Safety of osteoanabolic therapy: a decade of experience

Romosozumab versus parathyroid hormone receptor agonists: which osteoanabolic to choose and when?

Osteoanabolic agents are used as a first line treatment in patients at high fracture risk. The PTH receptor 1 (PTH1R) agonists teriparatide (TPTD) and abaloparatide (ABL) increase bone formation, bone mineral density (BMD), and bone strength by activating PTH receptors on osteoblasts. Romosozumab (ROMO), a humanized monoclonal antibody against sclerostin, dramatically but transiently stimulates bone formation and persistently reduces bone resorption. Osteoanabolic agents increase BMD and bone strength while being more effective than antiresorptives in reducing fracture risk in postmenopausal women. However, direct comparisons of the antifracture benefits of osteoanabolic therapies are limited. In a direct comparison of TPTD and ABL, the latter resulted in greater BMD increases at the hip. While no differences in vertebral or non-vertebral fracture risk were observed between the two drugs, ABL led to a greater reduction of major osteoporotic fractures. Adverse event profiles were similar between the two agents except for hypercalcemia, which occurred more often with TPTD. No direct comparisons of fracture risk reduction between ROMO and the PTH1R agonists exist. Individual studies have shown greater increases in BMD and bone strength with ROMO compared with TPTD in treatment-naive women and in women previously treated with bisphosphonates. Some safety aspects, such as a history of tumor precluding the use of PTH1R agonists, and a history of major cardiovascular events precluding the use of ROMO, should also be considered when choosing between these agents. Finally, convenience of administration, reimbursement by national health systems and length of clinical experience may influence patient choice.

Gli1+ Progenitors Mediate Glucocorticoid-Induced Osteoporosis In Vivo

For a wide range of chronic autoimmune and inflammatory diseases in both adults and children, synthetic glucocorticoids (GCs) are one of the most effective treatments. However, besides other adverse effects, GCs inhibit bone mass at multiple levels, and at different ages, especially in puberty. Although extensive studies have investigated the mechanism of GC-induced osteoporosis, their target cell populations still be obscure. Here, our data show that the osteoblast subpopulation among Gli1+ metaphyseal mesenchymal progenitors (MMPs) is responsive to GCs as indicated by lineage tracing and single-cell RNA sequencing experiments. Furthermore, the proliferation and differentiation of Gli1+ MMPs are both decreased, which may be because GCs impair the oxidative phosphorylation(OXPHOS) and aerobic glycolysis of Gli1+ MMPs. Teriparatide, as one of the potential treatments for GCs in bone mass, is sought to increase bone volume by increasing the proliferation and differentiation of Gli1+ MMPs in vivo. Notably, our data demonstrate teriparatide ameliorates GC-caused bone defects by targeting Gli1+ MMPs. Thus, Gli1+ MMPs will be the potential mesenchymal progenitors in response to diverse pharmaceutical administrations in regulating bone formation.

PTH 1-34 reduced apoptosis of MLO-Y4 osteocyte-like cells by activating autophagy and inhibiting ER stress under RPM conditions

Osteocytes, as mechanosensitive cells residing within bone tissue, hold a pivotal role in averting the occurrence and progression of osteoporosis. The apoptosis of osteocytes induced by unloading is one of the contributing factors to osteoporosis, although the underlying molecular mechanisms have not been fully elucidated. PTH 1-34 is known to promote bone formation and inhibit bone loss by targeting osteoblasts and osteocytes. However, it is not known whether PTH 1-34 can inhibit osteocyte apoptosis under unloading conditions and the molecular mechanisms involved. In this study, we employed a Random Positioning Machine (RPM) to emulate unloading conditions and cultured MLO-Y4 osteocyte-like cells, in order to unravel the mechanisms through which PTH 1-34 constrains osteocyte apoptosis amidst unloading circumstances. Our findings revealed that PTH 1-34 activated autophagy while suppressing endoplasmic reticulum stress by curtailing the generation of reactive oxygen species (ROS) in MLO-Y4 osteocyte-like cells during unloading conditions. By shedding light on the osteoporosis triggered by skeletal unloading, this study contributes vital insights that may pave the way for the development of pharmacological interventions.

The Risk of Developing Osteosarcoma After Teriparatide Use: A Systematic Review

Teriparatide is a recombinant human parathyroid hormone analog with anabolic mechanism of action utilized in the treatment of osteoporosis with well-established clinical efficacy. Its use is significantly hindered due to label warnings resulting from pre-clinical rat studies demonstrating an increased risk of osteosarcoma. However, clinical trials and post-marketing surveillance studies did not demonstrate any increased risk of osteosarcoma, even after prolonged periods of surveillance reaching up to 15 years, with most of the identified cases of osteosarcomas being solitary and predominantly attributed to other factors. This systematic review provides a comprehensive overview of the currently available literature and provides the highest level of clinical evidence towards demonstrating the lack of any substantial evidence towards osteosarcoma development in patients utilizing TPTD.

Definition and management of very high fracture risk in women with postmenopausal osteoporosis: a position statement from the Brazilian Society of Endocrinology and Metabolism (SBEM) and the Brazilian Association of Bone Assessment and Metabolism (ABRASSO)

Several drugs are available for the treatment of osteoporosis in postmenopausal women. Over the last decades, most patients requiring pharmacological intervention were offered antiresorptive drugs as first-line therapy, while anabolic agents were considered a last resource for those with therapeutic failure. However, recent randomized trials in patients with severe osteoporosis have shown that anabolic agents reduce fractures to a greater extent than antiresorptive medications. Additionally, evidence indicates that increases in bone mineral density (BMD) are maximized when patients are treated with anabolic agents first, followed by antiresorptive therapy. This evidence is key, considering that greater increases in BMD during osteoporosis treatment are associated with a more pronounced reduction in fracture risk. Thus, international guidelines have recently proposed an individualized approach to osteoporosis treatment based on fracture risk stratification, in which the stratification risk has been refined to include a category of patients at very high risk of fracture who should be managed with anabolic agents as first-line therapy. In this document, the Brazilian Society of Endocrinology and Metabolism and the Brazilian Association of Bone Assessment and Metabolism propose the definition of very high risk of osteoporotic fracture in postmenopausal women, for whom anabolic agents should be considered as first-line therapy. This document also reviews the factors associated with increased fracture risk, trials comparing anabolic versus antiresorptive agents, efficacy of anabolic agents in patients who are treatment naïve versus those previously treated with antiresorptive agents, and safety of anabolic agents.

Locally Applied Repositioned Hormones for Oral Bone and Periodontal Tissue Engineering: A Narrative Review

Bone and periodontium are tissues that have a unique capacity to repair from harm. However, replacing or regrowing missing tissues is not always effective, and it becomes more difficult as the defect grows larger. Because of aging and the increased prevalence of debilitating disorders such as diabetes, there is a considerable increase in demand for orthopedic and periodontal surgical operations, and successful techniques for tissue regeneration are still required. Even with significant limitations, such as quantity and the need for a donor area, autogenous bone grafts remain the best solution. Topical administration methods integrate osteoconductive biomaterial and osteoinductive chemicals as hormones as alternative options. This is a promising method for removing the need for autogenous bone transplantation. Furthermore, despite enormous investigation, there is currently no single approach that can reproduce all the physiologic activities of autogenous bone transplants. The localized bioengineering technique uses biomaterials to administer different hormones to capitalize on the host’s regeneration capacity and capability, as well as resemble intrinsic therapy. The current study adds to the comprehension of the principle of hormone redirection and its local administration in both bone and periodontal tissue engineering.

Secondary Osteoporosis and Metabolic Bone Diseases

Fragility fracture is a worldwide problem and a main cause of disability and impaired quality of life. It is primarily caused by osteoporosis, characterized by impaired bone quantity and or quality. Proper diagnosis of osteoporosis is essential for prevention of fragility fractures. Osteoporosis can be primary in postmenopausal women because of estrogen deficiency. Secondary forms of osteoporosis are not uncommon in both men and women. Most systemic illnesses and organ dysfunction can lead to osteoporosis. The kidney plays a crucial role in maintaining physiological bone homeostasis by controlling minerals, electrolytes, acid-base, vitamin D and parathyroid function. Chronic kidney disease with its uremic milieu disturbs this balance, leading to renal osteodystrophy. Diabetes mellitus represents the most common secondary cause of osteoporosis. Thyroid and parathyroid disorders can dysregulate the osteoblast/osteoclast functions. Gastrointestinal disorders, malnutrition and malabsorption can result in mineral and vitamin D deficiencies and bone loss. Patients with chronic liver disease have a higher risk of fracture due to hepatic osteodystrophy. Proinflammatory cytokines in infectious, autoimmune, and hematological disorders can stimulate osteoclastogenesis, leading to osteoporosis. Moreover, drug-induced osteoporosis is not uncommon. In this review, we focus on causes, pathogenesis, and management of secondary osteoporosis.

Plumbagin is a NF-κB-inducing kinase inhibitor with dual anabolic and antiresorptive effects that prevents menopausal-related osteoporosis in mice

Osteoporosis is caused by enhanced bone resorption and relatively reduced bone formation. There is an unmet need to develop new agents with both antiresorptive and anabolic effects to treat osteoporosis, although drugs with either effect alone are available. A small molecular compound, plumbagin, was reported to inhibit receptor activator of nuclear factor kappa-B ligand-induced osteoclast (OC) differentiation by inhibiting IκBα phosphorylation-mediated canonical NF-κB activation. However, the key transcriptional factor RelA/p65 in canonical NF-κB pathway functions to promote OC precursor survival but not terminal OC differentiation. Here, we found that plumbagin inhibited the activity of NF-κB inducing kinase, the key molecule that controls noncanonical NF-κB signaling, in an ATP/ADP-based kinase assay. Consistent with this, plumbagin inhibited processing of NF-κB2 p100 to p52 in the progenitor cells of both OCs and osteoblasts (OBs). Interestingly, plumbagin not only inhibited OC but also stimulated OB differentiation in vitro. Importantly, plumbagin prevented trabecular bone loss in ovariectomized mice. This was associated with decreased OC surfaces on trabecular surface and increased parameters of OBs, including OB surface on trabecular surface, bone formation rate, and level of serum osteocalcin, compared to vehicle-treated mice. In summary, we conclude that plumbagin is a NF-κB-inducing kinase inhibitor with dual anabolic and antiresorptive effects on bone and could represent a new class of agent for the prevention and treatment of osteoporosis.

PTH 1-34 promoted bone formation by regulating iron metabolism in unloading-induced bone loss

PTH 1-34 (teriparatide) is approved by FDA for the treatment of postmenopausal osteoporosis. Iron overload is a major contributing factor for bone loss induced by unloading. Whether iron metabolism is involved in the regulation of PTH 1-34 on unloading-induced osteoporosis has not yet been reported. Here, we found that PTH 1-34 attenuated bone loss in unloading mice. PTH 1-34 regulated the disturbance of iron metabolism in unloading mice by activating Nrf2 and further promoting hepcidin expression in the liver. In addition, the Nrf2 inhibitor selectively blocked hepcidin expression in the liver of unloading mice, which neutralized the inhibitory effect of PTH 1-34 on bone loss and the recovery of iron metabolism in unloading mice. Finally, we found that PTH 1-34 promoted the differentiation and inhibited apoptosis of osteoblasts by regulating iron metabolism and maintaining redox balance under unloading conditions. Our results suggested that PTH 1-34 promoted bone formation by regulating iron metabolism under unloading conditions.

Regulation of TNF-Induced Osteoclast Differentiation

Increased osteoclast (OC) differentiation and activity is the critical event that results in bone loss and joint destruction in common pathological bone conditions, such as osteoporosis and rheumatoid arthritis (RA). RANKL and its decoy receptor, osteoprotegerin (OPG), control OC differentiation and activity. However, there is a specific concern of a rebound effect of denosumab discontinuation in treating osteoporosis. TNFα can induce OC differentiation that is independent of the RANKL/RANK system. In this review, we discuss the factors that negatively and positively regulate TNFα induction of OC formation, and the mechanisms involved to inform the design of new anti-resorptive agents for the treatment of bone conditions with enhanced OC formation. Similar to, and being independent of, RANKL, TNFα recruits TNF receptor-associated factors (TRAFs) to sequentially activate transcriptional factors NF-κB p50 and p52, followed by c-Fos, and then NFATc1 to induce OC differentiation. However, induction of OC formation by TNFα alone is very limited, since it also induces many inhibitory proteins, such as TRAF3, p100, IRF8, and RBP-j. TNFα induction of OC differentiation is, however, versatile, and Interleukin-1 or TGFβ1 can enhance TNFα-induced OC formation through a mechanism which is independent of RANKL, TRAF6, and/or NF-κB. However, TNFα polarized macrophages also produce anabolic factors, including insulin such as 6 peptide and Jagged1, to slow down bone loss in the pathological conditions. Thus, the development of novel approaches targeting TNFα signaling should focus on its downstream molecules that do not affect its anabolic effect.

The therapeutic potential of mesenchymal stem cells in treating osteoporosis

Osteoporosis (OP), a common systemic metabolic bone disease, is characterized by low bone mass, increasing bone fragility and a high risk of fracture. At present, the clinical treatment of OP mainly involves anti-bone resorption drugs and anabolic agents for bone, but their long-term use can cause serious side effects. The development of stem cell therapy and regenerative medicine has provided a new approach to the clinical treatment of various diseases, even with a hope for cure. Recently, the therapeutic advantages of the therapy have been shown for a variety of orthopedic diseases. However, these stem cell-based researches are currently limited to animal models; the uncertainty regarding the post-transplantation fate of stem cells and their safety in recipients has largely restricted the development of human clinical trials. Nevertheless, the feasibility of mesenchymal stem cells to treat osteoporotic mice has drawn a growing amount of intriguing attention from clinicians to its potential of applying the stem cell-based therapy as a new therapeutic approach to OP in the future clinic. In the current review, therefore, we explored the potential use of mesenchymal stem cells in human OP treatment.

Gli1+ progenitors mediate bone anabolic function of teriparatide via Hh and Igf signaling

Teriparatide is the most widely prescribed bone anabolic drug in the world, but its cellular targets remain incompletely defined. The Gli1+ metaphyseal mesenchymal progenitors (MMPs) are a main source for osteoblasts in postnatal growing mice, but their potential response to teriparatide is unknown. Here, by lineage tracing, we show that teriparatide stimulates both proliferation and osteoblast differentiation of MMPs. Single-cell RNA sequencing reveals heterogeneity among MMPs, including an unexpected chondrocyte-like osteoprogenitor (COP). COP expresses the highest level of Hedgehog (Hh) target genes and the insulin-like growth factor 1 receptor (Igf1r) among all cell clusters. COP also expresses Pth1r and further upregulates Igf1r upon teriparatide treatment. Inhibition of Hh signaling or deletion of Igf1r from MMPs diminishes the proliferative and osteogenic effects of teriparatide. The study therefore identifies COP as a teriparatide target wherein Hh and insulin-like growth factor (Igf) signaling are critical for the osteoanabolic response in growing mice.

Bone turnover markers can predict healing time in medication-related osteonecrosis of the jaw

Objectives

Medication-related osteonecrosis of the jaw (MRONJ) is a severe and difficult-to-treat adverse event of bone-modifying agents. Therefore predictive strategies determining patients at risk for a prolonged healing duration are needed to optimize treatment. Thus, the present study evaluates whether or not bone turnover markers can be used to predict the healing duration in MRONJ patients.

Materials and methods

The present study is a retrospective data analysis of patients suffering from MRONJ and positive histology for Actinomyces spp., who were identified at the General Hospital Vienna from 2014 to 2018. During the first visit, the patients’ demographics and levels of bone formation parameters were compiled. Healing times were analysed by Cox regression in dependence on these factors.

Results

A total of 52 patients were identified who fulfilled the inclusion criteria. The indication for bone-modifying agents was breast cancer (n = 21), prostate cancer (n = 14), multiple myeloma (n = 6) and other malignant diseases (n = 11). In 43 (82.7%) of our patients, we were able to document complete mucosal healing. Furthermore, patients who responded faster to therapy showed higher levels of C-telopeptide (P < 0.05), osteocalcin (P < 0.05) and bone-specific alkaline phosphatase (P < 0.05), but lower levels of 1.25-dihydroxyvitamin D (P < 0.05) than slower responding patients. No correlation was found regarding parathyroid hormone or calcitonin levels. Interestingly, patients who had a slower response were less likely to report dental procedures, but more likely to report a history of chemotherapy.

Conclusion

CTX and osteocalcin levels may be used for predicting healing duration for MRONJ.

Switching to Denosumab or Bisphosphonates After Completion of Teriparatide Treatment in Women With Severe Postmenopausal Osteoporosis

OBJECTIVE

To compare bone mineral density (BMD) changes after 12 months of treatment with denosumab or bisphosphonates in postmenopausal women with severe osteoporosis after stopping teriparatide therapy.

METHODS

We retrospectively analyzed 140 postmenopausal women (mean age, 74.2 years) with severe osteoporosis who had been treated with teriparatide for 18 to 24 months at our outpatient clinic in a tertiary endocrine center between 2006 and 2015. After stopping teriparatide therapy, they continued treatment with a bisphosphonate (alendronate, risedronate, ibandronate, or zoledronic acid) or denosumab while receiving daily vitamin D and calcium. BMD at the lumbar spine (LS), total hip (TH), and femoral neck (FN) was measured by dual energy x-ray absorptiometry when teriparatide therapy was discontinued (baseline) and after 12 months of further treatment. Multivariate linear regression models were used to identify the predictors of BMD gain.

RESULTS

After stopping teriparatide therapy, 70 women continued treatment with bisphosphonates and 70 received denosumab. LS, but not TH or FN, BMD gain was significantly greater in the denosumab group than in the bisphosphonates group at 12 months. Multivariate analysis showed that BMD gain at the LS was negatively associated with bisphosphonate versus denosumab treatment and positively associated with baseline serum total procollagen type I N-terminal propeptide. BMD gains at the FN were predicted by higher baseline serum urate levels. BMD gains at the TH and FN were negatively associated with pretreatment BMD gains at the same site.

CONCLUSION

Twelve months after stopping teriparatide therapy, sequential denosumab treatment appeared to yield higher additional LS BMD gain on average compared with bisphosphonates treatment.

Various Therapeutic Methods for the Treatment of Medication-Related Osteonecrosis of the Jaw (MRONJ) and Their Limitations: A Narrative Review on New Molecular and Cellular Therapeutic Approaches

Medication-related osteonecrosis of the jaw (MRONJ) is one of the most interesting diseases in the field of maxillofacial surgery. In addition to bisphosphonates, the use of antiresorptive and antiangiogenic agents is known to be the leading cause. However, the exact pathogenesis of MRONJ has not been established, and various hypotheses have been proposed, such as oxidative stress-related theory. As a result, a definitive treatment protocol for MRONJ has not been identified, while various therapeutic approaches are applied to manage patients with MRONJ. Although the surgical approach to treat osteomyelitis of the jaw has been proven to be most effective, there are limitations, such as recurrence and delayed healing. Many studies and clinical trials are being conducted to develop another effective therapeutic modality. The use of some materials, including platelet concentrates and bone morphogenetic proteins, showed a positive effect on MRONJ. Among them, teriparatide is currently the most promising material, and it has shown encouraging results when applied to patients with MRONJ. Furthermore, cell therapy using mesenchymal stem cells showed promising results, and it can be the new therapeutic approach for the treatment of MRONJ. This review presents various treatment methods for MRONJ and their limitations while investigating newly developed and researched molecular and cellular therapeutic approaches along with a literature review.

Parathyroid Hormone Secretion and Receptor Expression Determine the Age-Related Degree of Osteogenic Differentiation in Dental Pulp Stem Cells

Objective: To demonstrate the levels of parathyroid hormone secretion and genetic expressions of parathyroid hormone (PTH) and PTH1 receptor (PTH1R) genes in the dental pulp stem cells (DPSCs) from different age groups before and after induction of osteogenic differentiation. In addition, we also wanted to check their correlation with the degree of osteogenic differentiation. Methods: Human primary DPSCs from three age groups (milk tooth (SHEDs), 7–12 years old; young DPSCs (yDPSCs), 20–40 years old; old DPSCs (oDPSCs), 60+ years old) were characterized for mesenchymal stem cell (MSC) markers. DPSCs were subjected to osteogenic differentiation and functional staining. Gene expression levels were analyzed by qRT-PCR. Surface receptor analysis was done by flow cytometry. Comparative protein levels were evaluated by ELISA. Results: All SHEDs, yDPSCs, and oDPSCs were found to be expressing mesenchymal stem cell markers. SHEDs showed more mineralization than yDPSCs and oDPSCs after osteogenic induction. SHEDs exhibited higher expression of PTH and PTH1R before and after osteogenic induction, and after osteogenic induction, SHEDs showed more expression for RUNX2, ALPL, and OCN. Higher levels of PTH were observed in SHEDs and yDPSCs, and the number of PTH1R positive cells was relatively lower in yDPSCs and oDPSCs than in SHEDs. After osteogenic induction, SHEDs were superior in the secretion of OPG, and the secretions of ALPL and PTH and the number of PTH1R positive cells were relatively low in the oDPSCs. Conclusions: The therapeutic quality of dental pulp stem cells is largely based on their ability to retain their stemness characteristics. This study emphasizes the criterion of aging, which affects the secretion of PTH by these cells, which in turn attenuates their osteogenic potential.

Desperate Times Call for Desperate Measures: Use of Continuous Subcutaneous 1-34 PTH Infusion for Postsurgical Hypoparathyroidism

Objective

This case highlights use of 1-34 PTH continuous infusion in a patient with postsurgical hypoparathyroidism.

Method

Clinical presentation and biochemical profile were monitored before and after 1-34 PTH infusion, with notable reduction in pill burden in a patient with postsurgical hypoparathyroidism.

Results

We present a case of postsurgical hypoparathyroidism following thyroidectomy for Graves disease. The patient was requiring a total of 34 pills daily and, despite medication compliance, her clinical and biochemical control was unsatisfactory. Following initiation of 1-34 PTH in the form of a subcutaneous pump, we were able to stop all calcium supplementation and reduce calcitriol to 0.5 mcg daily. Her current biochemical control as well as quality of life improved significantly on CSPI, calcitriol, and a daily serving of dietary calcium.

Conclusion

This case highlights the use of 1-34 PTH either as twice-daily dosing or continuous subcutaneous infusion for adult patients with hypoparathyroidism.

Recombinant human parathyroid hormone (1-84) replacement therapy in a child with hypoparathyroidism

First line conventional therapy of hypoparathyroidism comprises oral calcium and active vitamin D analogues. This approach may fail to correct hypocalcemia and hyperphosphatemia caused by the absence of parathyroid hormone and carries the risk of long-term complications including ectopic calcifications and renal damage. Full-length recombinant human parathyroid hormone (rhPTH[1-84]) is approved for the treatment of hypoparathyroidism in adults refractory to conventional therapy. To date, there is no data in children. Here, we report the successful use of rhPTH(1-84) in a 5-year old girl with hypoparathyroidism and concomitant chronic diarrhea manifesting as part of the autoimmune polyglandular syndrome type 1. Prior to starting rhPTH(1-84), the patient had been on conventional and later on rhPTH(1-34) continuous pump therapy. Conventional therapy failed to meet serum and urinary calcium target levels, whilst the pump therapy wasn't well tolerated and posed handling difficulties. Dose optimization for rhPTH(1-84) was informed by serum ionized calcium, spot urinary calcium-to-creatinine ratio and 24-hour urinary calcium excretion. Twice-daily subcutaneous injections of rhPTH(1-84) with a total dose of 3.35 μg/kg/d was well-tolerated, raised serum ionized calcium to target range (1.05-1.15 mmol/L) and normalized serum phosphate levels. Urinary calcium excretion was slightly above the recommended limit of 4 mg/kg/24 h, but improved compared to conventional therapy, with no evidence of nephrocalcinosis. Twice-daily administration stabilized serum calcium and phosphate levels compared to once-daily injections. rhPTH(1-84) treatment was well tolerated and the girl did not manifest any acute clinical complications of hypoparathyroidism throughout the entire observation period. Our experience with this case indicates that rhPTH(1-84) may be a physiological hormone replacement for managing hypoparathyroidism in children.

Osteogenic potential of the growth factors and bioactive molecules in bone regeneration

The growing need for treatment of the impaired bone tissue has resulted in the quest for the improvement of bone tissue regeneration strategies. Bone tissue engineering is trying to create bio-inspired systems with a coordinated combination of the cells, scaffolds, and bioactive factors to repair the damaged bone tissue. The scaffold provides a supportive matrix for cell growth, migration, and differentiation and also, acts as a delivery system for bioactive factors. Bioactive factors including a large group of cytokines, growth factors (GFs), peptides, and hormonal signals that regulate cellular behaviors. These factors stimulate osteogenic differentiation and proliferation of cells by activating the signaling cascades related to ossification and angiogenesis. GFs and bioactive peptides are significant parts of the bone tissue engineering systems. Besides, the use of the osteogenic potential of hormonal signals has been an attractive topic, particularly in osteoporosis-related bone defects. Due to the unstable nature of protein factors and non-specific effects of hormones, the engineering of scaffolds to the controlled delivery of these bioactive molecules has paramount importance. This review updates the growth factors, engineered peptides, and hormones that are used in bone tissue engineering systems. Also, discusses how these bioactive molecules may be linked to accelerating bone regeneration.

Safety and efficacy of teriparatide treatment for severe osteoporosis in patients with Duchenne muscular dystrophy

Osteoporosis is a major concern in patients with Duchenne muscular dystrophy. In this novel study of teriparatide treatment in 6 patients with severe osteoporosis, bone health (fractures, vertebral morphometry, and DXA) remained stable, with no adverse events. These findings will help inform future osteoporosis research in this challenging population.

INTRODUCTION

Despite standard therapy with vitamin D and bisphosphonates (BP), many patients with Duchenne muscular dystrophy (DMD) continue to sustain fragility fractures due to long-term glucocorticoid treatment and limited mobility. We aimed to evaluate the safety and efficacy of teriparatide for the treatment of severe osteoporosis in adolescent and young adult patients with DMD.

METHODS

We prospectively treated 6 patients with DMD who had severe osteoporosis with teriparatide 20 mcg subcutaneously daily for 1-2 years. Inclusion criteria were long-term glucocorticoid therapy, and severe osteoporosis despite treatment with BP, or intolerance to BP. We examined long bone and vertebral fracture outcomes, including vertebral morphometry measures, bone mineral density and content, bone formation markers, safety indices, and adverse events.

RESULTS

The mean age at teriparatide start was 17.9 years (range 13.9-22.1 years). All 6 patients were on daily glucocorticoids (mean ± SD; duration 10.9 ± 2.5 years) and 5 were non-ambulatory. Five patients had been treated with BP for 7.9 ± 4.2 years. All had vertebral and a history of long bone fragility fractures at baseline. Vertebral heights and Genant fracture grading remained stable. Long bone fracture rate appeared to decrease (from 0.84/year to 0.09/year); one patient sustained a long bone fracture at 6 months of treatment. Trajectories for change in bone mineral density and content were not different post- vs. pre-teriparatide. Procollagen type 1 amino-terminal propeptide (P1NP) increased, while laboratory safety indices remained stable and non-concerning. No adverse events were observed.

CONCLUSION

In six patients with DMD treated with teriparatide for severe osteoporosis, we observed stable bone health and modest increases in P1NP, without safety concerns. Further studies are needed to better understand teriparatide efficacy for treatment of osteoporosis in patients with DMD.

Breast Cancer and Microcalcifications: An Osteoimmunological Disorder?

The presence of microcalcifications in the breast microenvironment, combined with the growing evidences of the possible presence of osteoblast-like or osteoclast-like cells in the breast, suggest the existence of active processes of calcification in the breast tissue during a woman’s life. Furthermore, much evidence that osteoimmunological disorders, such as osteoarthritis, rheumatoid arthritis, or periodontitis influence the risk of developing breast cancer in women exists and vice versa. Antiresorptive drugs benefits on breast cancer incidence and progression have been reported in the past decades. More recently, biological agents targeting pro-inflammatory cytokines used against rheumatoid arthritis also demonstrated benefits against breast cancer cell lines proliferation, viability, and migratory abilities, both in vitro and in vivo in xenografted mice. Hence, it is tempting to hypothesize that breast carcinogenesis should be considered as a potential osteoimmunological disorder. In this review, we compare microenvironments and molecular characteristics in the most frequent osteoimmunological disorders with major events occurring in a woman’s breast during her lifetime. We also highlight what the use of bone anabolic drugs, antiresorptive, and biological agents targeting pro-inflammatory cytokines against breast cancer can teach us.

High fracture risk patients with glucocorticoid-induced osteoporosis should get an anabolic treatment first

Long-term glucocorticoid (GC) therapy induces glucocorticoid-induced osteoporosis (GIOP) and its associated fractures. Most specialty organizations recommend bisphosphonates as first-line therapies based only on bone mineral density efficacy data. Effective treatment of GIOP based on head-to-head trials with fracture endpoint has not yet been established. The pathophysiologic mechanisms of GIOP that lead to the detrimental effects on bone are not yet fully elucidated. Although GCs in an early and transitory period promote osteoclastic activity, in the current paper, we outline why GIOP is in fact a disease of the bone formation and then provide the rationale for the use of bone-forming agents as first-line therapy for patients with high fracture risk in GIOP.

Malic Enzyme Couples Mitochondria with Aerobic Glycolysis in Osteoblasts

The metabolic program of osteoblasts, the chief bone-making cells, remains incompletely understood. Here in murine calvarial cells, we establish that osteoblast differentiation under aerobic conditions is coupled with a marked increase in glucose consumption and lactate production but reduced oxygen consumption. As a result, aerobic glycolysis accounts for approximately 80% of the ATP production in mature osteoblasts. In vivo tracing with 13C-labeled glucose in the mouse shows that glucose in bone is readily metabolized to lactate but not organic acids in the TCA cycle. Glucose tracing in osteoblast cultures reveals that pyruvate is carboxylated to form malate integral to the malate-aspartate shuttle. RNA sequencing (RNA-seq) identifies Me2, encoding the mitochondrial NAD-dependent isoform of malic enzyme, as being specifically upregulated during osteoblast differentiation. Knockdown of Me2 markedly reduces the glycolytic flux and impairs osteoblast proliferation and differentiation. Thus, the mitochondrial malic enzyme functionally couples the mitochondria with aerobic glycolysis in osteoblasts.

Hypoparathyroidism

BACKGROUND

Hypoparathyroidism is a rare endocrine disorder characterized by hypocalcemia and low or undetectable levels of parathyroid hormone.

METHODS

This review is an evidence-based summary of hypoparathyroidism in terms of relevant pathophysiological, clinical, and therapeutic concepts.

RESULTS

Many clinical manifestations of hypoparathyroidism are due to the lack of the physiological actions of parathyroid hormone on its 2 major target organs: the skeleton and the kidney. The skeleton is inactive, accruing bone without remodeling it. The kidneys lose the calcium-conserving actions of parathyroid hormone and, thus, excrete a greater fraction of calcium. Biochemical manifestations, besides hypocalcemia and low or undetectable levels of parathyroid hormone, include hyperphosphatemia and low levels of 1,25-dihydroxyvitamin D. Calcifications in the kidney, brain, and other soft tissues are common. Removal of, or damage to, the parathyroid glands at the time of anterior neck surgery is, by far, the most likely etiology. Autoimmune destruction of the parathyroid glands and other genetic causes represent most of the other etiologies. Conventional treatment with calcium and active vitamin D can maintain the serum calcium level but high doses may be required, adding to the risk of long-term soft tissue calcifications. The advent of replacement therapy with recombinant human PTH(1-84) represents a major step in the therapeutics of this disease.

CONCLUSIONS

Advances in our knowledge of hypoparathyroidism have led to greater understanding of the disease itself and our approach to it.

Inducible expression of Wnt7b promotes bone formation in aged mice and enhances fracture healing

There remain unmet clinical needs for safe and effective bone anabolic therapies to treat aging-related osteoporosis and to improve fracture healing in cases of nonunion or delayed union. Wnt signaling has emerged as a promising target pathway for developing novel bone anabolic drugs. Although neutralizing antibodies against the Wnt antagonist sclerostin have been tested, Wnt ligands themselves have not been fully explored as a potential therapy. Previous work has demonstrated Wnt7b as an endogenous ligand upregulated during osteoblast differentiation, and that Wnt7b overexpression potently stimulates bone accrual in the mouse. The earlier studies however did not address whether Wnt7b could promote bone formation when specifically applied to aged or fractured bones. Here we have developed a doxycycline-inducible strategy where Wnt7b is temporally induced in the bones of aged mice or during fracture healing. We report that forced expression of Wnt7b for 1 month starting at 15 months of age greatly stimulated trabecular and endosteal bone formation, resulting in a marked increase in bone mass. We further tested the effect of Wnt7b on bone healing in a murine closed femur fracture model. Induced expression of Wnt7b at the onset of fracture did not affect the initial cartilage formation but promoted mineralization of the subsequent bone callus. Thus, targeted delivery of Wnt7b to aged bones or fracture sites may be explored as a potential therapy.

Teriparatide (rhPTH 1-34) treatment in the pediatric age: long-term efficacy and safety data in a cohort with genetic hypoparathyroidism

BACKGROUND

Hypoparathyroidism is characterized by the absence or inadequately low circulating concentrations of the parathyroid hormone, resulting in hypocalcemia, hyperphosphatemia, and elevated fractional excretion of calcium in the urine. The use of activated vitamin D analogs and calcium supplements represent conventional therapy. Subcutaneous recombinant human parathormone [rhPTH(1-34)] has been proposed as a substitutive treatment, even to avoid side effects of vitamin D and calcium.

OBJECTIVE

To assess the long-term safety and efficacy of rhPTH(1-34) in a pediatric cohort of patients with genetic hypoparathyroidism.

METHODS

The study is a 9.2-year self-controlled study of six pediatric patients (four males and two females, aged 9.4 ± 5.2) with DiGeorge, hypoparathyroidism-deafness-renal dysplasia (HDR) or autoimmune-candidiasis-polyendocrinopathy-ectodermal-dysplasia (APECED) syndrome, associated with autoimmune intestinal malabsorption in a patient. The presence of clinical signs of hypocalcemia and biochemical parameters, such as calcium, phosphate, alkaline phosphatase in the blood and calcium-creatinine ratio in urine, were compared during conventional treatment and rhPTH(1-34) (teriparatide, 12.5 μg twice daily).

RESULTS

The rhPTH(1-34) treatment allowed a reduction, although not always a complete suspension, of calcium supplementation and a slight reduction of calcitriol therapy. The number of tetanic episodes was reduced in four patients during the rhPTH(1-34) treatment. Mean blood calcium, alkaline phosphatase, and phosphate did not significantly change, while a significant reduction of the urinary calcium-to-creatinine ratio (0.55 ± 0.32 vs 0.16 ± 0.09, p = 0.03) was obtained. Renal ultrasound examination showed a worsening in three patients, while it did not change in the remaining three subjects during the follow-up.

CONCLUSIONS

In children with syndromic hypoparathyroidism presented here, replacement therapy with rhPTH(1-34) allowed to maintain adequate levels of the calcium and phosphate in the blood, normalize urinary calcium excretion, and reduce tetanic episodes. In patients with low compliance to conventional therapy or intestinal malabsorption, the use of rhPTH(1-34) could be considered, also to reduce the side effects of treatment with vitamin D and calcium.

Update on the safety and efficacy of teriparatide in the treatment of osteoporosis

Following the completion of the Fracture Prevention Trial, teriparatide was approved by the United States Food and Drug Administration and the European Medicine Agency as the first therapeutic anabolic agent for the treatment of postmenopausal women with severe osteoporosis. It subsequently received additional approval for the treatment of osteoporosis in men, and for the treatment of osteoporosis associated with glucocorticoid therapy in men and women at risk of fracture. In this review, we summarize the most important data concerning PTH 1-34 therapy before 2016 in the treatment of osteoporosis, and report some outstanding results published in the last 2 years. New data on safety will also discussed, together with the state of art of nonclassical utilization. Finally, in view of the recent approval of biosimilars, possible future landscapes are discussed.

Handling Parathormone Receptor Type 1 in Skeletal Diseases: Realities and Expectations of Abaloparatide

Musculoskeletal disorders represent an elevated socioeconomic burden for developed aging societies. Osteoporosis (OP) has been treated with antiresorptive therapies or with teriparatide that was until recently the only anabolic therapy. However, approval of osteoporosis treatment in postmenopausal women with abaloparatide, which is an analog of parathyroid hormone-related peptide (PTHrP), has created a new alternative for OP management. The success of this new treatment is related to differential mechanisms of activation of PTH receptor type 1 (PTH1R) by abaloparatide and PTH. Here, we address the distinguishing mechanisms of PTH1R activation; the effects of PTH1R stimulation in osteoblast, osteocytes, and chondrocytes; the differences between PTH and abaloparatide actions on PTH1R; potential safety concerns; and future perspectives about abaloparatide use in other musculoskeletal disorders.

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.

Osteoanabolic and dual action drugs

Teriparatide (TPTD) and abaloparatide (ABL) are the only osteoanabolic drugs available, at this time, for treatment of osteoporosis. TPTD is a 34-amino acid fragment that is identical in its primary sequence to the 34 amino acids of full-length human parathyroid hormone [hPTH(1-84)]. ABL is identical to parathyroid hormone-related peptide (PTHrP) through the first 22 residues with significantly different amino acids inserted thereafter, between residues 22 and 34. The osteoanabolic actions of PTH are due directly to its effects on cells of the osteoblast lineage and indirectly by stimulating IGF-I synthesis and suppressing sclerostin and associated enhancement of Wnt signalling. Both TPTD and ABL are ligands that bind to and activate the PTH receptor type 1 (PTHR1) receptor but they appear to do so differently: ABL favours the transient, more anabolic configuration of the receptor. Both TPTD and ABL reduce the risk of vertebral fractures and non-vertebral fractures. Both drugs are administered for a maximum of 24 months, and should be followed by an antiresorptive agent to maintain gains in bone mineral density (BMD). Romosozumab, a monoclonal antibody that binds to and inhibits sclerostin, appears to have dual actions by stimulating bone formation and reducing bone resorption. In the pivotal clinical trial, romosozumab, administered as a 210 mg monthly subcutaneous dose, significantly reduced new vertebral fractures and in a subsequent study reduced both vertebral and non-vertebral fractures.

Hypoparathyroidism: is it that easy to treat?

Hypoparathyroidism is a relatively rare endocrine disease characterised by either null or inappropriately low secretion of parathyroid hormone (PTH) for serum calcium levels. The other main laboratory findings include hypocalcaemia, inappropriately normal or high urine calcium excretion and hyperphosphataemia with low urine phosphate excretion. The management of hypoparathyroidism should be tailored to each individual case, which makes it a demanding undertaking in everyday clinical practice. In this review, we sought to focus on the diagnostic approach of hypoparathyroidism and the therapeutic challenges of the disease from a clinical perspective. Conventional treatment with vitamin D analogues and calcium salts is no longer the only available treatment, since replacement treatment with PTH(1-84) has recently been approved for the disease. However, the optimal treatment schedule is yet to be defined.

Comparative Effect of rhPTH(1-84) on Bone Mineral Density and Trabecular Bone Score in Hypoparathyroidism and Postmenopausal Osteoporosis

Parathyroid hormone (PTH) (1-84) improves lumbar spine (LS) areal bone mineral density (aBMD) and trabecular bone score (TBS) in hypoparathyroidism over a 2-year treatment period. Studies in osteoporosis have shown that with PTH(1-34) there is a significant increase in LS aBMD and TBS. In this article, we provide new data comparing the effects of the same form of PTH, namely recombinant human PTH, rhPTH(1-84), on aBMD and TBS in hypoparathyroid and osteoporotic patients over an 18-month treatment period. We studied 19 premenopausal (mean age 45.8 ± 11.8 years) and 16 postmenopausal (71 ± 8.4 years) hypoparathyroid women and 38 women with postmenopausal osteoporosis (71 ± 8.3 years). DXA (hologic) at LS, femoral neck, total hip, and distal one-third radius was assessed. Site-matched LS TBS data were extracted from deidentified spine DXA scans using the TBS iNsight software (version 2.1; Medimaps, Geneva, Switzerland). We observed a significant increase in LS aBMD in premenopausal and postmenopausal hypoparathyroid (3 ± 1.1%, p < 0.02 and 3.1 ± 1.4%, p < 0.05, respectively) and osteoporosis (6.2 ± 1.1%, p < 0.0001) patients after 18 months. There was a significant increase (3 ± 1.5%, p = 0.05) in TBS in premenopausal hypoparathyroid patients. A change in TBS was not observed in either postmenopausal group. One-third radius aBMD significantly declined in postmenopausal hypoparathyroid (-3.6 ± 1.1%, p < 0.01) and osteoporosis (-8 ± 1.4%, p < 0.0001) patients. Overall, there was a significantly greater increase in TBS in premenopausal hypoparathyroid than in osteoporosis patients (p < 0.0001) after adjusting for baseline values, age, BMI, and average daily dose of rhPTH(1-84). Comparing only postmenopausal women, the LS aBMD increase was greater in osteoporotic than hypoparathyroid subjects (p < 0.01). Our results demonstrate that rhPTH(1-84) administered for 18 months increases trabecular aBMD in hypoparathyroidism and postmenopausal osteoporosis with greater gains observed in the subjects with osteoporosis. The data suggest different effects of PTH on bone depending on the baseline skeletal structure, skeletal dynamics, compartments, and menopausal status. © 2018 American Society for Bone and Mineral Research.

New Directions in Treatment of Hypoparathyroidism

The history of parathyroid hormone (PTH) replacement therapy for hypoparathyroidism begins in 1929. In 2015, the Food and Drug Administration approved recombinant human PTH(1-84) [rhPTH(1-84)] as a treatment for hypoparathyroidism. Long-term studies of rhPTH(1-84), up to 6 years, have demonstrated continued efficacy of this replacement agent. Approaches to optimize PTH treatment in hypoparathyroidism include subcutaneous pump delivery systems, long-lived carrier molecules, and long-acting PTH analogues that show promise to prolong efficacy. Calcilytic compounds have been explored as a treatment for autosomal dominant hypocalcemia. Calcilytics are negative modulators of the calcium-sensing receptor and may present a therapeutic opportunity to increase endogenous PTH synthesis and secretion.

New therapeutic targets for osteoporosis

New anti-osteoporotic agents have been developed, potentially enriching the therapeutic armamentarium. Currently available osteoanabolic therapies are the parathyroid hormone (PTH) and PTH-related peptide (PTHrP) synthetic analogues, teriparatide and abaloparatide. Daily administration at doses of 20 and 80 μg, respectively, in contrast to continuous PTH secretion, leads to increased bone formation and reduces vertebral and non-vertebral fracture risk. Teriparatide is more effective than bisphosphonates (alendronate, risedronate) in increasing bone mineral density (BMD), improving bone architecture and reducing fracture risk. Abaloparatide leads to greater BMD gain, has greater anti-fracture efficacy regarding major osteoporotic fractures (upper arm, wrist, hip or clinical spine) compared with teriparatide (without a difference in morphometric vertebral and non-vertebral fractures), and has a lower risk of hypercalcaemia. Romosozumab, a sclerostin inhibitor, both induces bone formation and suppresses bone resorption. Administered at monthly subcutaneous doses of 210 mg, it reduces vertebral, non-vertebral and hip fracture risk compared with either placebo or alendronate. However, concerns have arisen about increased cardiovascular risk, which has suspended its approval by the FDA. Anabolic therapy should always be followed by administration of an anti-resorptive agent, such as bisphosphonates or denosumab, which preserves and may further increase BMD gain. Denosumab provides the greatest benefit for BMD when administered sequentially after its combination with teriparatide for 24 months and constitutes a reasonable option for patients at high risk of fracture. However, longitudinal data are needed to confirm the efficacy and safety of these therapeutic interventions.

FGF2 crosstalk with Wnt signaling in mediating the anabolic action of PTH on bone formation

The mechanisms of the anabolic effect of parathyroid hormone (PTH) in bone are not fully defined. The bone anabolic effects of PTH require fibroblast growth factor 2 (FGF2) as well as Wnt signaling and FGF2 modulates Wnt signaling in osteoblasts. In vivo PTH administration differentially modulated Wnt signaling in bones of wild type (WT) and in mice that Fgf2 was knocked out (Fgf2KO). PTH increased Wnt10b mRNA and protein in WT but not in KO mice. Wnt antagonist SOST mRNA and protein was significantly higher in KO group. However, PTH decreased Sost mRNA significantly in WT as well as in Fgf2KO mice, but to a lesser extent in Fgf2KO. Dickhopf 2 (DKK2) is critical for osteoblast mineralization. PTH increased Dkk2 mRNA in WT mice but the response was impaired in Fgf2KO mice. PTH significantly increased Lrp5 mRNA and phosphorylation of Lrp6 in WT but the increase was markedly attenuated in Fgf2KO mice. PTH increased β-catenin expression and Wnt/β-catenin transcriptional activity significantly in WT but not in Fgf2KO mice. These data suggest that the impaired bone anabolic response to PTH in Fgf2KO mice is partially mediated by attenuated Wnt signaling.

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In vivo PTH administration differentially modulated Wnt signaling in bones of WT and Fgf2KO mice.

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PTH treatment increased WNT10b and DKK2 expression in WT mice but the increase was blunted in Fgf2KO mice

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PTH increased Lrp5 mRNA and phosphorylation of Lrp6 in WT but the increase was markedly attenuated in Fgf2KO mice.

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PTH treatment increased β-catenin protein level and Wnt/β-catenin transcriptional activity in WT but not in Fgf2KO mice

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The impaired bone anabolic response to PTH in Fgf2KO mice is partially mediated by attenuated Wnt signaling.

Osteoanabolic Agents for Osteoporosis

Medications for osteoporosis are classified as either antiresorptive or anabolic. Whereas antiresorptive agents prevent bone resorption, anabolic agents promote new bone formation. Anabolics should be considered in individuals with severe osteoporosis, failure of alternative osteoporosis agents, intolerability or contraindications to other osteoporosis agents, and glucocorticoid-induced osteoporosis. There are currently two approved anabolic therapies, teriparatide and abaloparatide, and a third anabolic agent, romozosumab, is under review by the US Food and Drug Administration. Teriparatide and abaloparatide are administered as daily subcutaneous injections and have been shown to reduce vertebral and nonvertebral fractures significantly. The most common side effects are headache and nausea, but teriparatide and abaloparatide are generally well tolerated. The sequence of administration of anabolic therapy is important. Benefits of anabolics are attenuated in individuals with prior antiresorptive exposure; however, antiresorptive agents administered after anabolics consolidate bone mineral density gains.

Abaloparatide: Review of a Next-Generation Parathyroid Hormone Agonist

OBJECTIVE

To review the efficacy, safety, and economics of abaloparatide in the treatment of postmenopausal osteoporosis.

DATA SOURCES

PubMed (1966 to October 2017), Clinicaltrials.gov (October 2017), and Scopus (1970 to October 2017) were searched using abaloparatide, Tymlos, BA058, PTHrP 1-34 analog, and parathyroid hormone-related peptide 1-34 analog.

STUDY SELECTION AND DATA EXTRACTION

Human studies published in peer-reviewed publications in English were the primary sources for efficacy, safety, and economic data.

DATA SYNTHESIS

In the 2 randomized, published clinical studies of 24 weeks and 18 months duration, bone mineral density changes were higher for abaloparatide (lumbar spine, 6.7%-11.2%; femoral head, 3.1%-3.2%; total hip, 2.6%-4.2%) compared with placebo (lumbar spine, 0.6%-1.6%; femoral head, -0.4% to 0.8%; total hip, -0.1% to 0.4%; P < 0.05) and compared with teriparatide in the 24-week study (total hip 2.6% vs +0.5%, P < 0.05). New vertebral and nonvertebral fractures occurred in 0.6% and 2.7% of patients on abaloparatide compared with 4.2% and 4.7% on placebo in the 18-month study ( P < 0.05). Abaloparatide appears to have a somewhat higher risk for adverse effects, discontinuation as a result of adverse effects, and serious or severe adverse effects than teriparatide, but teriparatide has a higher risk for hypercalcemia. Pharmacoeconomic modeling appears to favor abaloparatide if differences in efficacy and cost are maintained.

CONCLUSION

Abaloparatide, which has less effect on osteoclasts, is an alternative to teriparatide in patients with postmenopausal osteoporosis who are at high risk for fractures or who have failed antiresorptive therapy based on initial clinical studies and economic modeling.

Hypoparathyroidism: disease update and new methods of treatment

Гипопаратиреоз характеризуется гипокальциемией при нормальном или низком уровне паратиреоидного гормона (ПТГ). ПТГ регулирует уровень кальция в крови, влияя на реабсорбцию кальция и фосфора в почках, а также витамин D-зависимое всасывание кальция из желудочно-кишечного тракта. Наиболее распространенной причиной гипопаратиреоза является повреждение околощитовидных желез в ходе хирургического вмешательства в области шеи, в основном по поводу заболеваний щитовидной железы. Стандартные методы лечения включают в себя назначение препаратов кальция и витамина D для поддержания уровня кальция на нижней границе референсного интервала с целью предупреждения гиперкальциурии. Однако в ряде случаев компенсация гипокальциемии требует использования высоких доз препаратов кальция и витамина D, что сопровождается выраженным колебанием уровня кальция крови, внескелетной кальцификацией и ухудшением функции почек. В настоящее время наиболее перспективным методом лечения гипопаратиреоза является заместительная терапия рекомбинантным человеческим ПТГ(1-84), который представляет собой полноразмерный ПТГ. ПТГ(1-84) способствует поддержанию стойкой нормокальциемии, улучшая качество жизни пациентов. Однако влияние ПТГ(1-84) на функцию почек, костный обмен и профилактику других осложнений гипопаратиреоза требует дальнейшего изучения.

Prevention of breast cancer skeletal metastases with parathyroid hormone

Advanced breast cancer is frequently associated with skeletal metastases and accelerated bone loss. Recombinant parathyroid hormone [teriparatide, PTH(1-34)] is the first anabolic agent approved in the US for treatment of osteoporosis. While signaling through the PTH receptor in the osteoblast lineage regulates bone marrow hematopoietic niches, the effects of anabolic PTH on the skeletal metastatic niche are unknown. Here, we demonstrate, using orthotopic and intratibial models of 4T1 murine and MDA-MB-231 human breast cancer tumors, that anabolic PTH decreases both tumor engraftment and the incidence of spontaneous skeletal metastasis in mice. Microcomputed tomography and histomorphometric analyses revealed that PTH increases bone volume and reduces tumor engraftment and volume. Transwell migration assays with murine and human breast cancer cells revealed that PTH alters the gene expression profile of the metastatic niche, in particular VCAM-1, to inhibit recruitment of cancer cells. While PTH did not affect growth or migration of the primary tumor, it elicited several changes in the tumor gene expression profile resulting in a less metastatic phenotype. In conclusion, PTH treatment in mice alters the bone microenvironment, resulting in decreased cancer cell engraftment, reduced incidence of metastases, preservation of bone microarchitecture and prolonged survival.

Proteasome inhibitor bortezomib is a novel therapeutic agent for focal radiation-induced osteoporosis

Bone atrophy and its related fragility fractures are frequent, late side effects of radiotherapy in cancer survivors and have a detrimental impact on their quality of life. In another study, we showed that parathyroid hormone 1-34 and anti-sclerostin antibody attenuates radiation-induced bone damage by accelerating DNA repair in osteoblasts. DNA damage responses are partially regulated by the ubiquitin proteasome pathway. In the current study, we examined whether proteasome inhibitors have similar bone-protective effects against radiation damage. MG132 treatment greatly reduced radiation-induced apoptosis in cultured osteoblastic cells. This survival effect was owing to accelerated DNA repair as revealed by γH2AX foci and comet assays and to the up-regulation of Ku70 and DNA-dependent protein kinase, catalytic subunit, essential DNA repair proteins in the nonhomologous end-joining pathway. Administration of bortezomib (Bzb) reversed the loss of trabecular bone structure and strength in mice at 4 wk after focal radiation. Histomorphometry revealed that Bzb significantly increased the number of osteoblasts and activity in the irradiated area and suppressed the number and activity of osteoclasts, regardless of irradiation. Two weeks of Bzb treatment accelerated DNA repair in bone-lining osteoblasts and thus promoted their survival. Meanwhile, it also inhibited bone marrow adiposity. Taken together, we demonstrate a novel role of proteasome inhibitors in treating radiation-induced osteoporosis.-Chandra, A., Wang, L., Young, T., Zhong, L., Tseng, W.-J., Levine, M. A., Cengel, K., Liu, X. S., Zhang, Y., Pignolo, R. J., Qin, L. Proteasome inhibitor bortezomib is a novel therapeutic agent for focal radiation-induced osteoporosis.

Hypoparathyroidism

Hypoparathyroidism is a disease characterized by inadequately low circulating concentrations of parathyroid hormone (PTH) resulting in low calcium levels and increased phosphate levels in the blood. Symptoms of the disease result from increased neuromuscular irritability caused by hypocalcaemia and include tingling, muscle cramps and seizures. The most common cause of the disease is inadvertent removal of, or injury to, the parathyroid glands during neck surgery, followed by genetic, idiopathic and autoimmune aetiologies. Conventional treatment includes activated vitamin D and/or calcium supplements, but this treatment does not fully replace the functions of PTH and can lead to short-term problems (such as hypocalcaemia, hypercalcaemia and increased urinary calcium excretion) and long-term complications (which include nephrocalcinosis, kidney stones and brain calcifications). PTH replacement has emerged as a new treatment option. Clinical trials using human PTH(1-34) and PTH(1-84) showed that this treatment was safe and effective in studies lasting up to 6 years. Recombinant human PTH(1-84) has been approved in the United States and Europe for the management of hypoparathyroidism; however, its effect on long-term complications is still being evaluated. Clinical practice guidelines, which describe the consensus of experts in the field, have been published and recognize the need for more research to optimize care. In this Primer, we summarize current knowledge of the prevalence, pathophysiology, clinical presentation and management of hypoparathyroidism.

24-Month Open-Label Teriparatide Once-Weekly Efficacy Research Trial Examining Bone Mineral Density in Subjects with Primary Osteoporosis and High Fracture Risk

Introduction

To clarify the additional efficacy and safety benefits of 24 months’ treatment with the once-weekly formulation of teriparatide, which is currently used for 72 weeks.

Methods

This was a multicenter, open-label, single-arm study conducted in Japan. Subjects who were 65 years or older with prevalent vertebral fractures received once-weekly subcutaneous injection of 56.5 μg teriparatide for 24 months. The main outcome measure was percentage change from baseline in lumbar (L2–L4) BMD measured by dual-energy X-ray absorptiometry.

Results

A total of 189 subjects received at least one dose of the once-weekly formulation of teriparatide. Lumbar, femoral neck, and total hip BMD increased significantly compared with baseline at Weeks 24, 48, 72, and 104. In addition, significant increases in lumbar (+1.5%) and femoral neck (+0.8%) BMD were noted at Week 104 compared with Week 72. Significant increases from baseline in BMD for radius 1/10 were noted at Weeks 24 and 104. No substantial increases were noted in the cumulative incidences of new vertebral fracture and other types of fracture after Week 72. The safety profile seen in the first 72 weeks remained unchanged until 104 weeks.

Conclusion

The once-weekly formulation of teriparatide is effective and safe for the treatment of osteoporosis over 24 months. The limitation of this study is that this was an open-label, single-arm study.

Funding: Asahi Kasei Pharma Corporation.

Clinical Trial Registration: JapicCTI-132276.

The Beneficial Effects of Bisphosphonate-enoxacin on Cortical Bone Mass and Strength in Ovariectomized Rats

Osteoporosis is a major age-related bone disease characterized by low bone mineral density and a high risk of fractures. Bisphosphonates are considered as effective agents treating osteoporosis. However, long-term use of bisphosphonates is associated with some serious side effects, which limits the widespread clinical use of bisphosphonates. Here, we demonstrate a novel type of bone-targeting anti-resorptive agent, bisphosphonate-enoxacin (BE). In this study, ovariectomized rat model was established and treated with PBS, zoledronate (50 μg/kg) and different dose of BE (5 mg/kg and 10 mg/kg), respectively. The rats subjected to sham-operation and PBS treatment were considered as control group. Then, micro-computed tomography scanning, biomechanical tests, nano-indentation test and Raman analysis were used to compare the effects of zoledronate and BE on cortical bone mass, strength, and composition in ovariectomized rats. We found that both zoledronate and BE were beneficial to cortical bone strength. Three-point bending and nano-indentation tests showed that zoledronate- and BE-treated groups had superior general and local biomechanical properties compared to the ovariectomized groups. Interestingly, it seemed that BE-treated group got a better biomechanical property than the zoledronate-treated group. Also, BE-treated group showed significantly increased proteoglycan content compared with the zoledronate-treated group. We hypothesized that the increased bone strength and biomechanical properties was due to altered bone composition after treatment with BE. BE, a new bone-targeting agent, may be considered a more suitable anti-resorptive agent to treat osteoporosis and other bone diseases associated with decreased bone mass.

Macrophages and skeletal health

Bone is in a constant state of remodeling, a process which was once attributed solely to osteoblasts and osteoclasts. Decades of research has identified many other populations of cells in the bone that participate and mediate skeletal homeostasis. Recently, osteal macrophages emerged as vital participants in skeletal remodeling and osseous repair. The exact mechanistic roles of these tissue-resident macrophages are currently under investigation. Macrophages are highly plastic in response to their micro-environment and are typically classified as being pro- or anti-inflammatory (pro-resolving) in nature. Given that inflammatory states result in decreased bone mass, proinflammatory macrophages may be negative regulators of bone turnover. Pro-resolving macrophages have been shown to release anabolic factors and may present a target for therapeutic intervention in inflammation-induced bone loss and fracture healing. The process of apoptotic cell clearance, termed efferocytosis, is mediated by pro-resolving macrophages and may contribute to steady-state bone turnover as well as fracture healing and anabolic effects of osteoporosis therapies. Parathyroid hormone is an anabolic agent in bone that is more effective in the presence of mature phagocytic macrophages, further supporting the hypothesis that efferocytic macrophages are positive contributors to bone turnover. Therapies which alter macrophage plasticity in tissues other than bone should be explored for their potential to treat bone loss either alone or in conjunction with current bone therapeutics. A better understanding of the exact mechanisms by which macrophages mediate bone homeostasis will lead to an expansion of pharmacologic targets for the treatment of osteoporosis and inflammation-induced bone loss.