteoporosis, with a Focus on 2 Monoclonal Antibodies

Osteoporosis is a common skeletal disease characterized by bone loss and subsequent increased risk of fragility fractures. Recent advances in our mechanistic understanding of molecular communications among osteoblasts, osteoclasts, and osteocytes give insight into the important roles of the canonical Wnt/β-catenin pathway and the RANK/RANKL/OPG pathway in the process of bone remodeling. Due to the translation of the canonical Wnt/β-catenin pathway and the RANK/RANKL/OPG pathway in the regulation of osteoblasts and osteoclasts, new targets have been studied in recent years, such as sclerostin and receptor activator of NF-κB ligand (RANKL). In this review, we first introduce the signaling pathways involved in interactions among osteoblasts, osteoclasts, and osteocytes. Next, we describe clinical trials of denosumab and romosozumab, which are monoclonal antibodies that target RANKL and sclerostin, respectively. We analyze the efficacy of these drugs and provide a profile for the management of osteoporosis.

Differing Effects of Parathyroid Hormone, Alendronate, and Odanacatib on Bone Formation and on the Mineralization Process in Intracortical and Endocortical Bone of Ovariectomized Rabbits

Bone is formed by deposition of a collagen-containing matrix (osteoid) that hardens over time as mineral crystals accrue and are modified; this continues until bone remodeling renews that site. Pharmacological agents for osteoporosis differ in their effects on bone remodeling, and we hypothesized that they may differently modify bone mineral accrual. We, therefore, assessed newly formed bone in mature ovariectomized rabbits treated with the anti-resorptive bisphosphonate alendronate (ALN-100µ g/kg/2×/week), the anabolic parathyroid hormone (PTH (1-34)-15µ g/kg/5×/week), or the experimental anti-resorptive odanacatib (ODN 7.5 µM/day), which suppresses bone resorption without suppressing bone formation. Treatments were administered for 10 months commencing 6 months after ovariectomy (OVX). Strength testing, histomorphometry, and synchrotron Fourier-transform infrared microspectroscopy were used to measure bone strength, bone formation, and mineral accrual, respectively, in newly formed endocortical and intracortical bone. In Sham and OVX endocortical and intracortical bone, three modifications occurred as the bone matrix aged: mineral accrual (increase in mineral:matrix ratio), carbonate substitution (increase in carbonate:mineral ratio), and collagen molecular compaction (decrease in amide I:II ratio). ALN suppressed bone formation but mineral accrued normally at those sites where bone formation occurred. PTH stimulated bone formation on endocortical, periosteal, and intracortical bone surfaces, but mineral accrual and carbonate substitution were suppressed, particularly in intracortical bone. ODN treatment did not suppress bone formation, but newly deposited endocortical bone matured more slowly with ODN, and ODN-treated intracortical bone had less carbonate substitution than controls. In conclusion, these agents differ in their effects on the bone matrix. While ALN suppresses bone formation, it does not modify bone mineral accrual in endocortical or intracortical bone. While ODN does not suppress bone formation, it slows matrix maturation. PTH stimulates modelling-based bone formation not only on endocortical and trabecular surfaces, but may also do so in intracortical bone; at this site, new bone deposited contains less mineral than normal.

Teriparatide Treatment Increases Mineral Content and Volume in Cortical and Trabecular Bone of Iliac Crest: A Comparison of Infrared Imaging With X-Ray-Based Bone Assessment Techniques

Teriparatide increases bone mass primarily through remodeling of older or damaged bone and abundant replacement with new mineralizing bone. This post hoc analysis investigated whether dual-energy X-ray absorptiometric (DXA) areal bone mineral density (aBMD) measurement adequately reflects changes of mineral and organic matrix content in cortical and trabecular bone. Paired biopsies and aBMD measurements were obtained before and at end of 2 years of teriparatide treatment from postmenopausal women with osteoporosis who were either alendronate pretreated (mean, 57.5 months) or osteoporosis-treatment naive. Biopsies were assessed by micro-computed tomography (μCT) to calculate mean cortical width (Ct.Wi), cortical area (Ct.Ar), and trabecular bone volume fraction (BV/TV). Fourier transformed infrared imaging (pixel size ∼6.3 × 6.3 μm² ) was utilized to calculate mineral and organic matrix density (mean absorption/pixel), as well as total mineral and organic contents of cortical and cancellous compartments (sum of all pixels in the compartment). Effect of pretreatment over time was analyzed using mixed model repeated measures. μCT derived Ct.Wi and BV/TV increased, accompanied by similar increases in the overall mineral contents of their respective bone compartments. Mineral density did not change. Marked increases in the total content of both mineral and organic matrix associated with volumetric growth in both compartments consistently exceeded those of aBMD. Increases in organic matrix exceeded increases in mineral content in both cortical and trabecular compartments. For percent changes, only change in Ct.Wi correlated to change in femoral neck aBMD (r = .38, p = 0.043), whereas no other significant correlations of Ct.Wi or BV/TV with lumbar spine, total hip, or femoral neck aBMD were demonstrable. These data indicate that 2 years of teriparatide treatment leads to an increased bone organic matrix and mineral content in the iliac crest. The magnitude of these increases in the iliac crest were not detected with conventional aBMD measurements at other skeletal sites. © 2018 American Society for Bone and Mineral Research.

The Effects of Long-term Administration of rhPTH(1-84) in Hypoparathyroidism by Bone Histomorphometry

Hypoparathyroidism is a rare disorder that is associated with abnormal bone properties. Recombinant human parathyroid hormone (1-84) [rhPTH(1-84)] in short-term studies has beneficial skeletal effects. Although rhPTH(1-84) will likely be used indefinitely, long-term effects on skeletal microstructure are unknown. We therefore studied histomorphometric changes with transiliac crest bone biopsies before and after 8.3 ± 1 years of rhPTH(1-84) in 13 hypoparathyroid subjects compared with 45 controls. Before institution of rhPTH(1-84), skeletal remodeling indices were markedly suppressed. With long-term treatment, indices of bone remodeling increased. Mineralizing surface increased by 26-fold (0.3 ± 1 to 7.9 ± 7%, p = 0.003), bone formation rate increased by 15-fold (0.003 ± 0.01 to 0.047 ± 0.05 μm² /μm/day, p = 0.007), osteoid width doubled (1.9 ± 1 to 4.3 ± 1 lamellae, p = 0.017), and osteoid surface tripled (3.3 ± 3 to 10.8 ± 6%, p = 0.011). Bone resorption as measured by eroded surface increased (4.6 ± 2 to 7.5 ± 3%, p = 0.021). Structural changes demonstrated intratrabecular tunneling, with increases in cancellous bone volume (19.6 ± 5 to 29.1 ± 11%, p = 0.017) and trabecular number (1.8 ± 1 to 2.5 ± 1 #/mm, p = 0.025). Cortical porosity tended to increase (6.3 ± 5 to 9.5 ± 3%, p = 0.07). Mineralizing surface, osteoid surface, and eroded surface surpassed control levels, as did cancellous bone volume, trabecular number, and cortical porosity. These data, the first to reflect such long exposure of any PTH for any disease, illustrate that PTH establishes and maintains a new skeletal state for at least 8 years in hypoparathyroidism. © 2018 American Society for Bone and Mineral Research.

Effects of osteoporosis drug treatments on cortical and trabecular bone in the femur using DXA-based 3D modeling

Effects of osteoporosis drugs on proximal femur cortical and trabecular bone were studied using dual-energy x-ray absorptiometry (DXA)-based 3D modeling method. Changes observed in this head-to-head study were consistent with those obtained using computed tomography in the literature.

INTRODUCTION

The aim of the present study was to assess the effects of osteoporosis drugs on cortical and trabecular bone at the proximal femur using DXA-based 3D modeling.

METHODS

We retrospectively analyzed 155 patients stratified by treatments: naive of treatment (NAIVE), alendronate (AL), denosumab (DMAB), and teriparatide (TPTD). DXA scans were performed at baseline and after treatment, and areal bone mineral density at spine and femur were measured. A software algorithm (3D-SHAPER) was used to derive 3D models from hip DXA scans and compute: trabecular and cortical volumetric BMD (vBMD), cortical thickness (Cth), and cortical surface BMD (cortical sBMD). Changes from baseline were normalized at 24 months and evaluated in terms or percentage.

RESULTS

After 24 months, a non-significant decrease was observed for trabecular vBMD, Cortical sBMD, Cth, and cortical vBMD (- 2.3, - 0.8, - 0.3, and - 0.5%) in the NAIVE group. Under AL and DMAB, significant increases were observed in trabecular vBMD (3.8 and 7.3%), cortical vBMD (1.4 and 2.0%), and cortical sBMD (1.5 and 3.6%). An increase in Cth was observed in patients under DMAB (1.8%). Under TPTD, a significant increase in Trabecular vBMD was observed (5.9%) associated with a non-significant increase of Cth (+ 1%) concomitant with a decrease in cortical vBMD (- 1.1%).

CONCLUSION

Results obtained in this head-to-head study are consistent with those obtained using computed tomography in the literature. DXA-based modeling techniques could complement standard DXA examination to monitor treatment effects on trabecular and cortical compartments.

Effect of Teriparatide Treatment on Circulating Periostin and Its Relationship to Regulators of Bone Formation and BMD in Postmenopausal Women With Osteoporosis

CONTEXT

Treatment of postmenopausal osteoporosis with teriparatide parathyroid hormone amino terminal 1-34 increases bone formation and improves bone microarchitecture. A possible modulator of action is periostin. In vitro experiments have shown that periostin might regulate osteoblast differentiation and bone formation through Wnt signaling. The effect of teriparatide on periostin is not currently known.

OBJECTIVES

To determine the effect of teriparatide treatment on circulating levels of periostin and other regulators of bone formation and investigate how changes in periostin relate to changes in bone turnover markers, regulators of bone formation, and bone mineral density (BMD).

PARTICIPANTS AND DESIGN

Twenty women with osteoporosis; a 2-year open-label single-arm study.

INTERVENTION

Teriparatide 20 µg was administered by subcutaneous injection daily for 104 weeks. Periostin, sclerostin, and Dickkopf-related protein 1, procollagen type I N-terminal propeptide (PINP), and C-telopeptide of type I collagen were measured in fasting serum collected at baseline (two visits) and then at weeks 1, 2, 4, 12, 26, 52, 78, and 104. BMD was measured at the lumbar spine, total hip, and femoral neck using dual energy x-ray absorptiometry.

RESULTS

Periostin levels increased by 6.6% [95% confidence interval (CI), -0.4 to 13.5] after 26 weeks of teriparatide treatment and significantly by 12.5% (95% CI, 3.3 to 21.0; P < 0.01) after 52 weeks. The change in periostin correlated positively with the change in the lumbar spine BMD at week 52 (r = 0.567; 95% CI, 0.137 to 0.817; P < 0.05) and femoral neck BMD at week 104 (r = 0.682; 95% CI, 0.261 to 0.885; P < 0.01).

CONCLUSIONS

Teriparatide therapy increases periostin secretion; it is unclear whether this increase mediates the effect of the drug on bone.

Local delivery of a novel PTHrP via mesoporous bioactive glass scaffolds to improve bone regeneration in a rat posterolateral spinal fusion model

With the development of tissue engineering, bone defects, such as fractured long bones or cavitary lesions, may be efficiently repaired and reconstructed using bone substitutes. However, high rates of fusion failure remain unavoidable in spinal fusion surgery owing to the lack of appropriate materials for bone regeneration under such challenging conditions. Parathyroid hormone (PTH), a major regulator of bone remodeling, exerts both anabolic and catabolic effects. In this study, we modified PTH(1-34) and designed and synthesized a novel PTH-related peptide, namely PTHrP-1. Further, we fabricated a local PTHrP delivery device from mesoporous bioactive glass (MBG) to address the need for a suitable material in spinal fusion surgery. Using MBG scaffolds as a control, the biological properties of PTHrP-MBG scaffolds were evaluated in terms of attachment, proliferation, and alkaline phosphatase activity, as well as osteogenic gene and angiogenic gene expression in co-cultured rat bone marrow mesenchymal stem cells (rBMSCs) in vitro. Furthermore, PTHrP-1-MBG scaffolds were tested in a rat posterolateral spinal fusion model. Our data showed that PTHrP-1-MBG scaffolds possessed good ability to facilitate attachment and stimulation of rBMSC proliferation and differentiation. Importantly, the in vivo results revealed that the PTHrP-1-MBG scaffolds facilitated faster new bone formation and a higher rate and quality of spinal fusion. Therefore, the results suggest that devices consisting of the present novel PTHrP and MBG possess wider potential applications in bone regeneration and should serve as a promising bone substitute for spinal fusion.

Bone-related Circulating MicroRNAs miR-29b-3p, miR-550a-3p, and miR-324-3p and their Association to Bone Microstructure and Histomorphometry

The assessment of bone quality and the prediction of fracture risk in idiopathic osteoporosis (IOP) are complex prospects as bone mineral density (BMD) and bone turnover markers (BTM) do not indicate fracture-risk. MicroRNAs (miRNAs) are promising new biomarkers for bone diseases, but the current understanding of the biological information contained in the variability of miRNAs is limited. Here, we investigated the association between serum-levels of 19 miRNA biomarkers of idiopathic osteoporosis to bone microstructure and bone histomorphometry based upon bone biopsies and µCT (9.3 μm) scans from 36 patients. Four miRNAs were found to be correlated to bone microarchitecture and seven miRNAs to dynamic histomorphometry (p < 0.05). Three miRNAs, namely, miR-29b-3p, miR-324-3p, and miR-550a-3p showed significant correlations to histomorphometric parameters of bone formation as well as microstructure parameters. miR-29b-3p and miR-324-p were found to be reduced in patients undergoing anti-resorptive therapy. This is the first study to report that serum levels of bone-related miRNAs might be surrogates of dynamic histomorphometry and potentially reveal changes in bone microstructure. Although these findings enhance the potential value of circulating miRNAs as bone biomarkers, further experimental studies are required to qualify the clinical utility of miRNAs to reflect dynamic changes in bone formation and microstructure.

Effect of osteoporosis treatment agents on the cortical bone osteocyte microenvironment in adult estrogen-deficient, osteopenic rats

Though osteoporosis is a significant cause of disability worldwide, treatment with pharmacologic agents decreases risk of fragility fracture. Though these treatments act through the bone remodeling system to improve bone mass, it is unclear if they alter the response of bone to mechanical loading at the level of the osteocyte. This pre-clinical study determined the relationship between microstructural bone tissue properties and osteocyte lacunar size and density to strain around osteocytes with standard osteoporosis treatment or sequential therapies. Six-month-old female ovariectomized (OVX) Sprague-Dawley rats were cycled through various sequences of pharmacological treatments [alendronate (Aln), raloxifene (Ral) and human parathyroid hormone-1,34 (PTH)] for three month intervals, over nine months. Linear nanoindentation mapping was used to determine Young's modulus in perilacunar and bone matrix regions around cortical bone osteocyte lacunae. Measurements of lacunar diameter and density were completed. Treatment-related differences in Young's modulus in the perilacunar and bone matrix regions were not observed. We confirmed previous data that showed that the bone matrix region was stiffer than the perilacunar matrix region. Whole bone material properties were correlated to perilacunar matrix stiffness. Finite element models predicted a range of mechanical strain amplification factors estimated at the osteocyte across treatment groups. In summary, though the perilacunar matrix near cortical osteocyte lacuna is not as stiff as bone matrix further away, osteoporosis treatment agents do not affect the stiffness of bone tissue near osteocyte lacunae.

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Monotherapy with osteoporosis treatment agents does not affect the stiffness of bone tissue around osteocyte lacunae.

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Sequential use of osteoporosis treatment agents does not affect bone tissue stiffness around osteocyte lacunae.

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Perilacunar cortical bone tissue is not as stiff as bone matrix further from osteocyte lacunae.

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Whole bone material properties are negatively correlated to the stiffness of perilacunar bone tissue.

Romosozumab (sclerostin monoclonal antibody) versus teriparatide in postmenopausal women with osteoporosis transitioning from oral bisphosphonate therapy: a randomised, open-label, phase 3 trial

BACKGROUND

Previous bisphosphonate treatment attenuates the bone-forming effect of teriparatide. We compared the effects of 12 months of romosozumab (AMG 785), a sclerostin monoclonal antibody, versus teriparatide on bone mineral density (BMD) in women with postmenopausal osteoporosis transitioning from bisphosphonate therapy.

METHODS

This randomised, phase 3, open-label, active-controlled study was done at 46 sites in North America, Latin America, and Europe. We enrolled women (aged ≥55 to ≤90 years) with postmenopausal osteoporosis who had taken an oral bisphosphonate for at least 3 years before screening and alendronate the year before screening; an areal BMD T score of -2·5 or lower at the total hip, femoral neck, or lumbar spine; and a history of fracture. Patients were randomly assigned (1:1) via an interactive voice response system to receive subcutaneous romosozumab (210 mg once monthly) or subcutaneous teriparatide (20 μg once daily). The primary endpoint was percentage change from baseline in areal BMD by dual-energy x-ray absorptiometry at the total hip through month 12 (mean of months 6 and 12), which used a linear mixed effects model for repeated measures and represented the mean treatment effect at months 6 and 12. All randomised patients with a baseline measurement and at least one post-baseline measurement were included in the efficacy analysis. This trial is registered with ClinicalTrials.gov, number NCT01796301.

FINDINGS

Between Jan 31, 2013, and April 29, 2014, 436 patients were randomly assigned to romosozumab (n=218) or teriparatide (n=218). 206 patients in the romosozumab group and 209 in the teriparatide group were included in the primary efficacy analysis. Through 12 months, the mean percentage change from baseline in total hip areal BMD was 2·6% (95% CI 2·2 to 3·0) in the romosozumab group and -0·6% (-1·0 to -0·2) in the teriparatide group; difference 3·2% (95% CI 2·7 to 3·8; p<0·0001). The frequency of adverse events was generally balanced between treatment groups. The most frequently reported adverse events were nasopharyngitis (28 [13%] of 218 in the romosozumab group vs 22 [10%] of 214 in the teriparatide group), hypercalcaemia (two [<1%] vs 22 [10%]), and arthralgia (22 [10%] vs 13 [6%]). Serious adverse events were reported in 17 (8%) patients on romosozumab and in 23 (11%) on teriparatide; none were judged treatment related. There were six (3%) patients in the romosozumab group compared with 12 (6%) in the teriparatide group with adverse events leading to investigational product withdrawal.

INTERPRETATION

Transition to a bone-forming agent is common practice in patients treated with bisphosphonates, such as those who fracture while on therapy. In such patients, romosozumab led to gains in hip BMD that were not observed with teriparatide. These data could inform clinical decisions for patients at high risk of fracture.

FUNDING

Amgen, Astellas, and UCB Pharma.

Greater Gains in Spine and Hip Strength for Romosozumab Compared With Teriparatide in Postmenopausal Women With Low Bone Mass

Romosozumab is a monoclonal antibody that inhibits sclerostin and has been shown to reduce the risk of fractures within 12 months. In a phase II, randomized, placebo-controlled clinical trial of treatment-naïve postmenopausal women with low bone mass, romosozumab increased bone mineral density (BMD) at the hip and spine by the dual effect of increasing bone formation and decreasing bone resorption. In a substudy of that trial, which included placebo and teriparatide arms, here we investigated whether those observed increases in BMD also resulted in improvements in estimated strength, as assessed by finite element analysis. Participants received blinded romosozumab s.c. (210 mg monthly) or placebo, or open-label teriparatide (20 μg daily) for 12 months. CT scans, obtained at the lumbar spine (n = 82) and proximal femur (n = 46) at baseline and month 12, were analyzed with finite element software (VirtuOst, O.N. Diagnostics) to estimate strength for a simulated compression overload for the spine (L₁ vertebral body) and a sideways fall for the proximal femur, all blinded to treatment assignment. We found that, at month 12, vertebral strength increased more for romosozumab compared with both teriparatide (27.3% versus 18.5%; p = 0.005) and placebo (27.3% versus -3.9%; p < 0.0001); changes in femoral strength for romosozumab showed similar but smaller changes, increasing more with romosozumab versus teriparatide (3.6% versus -0.7%; p = 0.027), and trending higher versus placebo (3.6% versus -0.1%; p = 0.059). Compartmental analysis revealed that the bone-strengthening effects for romosozumab were associated with positive contributions from both the cortical and trabecular bone compartments at both the lumbar spine and hip. Taken together, these findings suggest that romosozumab may offer patients with osteoporosis a new bone-forming therapeutic option that increases both vertebral and femoral strength within 12 months. © 2017 American Society for Bone and Mineral Research.

Using Osteoporosis Therapies in Combination

PURPOSE OF REVIEW

The objective of this review is to update evidence regarding the use of osteoporosis drugs in sequence or in combination to optimize increases in bone mass and strength.

RECENT FINDINGS

Simultaneous use of denosumab plus teriparatide produces larger increases in BMD than does monotherapy. The use of bisphosphonates or denosumab after teriparatide results in progressive gains in BMD. When switching from bisphosphonates and especially denosumab to teriparatide, an overlap of 6-12 months may prevent the transient loss of BMD in cortical sites. Phase 3 trials document fracture risk reduction with anabolic therapy for 12-18 months followed by an anti-remodeling drug. With the exception of adding teriparatide to ongoing denosumab therapy, there is little evidence to support the use of more than one osteoporosis drug at a time. In contrast, sequential therapy regimens of anabolic drugs followed by potent anti-remodeling agents will be the new standard for treating patients at imminent risk of fracture.

Starch-derived absorbable polysaccharide hemostat enhances bone healing via BMP-2 protein

Surgical hemostasis is critical in reducing the likelihood of excessive bleeding and blood transfusion. In treating some cases, commonly used hemostatic agent showed limited efficacy and prolonged degradation and clearance, causing an inhibition of bone healing. Starch absorbable polysaccharide (SAPH) is a novel hemostatic agent made from a plant starch, which can be completely absorbed and achieve better hemostatic effects than many commonly used hemostatic agents. However, whether SAPH can induce a promotion of bone healing remains unknown. In this study, we used a model of rabbit parietal bone defect and a mouse osteoblast cell line MC3T3-E1 to evaluate the effects of SAPH on bone healing. We found that SAPH significantly decreased bone healing scores, reduced defective area of parietal bone, and increased the areas of bone trabeculae and cavitas medullaris. In addition, SAPH enhanced MC3T3-E1 osteoblasts proliferation, up-regulated the expressions of alkaline phosphatase (ALP) and osteocalcin and increased the level of bone morphogenetic protein 2 (BMP-2) in MC3T3-E1 osteoblasts. These SAPH-induced benefits in MC3T3-E1 osteoblasts were significantly abolished by the application of BMP-2-siRNA. These findings suggested that SAPH enhances bone healing, promotes the proliferation, differentiation and maturation of osteoblast by up-regulating BMP-2 expression in osteoblastic cells.

Time course of disassociation of bone formation signals with bone mass and bone strength in sclerostin antibody treated ovariectomized rats

Sclerostin antibodies increase bone mass by stimulating bone formation. However, human and animal studies show that bone formation increases transiently and returns to pre-treatment level despite ongoing antibody treatment. To understand its mechanism of action, we studied the time course of bone formation, correlating the rate and extent of accrual of bone mass and strength after sclerostin antibody treatment. Ovariectomized (OVX) rats were treated with a sclerostin-antibody (Scle-ab) at 20mg/kg sc once weekly and sacrificed at baseline and 2, 3, 4, 6, and 8weeks post-treatment. In Scle-ab treated rats, serum PINP and OCN rapidly increased at week 1, peaked around week 3, and returned to OVX control levels by week 6. Transcript analyses from the distal femur revealed an early increase in bone formation followed by a sustained decrease in bone resorption genes. Lumbar vertebral (LV) osteoblast surface increased 88% by week 2, and bone formation rate (BFR/BS) increased 138% by week 4. Both parameters were below OVX control by week 8. Bone formation was primarily a result of modeling based formation. Endocortical and periosteal BFR/BS peaked around week 4 at 313% and 585% of OVX control, respectively. BFR/BS then declined but remained higher than OVX control on both surfaces through week 8. Histomorphometric analyses showed LV-BV/TV did not further increase after week 4, while BMD continued to increase at LV, mid femur (MF), and femoral neck (FN) through week 8. Biomechanical tests showed a similar improvement in bone strength through 8weeks in MF and FN, but bone strength plateaued between weeks 6 and 8 for LV. Our data suggest that bone formation with Scle-ab treatment is rapid and modeling formation dominated in OVX rats. Although transient, the bone formation response persists longer in cortical than trabecular bone.

Efficacy and safety of teriparatide in bisphosphonate-pretreated and treatment-naive patients with osteoporosis at high risk of fracture: Post hoc analysis of a prospective observational study

BACKGROUND

Teriparatide is the first anabolic agent shown to reduce the risk of fractures in patients with osteoporosis. In Japan, teriparatide is prescribed to treat patients at high risk of fracture. Given that bisphosphonates are commonly used prior to teriparatide as treatment for osteoporosis, information on the effectiveness and safety of teriparatide with or without previous bisphosphonate treatment is helpful for physicians in clinical practice. This study aims to report the effectiveness and safety of teriparatide in treatment-naive and bisphosphonate-pretreated patients in Japan as real-world evidence.

METHODS

A post hoc analysis of a postmarketing surveillance study was conducted in Japanese patients with osteoporosis at high risk of fracture who received 24-month treatment of daily teriparatide. Changes in bone turnover biomarkers and bone mineral density and incidence of new fractures were analyzed in treatment-naive as well as bisphosphonate-pretreated patients.

RESULTS

The analysis included 1433 patients (treatment-naive, n = 659; bisphosphonate-pretreated, n = 774). Bone mineral density increased significantly from baseline at 24 months in both treatment-naive (lumbar spine, 13.45%; femoral neck, 5.16%; total hip, 4.46%) and bisphosphonate-pretreated (lumbar spine, 11.20%; femoral neck, 2.22%; total hip, 0.67%) patients. The incidence rates of new vertebral and nonvertebral fractures at 24 months were 1.69% and 3.37%, respectively, in treatment-naive patients and 3.60% and 5.56%, respectively, in bisphosphonate-pretreated patients. The incidence of adverse drug reactions was 6% in treatment-naive patients and 10% in bisphosphonate-pretreated patients. The most common adverse drug reaction in treatment-naive and bisphosphonate-pretreated patients was nausea (0.91%) and hyperuricaemia (1.81%), respectively.

CONCLUSIONS

In this post hoc analysis, no new safety concerns and similar effectiveness of teriparatide were observed in Japanese patients with osteoporosis at high risk of fracture, regardless of their previous treatment status with bisphosphonates.

Treatment Sequence Matters: Anabolic and Antiresorptive Therapy for Osteoporosis

The effects of anabolic medications (teriparatide [TPTD] and parathyroid hormone [PTH]) differ in patients who have received recent treatment with potent antiresorptives. This perspective reviews studies evaluating bone density (BMD) and histomorphometric effects of treatment sequences beginning with TPTD/PTH followed by potent antiresorptives and those beginning with potent antiresorptives followed by switching to or adding TPTD. Effect of treatment sequence on spine BMD outcome is minor, with modest quantitative differences. However, when individuals established on potent bisphosphonates are switched to TPTD, hip BMD declines below baseline for at least the first 12 months after the switch to TPTD. This transient hip BMD loss is more prominent when the antiresorptive is denosumab; in this setting, hip BMD remains below baseline for almost a full 24 months. In a controlled comparison of those who switched from alendronate to TPTD versus those who added TPTD to ongoing alendronate, the effect on hip BMD was improved with combination therapy. Furthermore, hip strength improved with the addition of TPTD to ongoing alendronate, whereas it was neutral after switching from alendronate to TPTD, primarily due to the effect on cortical bone. Bone biopsy studies indicate that TPTD stimulates bone formation in patients who have not been treated previously as well as in patients on prior and ongoing bisphosphonates. Histomorphometric evidence suggests that use of alendronate with TPTD blocks the TPTD-induced increase in cortical porosity. When possible, we suggest anabolic therapy first, followed by potent antiresorptive therapy. The common practice of switching to TPTD only after patients have an inadequate response to antiresorptives (intercurrent fracture or inadequate BMD effect) is not the optimal utilization of anabolic treatment. In fact, this may result in transient loss of hip BMD and strength. In this setting, continuing a potent antiresorptive while starting TPTD might improve hip outcomes. © 2017 American Society for Bone and Mineral Research.

Parathyroid hormone 1-34 and skeletal anabolic action: The use of parathyroid hormone in bone formation

Intermittently administered parathyroid hormone (PTH 1-34) has been shown to promote bone formation in both human and animal studies. The hormone and its analogues stimulate both bone formation and resorption, and as such at low doses are now in clinical use for the treatment of severe osteoporosis. By varying the duration of exposure, parathyroid hormone can modulate genes leading to increased bone formation within a so-called 'anabolic window'. The osteogenic mechanisms involved are multiple, affecting the stimulation of osteoprogenitor cells, osteoblasts, osteocytes and the stem cell niche, and ultimately leading to increased osteoblast activation, reduced osteoblast apoptosis, upregulation of Wnt/β-catenin signalling, increased stem cell mobilisation, and mediation of the RANKL/OPG pathway. Ongoing investigation into their effect on bone formation through 'coupled' and 'uncoupled' mechanisms further underlines the impact of intermittent PTH on both cortical and cancellous bone. Given the principally catabolic actions of continuous PTH, this article reviews the skeletal actions of intermittent PTH 1-34 and the mechanisms underlying its effect.

CITE THIS ARTICLE

L. Osagie-Clouard, A. Sanghani, M. Coathup, T. Briggs, M. Bostrom, G. Blunn. Parathyroid hormone 1-34 and skeletal anabolic action: The use of parathyroid hormone in bone formation. Bone Joint Res 2017;6:14-21. DOI: 10.1302/2046-3758.61.BJR-2016-0085.R1.

Abaloparatide: Recombinant human PTHrP (1-34) anabolic therapy for osteoporosis

The treatment of osteoporosis is generally either by inhibition of bone resorption with antiresorptive agents or by stimulation of bone formation with anabolic agents. Currently, teriparatide (recombinant human parathyroid hormone 1-34 [rhPTH (1-34)]) is the only available approved anabolic agent in the U.S. Other anabolic agents are under investigation however. Abaloparatide is recombinant human parathyroid hormone-related peptide 1-34. This agent is an anabolic agent that appears more potent than teriparatide, and it may have more rapid onset of fracture reduction than teriparatide. It is currently undergoing FDA review, with approval expected in 2017.

Influence of Teriparatide and Ibandronate on Cortical Bone in New Zealand White Rabbits: A HR-QCT Study

Teriparatide (TPTD) is known to increase the cortical thickness and porosity. The purpose of the present study was to determine whether switching from TPTD to ibandronate (IBN) would be useful for improving cortical bone parameters as assessed using high-resolution quantitative computed tomography (HR-QCT) analyses in mature rabbits. Forty-two female New Zealand white rabbits (18-22 weeks old) were randomized into six groups of 7 animals each as follows: 4-week vehicle administration group, 4-week TPTD administration group (20 μg/kg, subcutaneously [s.c.], daily), 12-week vehicle administration group, 4-week TPTD administration + 8-week vehicle administration group, 4-week TPTD administration + 8-week lower-dose IBN administration group (20 μg/kg, s.c., every 4 weeks), and 4-week TPTD administration + 8-week higher-dose IBN administration group (100 μg/kg, s.c., every 4 weeks). After the 4- or 12-week experimental period, the cortical bone of the distal femoral diaphysis was processed for HR-QCT analysis. The 4-week TPTD administration increased the pore ratio, number, and density as well as the cortical area, thickness, and bone mineral content (BMC), without significant influencing the volumetric bone mineral density (BMD). The 4-week TPTD administration + 8-week vehicle administration decreased the pore ratio, number, and density as well as the cortical area and thickness, compared with the 4-week TPTD administration, but the pore ratio, cortical area, and thickness were still higher compared with the 12-week vehicle administration. The 4-week TPTD administration + 8-week higher-dose IBN administration, but not the 4-week TPTD administration + 8-week lower-dose IBN administration, increased the cortical area, thickness, BMC, and volumetric BMD and decreased the pore ratio, but not the pore number or density, compared with the 4-week TPTD administration + 8-week vehicle administration. These results suggest that higher-dose IBN after TPTD therapy has a beneficial effect on the BMC, volumetric BMD, cortical area, thickness, and porosity in mature rabbits.

Hip structure analysis by DXA of teriparatide treatment: A 24-month follow-up clinical study

OBJECTIVE

The objective of this study was to perform a hip structure analysis (HSA) of teriparatide (TPTD) treatment in women with postmenopausal osteoporosis.

METHODS

The study included 96 patients with postmenopausal osteoporosis and received 20 μg TPTD daily. HSA was performed by dual-energy X-ray absorptiometry.

RESULTS

The percent changes from baseline for the cross-sectional moment of inertia, section modulus, buckling ratio, and femoral strength index based on HSA results were 9.8% (p < 0.01), 10.7%, 3.3%, and 14.9% (p < 0.01), respectively, at 24 months.

CONCLUSION

Based on the HSA results obtained with DXA, TPTD was effective for hip structures.

Improvement of cancellous bone microstructure in patients on teriparatide following alendronate pretreatment

An increase in procollagen type I amino-terminal propeptide (PINP) early after teriparatide initiation was shown to correlate with increased lumbar spine areal BMD and is a good predictor of the anabolic response to teriparatide. Few data exist correlating PINP and bone microstructure, and no data exist in patients on teriparatide following prior potent antiresorptive treatment. This exploratory analysis aimed to investigate the effects of teriparatide on cancellous bone microstructure and correlations of bone markers with microstructure in alendronate-pretreated patients. This was a post hoc analysis of changes in bone markers and three-dimensional indices of bone microstructure in paired iliac crest biopsies from a prospective teriparatide treatment study in postmenopausal women with osteoporosis who were either treatment-naïve (TN, n=16) or alendronate-pretreated (ALN, n=29) at teriparatide initiation. Teriparatide (20μg/day) was given for 24months; biopsies were taken at baseline and endpoint, and serum concentrations of PINP and type 1 collagen cross-linked C-telopeptide (βCTX) were measured at intervals up to 24months. In the TN and ALN groups, respectively, mean (SD) increases in three-dimensional bone volume/tissue volume were 105 (356)% (P=0.039) and 55 (139)% (P<0.005) and trabecular thickness 30.4 (30)% (P<0.001) and 30.8 (53)% (P<0.001). No significant changes were observed in trabecular number or separation. In the ALN patients, 3-month change of neither PINP nor βCTX correlated with indices of cancellous bone microstructure. However, 12-month changes in biochemical bone markers correlated significantly with improvements in bone volume/tissue volume, r=0.502 (P<0.01) and r=0.378 (P<0.05), trabecular number, r=0.559 (P<0.01) and r=0.515 (P<0.01), and reduction of trabecular separation, r=-0.432 (P<0.05) and r=-0.530 (P<0.01), for PINP and βCTX, respectively. We conclude that cancellous bone microstructure improved with teriparatide therapy irrespective of prior antiresorptive use.

Teriparatide for osteoporosis: importance of the full course

Teriparatide (TPTD) is the only currently available therapeutic agent that increases the formation of new bone tissue and can provide some remediation of the architectural defects in the osteoporotic skeleton. The use of teriparatide clinically is limited to 24 months. We review clinical findings during daily teriparatide treatment over time. Teriparatide appears to increase bone formation more than bone resorption as determined biochemically and histologically. Teriparatide exerts its positive effects on bone formation in two distinct fashions. The first is direct stimulation of bone formation that occurs within active remodeling sites (remodeling-based bone formation) and on surfaces of bone previously inactive (modeling-based bone formation). The second is an increase in the initiation of new remodeling sites. Both processes contribute to the final increase in bone density observed by non-invasive tools such as DXA. Remodeling is the repair process by which skeletal tissue is maintained in a young healthy state, and when stimulated by TPTD is associated with a positive bone balance within each remodeling cavity. It seems likely therefore that this component will contribute to the anti-fracture efficacy of TPTD. Teriparatide reduces the risk of fracture, and this effect appears to increase with longer duration of therapy. The use of novel treatment regimens, including shorter courses, should be held in abeyance until controlled clinical trials are completed to define the relative fracture benefits of such approaches in comparison to the 24-month daily use of the agent. Summary In patients with osteoporosis at high risk for fracture, the full continuous 24-month course with teriparatide results in improved skeletal health and outcomes than shorter time periods.

A Longitudinal Study of Skeletal Histomorphometry at 6 and 24 Months Across Four Bone Envelopes in Postmenopausal Women With Osteoporosis Receiving Teriparatide or Zoledronic Acid in the SHOTZ Trial

Previously, we reported the effects of teriparatide (TPTD) and zoledronic acid (ZOL) on bone formation based on biochemical markers and bone histomorphometry of the cancellous envelope at month 6 in postmenopausal women with osteoporosis who participated in the 12-month primary Skeletal Histomorphometry in Subjects on Teriparatide or Zoledronic Acid Therapy (SHOTZ) study. Patients were eligible to enter a 12-month extension on their original treatment regimen: TPTD 20 μg/day (s.c. injection) or ZOL 5 mg/year (i.v. infusion). A second biopsy was performed at month 24. Here we report longitudinal changes between and within each treatment group in the cancellous, endocortical, intracortical, and periosteal bone envelopes in patients with evaluable biopsies at months 6 and 24 (paired data set: TPTD, n = 10; ZOL, n = 9). Between-group differences are also reported in the larger set of patients with evaluable biopsies at month 6 (TPTD, n = 28; ZOL, n = 30). Data from the cancellous envelope at month 6 or month 24 provided a reference to compare differences across envelopes within each treatment group. The 24-month results extend our earlier report that TPTD and ZOL possess different tissue-level mechanisms of action. Moreover, these differences persisted for at least 2 years in all four bone envelopes. Few longitudinal differences were observed within or across bone envelopes in ZOL-treated patients, suggesting that the low bone formation indices at month 6 persisted to month 24. Conversely, the magnitude of the effect of TPTD on bone formation varied across individual envelopes: median values for mineralizing surface (MS/BS) and bone formation rate (BFR/BS) at month 6 were approximately 3-fold to 5-fold higher in the endocortical and intracortical envelopes compared to the cancellous envelope. Although MS/BS and BFR/BS declined in these envelopes at month 24, median values continued to exceed, or were not significantly different from, those in the cancellous envelope. This study demonstrates for the first time that bone formation indices are higher with TPTD treatment than with ZOL in all four bone envelopes and the difference persists for at least 2 years. Moreover, the magnitude of the effect of TPTD in cortical bone remains robust at 24 months. © 2016 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research (ASBMR).

Efficacy of osteoporosis pharmacotherapies in preventing fracture among oral glucocorticoid users: a network meta-analysis

Efficacy of osteoporosis medication is not well-established among patients taking oral glucocorticoids. We assessed the efficacy of approved osteoporosis pharmacotherapies in preventing fracture by combining data from randomized controlled trials. Teriparatide, risedronate, and etidronate were associated with decreased vertebral fracture risk.

INTRODUCTION

Several osteoporosis drugs are approved for the prevention and treatment of glucocorticoid (GC)-induced osteoporosis. However, the efficacy of these treatments among oral GC users is still limited. We aimed to examine the comparative efficacy of osteoporosis treatments among oral GC users.

METHODS

We updated a systematic review through to March 2015 to identify all double-blinded randomized controlled trials (RCTs) that examined osteoporosis treatment among oral GC users. We used a network meta-analysis with informative priors to derive comparative risk ratios (RRs) and 95 % credible intervals (95 % CrI) for vertebral and non-vertebral fracture and mean differences in lumbar spine (LS) and femoral neck (FN) bone mineral density (BMD). Treatment ranking was estimated using the surface under the cumulative ranking curve (SUCRA) statistic. A meta-regression was completed to assess a subgroup effect between patients with prior GC exposures and GC initiators.

RESULTS

We identified 27 eligible RCTs examining nine active comparators. Etidronate (RR, 0.41; 95%CrI = 0.17-0.90), risedronate (RR = 0.30, 95%CrI = 0.14-0.61), and teriparatide (RR = 0.07, 95%CrI = 0.001-0.48) showed greater efficacy than placebo in preventing vertebral fractures; yet, no treatment effects were statistically significant in reducing non-vertebral fractures. Alendronate, risedronate, and etidronate increased LS BMD while alendronate and raloxifene increased FN BMD. In preventing vertebral fractures, teriparatide was ranked as the best treatment (SUCRA: 77 %), followed by risedronate (77 %) and zoledronic acid (76 %). For non-vertebral fractures, teriparatide also had the highest SUCRA (69 %), followed by risedronate (64 %). No subgroup effect was identified with regards to prior GC exposure.

CONCLUSIONS

Despite weak trial evidence available for fracture prevention among GC users, we identified several drugs that are likely to prevent osteoporotic fracture. Teriparatide, risedronate, and etidronate were associated with decreased vertebral fracture risk.

PTH(1-84) Administration in Hypoparathyroidism Transiently Reduces Bone Matrix Mineralization

Patients with hypoparathyroidism have low circulating parathyroid (PTH) levels and higher cancellous bone volume and trabecular thickness. Treatment with PTH(1-84) was shown to increase abnormally low bone remodeling dynamics. In this work, we studied the effect of 1-year or 2-year PTH(1-84) treatment on cancellous and cortical bone mineralization density distribution (Cn.BMDD and Ct.BMDD) based on quantitative backscattered electron imaging (qBEI) in paired transiliac bone biopsy samples. The study cohort comprised 30 adult hypoparathyroid patients (14 treated for 1 year; 16 treated for 2 years). At baseline, Cn.BMDD was shifted to higher mineralization densities in both treatment groups (average degree of mineralization Cn.CaMean +3.9% and +2.7%, p < 0.001) compared to reference BMDD. After 1-year PTH(1-84), Cn.CaMean was significantly lower than that at baseline (-6.3%, p < 0.001), whereas in the 2-year PTH(1-84) group Cn.CaMean did not differ from baseline. Significant changes of Ct.BMDD were observed in the 1-year treatment group only. The change in histomorphometric bone formation (mineralizing surface) was predictive for Cn.BMDD outcomes in the 1-year PTH(1-84) group, but not in the 2-year PTH(1-84) group. Our findings suggest higher baseline bone matrix mineralization consistent with the decreased bone turnover in hypoparathyroidism. PTH(1-84) treatment caused differential effects dependent on treatment duration that were consistent with the histomorphometric bone formation outcomes. The greater increase in bone formation during the first year of treatment was associated with a decrease in bone matrix mineralization, suggesting that PTH(1-84) exposure to the hypoparathyroid skeleton has the greatest effects on BMDD early in treatment.

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.

Development of an in vivo rabbit ulnar loading model

Ulnar and tibial cyclic compression in rats and mice have become the preferred animal models for investigating the effects of mechanical loading on bone modeling/remodeling. Unlike rodents, rabbits provide a larger bone volume and normally exhibit intracortical Haversian remodeling, which may be advantageous for investigating mechanobiology and pharmaceutical interventions in cortical bone. Therefore, the objective of this study was to develop and validate an in vivo rabbit ulnar loading model. Ulnar tissue strains during loading of intact forelimbs were characterized and calibrated to applied loads using strain gauge measurements and specimen-specific finite element models. Periosteal bone formation in response to varying strain levels was measured by dynamic histomorphometry at the location of maximum strain in the ulnar diaphysis. Ulnae loaded at 3000 microstrain did not exhibit periosteal bone formation greater than the contralateral controls. Ulnae loaded at 3500, 4000, and 4500 microstrain exhibited a dose-dependent increase in periosteal mineralizing surface (MS/BS) compared with contralateral controls during the second week of loading. Ulnae loaded at 4500 microstrain exhibited the most robust response with significantly increased MS/BS at multiple time points extending at least 2weeks after loading was ceased. Ulnae loaded at 5250 microstrain exhibited significant woven bone formation. Rabbits required greater strain levels to produce lamellar and woven bone on periosteal surfaces compared with rats and mice, perhaps due to lower basal levels of MS/BS. In summary, bone adaptation during rabbit ulnar loading was tightly controlled and may provide a translatable model for human bone biology in preclinical investigations of metabolic bone disease and pharmacological treatments.