New bone formation with teriparatide [human parathyroid hormone-(1-34)] is not retarded by long-term pretreatment with alendronate, estrogen, or raloxifene in ovariectomized rats

Conditional Loss of Nmp4 in Mesenchymal Stem Progenitor Cells Enhances PTH-Induced Bone Formation

Activation of bone anabolic pathways is a fruitful approach for treating severe osteoporosis, yet FDA-approved osteoanabolics, eg, parathyroid hormone (PTH), have limited efficacy. Improving their potency is a promising strategy for maximizing bone anabolic output. Nmp4 (Nuclear Matrix Protein 4) global knockout mice exhibit enhanced PTH-induced increases in trabecular bone but display no overt baseline skeletal phenotype. Nmp4 is expressed in all tissues; therefore, to determine which cell type is responsible for driving the beneficial effects of Nmp4 inhibition, we conditionally removed this gene from cells at distinct stages of osteogenic differentiation. Nmp4-floxed (Nmp4fl/fl ) mice were crossed with mice bearing one of three Cre drivers including (i) Prx1Cre+  to remove Nmp4 from mesenchymal stem/progenitor cells (MSPCs) in long bones; (ii) BglapCre+  targeting mature osteoblasts, and (iii) Dmp1Cre+  to disable Nmp4 in osteocytes. Virgin female Cre+  and Cre- mice (10 weeks of age) were sorted into cohorts by weight and genotype. Mice were administered daily injections of either human PTH 1-34 at 30 μg/kg or vehicle for 4 weeks or 7 weeks. Skeletal response was assessed using dual-energy X-ray absorptiometry, micro-computed tomography, bone histomorphometry, and serum analysis for remodeling markers. Nmp4fl/fl ;Prx1Cre+  mice virtually phenocopied the global Nmp4-/- skeleton in the femur, ie, a mild baseline phenotype but significantly enhanced PTH-induced increase in femur trabecular bone volume/total volume (BV/TV) compared with their Nmp4fl/fl ;Prx1Cre- controls. This was not observed in the spine, where Prrx1 is not expressed. Heightened response to PTH was coincident with enhanced bone formation. Conditional loss of Nmp4 from the mature osteoblasts (Nmp4fl/fl ;BglapCre+ ) failed to increase BV/TV or enhance PTH response. However, conditional disabling of Nmp4 in osteocytes (Nmp4fl/fl ;Dmp1Cre+ ) increased BV/TV without boosting response to hormone under our experimental regimen. We conclude that Nmp4-/- Prx1-expressing MSPCs drive the improved response to PTH therapy and that this gene has stage-specific effects on osteoanabolism. © 2022 American Society for Bone and Mineral Research (ASBMR).

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.

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.

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.

Enhancement of peri-implant bone formation via parathyroid hormone administration in a rat model at risk for medication-related osteonecrosis of the jaw

Purpose

Dental implant-associated medication-related osteonecrosis of the jaw has been frequently reported in patients administered bisphosphonates (BPs) to prevent osteoporosis. The aim of this study was to investigate the effect of intermittent administration of parathyroid hormone (PTH) on peri-implant bone in the maxillae of ovariectomized rats systemically administered BPs.

Methods

Thirty 8-week-old female Sprague-Dawley rats were randomly divided into 3 groups. The OVX-ZP group included ovariectomized rats administered 60 µg/kg of zoledronate once a week for 6 weeks and 30 µg/kg PTH after implant installation. The OVX-Z group included ovariectomized rats administered 60 µg/kg of zoledronate once a week for 6 weeks and saline after implant installation, and the control group included rats that underwent a sham operation and were then administered saline. Rats were sacrificed 4 weeks after implant placement for histomorphometric and micro-computed tomography (CT) analyses.

Results

The average bone area percentage was greater in the OVX-ZP group than in the OVX-Z group (53.4%±4.0% vs. 28.9%±9.5%, P=0.01). The bone-to-implant contact ratio was 50.8%±1.4% in the OVX-ZP group and 16.9%±2.4% in the OVX-Z group (P=0.012). The average bone volume ratio as shown on micro-CT was 31.3%±19.8% in the OVX-ZP group and 19.4%±9.3% in the OVX-Z group (P=0.045). The OVX-ZP and OVX-Z groups displayed similar trabecular thickness (0.06±0.004 mm vs. 0.06±0.002 mm) (P>0.05) and trabecular separation (0.21±0.02 mm vs. 0.29±0.13 mm) (P>0.05). However, the number of trabeculae in the OVX-ZP group was significantly higher than that in the OVX-Z group (4.3±1.33/mm³ vs. 2.2±0.19/mm³) (P=0.024).

Conclusions

The present findings indicate that intermittently-administered PTH can promote peri-implant bone formation and suggest that PTH administration may aid in effective treatment for medication-related osteonecrosis of the jaw after dental implantation.

Loss of Nmp4 optimizes osteogenic metabolism and secretion to enhance bone quality

A goal of osteoporosis therapy is to restore lost bone with structurally sound tissue. Mice lacking the transcription factor nuclear matrix protein 4 (Nmp4, Zfp384, Ciz, ZNF384) respond to several classes of osteoporosis drugs with enhanced bone formation compared with wild-type (WT) animals. Nmp4-/- mesenchymal stem/progenitor cells (MSPCs) exhibit an accelerated and enhanced mineralization during osteoblast differentiation. To address the mechanisms underlying this hyperanabolic phenotype, we carried out RNA-sequencing and molecular and cellular analyses of WT and Nmp4-/- MSPCs during osteogenesis to define pathways and mechanisms associated with elevated matrix production. We determined that Nmp4 has a broad impact on the transcriptome during osteogenic differentiation, contributing to the expression of over 5,000 genes. Phenotypic anchoring of transcriptional data was performed for the hypothesis-testing arm through analysis of cell metabolism, protein synthesis and secretion, and bone material properties. Mechanistic studies confirmed that Nmp4-/- MSPCs exhibited an enhanced capacity for glycolytic conversion: a key step in bone anabolism. Nmp4-/- cells showed elevated collagen translation and secretion. The expression of matrix genes that contribute to bone material-level mechanical properties was elevated in Nmp4-/- cells, an observation that was supported by biomechanical testing of bone samples from Nmp4-/- and WT mice. We conclude that loss of Nmp4 increases the magnitude of glycolysis upon the metabolic switch, which fuels the conversion of the osteoblast into a super-secretor of matrix resulting in more bone with improvements in intrinsic quality.

Short-Term Teriparatide and Recombinant Human Bone Morphogenetic Protein-2 for Regenerative Approach to Medication-Related Osteonecrosis of the Jaw: A Preliminary Study

Our objective was to examine whether adjunct teriparatide administration and local application of recombinant human bone morphogenetic protein-2 (rhBMP-2) is beneficial for the regeneration of jaw bone in patients with medication-related osteonecrosis of the jaw (MRONJ). This study enrolled 17 patients diagnosed with MRONJ. All patients received sequestrectomy under general or local anesthesia with suspension of bisphosphonate. The bone regeneration ratio was compared on cone beam computed tomography (CBCT) scans, acquired immediately post-operation and after 6 months. The patients were divided into groups, based on their treatment regimens: teriparatide combined with rhBMP-2 (parathyroid hormone [PTH]+BMP), rhBMP-2 (BMP), and the control. Biochemical markers were also evaluated at the baseline (T0), 1 month (T1), and 3 months (T2) after surgery. Significant increase was observed in the values of the biochemical markers, serum osteocalcin, and serum C-terminal telopeptide cross-link of type I collagen, within 3 months of surgery in the PTH+BMP group, whereas the mean value in the BMP group did not show a significant change. In all groups, the MRONJ lesions were healed and new bone formation was detected in the CBCT images. The regeneration ratio was significantly greater in the group PTH+BMP than in the BMP and control groups. Significantly greater amount of bone formation was observed in the group PTH+BMP than in the BMP and control groups. Local application of rhBMP-2 alone also had a beneficial effect on bone regeneration but was not more significant than control. Based on these findings, administration of short-term teriparatide with rhBMP-2 in MRONJ patients may maximize the regeneration of bone after surgery. © 2017 American Society for Bone and Mineral Research.

Intermittent Parathyroid Hormone After Prolonged Alendronate Treatment Induces Substantial New Bone Formation and Increases Bone Tissue Heterogeneity in Ovariectomized Rats

Postmenopausal osteoporosis is often treated with bisphosphonates (eg, alendronate, [ALN]), but oversuppression of bone turnover by long-term bisphosphonate treatment may decrease bone tissue heterogeneity. Thus, alternate treatment strategies after long-term bisphosphonates are of great clinical interest. The objective of the current study was to determine the effect of intermittent parathyroid hormone (PTH) following 12 weeks of ALN (a bisphosphonate) treatment in 6-month-old, ovariectomized (OVX) rats on bone microarchitecture, bone remodeling dynamics, and bone mechanical properties at multiple length scales. By using in vivo μCT and 3D in vivo dynamic bone histomorphometry techniques, we demonstrated the efficacy of PTH following ALN therapy for stimulating new bone formation, and increasing trabecular thickness and bone volume fraction. In healthy bone, resorption and formation are coupled and balanced to sustain bone mass. OVX results in resorption outpacing formation, and subsequent bone loss and reduction in bone tissue modulus and tissue heterogeneity. We showed that ALN treatment effectively reduced bone resorption activity and regained the balance with bone formation, preventing additional bone loss. However, ALN treatment also resulted in significant reductions in the heterogeneity of bone tissue mineral density and tissue modulus. On the other hand, PTH treatment was able to shift the bone remodeling balance in favor of formation, with or without a prior treatment with ALN. Moreover, by altering the tissue mineralization, PTH alleviated the reduction in heterogeneity of tissue material properties induced by prolonged ALN treatment. Furthermore, switching to PTH treatment from ALN improved bone's postyield mechanical properties at both the whole bone and apparent level compared to ALN alone. The current findings suggest that intermittent PTH treatment should be considered as a viable treatment option for patients with prior treatment with bisphosphonates. © 2017 American Society for Bone and Mineral Research.

Bone Mineral Density Response from Teriparatide in Patients with Osteoporosis

BACKGROUND

A review of data from large clinical trials reported more than 90% of subjects significantly improved their bone mineral density (BMD) at the lumbar spine (LS) with teriparatide (TPTD) (bone 39:1268-1275, 1). However, our clinical experience suggests that many patients may be non-responders, raising questions as to the true efficacy of TPTD in improving BMD in osteoporotic patients.

QUESTIONS/PURPOSES

The purpose of the study is to determine the rate of improvement in BMD following 18-24 months of teriparatide (TPTD) in patients with osteoporosis within an orthopedic hospital setting.

METHODS

This is a retrospective chart review of patients with osteoporosis who completed 18-24 months of TPTD therapy. The primary endpoint was the change in BMD at lumbar spine (LS) and hip-femoral neck (FN) and total hip (TH) following treatment. Secondary endpoints included the effect of prior bisphosphonate therapy, age, body mass index (BMI) and family history of fracture on BMD response, and the changes in bone-specific markers during active treatment.

RESULTS

Seventy-eight women and men with mean T-scores at the LS = -2.63 met the inclusion criteria. The overall group showed a 10.7% increase in LS-BMD after 24 months of TPTD. Eighty-three percent were considered responders defined as ≥3.0% increase in LS-BMD. Non-responders (16.7%) had mean LS-BMD change = -1.41%. No difference in baseline vitamin D, calcium, creatinine, BMI, age, gender, prior fracture history, or bisphosphonate use was observed between responders and non-responders. No consistent pattern of change in measures of bone markers was noted between responders and non-responders.

CONCLUSION

Eighty-three percent of patients with osteoporosis showed a >3% increase in BMD after TPTD treatment. Baseline parameters, prior bisphosphonate therapy, and the changes in bone markers showed no correlation with final BMD outcome.

Bisphosphonate Pre-Treatment Diminishes the Therapeutic Benefits of Teriparatide in Japanese Osteoporotic Patients

Osteoporosis (OP) is the most common multifactorial metabolic bone disorder worldwide. It remains unclear whether bisphosphonate (BP) pre-treatment affects the anabolic bone metabolism in OP patients treated with teriparatide (TPTD), a recombinant form of parathyroid hormone 1-34. This study is the first to evaluate the clinical outcomes of daily TPTD administration in Japanese OP patients and aimed to clarify how BP pre-treatment influences the efficacy of TPTD. We enrolled 112 patients diagnosed as primary OP who received TPTD. Subjects were classified as OP treatment-naïve patients (TPTD alone group) or patients previously treated with BP (BP pre-treated group). We measured serum bone-specific alkaline phosphatase (BAP) as a bone formation marker, urinary cross-linked N-terminal telopeptide of type I collagen (NTX) as a bone resorption marker, and bone mineral density (BMD) of lumbar vertebrae (L-BMD) and bilateral total hips (H-BMD). In both groups, BAP and NTX increased until 6 months and then decreased thereafter. The percent changes of both markers in BP pre-treated group were more increased than those in TPTD alone group. L-BMD increased significantly in both groups. The percent increase of L-BMD in the TPTD alone group was significantly higher than that in the BP pre-treated group. H-BMD rose significantly in the TPTD alone group, but not in BP pre-treated group. BP pre-treatment appears to diminish the degree of the TPTD-mediated increase in BMD. Thus, it is preferable to administer TPTD ahead of BP treatment in patients with severe OP.

Co-administration of antiresorptive and anabolic agents: a missed opportunity

Co-administration of antiresorptive and anabolic therapies has appeal because these treatments target the two main abnormalities in bone remodeling responsible for bone loss and microstructural deterioration. Antiresorptives reduce the number of basic multicellular units (BMUs) remodeling bone and reduce the volume of bone each BMU resorbs. Intermittent parathyroid hormone (PTH) increases the volume of bone formed by existing BMUs and those generated by PTH administration. PTH also increases bone formation by stimulating the differentiation, maturation, and longevity of osteoblast lineage cells residing upon quiescent bone surfaces. Despite these rationally targeted actions, enthusiasm for this approach waned when combined therapy blunted the increase in areal bone mineral density (aBMD) relative to that produced by PTH. Although many studies have since reported additive effects of combined therapy, whatever the aBMD result (blunting, additive, or null), these outcomes give little, if any, insight into changes in bone's material composition or microstructure and give misleading information concerning the net effects on bone strength. Combined therapy remains a potentially valuable approach to therapy. Because studies of antifracture efficacy comparing combined with single therapy are unlikely to be performed in humans, efforts should be directed toward improving methods of quantifying the net effects of combined therapy on bone's material composition, microarchitecture, and strength.

μCT-based, in vivo dynamic bone histomorphometry allows 3D evaluation of the early responses of bone resorption and formation to PTH and alendronate combination therapy

Current osteoporosis treatments improve bone mass by increasing net bone formation: anti-resorptive drugs such as bisphosphonates block osteoclast activity, while anabolic agents such as parathyroid hormone (PTH) increase bone remodeling, with a greater effect on formation. Although these drugs are widely used, their role in modulating formation and resorption is not fully understood, due in part to technical limitations in the ability to longitudinally assess bone remodeling. Importantly, it is not known whether or not PTH-induced bone formation is independent of resorption, resulting in controversy over the effectiveness of combination therapies that use both PTH and an anti-resorptive. In this study, we developed a μCT-based, in vivo dynamic bone histomorphometry technique for rat tibiae, and applied this method to longitudinally track changes in bone resorption and formation as a result of treatment with alendronate (ALN), PTH, or combination therapy of both PTH and ALN (PTH+ALN). Correlations between our μCT-based measures of bone formation and measures of bone formation based on calcein-labeled histology (r=0.72-0.83) confirm the accuracy of this method. Bone remodeling parameters measured through μCT-based in vivo dynamic bone histomorphometry indicate an increased rate of bone formation in rats treated with PTH and PTH+ALN, together with a decrease in bone resorption measures in rats treated with ALN and PTH+ALN. These results were further supported by traditional histology-based measurements, suggesting that PTH was able to induce bone formation while bone resorption was suppressed.

Long-term treatment with eldecalcitol (1α, 25-dihydroxy-2β- (3-hydroxypropyloxy) vitamin D3) suppresses bone turnover and leads to prevention of bone loss and bone fragility in ovariectomized rats

The purpose of this study is to estimate the efficacy of eldecalcitol (1α, 25-Dihydroxy-2β- (3-hydroxypropyloxy) vitamin D3; ELD) on bone metabolism after long-term administration. Six-month-old Wistar-Imamichi rats were ovariectomized (OVX) and administered ELD orally at doses of 7.5, 15, or 30 ng/kg daily. Bone mineral density (BMD), urinary excretion of deoxypyridinoline (DPD), a bone resorption marker, and serum total alkaline phosphatase (ALP), a surrogate marker of bone formation, were assessed after 3, 6, and 12 months of treatment. After 12 months of treatment, the biomechanical strength of the L4 lumbar vertebra and femoral shaft was measured, and bone histomorphometry was performed on the L3 lumbar vertebra and the tibia diaphysis. ELD prevented OVX-induced decreases in BMD of the lumbar vertebrae and femur throughout the treatment period. ELD significantly suppressed OVX-induced increases in urinary DPD excretion throughout the treatment period with minimal effects on ALP. OVX resulted in significant decreases in ultimate load and stiffness of the L4 lumbar vertebra and femoral shaft, and ELD significantly prevented the reduction in these biomechanical parameters. Bone histomorphometry at the L3 lumbar vertebra revealed that OVX induced increases in bone resorption parameters (osteoclast surface and osteoclast number) and bone formation parameters (osteoblast surface, osteoid surface, and bone formation rate), and ELD suppressed these parameters after 12 months treatment. Activation frequency, which was elevated in the OVX/vehicle group, was significantly suppressed to baseline levels in ELD-treated groups, indicating that ELD maintained bone turnover at a normal level. ELD also prevented OVX-induced deterioration of microstructure in trabecular and cortical bone. These results indicated that long-term treatment of OVX rats with ELD suppressed bone turnover, and prevented OVX-induced bone loss, deterioration of bone microstructure, and reduction in bone biomechanical strength.

Treatment of post-menopausal osteoporosis: beyond bisphosphonates

Osteoporosis is a highly prevalent condition, characterized by compromised bone strength and fragility fractures and with an important associated socio-economic burden. Bisphosphonates are well established as the first line treatment for osteoporosis. However, while randomized control trials have in general demonstrated reasonable anti-fracture efficacy at the spine, they have shown moderate reduction in fracture incidence for non-vertebral sites. Furthermore, oral bisphosphonates are commonly associated with adverse gastrointestinal effects and both oral and parenteral bisphosphonates have been linked with osteonecrosis of the jaw and atypical femoral fracture, two rare but debilitating side effects. In addition, bisphosphonates are not recommended in patients with GFR <35 ml/min/1.73 m(2). Hence, there is a clear requirement for newer agents, which are able to reduce fracture risk further, whilst overcoming the limitations of bisphosphonates. Over the past 20 years, knowledge and a deeper understanding of the various signalling pathways involved in bone remodelling has increased, enabling identification of additional targets for therapy. This review focuses on these newer therapies and includes anti-resorptive agents such as raloxifene and other selective oestrogen receptor modulators, the monoclonal antibody denosumab (which inhibits the RANKL pathway), odanacatib, a cathepsin K inhibitor and the anabolic agents, PTH analogue; PTH (1-34) and anti-sclerostin antibodies (activator of the Wnt pathway). Strontium ranelate will not be reviewed as recent reports highlight concerns surrounding its cardiovascular safety and together with an apparent increased risk of thrombosis, its future use remains uncertain. Some of these agents such as raloxifene, denosumab and teriparatide are already in clinical use whilst others are at varying stages of development. This review will provide an overview of the mechanisms of action of these therapeutic agents on the skeleton and assess their efficacy in osteoporosis and fracture prevention.

Effect of combined teriparatide and monthly minodronic acid therapy on cancellous bone mass in ovariectomized rats: a bone histomorphometry study

The purpose of the present study was to determine whether teriparatide and monthly minodronic acid would have an additive effect on cancellous bone mass in ovariectomized rats. Seven-week-old female Sprague-Dawley rats were randomized into five groups of 10 animals each, including a sham-operation+vehicle group, an ovariectomy (OVX)+vehicle group, an OVX+minodronic acid (6 μg/kgs.c., every 4 weeks) group, an OVX+teriparatide (20 μg/kgs.c., daily) group, and an OVX+minodronic acid+teriparatide group. After the 12-week experimental period, static and dynamic histomorphometric analyses were performed on the cancellous bone of the tibial proximal metaphysis. OVX decreased the bone volume per total volume (BV/TV) and the trabecular number (Tb.N) and increased the trabecular separation (Tb.Sp) as a result of increased bone remodeling. Minodronic acid prevented the OVX-induced decreases in BV/TV, while teriparatide increased the BV/TV and trabecular width (Tb.Wi) beyond the values of the sham controls. Minodronic acid prevented, but teriparatide only mitigated, the OVX-induced decrease in Tb.N, although both drugs similarly prevented the OVX-induced increase in Tb.Sp. A combination of teriparatide and minodronic acid further increased the BV/TV and Tb.N and decreased the Tb.Sp as a result of the suppression of bone remodeling, compared with teriparatide alone. These results suggest the differential effect of teriparatide and monthly minodronic acid on cancellous bone structure and the additive effect of the two drugs on cancellous bone mass in OVX rats.

Distinctive role of 6-month teriparatide treatment on intractable bisphosphonate-related osteonecrosis of the jaw

The administration of teriparatide (TPTD) in conjunction with periodontal care could provide faster and more favorable clinical outcomes in previously refractory bisphosphonate-related osteonecrosis of the jaws (BRONJ) cases compared to conventional dental care, combination of surgery and antimicrobial treatment. We also found that underlying vitamin D levels might influence the response to TPTD treatment.

INTRODUCTION

Treatment of BRONJ is quite challenging and there are no standard treatment modalities. In this retrospective, longitudinal study, we examined whether additional TPTD administration could be beneficial for the resolution of BRONJ lesions compared to conservative management, such as antimicrobial treatment with or without surgery, and also studied the factors influencing the response to TPTD.

METHODS

Twenty-four cases of intractable BRONJ were included: 15 subjects were assigned to the TPTD group and the other 9 subjects, who refused TPTD administration, were assigned to the non-TPTD group. All subjects in both groups continued calcium and vitamin D supplementation and the TPTD group additionally received a daily subcutaneous injection of 20 μg TPTD for 6 months.

RESULTS

While 60.0% of the non-TPTD group showed one stage of improvement in BRONJ, 40.0% of the group did not show any improvement in disease status. In the TPTD group, 62.5% of the treated subjects showed one stage of improvement and the other 37.5% demonstrated a marked improvement, including two stages of improvement or complete healing, and there was not a single case that did not improve. The clinical improvement of BRONJ was statistically better in the TPTD group after the 6-month treatment (p < 0.05). Moreover, patients with higher baseline serum 25(OH)D levels showed better clinical therapeutic outcomes with TPTD.

CONCLUSIONS

We observed the beneficial effects of TPTD on BRONJ, and subjects with optimal serum vitamin D concentrations seemed to reap the maximum therapeutic effects of TPTD. A prospective, randomized, controlled trial should be needed to further evaluate the therapeutic efficacy of TPTD in the resolution of BRONJ.

A probable case of oral bisphosphonate-associated osteonecrosis of the jaw and recovery with parathyroid hormone treatment

INTRODUCTION

Bisphosphonates are effective for treating osteoporosis, Paget's disease of bone, and malignancy-associated bone diseases. Bisphosphonate-associated osteonecrosis of the jaw (ONJ) is a rare but serious adverse effect of bisphosphonate therapy. Due to inhibitory actions on bone turnover, bisphosphonate therapy may result in the accumulation of microdamage.

CASE SUMMARY

A 74-year-old Korean woman (height, 150 cm; weight, 51 kg) was referred to the Department of Endocrinology and Metabolism, Ajou University School of Medicine, Suwon, South Korea, for evaluation of pain and persistent abnormal exposure of jaw bone after extraction of teeth. She had been receiving weekly oral alendronate treatment for osteoporosis for ~5 years. The patient had the clinical features of bisphosphonate-associated osteonecrosis of the mandible, which was precipitated by teeth extraction ~14 months prior to the outpatient referral visit. At her clinical baseline visit, serum hormone concentrations and bone turnover markers were as follows: thyroid-stimulating hormone, 0.88 μIU/mL (reference range, 0.25-5.00 μIU/mL); 25-hydroxyvitamin D3, 20.9 (9.0-37.6) ng/mL; parathyroid hormone (PTH), 57 (11-62) pg/mL; serum osteocalcin, 8.7 (12.9-55.9) ng/mL; and urine N-telopeptide 21 (26-124) nM/mM creatinine. She had multiple systemic risk factors for ONJ, including older age, type 2 diabetes mellitus, and long duration of bisphosphonate therapy. There was no mandibular lesion improvement despite repeated surgical procedures performed within a 14-month period. Bisphosphonate therapy was discontinued and PTH therapy was started. After 2 months, exposed oral mucosa had healed. After 4 months of treatment, the pain had completely subsided, and after 6 months the patient's eating and drinking habits returned. The serum concentration of osteocalcin, a bone formation marker, which was initially suppressed (8.7 ng/mL), increased 174% (15.1 ng/mL) from baseline after 6 months of treatment with PTH.

CONCLUSIONS

Here we report a probable case of oral bisphosphonate-associated ONJ featuring suppressed bone turnover. Treatment with the bone formation-stimulating agent PTH was beneficial.

Local administration of alendronate reduced peri-tunnel bone loss and promoted graft-bone tunnel healing with minimal systemic effect on bone in contralateral knee

Continued systemic administration of alendronate was reported to reduce peri-tunnel bone resorption and promoted graft-bone tunnel healing at the early stage post-anterior cruciate ligament (ACL) reconstruction. However, systemic increase in bone mineral density (BMD) in the contralateral intact knee was observed. We tested if single local administration of alendronate into the bone tunnel during ACL reconstruction could achieve similar benefits yet without the systemic effect on bone. Seventy-two rats with unilateral ACL reconstruction were divided into three groups: saline, low-dose (6 μg/kg) and mid-dose (60 μg/kg) alendronate. For local administration, alendronate was applied to the bone tunnels for 2 min before graft insertion and repair. At weeks 2 and 6, the reconstructed complex was harvested for high-resolution computed tomography (vivaCT) imaging followed by biomechanical test or histology. Our results showed that local administration of low-dose alendronate showed comparable benefits on the reduction of peri-tunnel bone loss, enhancement of bone tunnel mineralization, tunnel graft integrity, graft osteointegration and mechanical strength of the reconstructed complex at early stage post-reconstruction, yet with minimal systemic effect on mineralized tissue at the contralateral intact knee. A single local administration of alendronate at the low-dose therefore might be used to promote early tunnel graft healing post-reconstruction.

Teriparatide and the treatment of bisphosphonate-related osteonecrosis of the jaw: a rat model

OBJECTIVES

The objectives of this study were to establish a bisphosphonate-related osteonecrosis of the jaw (BRONJ) rat model and to analyse the effects of teriparatide (TP) on this model.

METHODS

Sprague-Dawley rats were divided into three groups: I-zoledronic acid (ZA, n = 10); II-ZA and teriparatide (ZA + TP, n = 10); III-control (n = 10). Osteonecrosis was induced by administering zoledronic acid to groups ZA and ZA + TP. A week after the injections, rats underwent extraction of the first left mandibular molar. Following a four week period, TP was administered to the ZA + TP group for 28 days. Upon killing, extraction sockets were examined clinically, radiologically and histopathologically.

RESULTS

Clinical examination revealed necrotic bone exposure in none of the animals. MicroCT (µCT) examination showed that bone mineral density of the newly formed bone in the extraction socket was lower in the ZA group than in the ZA + TP group (p < 0.05). Histopathological examination revealed that only the ZA and ZA + TP groups developed osteonecrosis, and the osteonecrotic bone area in the ZA group was larger than that in the ZA + TP group (p < 0.05). Tartrate-resistant acid phosphatase (TRAcP) enzyme histochemistry revealed that the number of detached and large osteoclasts were higher in the ZA group than in other groups, whereas the number of apoptotic osteoclasts in both ZA and ZA + TP groups were higher than in the control group (p < 0.05).

CONCLUSIONS

Our data indicate that bisphosphonate-related osteonecrosis of the jaw model used in the present study is an attractive model to investigate treatment modalities and that TP might be an effective treatment in BRONJ.

Bisphosphonate-induced reductions in rat femoral bone energy absorption and toughness are testing rate-dependent

Bisphosphonates have been used for years to suppress bone turnover and reduce fracture risk. Bisphosphonates have recently been associated with atypical femoral fractures, which are catastrophic, low trauma, brittle fractures that appear to occur more frequently than in untreated individuals. Previous work using a dog model has demonstrated bisphosphonate-induced reductions in bone toughness (the inverse of brittleness), yet data are lacking to show this occurs in rodents. The goal of this study was to determine if bisphosphonate-induced alterations in toughness could be quantified in rats. At 26 weeks of age, skeletally mature rats (n = 32 total) were given an injection of either zoledronate (100 μg/kg body weight) or vehicle (0.5 ml saline). Five weeks post-injection, both femora were collected and analyzed for geometry and mechanical properties. To assess the effect of testing rate on the biomechanical outcomes, the left femora were broken at 2 mm/min, while the right femora were broken at 20 mm/min. The results showed a significantly lower energy to failure in zoledronate-treated animals compared to vehicle at the slow testing rate (-15%, p < 0.05) with no difference at the faster rate. While there was not a significant interaction between drug and testing rate for toughness to fracture (p = 0.07), toughness between ultimate stress and fracture was significantly lower with zoledronate only at the slow rate (-40%, p < 0.05). These data document that bisphosphonate-induced reductions in energy absorption and toughness can be quantified in rats yet they are highly dependent on testing rate.

Short-term teriparatide therapy as an adjunctive modality for bisphosphonate-related osteonecrosis of the jaws

To review the effect of teriparatide as an adjunctive modality for bisphosphonate-related osteonecrosis of the jaws (BRONJ), we describe a series of cases of teriparatide therapy for the treatment of BRONJ and serial changes of serum osteoclacin (s-OC) and serum C-terminal telopeptide cross-link of type I collagen (s-CTX).

INTRODUCTION

Management of BRONJ is quite challenging and the currently recommended modalities for BRONJ are still suboptimal. For the improvement of bony remodeling, some clinicians advocated bisphosphonate holiday although validity of this drug holiday has been debated so far. Recently, the use of teriparatide was introduced in several cases, but the number of the publication is limited and mostly anecdotal so far.

METHOD

Bisphosphonate was suspended and teriparatide was given to six patients diagnosed with BRONJ by single bone specialist. Medical record review and interviews were carried out. S-CTX and s-OC were measured at the baseline, 2 months and 3 months later teriparatide therapy. The outcome of the treatment and the change of biochemical markers were compared.

RESULT

In all six patients, s-OC values were significantly elevated within 2 months after teriparatide treatment and the BRONJ lesions were healed. S-CTX values were also elevated in four patients, whereas those of the rest two patients stayed within minimal change. The change was marginally significant at 3 months.

CONCLUSION

In terms of the multifactorial etiology of BRONJ, bone formation suppression was noticed in the patients. Based upon this finding, the short-term use of teriparatide might be beneficial to the resolution of BRONJ lesions by improving suppressed bone remodeling.

Pharmacodynamic responses to combined treatment regimens with the calcium sensing receptor antagonist JTT-305/MK-5442 and alendronate in osteopenic ovariectomized rats

Parathyroid hormone (PTH) is the anabolic standard of care for patients with severe osteoporosis. The CaSR allosteric antagonist JTT-305/MK-5442, a PTH secretagogue, could offer an oral osteoanabolic treatment alternative for postmenopausal women with osteoporosis. Here we disclose the pharmacokinetic profile of JTT-305/MK-5442 and its activity on bone remodeling in ovariectomized (OVX) osteopenic rats. Daily treatments (0.3 to 2.4 mg/kg/d) for 12 weeks resulted in plateaued BMD increases (3.8 to 5.3%) at axial and appendicular skeletal sites. However, treatment effects were not statistically significant, in agreement with effects seen in animals treated with low dose PTH (1-84) (5 μg/kg/d). In a consecutive study we tested JTT-305/MK-5442 effects on bone formation in OVX-rats challenged with combined alendronate (ALN) treatment paradigms. At 7 month, JTT-305/MK-5442 treatment significantly increased BMD in lumbar vertebrae (LV), while no change in BMD was observed in femora or tibiae. ALN add-on co-treatment produced incremental increases in LV, distal femur (DF) and proximal tibia (PT) BMD over the respective ALN control. Histological analyses confirmed modest increases in mineralized surface (MS/BS) and bone formation rate (30.5±1.9%) on trabecular surfaces by JTT-305/MK-5442. As expected, ALN administration profoundly reduced bone formation, however, JTT-305/MK-5442 significantly stimulated MS/BS and BFR in ALN treated groups. In summary, JTT-305/MK-5442 acts as a PTH secretagogue in the osteopenic OVX-rat, eliciting consistent, though modest effects on remediation of BMD due to estrogen depletion. Induction of bone formation by JTT-305/MK-5442 at trabecular bone surfaces appears to be resilient to ALN-mediated suppression of bone formation. This study provides for the first time, a mechanistic evaluation of combination treatment of a PTH secretagogue with ALN.

Combination therapy with eldecalcitol and alendronate has therapeutic advantages over monotherapy by improving bone strength

Eldecalcitol (ED-71), a 2β-hydroxypropyloxy derivative of 1α,25(OH)(2)D(3), inhibits bone resorption more potently than does alfacalcidol while maintaining osteoblastic function in an estrogen-deficient, high-turnover osteoporosis rat model. Alendronate (ALN) has been reported to increase bone mass by suppressing bone resorption mainly by inducing apoptosis of osteoclasts. The aim of this study was to clarify the combination effect of ED-71 and ALN on bone loss in ovariectomized rats. Wistar-Imamichi rats (32weeks old) were ovariectomized and randomly assigned to 10 groups (n=9-11); 11 rats were sham-operated. Rats were orally administered either vehicle alone, ALN (0.05, 0.2mg/kg), ED-71 (0.015, 0.03μg/kg), or a combination of ALN and ED-71. The treatment started 2weeks after surgery and continued for 12weeks. ED-71 significantly increased calcium and phosphorus in serum and urine; however, the mean values were within the normal range. Bone mineral density (BMD) and maximum load in both the lumbar spine and femur significantly increased with ED-71 monotherapy, and showed a tendency to increase with ALN monotherapy. Compared with ALN monotherapy, the combination of ALN and ED-71 significantly increased BMD and maximum load in both the lumbar spine and femur, suggesting that the combination therapy is more beneficial than ALN monotherapy in this protocol. The combination treatment had an additive suppressive effect on eroded surface and osteoclast number, with the suppressive effect more potent than either ALN or ED-71 monotherapy. Moreover, the combination therapy partially counteracted the suppressive effects of ALN on bone formation and on the histomorphometric indices of osteoblast number and activity. Interestingly, ALN had no effect on the anabolic action of ED-71. In conclusion, the combination therapy of ALN and ED-71 has therapeutic advantages over ALN monotherapy in terms of improving bone mechanical strength without excessive suppression of bone turnover.

Densitometry, radiography, and histological assessment of collagen as methods to evaluate femoral bones in an experimental model of osteoporosis

SUMMARY

All methods to detect experimental loss of bone present technique limitations. The sensitivities of image and histological analyses to detect the effects of teriparatide in rats with bone loss after ovariectomy were evaluated. All methods were qualitatively valid.

INTRODUCTION

The standardization of methods to assess bone loss after ovariectomy is crucial to establish the degree of experimental osteoporosis. In general, methods per image or histological techniques are used. To validate these two ways to determine the degree of bone loss in ovariectomized rats, we evaluated the sensitivities of bone densitometry, conventional radiography, and histological analysis of the area occupied by collagen, detecting the effects of teriparatide treatment in the femur of ovariectomized rats with bone loss.

METHODS

Wistar rats were divided into three groups: a control group, in which the animals were only subjected to laparotomy; an ovariectomized group, in which bilateral removal of the ovaries was performed; and an ovariectomized + teriparatide group, in which bilateral removal of the ovaries was performed, and the animals were treated with 3 μg/100 g/day of teriparatide. Three months following the ovariectomy, bone densitometry, radiographic densitometry, and histological analysis of the area occupied by collagen fibers were carried out in the femur diaphysis.

RESULTS

The bone densitometry revealed 11.2% reduction in femur density; in the conventional radiography, the loss of bone mass was 14.5%, and with the histological analysis, a 40.9% reduction in the area occupied by collagen was detected in the femur diaphysis.

CONCLUSIONS

In conclusion, histological analysis could not be quantitatively compared with the methods of bone densitometry and conventional radiography; however, all of these methods were qualitatively valid for assessing the loss of bone stemming from ovariectomy and the therapeutic effect of teriparatide in the prevention of osteoporosis.

Effect of teriparatide on induced tooth displacement in ovariectomized rats: a histomorphometric analysis

INTRODUCTION

The aim of this study was to evaluate morphologically the effect of teriparatide on induced orthodontic movement of the maxillary first molars in ovariectomized rats.

METHODS

Ovariectomized Wistar rats (n = 16), ovariectomized rats treated with teriparatide (n = 16), and nonovariectomized rats (n = 16) had orthodontic tooth movement for 5 and 7 days. The group treated with teriparatide received a subcutaneous injection (Forteo, Eli Lilly, Indianapolis, Ind; 30 μg/kg/day) for 90 days after the ovariectomy. Histologic sections obtained from the maxilla were prepared for the morphometric analysis of dental movement, the thickness of the periodontal ligament, and the number of osteoclasts in the pressure and tension areas of the apex of the root and alveolar crest in the distal root of the maxillary first molars.

RESULTS

The ovariectomized rats treated with teriparatide had similar responses at 5 and 7 days after the induced dental movements compared with the untreated ovariectomized group. Both ovariectomized groups had greater molar movement on day 7 day compared with the controls (P <0.05). There were no statistically significant differences between groups in the spacing of the periodontal ligament or the number of osteoclasts in the areas studied.

CONCLUSIONS

These data suggest that the treatment of osteoporosis with teriparatide is a good alternative for patients undergoing orthodontic treatment.

Teriparatide [rhPTH (1-34)], but not strontium ranelate, demonstrated bone anabolic efficacy in mature, osteopenic, ovariectomized rats

We compared teriparatide (TPTD) and strontium ranelate (SR) efficacy on bone formation activity in a mature rat model of estrogen-deficiency bone loss. Rats were ovariectomized (OVX) at age 6 months and permitted to lose bone for 2 months to establish osteopenia before initiation of treatment with TPTD (5 or 15 μg/kg · d sc) or SR (150 or 450 mg/kg · d oral gavage). After 3 wk, RT-PCR analyses of bone formation genes in the distal femur metaphysis showed significant elevation of collagen 1α2, osteocalcin, bone sialoprotein, alkaline phosphatase, and Runx2 gene expression at both TPTD doses, relative to OVX controls. SR had no significant effect on expression of these genes. TPTD treatment for 12 wk dose dependently increased lumbar vertebral (LV) and femoral midshaft bone mineral content (BMC) and bone mineral density over pretreatment and age-matched OVX controls. SR 150 increased BMC, and SR 450 increased BMC and bone mineral density of femoral midshaft and LV over OVX controls. There were significant dose-dependent TPTD increases of LV and femoral neck strength, and TPTD 15 also increased midshaft strength compared with pretreatment and age-matched OVX controls. SR did not enhance bone strength relative to pretreatment or age-matched OVX controls. Histomorphometry of the proximal tibial metaphysis showed dose-dependent effects of TPTD on trabecular area, number, width, and osteoblast surface, bone mineralizing surface, and bone formation rate relative to pretreatment and age-matched OVX controls, whereas SR had no effect on these parameters. These findings confirmed the bone anabolic efficacy of teriparatide, but not SR in mature, osteopenic, OVX rats.

The effects of parathyroid hormone applied at different regimes on the trochanteric region of the femur in ovariectomized rat model of osteoporosis

This study aims to investigate the effects of two application frequencies of parathyroid hormone on the trochanteric region of rat femur. Forty-three-month-old female Sprague-Dawley rats were divided into 4 groups (n = 10/group). Three groups were ovariectomized, and 8 weeks later they were administered the following treatments (5 weeks): soy-free diet (OVX), subcutaneously injected PTH (0.040 mg/kg) 5 days a week (PTH 5x/w), subcutaneously injected PTH (0.040 mg/kg) every 2 days (PTH e2d), and a sham group. The values of the biomechanical and histomorphometric parameters showed higher results in 5x/w animals in comparison to the OVX and PTH 2ed groups. The ratio between bone diameter/marrow diameter (B.Dm/Ma.Dm) in subtrochanteric cross sections did not show any significant differences between PTH 5x/w and PTH e2d. The increased bone formation rate was observed under PTH treatment in both groups mainly at the endosteal side. The endosteum seems here to be one of the targets of PTH with an accelerate bone formation and a pronounced filling-in of intracortical cavities with higher intensity for the PTH 5x/w in comparison to PTH e2d rats.

Cathepsin K inhibitors prevent bone loss in estrogen-deficient rabbits

Two cathepsin K inhibitors (CatKIs) were compared with alendronate (ALN) for their effects on bone resorption and formation in ovariectomized (OVX) rabbits. The OVX model was validated by demonstrating significant loss (9.8% to 12.8%) in lumbar vertebral bone mineral density (LV BMD) in rabbits at 13-weeks after surgery, which was prevented by estrogen or ALN. A potent CatKI, L-006235 (L-235), dosed at 10 mg/kg per day for 27 weeks, significantly decreased LV BMD loss (p < .01) versus OVX-vehicle control. ALN reduced spine cancellous mineralizing surface by 70%, whereas L-235 had no effect. Similarly, endocortical bone-formation rate and the number of double-labeled Haversian canals in the femoral diaphysis were not affected by L-235. To confirm the sparing effects of CatKI on bone formation, odanacatib (ODN) was dosed in food to achieve steady-state exposures of 4 or 9 µM/day in OVX rabbits for 27 weeks. ODN at both doses prevented LV BMD loss (p < .05 and p < .001, respectively) versus OVX-vehicle control to levels comparable with sham or ALN. ODN also dose-dependently increased BMD at the proximal femur, femoral neck, and trochanter. Similar to L-235, ODN did not reduce bone formation at any bone sites studied. The positive and highly correlative relationship of peak load to bone mineral content in the central femur and spine suggested that ODN treatment preserved normal biomechanical properties of relevant skeletal sites. Although CatKIs had similar efficacy to ALN in preventing bone loss in adult OVX rabbits, this novel class of antiresorptives differs from ALN by sparing bone formation, potentially via uncoupling bone formation from resorption.

Intermittent parathyroid hormone administration counteracts the adverse effects of glucocorticoids on osteoblast and osteocyte viability, bone formation, and strength in mice

Glucocorticoids act directly on bone cells to decrease production of osteoblasts and osteoclasts, increase osteoblast and osteocyte apoptosis, and prolong osteoclast life span. Conversely, daily injections of PTH decrease osteoblast and osteocyte apoptosis and increase bone formation and strength. Using a mouse model, we investigated whether the recently demonstrated efficacy of PTH in glucocorticoid-induced bone disease results from the ability of this therapeutic modality to counteract at least some of the direct effects of glucocorticoids on bone cells. Glucocorticoid administration to 5- to 6-month-old Swiss-Webster mice for 28 d increased the prevalence of osteoblast and osteocyte apoptosis and decreased osteoblast number, activation frequency, and bone formation rate, resulting in reduced osteoid, wall and trabecular width, bone mineral density, and bone strength. In contrast, daily injections of PTH caused a decrease in osteoblast and osteocyte apoptosis and an increase in osteoblast number, activation frequency, bone formation rate, bone mineral density, and bone strength. The decreased osteocyte apoptosis was associated with increased bone strength. When the two agents were combined, all the adverse effects of glucocorticoid excess on bone were prevented. Likewise, in cultured osteoblastic cells, PTH attenuated the adverse effects of glucocorticoids on osteoblast survival and Wnt signaling via an Akt phosphorylation-dependent mechanism. We conclude that intermittent PTH administration directly counteracts the key pathogenetic mechanisms of glucocorticoid excess on bone, thus providing a mechanistic explanation of its efficacy against glucocorticoid-induced osteoporosis.

Effects of teriparatide, alendronate, or both in women with postmenopausal osteoporosis

CONTEXT

Teriparatide increases both bone formation and bone resorption.

OBJECTIVE

We sought to determine whether combining teriparatide with an antiresorptive agent would alter its anabolic action.

DESIGN AND SETTING

This was a randomized controlled trial conducted in a single university hospital.

PATIENTS AND INTERVENTION

We randomized 93 postmenopausal women with low bone mineral density (BMD) to alendronate 10 mg daily (group 1), teriparatide 40 microg sc daily (group 2), or both (group 3) for 30 months. Teriparatide was begun at month 6.

MAIN OUTCOME MEASURES

BMD of the lumbar spine, proximal femur, proximal radius, and total body was measured by dual-energy x-ray absorptiometry (DXA) every 6 months. Lumbar spine trabecular BMD was measured at baseline and month 30 by quantitative computed tomography. Serum osteocalcin, N-terminal propeptide of type 1 collagen, and N-telopeptide levels were assessed frequently. Women who had at least one repeat DXA scan on therapy were included in the analyses (n = 69).

RESULTS

DXA spine BMD increased more in women treated with teriparatide alone than with alendronate alone (18 +/- 11 vs. 7 +/- 4%; P < 0.001) or both (18+/-11 vs. 12 +/- 9%; P = 0.045). Similarly, femoral neck BMD increased more in women treated with teriparatide alone than with alendronate alone (11 +/- 5 vs. 4 +/- 4%; P < 0.001) or both (11 +/- 5 vs. 3 +/- 5%; P < 0.001). Quantitative computed tomography spine BMD increased 1 +/- 7, 61 +/- 31, and 24 +/- 24% in groups 1, 2, and 3 (P < 0.001 for all comparisons). Serum osteocalcin, N-terminal propeptide of type 1 collagen, and cross-linked N-telopeptides of type I collagen increased more with teriparatide alone than with both (P < 0.001 for each marker).

CONCLUSION

Alendronate reduces the ability of teriparatide to increase BMD and bone turnover in women.

RAGE supports parathyroid hormone-induced gains in femoral trabecular bone

Parathyroid hormone (PTH) restores bone mass to the osteopenic skeleton, but significant questions remain as to the underlying mechanisms. The receptor for advanced glycation end products (RAGE) is a multiligand receptor of the immunoglobulin superfamily; however, recent studies indicate a role in bone physiology. We investigated the significance of RAGE to hormone-induced increases in bone by treating 10-wk-old female Rage-knockout (KO) and wild-type (WT) mice with human PTH-(1-34) at 30 microg.kg(-1).day(-1) or vehicle control, 7 days/wk, for 7 wk. PTH produced equivalent relative gains in bone mineral density (BMD) and bone mineral content (BMC) throughout the skeleton in both genotypes. PTH-mediated relative increases in cortical area of the midshaft femur were not compromised in the null mice. However, the hormone-induced gain in femoral cancellous bone was significantly attenuated in Rage-KO mice. The loss of RAGE impaired PTH-mediated increases in femoral cancellous bone volume, connectivity density, and trabecular number but did not impact increases in trabecular thickness or decreases in trabecular spacing. Disabling RAGE reduced femoral expression of bone formation genes, but their relative PTH-responsiveness was not impaired. Neutralizing RAGE did not attenuate vertebral cancellous bone response to hormone. Rage-null mice exhibited an attenuated accrual rate of bone mass, with the exception of the spine, and an enhanced accrual rate of fat mass. We conclude that RAGE is necessary for key aspects of the skeleton's response to anabolic PTH. Specifically, RAGE is required for hormone-mediated improvement of femoral trabecular architecture but not intrinsically necessary for increasing cortical thickness.

Identification of novel biphenyl carboxylic acid derivatives as novel antiresorptive agents that do not impair parathyroid hormone-induced bone formation

Bisphosphonates are widely used in the treatment of osteoporosis, but they inhibit bone formation and blunt the anabolic effect of PTH. Here we describe a novel series of compounds that have potent antiresorptive effects in vitro and in vivo that do not adversely affect osteoblast function. The effects of the compounds on osteoclast formation and survival were studied on mouse osteoclasts generated from bone marrow macrophages and on osteoblast function using primary mouse calvarial osteoblast cultures and bone nodule cultures. Studies were performed in vivo using sham-operated or ovariectomized mice. The most potent compound tested was ABD350, a halogen-substituted derivative of the parent compound ABD56 in which the labile ester bond was replaced by a reduced ketone link, with IC50 osteoclast formation at a concentration of 1.3 microm. All compounds inhibited receptor activator of nuclear factor-kappaB ligand-induced inhibitor of nuclear factor kappaB phosphorylation and caused osteoclast apoptosis but no inhibitory effects on osteoblast function were observed at concentrations of up to 20 microm. ABD350 prevented ovariectomy-induced bone loss when given ip (5 mg/kg.d), whereas ABD56 was only partially effective at this dose. In contrast to the bisphosphonate alendronate, ABD350 had no inhibitory effect on PTH-induced bone formation in ovariectomized mice. In conclusion, the biphenyl carboxylic acid derivatives like ABD350 represent a new class of antiresorptive drugs that inhibit osteoclast activity but have no significant inhibitory effects on osteoblast activity in vitro or PTH-induced bone formation in vivo.

Effects of two years of daily teriparatide treatment on BMD in postmenopausal women with severe osteoporosis with and without prior antiresorptive treatment

Previous antiresorptive (AR) treatment may influence the response to teriparatide. We examined BMD response and safety in a subgroup of 503 postmenopausal women with osteoporosis who received teriparatide for 24 mo. Patients were divided into three groups based on their prior AR treatment: treatment-naïve (n = 84); pretreated with no evidence of inadequate treatment response (n = 134); and pretreated showing an inadequate response to AR treatment (n = 285), which was predefined based on the occurrence of fractures, persistent low BMD, and/or significant BMD loss while on therapy. Changes in BMD from baseline were analyzed using mixed model repeated measures. Lumbar spine BMD increased significantly from baseline at 6, 12, 18, and 24 mo in all three groups. The mean gain in spine BMD over 24 mo was greater in the treatment-naïve group (0.095 g/cm(2); 13.1%) than in the AR pretreated (0.074 g/cm(2); 10.2%; p < 0.005) and inadequate AR responder (0.071 g/cm(2); 9.8%; p < 0.001) groups. The corresponding increases in total hip BMD were 3.8%, 2.3%, and 2.3%, respectively. Early decreases in hip BMD in the inadequate AR responder group were reversed by 18 mo of treatment. Increases in BMD between 18 and 24 mo were highly significant. Nausea (13.3%) and arthralgia (11.7%) were the most commonly reported adverse events. Asymptomatic hypercalcemia was reported in 5.0% of patients. Teriparatide treatment for 24 mo is associated with a significant increase in BMD in patients with and without previous AR use. Prior AR treatment modestly blunted the BMD response to teriparatide. Safety was consistent with current prescribing label information.

Hyperlipidemia impairs osteoanabolic effects of PTH

Epidemiological and in vitro studies have suggested that hyperlipidemia/oxidized phospholipids adversely affect bone. We recently found that oxidized phospholipids attenuate PTH-induced cAMP and immediate-early gene (IEG) expression in MC3T3-E1 cells, raising concerns that clinical hyperlipidemia may attenuate osteoanabolic effects of PTH in vivo. Thus, we studied whether intermittent PTH treatment has differential osteoanabolic effects in wildtype (C57BL/6) and hyperlipidemic (LDLR(-/-)) mice. Consistent with our previous in vitro studies, induction of IEGs in calvarial tissue, 45 min after a single dose of recombinant hPTH(1-34), was attenuated in LDLR(-/-) mice compared with C57BL/6 mice. Daily hPTH(1-34) injections for 5 wk significantly increased total and cortical BMD and BMC, assessed by pQCT, in C57BL/6 mice. However, this induction was completely abrogated in LDLR(-/-) mice. Similarly, PTH(1-34) failed to increase BMD in another hyperlipidemic mouse model, ApoE(-/-) mice. Histomorphometric analysis showed that trabecular bone of both mice responded similarly to PTH(1-34). Structural parameters improved significantly in response to PTH(1-34) in both mouse strains, although to a lesser degree in LDLR(-/-) mice. With PTH(1-34) treatment, osteoblast surface trended toward an increase in C57BL/6 mice and increased significantly in LDLR(-/-) mice. PTH(1-34) did not alter resorption parameters significantly, except for the eroded surface (ES/BS), which was reduced in the C57BL/6 but not in the LDLR(-/-) mice. These results show that PTH(1-34) has adverse effects on cortical bones of the hyperlipidemic mice, suggesting that the therapeutic effects of PTH may be compromised in the presence of hyperlipidemia.

Effect of prior and ongoing raloxifene therapy on response to PTH and maintenance of BMD after PTH therapy

Women with osteoporosis on raloxifene were randomized to 1-34hPTH + raloxifene or raloxifene alone for one year. In the PTH + raloxifene group, bone turnover increased 125-584%, spine BMD increased 9.6%, hip BMD increased 1.2-3.6% and radius BMD declined 4.3%. During the follow-up year, on continued raloxifene, BMD declined slightly at all sites except the femoral neck.

INTRODUCTION

The influence of prior antiresorptives on response to 1-34PTH and the ability to maintain BMD gains might differ for antiresorptive agents with different potencies. The objectives were to evaluate biochemical and bone density responses to 1-34PTH in patients on prior and ongoing raloxifene and to determine whether raloxifene maintains bone gains.

METHODS

Forty-two postmenopausal women with osteoporosis on raloxifene were randomized to raloxifene alone or 1-34PTH daily for 12 months (continuing raloxifene). Women were then followed for 12 months on raloxifene alone. Bone turnover markers and BMD were measured at baseline and at 3, 6, 12, 18 and 24 months.

RESULTS

Biochemical indices increased rapidly during PTH treatment with peak increments of 125-584% for the three markers (p<0.001 vs. baseline). After one year of PTH, mean BMD increases were 9.6% for spine, 2.7% for total hip, 3.6% for trochanter (all p<0.005) and 1.2% in femoral neck (NS), while BMD declined 4.3% in the radius (p=0.003). After PTH withdrawal, on continued raloxifene, BMD declined slightly (0.7-2.9% losses; NS) at all sites, except the femoral neck, where BMD increased modestly (p=0.04). At 24 months, spine and femoral neck BMD remained significantly higher than baseline, while radius BMD remained significantly lower (all p<0.04).

CONCLUSION

Substantial gains in BMD of the spine and hip, but not the radius, are seen with one year of PTH treatment in patients on prior raloxifene. After PTH is discontinued, raloxifene partially maintains PTH-induced BMD gains in the spine and hip.

Effects of previous antiresorptive therapy on the bone mineral density response to two years of teriparatide treatment in postmenopausal women with osteoporosis

INTRODUCTION

EUROFORS was a 2-yr prospective, randomized trial of postmenopausal women with established osteoporosis, designed to investigate various sequential treatments after teriparatide 20 microg/d for 1 yr. The present secondary analysis examined the effects of 2 yr of open-label teriparatide in women previously treated with antiresorptive drugs for at least 1 yr.

METHODS

A subgroup of 245 women with osteoporosis who had 2 yr of teriparatide treatment were stratified by previous predominant antiresorptive treatment into four groups: alendronate (n=107), risedronate (n=59), etidronate (n=30), and non-bisphosphonate (n=49). Bone mineral density (BMD) at the lumbar spine and hip was determined after 6, 12, 18, and 24 months, and bone formation markers were measured after 1 and 6 months.

RESULTS

Significant increases in bone formation markers occurred in all groups after 1 month of teriparatide treatment. Lumbar spine BMD increased at all visits, whereas a transient decrease in hip BMD, which was subsequently reversed, was observed in all groups. BMD responses were similar in all previous antiresorptive groups. Previous etidronate users showed a higher increase at the spine but not at the hip BMD. Duration of previous antiresorptive therapy and lag time between stopping previous therapy and starting teriparatide did not affect the BMD response at any skeletal site. Treatment-emergent adverse events were similar to those reported in treatment-naive postmenopausal women with osteoporosis treated with teriparatide.

CONCLUSIONS

Teriparatide induces positive effects on BMD and markers of bone formation in postmenopausal women with established osteoporosis, regardless of previous long-term exposure to antiresorptive therapies.

Additive effects of PTH and bisphosphonates on the bone healing response to metaphyseal implants in rats

BACKGROUND

When PTH is used to increase the amount of bone in osteoporotic patients, combination with bisphosphonates is known to attenuate the response. This might be explained by the reduced number of remodeling sites after bisphosphonate treatment, which reduces the number of cells able to respond to PTH. However, in a repair situation after trauma, a large number of osteoblasts reside in the wound site. If their activity is no longer coupled to osteoclasts, decreased resorption by bisphosphonates and stimulation of osteoblastic activity by PTH should both (independently) increase bone formation. Thus, we hypothesized that in contrast to the case in osteoporosis treatment, PTH and bisphosphonates have an additive effect in situations involving bone regeneration.

MATERIAL AND METHODS

Stainless steel screws, either coated with biphosphonates or uncoated, were inserted in 46 rat tibias. This normally elicits a bone repair response, leading to a gradual increase in the strength of screw fixation. Half of the rats also received daily injections of teriparatide (PTH). Thus, there were 4 groups: control, bisphosphonate, PTH, and bisphosphonate plus PTH. Pull-out force and energy were measured after 2 weeks.

RESULTS

The combined treatment had the strongest effect. It doubled the pull-out force and tripled the pull-out energy, compared to untreated controls. Also, bisphosphonate or PTH alone increased the pull-out force and energy, although less. No treatment cross-dependency was observed.

INTERPRETATION

Because bisphosphonates mainly influence osteoclasts, and intermittent administration of PTH mainly influences osteoblasts, our findings indicate that to a large extent these cells work without coupling in this model. It appears that bisphosphonates are unlikely to attenuate the response to PTH during the formation of new bone.

Raloxifene effects on thyroid gland morphology in ovariectomized rats

We aimed to analyze the effects of raloxifene and estrogen on thyroid gland morphology of ovariectomized rats. Raloxifene treatment led to effects similar to those of estrogen on thyroid glands from ovariectomized rats, so that both were able to normalize the changes detected after ovariectomy.

Effects of genistein on vertebral trabecular bone microstructure, bone mineral density, microcracks, osteocyte density, and bone strength in ovariectomized rats

Until now, the effects of phytoestrogen on bone in both women and ovarian hormone-deficient animal models of osteoporosis have remained uncertain. We have aimed here to investigate the effect of genistein (GEN) on trabecular bone quality in ovariectomized (OVX) rats. Forty 7-month-old female Sprague-Dawley rats were randomly divided into the following four groups: OVX, sham-operated (SHAM), treated with 17beta-estradiol (EST, 10 microg x kg(-1) x day(-1)), and GEN (5 mg x kg(-1) x day(-1)). At 15 weeks postoperation, the compressive test was performed on the L5 vertebral body; additionally, microcomputed tomography (micro-CT) assessment was performed to estimate the bone mineral density (BMD) and microstructure parameters of the L6 vertebral body. After fatigue damage testing, the L6 vertebral body was bulk-stained in 1% basic fuchsin and embedded in methylmethacrylate. The L4 vertebral body was embedded in methylmethacrylate for dynamic histomorphometry analysis without staining. Mounted bone slices were used to measure microcrack parameters, empty osteocyte lacuna density (e.Lc.Dn), and osteocyte density (Ot.N/T.Ar). Maximum loading (ML) and Ot.N/T.Ar were significantly lower in the OVX group than in the other groups. E.Lc.Dn was significantly decreased in GEN and EST groups compared to the OVX group. ML was significantly decreased in the GEN group compared to the SHAM group. Microcrack density, microcrack surface density, and microcrack length were significantly increased in the OVX group compared to the other groups. Mineral apposition rate was significantly decreased in the OVX group compared to the SHAM and GEN groups. Bone formation rate was significantly decreased in the OVX group compared to other groups. There were no significant differences with regard to mineralizing surface among the four groups. Volumetric BMD at organ was significantly lower in OVX, EST, and GEN groups than in the SHAM group. Bone mineral content was significantly lower in the OVX group than in the SHAM group. Bone volume fraction and trabecular number were significantly decreased in OVX, EST, and GEN groups compared to the SHAM group. Structure model index was significantly lower in the SHAM group than in OVX, EST, and GEN groups. Trabecular separation was significantly increased in the OVX group compared to SHAM and EST groups. There were no significant differences with regard to the trabecular thickness (Tb,Th) between SHAM, GEN, and OVX groups. Tb.Th was significantly lower in the EST group than in the SHAM group. Connectivity density (Conn.D) was significantly lower in the OVX group than in SHAM and GEN groups, and Conn. D was significantly lower in the EST group than in GEN. In conclusion, the present study demonstrates that GEN preserved the biomechanical quality of the trabecular bone regardless of the microstructure and BMD.

Cancer treatment-related bone loss: a review and synthesis of the literature

Cancer therapy can result in significant bone loss and increased risk of fragility fracture. Chemotherapy, aromatase inhibitors, and gonadotropin-releasing hormone analogues contribute to increases in the rate of bone remodelling and reduce bone mineral density. Patients with prostate cancer on androgen deprivation therapy experience an increase in the risk of fracture. New research has demonstrated the key role played by bisphosphonates in preventing declines in bone density and increases in bone remodelling. Novel antiresorptive agents targeting receptor activator of nuclear factor κB ligand have great potential in skeletal protection and prevention of bone loss related to cancer therapy. Early assessment of skeletal health, followed by initiation of calcium, vitamin D, and an exercise program are valuable in the prevention and treatment of osteoporosis. In addition, individuals at increased risk for fracture should be offered antiresorptive therapy. Early data have demonstrated that bisphosphonates are able to prevent the bone loss and increased bone remodelling associated with cancer therapy, including aromatase inhibition and androgen deprivation therapy. The present paper reviews the new research and advances in the management of bone loss associated with both cancer therapy and estrogen deficiency in the postmenopausal female.

Risedronate did not block the maximal anabolic effect of PTH in aged rats

The study was designed to investigate if pre-treating rats with a therapeutic equivalent dose of risedronate blunted the anabolic effects of PTH, and whether a withdrawal period prior to PTH treatment would alter any effect of risedronate on PTH treatment. Skeletally mature rats were treated for 18 weeks with vehicle, risedronate, or risedronate for 8 weeks followed by vehicle for 10 weeks (withdrawal period). At the end of this period, animals were treated for a further 12 weeks with PTH or PTH vehicle. Trabecular and cortical bone mass were monitored by serial pQCT, or by DXA and microCT. Bone histomorphometry was performed on the proximal tibiae and tibial shafts for bone turnover parameters at week 40. Risedronate alone moderately increased while PTH alone markedly increased trabecular bone mass at the proximal tibial (35% and 200%, respectively) and lumbar vertebral body (14% and 36%, respectively). The maximum bone gains were similar with and without pretreatment with risedronate as compared to the PTH alone. Continuous administration of risedronate for 18 weeks prior to PTH treatment had lower percentage increases in proximal tibial BMD during the first 8 weeks of PTH treatments, and had lower active bone forming surface and bone formation rates after being treated with PTH 12 weeks as compared to the PTH alone group. However, with the 10-week withdrawal period, risedronate did not blunt the stimulatory effect of PTH on osteoblast activity as shown by similar bone formation rates as with PTH alone. Our findings suggest that while risedronate pretreatment may slow the bone anabolic response to PTH, a withdrawal period prior to PTH treatment allows osteoblastic activity to respond normally to PTH stimulation.

Biology of RANK, RANKL, and osteoprotegerin

The discovery of the receptor activator of nuclear factor-κB ligand (RANKL)/RANK/osteoprotegerin (OPG) system and its role in the regulation of bone resorption exemplifies how both serendipity and a logic-based approach can identify factors that regulate cell function. Before this discovery in the mid to late 1990s, it had long been recognized that osteoclast formation was regulated by factors expressed by osteoblast/stromal cells, but it had not been anticipated that members of the tumor necrosis factor superfamily of ligands and receptors would be involved or that the factors involved would have extensive functions beyond bone remodeling. RANKL/RANK signaling regulates the formation of multinucleated osteoclasts from their precursors as well as their activation and survival in normal bone remodeling and in a variety of pathologic conditions. OPG protects the skeleton from excessive bone resorption by binding to RANKL and preventing it from binding to its receptor, RANK. Thus, RANKL/OPG ratio is an important determinant of bone mass and skeletal integrity. Genetic studies in mice indicate that RANKL/RANK signaling is also required for lymph node formation and mammary gland lactational hyperplasia, and that OPG also protects arteries from medial calcification. Thus, these tumor necrosis factor superfamily members have important functions outside bone. Although our understanding of the mechanisms whereby they regulate osteoclast formation has advanced rapidly during the past 10 years, many questions remain about their roles in health and disease. Here we review our current understanding of the role of the RANKL/RANK/OPG system in bone and other tissues.

The effects of combination of alendronate and human parathyroid hormone(1-34) on bone strength are synergistic in the lumbar vertebra and additive in the femur of C57BL/6J mice

A cyclic PTH regimen is as effective as a daily regimen on bone density gain in humans and in improving bone quality in mice. Our previous murine study evaluated the effects of a cyclic PTH regimen in the absence of a bisphosphonate, whereas our human study addressed the effects of a cyclic PTH regimen in the presence of ongoing alendronate (ALN) treatment. Accordingly, the current study examined the effects of cyclic or daily PTH regimens in combination with ALN on bone quality and bone density in mice. Twenty-week-old, female C57BL/6J mice were treated with the following sc injections (n = 10): 1) vehicle for 5 d/wk (control); 2) ALN (20 microg/kg x d) 3 d/wk (ALN); 3) human PTH(1-34) (40 microg/kg x d) 5 d/wk (daily PTH); 4) daily PTH in addition to ALN (daily PTH plus ALN); 5) PTH 5 d/wk and vehicle 5 d/wk alternating weekly (cyclic PTH); 6) cyclic PTH in addition to ALN (cyclic PTH plus ALN); and 7) PTH and ALN alternating weekly (alt PTH and ALN). Bone mineral density was measured weekly by dual-energy x-ray absorptiometry, and at 7 wk, bone markers, bone structure, and bone strength were evaluated by biochemical assays, peripheral quantitative computed tomography and mechanical testing, respectively. At 7 wk, all treatments significantly increased femoral and vertebral bone mineral density. ALN slightly decreased endosteal circumference, whereas PTH increased periosteal circumference, resulting in significant increases in femoral cortical thickness in all groups. PTH and ALN enhanced bone strength synergistically in the lumbar vertebrae and additively in the femur. Combined therapy, however, had no effects on bone markers. The results show that combinations of ALN and PTH, in both daily and cyclic regimens, produce more beneficial effects than treatment with either agent alone, suggesting that the mechanisms of actions of ALN and PTH on bone quality may be complementary.

The RANKL/RANK/OPG pathway

Understanding of osteoclast formation and activation has advanced considerably since the discovery of the RANKL/RANK/OPG system in the mid 1990s. Osteoblasts and stromal stem cells express receptor activator of NF-jB ligand (RANKL), which binds to its receptor, RANK, on the surface of osteoclasts and their precursors. This regulates the differentiation of precursors into multinucleated osteoclasts and osteoclast activation and survival both normally and in most pathologic conditions associated with increased bone resorption. Osteoprotegerin (OPG) is secreted by osteoblasts and osteogenic stromal stem cells and protects the skeleton from excessive bone resorption by binding to RANKL and preventing it from interacting with RANK. The RANKL/OPG ratio in bone marrow is thus an important determinant of bone mass in normal and disease states. RANKL/RANK signaling also regulates lymph node formation and mammary gland lactational hyperplasia in mice, and OPG protects large arteries of mice from medial calcification. This article reviews the roles of the RANKL/RANK/OPG system in bone and other tissues.