Orthopedic uses of teriparatide

Comparing musculoskeletal and connective tissue disorder risks of teriparatide and abaloparatide in osteoporosis: an analysis based on FDA adverse event reporting system (FAERS)

BACKGROUND

Osteoporosis (OP), characterized by low bone mass and increased fracture risk, is a prevalent skeletal disorder. Teriparatide (TP) and abaloparatide (ABL) are anabolic agents that may reduce fracture incidence, but their impact on musculoskeletal and connective tissue disorders (MCTD) risk is uncertain.

RESEARCH DESIGN AND METHODS

A retrospective, observational disproportionality analysis was conducted utilizing FAERS data from Q1 2004 to Q3 2023, where TP or ABL was identified as the primary suspect drug. Multiple data mining algorithms, including reporting odds ratio (ROR), proportional reporting ratio (PRR), Bayesian confidence propagation neural network (BCPNN), and multi-item gamma Poisson shrinker (MGPS), were employed to detect MCTD safety signals.

RESULTS

A total of 366,747 TP-related and 422,377 ABL-related cases were identified, predominantly among female patients aged ≥45 years. The top specific AEs involved musculoskeletal, connective tissue, and administration site disorders. Comparative analysis revealed a higher frequency of AEs related to the nervous, cardiovascular, and gastrointestinal systems for ABL compared to TP. Both drugs exhibited strong signals for arthralgia, limb pain, back pain, muscle spasms, bone pain, muscle pain, and muscle weakness.

CONCLUSION

The analysis suggests a potential MCTD risk with TP and ABL treatment in OP patients, highlighting the need for AE monitoring and management in clinical practice. This contributes to a better understanding of the safety profiles of these anabolic medications.

The efficacy of teriparatide (Cinnopar®) on bone repair in mandibular fractures: A single blinded randomized clinical trial

This study focused on the effects of teriparatide (CinnoPar) on healing and postoperative complications in mandibular bone fractures. In this single-blind randomized controlled trial, 30 patients with a mandibular fracture hospitalized for open reduction internal fixation were randomly assigned to the intervention (I) (n = 15) and control (C) (n = 15) groups. Both groups received daily acetaminophen and cephalexin for 1 week. For 1 month, Group I received daily subcutaneous teriparatide injections. The Radiographic Union Scale of the Mandible (RUSM) was used to assess mandibular bone fusion subjectively, and the Hounsfield unit (HU) was used to objectively assess radiodensity in a computed tomography (CT) scan. In both groups, the visual analog scale (VAS) score was used to assess postoperative complications such as pain, swelling, wound opening, pus secretion, and bitter taste. There was no significant difference in bone repair between the two groups in this study (P > 0.05). Teriparatide also had no effect on the postoperative complication rate in the control group (P > 0.05). Within the limitations of the study it seems that in mandibular fractures, teriparatide did not affect bone fusion or postoperative complications, so its use is not recommended for better bone fusion and fewer postoperative complications of mandibular fracture during the first month.

Effects of local single dose administration of parathormone on the early stages of osseointegration: A pre-clinical study

The present study aimed to evaluate the effect of parathormone (PTH) administered directly to the implant's surface prior to insertion, using a large translational animal model. Sixty titanium implants were divided into four groups: (i) Collagen, control group, where implants were coated with Type-I Bovine-collagen, and three experimental groups, where implants received varying doses of PTH: (ii) 12.5, (iii) 25, and (iv) 50 μg, prior to placement. Fifteen female sheep (~2 years old, weighing ~65 kg) received four implants in an interpolated fashion in C3, C4 or C5 vertebral bodies. After 3-, 6- and 12-weeks, samples were harvested, histologically processed, qualitatively and quantitatively assessed for bone-to-implant contact (BIC) and bone area fraction occupancy (BAFO). BIC yielded lower values at 6-weeks for 50 μg relative to the control group, with no significant differences, when compared to the 12.5- and 25-μg. No significant differences were detected at 6-weeks between collagen, 12.5- and 25-μg groups. At 3- and 12-weeks, no differences were detected for BIC among PTH groups. With respect to BAFO, no significant differences were observed between the control and experimental groups independent of PTH concentration and time in vivo. Qualitative observations at 3-weeks indicated the presence of a more mature bone near the implant's surface with the application of PTH, however, no significant differences in new bone formation or healing patterns were observed at 6- and 12-weeks. Single local application of different concentrations of PTH on titanium implant's surface did not influence the osseointegration at any time-point evaluation in low-density bone.

PTH1-34 improves devitalized allogenic bone graft healing in a murine femoral critical size defect

The treatment of large segmental defects of long bones resulting from trauma, infection, or bone tumor resections is a major challenge for orthopedic surgeons. The reconstruction of bone defects with acellular allografts can be used as an osteoconductive approach. However, devitalized allografts are associated with high rates of clinical failure as a result of poor intrinsic osteoinduction properties and a lack of further remodeling. Nevertheless, evidence suggests that due to its anabolic properties, teriparatide (PTH_1-34) could be effective as an adjuvant therapy for massive allograft healing. Therefore, our goal was to investigate in a murine critical-sized defect model whether the intermittent administration of PTH_1-34 improves the incorporation and revitalization of acellular structural bone allografts. Thus, a 2.5-mm critical-sized defect was established in the right femur of C57BL/6 mice, followed by the reconstruction with a devitalized cortical structural allograft. A titanium micro locking plate was applied to the anterior femoral surface and secured in place with self-tapping locking screws. Subsequently, daily doses of PTH_1-34 (30, and 40 µg/kg) or saline were administered to the mice for 14 days after surgery. The mice were maintained without PTH_1-34 therapy for an additional 7 days before being euthanized at 3 weeks post-surgery. Bone graft consolidation was assessed on radiographic images and by histomorphometric analysis. Additionally, to determine the frequency of osteoprogenitor cells in the bone marrow and their in vitro osteogenic capacity, stromal cells were isolated from the bone marrow of animals treated with 30 or 40 µg/kg/day of PTH_1-34 following the same protocol used for the experimental animals. Our results suggest that intermittent PTH_1-34 treatment at 30 µg/kg/day after femoral allograft reconstruction surgery accelerated the healing process as evidenced by new bone formation induced on endosteal and periosteal surfaces, enhanced revitalization of allogeneic graft, and increased frequency and osteogenic capacity of bone marrow stromal cells (BMSC). These findings should encourage further studies aimed at investigating the potential therapeutic use of intermittent PTH_1-34, specifically with regards to the optimal dosing regimen in clinically challenging orthopedic scenarios.

Treatment of an Acromial Stress Fracture After Reverse Total Shoulder Arthroplasty With Teriparatide: A Case Report

CASE

A 78-year-old woman who underwent reverse total shoulder arthroplasty (RTSA) for proximal humerus fracture developed a Type-3 acromial stress fracture, resulting in increased pain and decreased function 9 months post-op. She was managed nonoperatively with adjunctive teriparatide (FORTEO), and after a 4-month course, she had regained excellent motion and achieved union.

CONCLUSION

Teriparatide is a viable adjunct in treating patients nonoperatively with acromial stress fractures after RTSA.

The Effect of Parathyroid Hormone Analogues When Added to Mineralized Bone Xenografts

Implants can be a treatment option when there is sufficient quantity and quality of bone to provide support for long-term success. In the reconstruction of defects, autogenous bone remains the gold standard for its osteogenic and compatibility properties. However, the disadvantage of secondary surgery and the associated donor site morbidity prompts researchers to develop the ideal bone substitute for optimum bone reconstruction. Parathyroid hormone (PTH1-34) has provided a new option for improvement in bone regeneration. This study used a pig model to evaluate the effectiveness of parathyroid hormone when added to a xenograft, Bio-Oss, in reconstructing mandible defects. Six domestic pigs were used to create 3 posterior mandibular defects measuring 2 × 1-cm bilaterally with a total of 36 defects to simulate tooth extraction sites in humans. The defects were grafted in random order and divided into 3 groups as follows: control (no graft), Bio-Oss without PTH, and Bio-Oss with PTH. Defects were assessed with cone beam computerized tomography (CBCT), micro computerized tomography (microCT), nanoindentation, and histology. Results showed that adding PTH1-34 significantly enhanced the graft construct. CBCT showed a significant increase in the degree of bone mineralization. Nanoindentation showed increased hardness of regenerated bone and accelerated bone mineralization with PTH. MicroCT analysis revealed a trend toward higher bone regeneration and mineralization. The histological analysis showed a positive trend of the increase in cortical bone thickness and mineral apposition rate. In conclusion, the local addition of PTH1-34 to a xenograft has shown promising results to enhance bone regeneration in the reconstruction of mandibular defects.

Teriparatide for treating delayed union and nonunion: A systematic review

INTRODUCTION

Fracture nonunion remains a great challenge for orthopaedic surgeons. Approximately 5-10% of bone fractures do not heal promptly, and require another surgical procedure. Previously, several small studies have found that teriparatide, a parathyroid hormone (PTH) analogue, has been found to induce union in those with delayed union and nonunion. However, to date, no systematic reviews regarding the use of teriparatide for delayed union and nonunion are available. The present review aims to investigate the safety and efficacy of teriparatide in delayed union and nonunion.

METHODS

Systematic literature search was performed in PubMed, ScienceDirect, and Google Scholar until September 26, 2019. We included studies involving adult patients (age >16 years) diagnosed with delayed union or nonunion fracture regardless of location (long bone, short bone, flat bone or irregular bone). The language was restricted to English and Indonesian. Outcomes that were recorded were fracture union and adverse events.

RESULTS

Initial search found 5416 abstract and titles. Of these, 20 articles consisting of 64 subjects were retrieved. Of these, 15 case reports, 4 case series, and one prospective study were included. All of the studies administered subcutaneous injection of teriparatide 20 μg/day with mean duration of 7.3 ± 1.5 weeks to 9.7 months. Sixty-one (95.3%) of 64 subjects developed complete union. The follow-up ranged from 3 to 24 months. No side effects occurred during the follow-up period.

CONCLUSIONS

Limited evidence demonstrates that daily subcutaneous injection of teriparatide 20 μg is a potential new safe treatment for delayed union and nonunion with no side effects. We highly suggest the use of such drug, as it is highly effective and safe. However, further clinical studies are required to investigate its safety and efficacy.

Current and Future Concepts for the Treatment of Impaired Fracture Healing

Bone regeneration represents a complex process, of which basic biologic principles have been evolutionarily conserved over a broad range of different species. Bone represents one of few tissues that can heal without forming a fibrous scar and, as such, resembles a unique form of tissue regeneration. Despite a tremendous improvement in surgical techniques in the past decades, impaired bone regeneration including non-unions still affect a significant number of patients with fractures. As impaired bone regeneration is associated with high socio-economic implications, it is an essential clinical need to gain a full understanding of the pathophysiology and identify novel treatment approaches. This review focuses on the clinical implications of impaired bone regeneration, including currently available treatment options. Moreover, recent advances in the understanding of fracture healing are discussed, which have resulted in the identification and development of novel therapeutic approaches for affected patients.

Anabolic Strategies to Augment Bone Fracture Healing

PURPOSE OF REVIEW

The development of therapeutics that target anabolic pathways involved in skeletogenesis is of great importance with regard to disease resulting in bone loss, or in cases of impaired bone repair. This review aims to summarize recent developments in this area.

RECENT FINDINGS

A greater understanding of how drugs that modulate signaling pathways involved in skeletogenesis exert their efficacy, and the molecular mechanisms resulting in bone formation has led to novel pharmacological bone repair strategies. Furthermore, crosstalk between pathways and molecules has suggested signaling synergies that may be exploited for enhanced tissue formation. The sequential pharmacological stimulation of the molecular cascades resulting in tissue repair is a promising strategy for the treatment of bone fractures. It is proposed that a therapeutic strategy which mimics the natural cascade of events observed during fracture repair may be achieved through temporal targeting of tissue repair pathways.

Teriparatide for treatment of patients with bisphosphonate-associated atypical fracture of the femur

The Fracture Improvement with Teriparatide (Fix-IT) study randomized 13 women with an atypical femur fracture to immediate vs delayed teriparatide therapy; all were followed for 12 months. Results suggested a trend for superior healing and lesser bone mineral density declines in the immediate vs delayed group with no differences in adverse events.

PURPOSE

Little clinical data are available on the use of teriparatide for the treatment of bisphosphonate-associated atypical femur fractures (AFF). The goal of the Fix-IT study was to determine if immediate therapy with teriparatide was superior for fracture healing after an AFF compared to a 6-month delay in teriparatide therapy.

METHODS

This randomized pilot clinical trial included 13 women with an AFF who were randomized to immediate teriparatide vs a delay of 6 months. All were followed for 12 months on teriparatide. The primary outcomes included individual and composite measures of radiologic bone healing (scored 1 point [no healing] to 4 points [complete healing]) at 6 and 12 months. Secondary outcomes included bone mineral density of the unfractured contralateral hip, spine, 1/3 distal radius, and adverse events.

RESULTS

We found there was a trend for superior healing with the composite score (12.6 vs 11.2 at 6 months and 15.4 vs 13.2 at 12 months), and lesser bone mineral density declines at the 1/3 distal radius (12-month change - 1.9 vs - 6.1%) in the immediate vs the delayed group. There were no differences in adverse events. There was one implant failure in the delayed group.

CONCLUSIONS

There is a preliminary signal for greater improvements with immediate teriparatide therapy vs delayed therapy. However, because an AFF is a rare event, and only a small number of patients were included, the results must be interpreted with caution.

Teriparatide anabolic therapy as potential treatment of type II dens non-union fractures

Odontoid fractures account for 5% to 15% of all cervical spine injuries and 1% to 2% of all spine fractures. Type II fractures are the most common fracture pattern in elderly patients. Treatment (rigid and non-rigid immobilization, anterior screw fixation of the odontoid and posterior C1-C2 fusion) remains controversial and represents a unique challenge for the treating surgeon. The aims of treatment in the elderly is to quickly restore pre-injury function while decreasing morbidity and mortality associated with inactivity, immobilization with rigid collar and prolonged hospitalization. Conservative treatment of type II odontoid fractures is associated with relatively high rates of non-union and in a few cases delayed instability. Options for treatment of symptomatic non-unions include surgical fixation or prolonged rigid immobilization. In this report we present the case of a 73-year-old woman with post-traumatic odontoid non-union successfully treated with Teriparatide systemic anabolic therapy. Complete fusion and resolution of the symptoms was achieved 12 wk after the onset of the treatment. Several animal and clinical studies have confirmed the potential role of Teriparatide in enhancing fracture healing. Our case suggests that Teriparatide may have a role in improving fusion rates of C2 fractures in elderly patients.

Effect of osteoporosis medications on fracture healing

Antiosteoporotic medications are often used to concurrently treat a patient's fragility fractures and underlying osteoporosis. This review evaluates the existing literature from animal and clinical models to determine these drugs' effects on fracture healing. The data suggest that these medications may enhance bone healing, yet more thorough prospective studies are warranted. Pharmacologic agents that influence bone remodeling are an essential component of osteoporosis management. Because many patients are first diagnosed with osteoporosis when presenting with a fragility fracture, it is critical to understand how osteoporotic medications influence fracture healing. Vitamin D and its analogs are essential for the mineralization of the callus and may also play a role in callus formation and remodeling that enhances biomechanical strength. In animal models, antiresorptive medications, including bisphosphonates, denosumab, calcitonin, estrogen, and raloxifene, do not impede endochondral fracture healing but may delay repair due to impaired remodeling. Although bisphosphonates and denosumab delay callus remodeling, they increase callus volume and result in unaltered biomechanical properties. Calcitonin increases cartilage formation and callus maturation, resulting in improved biomechanical properties. Parathyroid hormone, an anabolic agent, has demonstrated promise in animal models, resulting in accelerated healing with increased callus volume and density, more rapid remodeling to mature bone, and improved biomechanical properties. Clinical data with parathyroid hormone have demonstrated enhanced healing in distal radius and pelvic fractures as well as postoperatively following spine surgery. Strontium ranelate, which may have both antiresorptive and anabolic properties, affects fracture healing differently in normal and osteoporotic bone. While there is no effect in normal bone, in osteoporotic bone, strontium ranelate increases callus bone formation, maturity, and mineralization; forms greater and denser trabeculae; and improves biomechanical properties. Further clinical studies with these medications are needed to fully understand their effects on fracture healing in order to simultaneously treat fragility fractures and underlying osteoporosis.

A Guide to Improving the Care of Patients with Fragility Fractures, Edition 2

Over the past 4 decades, much has been learned about the pathophysiology and treatment of osteoporosis, the prevention of fragility fractures, and the perioperative management of patients who have these debilitating injuries. However, the volume of published literature on this topic is staggering and far too voluminous for any clinician to review and synthesize by him or herself. This manuscript thoroughly summarizes the latest research on fragility fractures and provides the reader with valuable strategies to optimize the prevention and management of these devastating injuries. The information contained in this article will prove invaluable to any health care provider or health system administrator who is involved in the prevention and management of fragility hip fractures. As providers begin to gain a better understanding of the principles espoused in this article, it is our hope that they will be able to use this information to optimize the care they provide for elderly patients who are at risk of or who have osteoporotic fractures.

[Use of osteoanabolics in fracture nonunion]

BACKGROUND

The treatment of fracture nonunion (pseudarthrosis) is often lengthy and debilitating for the patient. There are operative and conservative therapies available.

RESEARCH QUESTION

Does the systemic use of osteoanabolic acting substances (osteoanabolics) lead to an acceleration of the delayed fracture healing and/or strengthening of the fracture? Which types of pseudarthrosis are suitable for this treatment option?

MATERIALS AND METHODS

A literature review was carried out focusing on the systemic anabolic therapy options for the treatment of delayed healing of fractures or pseudarthrosis. Additionally, our own case studies are presented.

RESULTS

Teriparatide and strontium ranelate have a positive effect on the healing of fractures in animal studies and in humans. There are also case studies on the use of both substances in delayed fracture healing or pseudarthrosis. The scientific knowledge regarding teriparatide is significantly more comprehensive. However, prospective randomized trials are lacking so far.

CONCLUSION

The systemic use of anabolics can be a therapeutic option, especially for biological reactive pseudarthrosis. However, these are off-label treatments and contraindications should be especially well heeded. Because of the numerous positive results, from the point of view of teriparatide treatment, a multicentric, prospective randomized study on the treatment of aseptic pseudarthrosis should be initiated.

Use of Teriparatide to improve fracture healing: What is the evidence?

Teriparatide is a recombinant form of the biologically active component of Parathyroid hormone. It has been shown to increase bone mass and prevent fractures in osteoporotic bone. It is licensed by the Food and Drug Administration for the treatment of Osteoporosis. Over the last decade, a growing body of evidence has accumulated suggesting a role for Teriparatide in the management of fractures. Studies in both normal and delayed healing models have shown improvement in callus volume and mineralisation, bone mineral content, rate of successful union and strength at fracture sites. However most of these results have been derived from animal studies. The majority of this research on humans has comprised low level evidence, with few randomised controlled trials, many case reports and case series. Nevertheless, the results from these studies seem to support research from animal models. This has led to a growing number of clinicians using Teriparatide “off license” to treat fractures and non-unions in their patients. This review presents a critical appraisal of the current evidence supporting the use of Teriparatide for fracture healing, delayed unions and non unions and in the setting of osteoporotic fractures, the studies producing this evidence and their transferability to human beings.

Radiographic features of teriparatide-induced healing of femoral fractures

Teriparatide is a drug that is used to increase bone remodeling, formation, and density for the treatment of osteoporosis. We present three cases of patients with a femoral insufficiency fracture. The patients were administered teripatatide in an attempt to treat severe osteoporosis and to enhance fracture healing. We found several radiographic features around the femoral fractures during the healing period. 1) Callus formation was found at a very early stage in the treatment. Teriparatide substantially increased the unusually abundant callus formation around the fracture site at 2 weeks. Moreover, this callus formation continued for 8 weeks and led to healing of the fracture. 2) Abundant callus formation was found circumferentially around the cortex with a ‘cloud-like’ appearance. 3) Remodeling of the teriparatide-induced callus formation was found to be part of the normal fracture healing process. After 1 year, normal remodeling was observed on plain radiographs. These findings indicate that teriparatide can be used as an adjuvant therapy in the management of femoral insufficiency fractures.

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Radiographic features of teriparatide-induced healing of femoral fractures were assessed.

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Teriparatide accelerated and enhanced fracture healing of femoral fractures

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Teriparatide-induced fracture healing was followed by a normal fracture healing process.

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Teriparatide can be used as an adjuvant therapy in the management of femoral insufficiency fractures.

A literature review and case series of accelerating fracture healing in postmenopausal osteoporotic working women

Majority of fractures do not cause significant long-term morbidity and mortality. A 10% of these fractures result in impaired fracture healing, drastically affecting quality of life in affected patients. Satisfactory healing of these osteoporotic fractures are critically important to functional recovery, morbidity, and quality of life. Some therapies for osteoporosis may affect the processes associated with bone repair. For example, bisphosphonates in experimental models are associated with increased callus size and mineralization, reduced callus remodeling, and improved mechanical strength. Local and systemic bisphosphonate treatment may improve implant fixation. No negative impact on fracture healing has been observed, even after major surgery or when administered immediately after fracture. For the osteoanabolic agent teriparatide, case reports and a randomized trial have produced mixed results, but they are consistent with a positive impact of teriparatide on fracture healing. At this point, therefore, there is no evidence that osteoporosis therapies are detrimental to fracture healing with some promising experimental evidence for positive effects on healing, notably for those agents whose actions are primarily anabolic.

Osteoporosis and its complications

This article provides an overview of the current burden of osteoporosis and its complications in today's health care system. The impact of osteoporosis on patients' quality of life and direct financial consequences to the entire health care system are emphasized to highlight the need for increased knowledge and awareness of its complications if left untreated or treated incorrectly. Special attention is given to hip fracture and vertebral compression fracture, stressing the importance of diagnosing osteoporosis before fragility fractures occur. Models for improved care of fragility fractures during follow-up in the outpatient setting and the use of pharmacologic agents are discussed.

Pharmacological management of osteogenesis

Osteogenesis and bone remodeling are complex biological processes that are essential for the formation of new bone tissue and its correct functioning. When the balance between bone resorption and formation is disrupted, bone diseases and disorders such as Paget's disease, fibrous dysplasia, osteoporosis and fragility fractures may result. Recent advances in bone cell biology have revealed new specific targets for the treatment of bone loss that are based on the inhibition of bone resorption by osteoclasts or the stimulation of bone formation by osteoblasts. Bisphosphonates, antiresorptive agents that reduce bone resorption, are usually recommended as first-line therapy in women with postmenopausal osteoporosis. Numerous studies have shown that bisphosphonates are able to significantly reduce the risk of femoral and vertebral fractures. Other antiresorptive agents indicated for the treatment of osteoporosis include selective estrogen receptor modulators, such as raloxifene. Denosumab, a human monoclonal antibody, is another antiresorptive agent that has been approved in Europe and the USA. This agent blocks the RANK/RANKL/OPG system, which is responsible for osteoclastic activation, thus reducing bone resorption. Other approved agents include bone anabolic agents, such as teriparatide, a recombinant parathyroid hormone that improves bone microarchitecture and strength, and strontium ranelate, considered to be a dual-action drug that acts by both osteoclastic inhibition and osteoblastic stimulation. Currently, anti-catabolic drugs that act through the Wnt-β catenin signaling pathway, serving as Dickkopf-related protein 1 inhibitors and sclerostin antagonists, are also in development. This concise review provides an overview of the drugs most commonly used for the control of osteogenesis in bone diseases.

PTH [1-34]-induced alterations of the subchondral bone provoke early osteoarthritis

OBJECTIVE

To test the hypothesis that changes in the subchondral bone induced by parathyroid hormone (PTH [1-34]) reciprocally affect the integrity of the articular cartilage within a naïve osteochondral unit in vivo.

DESIGN

Daily subcutaneous injections of 10 μg PTH [1-34]/kg were given to adult rabbits for 6 weeks, controls received saline. Blood samples were continuously collected to monitor renal function. The subchondral bone plate and subarticular spongiosa of the femoral heads were separately assessed by micro-computed tomography. Articular cartilage was evaluated by macroscopic and histological osteoarthritis scoring, polarized light microscopy, and immunohistochemical determination of type-I, type-II, type-X collagen contents, PTH [1-34] receptor and caspase-3 expression. Absolute and relative extents of hyaline and calcified articular cartilage layers were measured histomorphometrically. The correlation between PTH-induced changes in subchondral bone and articular cartilage was determined.

RESULTS

PTH [1-34] enhanced volume, mineral density, and trabecular thickness within the subarticular spongiosa, and increased thickness of the calcified cartilage layer (all P < 0.05). Moreover, PTH [1-34] led to cartilage surface irregularities and reduced matrix staining (both P < 0.03). These early osteoarthritic changes correlated with and were ascribed to the increased thickness of the calcified cartilage layer (P = 0.026) and enhanced mineral density of the subarticular spongiosa (P = 0.001).

CONCLUSIONS

Modifications of the subarticular spongiosa by PTH [1-34] cause broadening of the calcified cartilage layer, resulting in osteoarthritic cartilage degeneration. These findings identify a mechanism by which PTH-induced alterations of the normal subchondral bone microarchitecture may provoke early osteoarthritis.

The role of recombinant PTH in human fracture healing: a systematic review

OBJECTIVES

Human parathyroid hormone (PTH) is known to be efficacious in the treatment of osteoporosis and reduction of risk of vertebral and nonvertebral fractures; however, its role in the enhancement of human fracture healing is controversial. Our objective is to conduct a systematic literature review on the use of recombinant PTH in human fracture healing to (1) evaluate the evidence for recombinant PTH in human fracture healing and (2) assess whether there are notable differences between previous case reports and prospective trials.

DATA SOURCES

We performed a literature search in PubMed, EMBASE, Web of Science, and the Cochrane Database of Systematic Reviews for "teriparatide," "PTH (1-84)," "fracture," and "healing."

STUDY SELECTION

References of retrieved articles were screened for additional studies, and exclusion criteria were applied.

DATA EXTRACTION

Due to the limited publications on the subject, case reports and case series were included in our data analysis.

DATA SYNTHESIS

Due to the limited publications on the subject, our data are presented in simple tabular format.

CONCLUSIONS

Our literature review yielded 16 publications on the use of recombinant PTH in human fracture healing and 2 randomized controlled trial with 1 retrospective subgroup analysis. There continues to be anecdotal evidence for the use of recombinant PTH to enhance fracture healing. There are discrepancies in study design in the randomized controlled trials and the majority of case reports and, additional prospective studies are warranted.

Runx1 is critical for PTH-induced onset of mesenchymal progenitor cell chondrogenic differentiation

Parathyroid hormone (PTH) plays a critical role in the regulation of chondrogenesis. In this study, we have found for the first time that Runt-related transcription factor 1 (Runx1) contributes to PTH-induced chondrogenesis. Upon PTH treatment, limb bud mesenchymal progenitor cells in micromass culture showed an enhanced chondrogenesis, which was associated with a significant increase of chondrogenic marker gene expression, such as type II collagen and type X collagen. Runx1 was also exclusively expressed in cells treated with PTH at the onset stage of chondrogenesis. Knockdown of Runx1 completely blunted PTH-mediated chondrogenesis. Furthermore, PTH induced Runx1 expression and chondrogenesis were markedly reduced by inhibition of protein kinase A (PKA) signaling. Taken together, our present study indicates that chondrogenesis induced by PTH in mesenchymal progenitor cells is mediated by Runx1, which involves the activation of PKA. These data provide a novel insight into understanding the molecular mechanisms behind PTH-enhanced cartilage regeneration.

Parathyroid hormone [1-34] improves articular cartilage surface architecture and integration and subchondral bone reconstitution in osteochondral defects in vivo

OBJECTIVE

The 1-34 amino acid segment of the parathyroid hormone (PTH [1-34]) mediates anabolic effects in chondrocytes and osteocytes. The aim of this study was to investigate whether systemic application of PTH [1-34] improves the repair of non-osteoarthritic, focal osteochondral defects in vivo.

DESIGN

Standardized cylindrical osteochondral defects were bilaterally created in the femoral trochlea of rabbits (n = 8). Daily subcutaneous injections of 10 μg PTH [1-34]/kg were given to the treatment group (n = 4) for 6 weeks, controls (n = 4) received saline. Articular cartilage repair was evaluated by macroscopic, biochemical, histological and immunohistochemical analyses. Reconstitution of the subchondral bone was assessed by micro-computed tomography. Effects of PTH [1-34] on synovial membrane, apoptosis, and expression of the PTH receptor (PTH1R) were determined.

RESULTS

Systemic PTH [1-34] increased PTH1R expression on both, chondrocytes and osteocytes within the repair tissue. PTH [1-34] ameliorated the macro- and microscopic aspect of the cartilaginous repair tissue. It also enhanced the thickness of the subchondral bone plate and the microarchitecture of the subarticular spongiosa within the defects. No significant correlations were established between these coexistent processes. Apoptotic levels, synovial membrane, biochemical composition of the repair tissue, and type-I/II collagen immunoreactivity remained unaffected.

CONCLUSIONS

PTH [1-34] emerges as a promising agent in the treatment of focal osteochondral defects as its systemic administration simultaneously stimulates articular cartilage and subchondral bone repair. Importantly, both time-dependent mechanisms of repair did not correlate significantly at this early time point and need to be followed over prolonged observation periods.

PTH-enhanced structural allograft healing is associated with decreased angiopoietin-2-mediated arteriogenesis, mast cell accumulation, and fibrosis

Recombinant parathyroid hormone (rPTH) therapy has been evaluated for skeletal repair in animal studies and clinical trials based on its known anabolic effects, but its effects on angiogenesis and fibrosis remain poorly understood. We examined the effects of rPTH therapy on blood vessel formation and osseous integration in a murine femoral allograft model, which caused a significant increase in small vessel numbers, and decreased large vessel formation (p < 0.05). Histology showed that rPTH also reduced fibrosis around the allografts to similar levels observed in live autografts, and decreased mast cells at the graft-host junction. Similar effects on vasculogenesis and fibrosis were observed in femoral allografts from Col1caPTHR transgenic mice. Gene expression profiling revealed rPTH-induced angiopoietin-1 (8-fold), while decreasing angiopoietin-2 (70-fold) at day 7 of allograft healing. Finally, we show anti-angiopoietin-2 peptibody (L1-10) treatment mimics rPTH effects on angiogenesis and fibrosis. Collectively, these findings show that intermittent rPTH treatment enhances structural allograft healing by two processes: (1) anabolic effects on new bone formation via small vessel angiogenesis, and (2) inhibition of angiopoietin-2-mediated arteriogenesis. The latter effect may function as a vascular sieve to limit mast cell access to the site of tissue repair, which decreases fibrosis around and between the fractured ends of bone. Thus, rPTH therapy may be generalizable to all forms of tissue repair that suffer from limited biointegration and excessive fibrosis.

Emerging ideas: Engineering the periosteum: revitalizing allografts by mimicking autograft healing

BACKGROUND

To fulfill the need for large volumes, devitalized allografts are used to treat massive bone defects despite a 60%, 10-year postimplantation fracture rate. Allograft healing is inferior to autografts where the periosteum orchestrates remodeling.

HYPOTHESIS

By augmenting allografts with a tissue engineered periosteum consisting of tunable and degradable, poly(ethylene glycol) (PEG) hydrogels for mesenchymal stem cell (MSC) transplantation, the functions critical for periosteum-mediated healing will be identified and emulated.

METHOD OF STUDY

PEG hydrogels will be designed to emulate periosteum-mediated autograft healing to revitalize allografts. We will exploit murine femoral defect models for these approaches. Critical-sized, 5-mm segmental defects will be created and filled with decellularized allograft controls or live autograft controls. Alternatively, defects will be treated with our experimental approaches: decellularized allografts coated with MSCs transplanted via degradable PEG hydrogels to mimic progenitor cell densities and persistence during autograft healing. Healing will be evaluated for 9 weeks using microcomputed tomography, mechanical testing, and histologic analysis. If promising, MSC densities, hydrogel compositions, and genetic methods will be used to isolate critical aspects of engineered periosteum that modulate healing. Finally, hydrogel biochemical characteristics will be altered to initiate MSC and/or host-material interactions to further promote remodeling of allografts.

SIGNIFICANCE

This approach represents a novel tissue engineering strategy whereby degradable, synthetic hydrogels will be exploited to emulate the periosteum. The microenvironment, which will mediate MSC transplantation, will use tunable PEG hydrogels for isolation of critical allograft revitalization factors. In addition, hydrogels will be modified with biochemical cues to further augment allografts to reduce or eliminate revision surgeries associated with allograft failures.

Accelerated fracture healing with teriparatide

Satisfactory healing of the osteoporotic fracture is critically important to functional recovery, morbidity, and quality of life. Some therapies for osteoporosis may affect the processes associated with bone repair. For example, bisphosphonates in experimental models are associated with increased callus size and mineralization, reduced callus remodeling, and improved mechanical strength. Local and systemic bisphosphonate treatment may improve implant fixation. No negative impact on fracture healing has been observed, even after major surgery or when administered immediately after fracture. For the osteoanabolic agent teriparatide, case reports and a randomized trial have produced mixed results, but they are consistent with a positive impact of teriparatide on fracture healing. Some of the agents currently being developed for osteoporosis, notably sclerostin and DKK1 antibodies have shown a beneficial effect on fracture healing. At this point, therefore, there is no evidence that osteoporosis therapies are detrimental to fracture healing with some promising experimental evidence for positive effects on healing, notably for those agents whose actions are primarily anabolic.

Biologic adjuvants for fracture healing

Bone tissue has an exceptional quality to regenerate to native tissue in response to injury. However, the fracture repair process requires mechanical stability or a viable biological microenvironment or both to ensure successful healing to native tissue. An improved understanding of the molecular and cellular events that occur during bone repair and remodeling has led to the development of biologic agents that can augment the biological microenvironment and enhance bone repair. Orthobiologics, including stem cells, osteoinductive growth factors, osteoconductive matrices, and anabolic agents, are available clinically for accelerating fracture repair and treatment of compromised bone repair situations like delayed unions and nonunions. Preclinical and clinical studies using biologic agents like recombinant bone morphogenetic proteins have demonstrated an efficacy similar or better than that of autologous bone graft in acute fracture healing. A lack of standardized outcome measures for comparison of biologic agents in clinical fracture repair trials, frequent off-label use, and a limited understanding of the biological activity of these agents at the bone repair site have limited their efficacy in clinical applications.

Role of teriparatide in accelerating metatarsal stress fracture healing: a case series and review of literature

Bone fractures are one of the leading causes of emergency room visits worldwide, with approximately 8 million bony fractures occurring annually in the US alone. Although the majority of fractures do not cause significant long-term morbidity and mortality, approximately 10% of these fractures result in impaired fracture healing, drastically affecting quality of life in affected patients. By increasing bone formation, teriparatide, an anabolic agent used in the treatment of postmenopausal osteoporosis, has shown promise in accelerating the rate of fracture healing. We present two patients with impaired healing of metatarsal fractures who were subsequently treated with teriparatide. Both patients experienced successful bony union of the fracture after the use of teriparatide. These findings suggest that teriparatide may be useful in the clinical setting for the acceleration of fracture healing, especially in patients who are at risk for impaired fracture healing.

Implications for fracture healing of current and new osteoporosis treatments: an ESCEO consensus paper

Osteoporotic fracture healing is critical to clinical outcome in terms of functional recovery, morbidity, and quality of life. Osteoporosis treatments may affect bone repair, so insights into their impact on fracture healing are important. We reviewed the current evidence for an impact of osteoporosis treatments on bone repair. Treatment with bisphosphonate in experimental models is associated with increased callus size and mineralization, reduced callus remodeling, and improved mechanical strength. Local and systemic bisphosphonate treatment may improve implant fixation. No negative impact on fracture healing has been observed, even after major surgery or when administered immediately after fracture. Experimental data for denosumab and raloxifene suggest no negative implications for bone repair. The extensive experimental results for teriparatide indicate increased callus formation, improved biomechanical strength, and greater external callus volume and total bone mineral content and density. Case reports and a randomized trial have produced mixed results but are consistent with a positive impact of teriparatide on clinical fracture healing. Studies with strontium ranelate in models of fracture healing indicate that it is associated with improved bone microstructure, callus volume, and biomechanical properties. Finally, there is experimental evidence for a beneficial effect of some of the agents currently being developed for osteoporosis, notably sclerostin antibody and DKK1 antibody. There is currently no evidence that osteoporosis treatments are detrimental for bone repair and some promising experimental evidence for positive effects on healing, notably for agents with a bone-forming mode of action, which may translate into therapeutic applications.

Endogenous tissue engineering: PTH therapy for skeletal repair

Based on its proven anabolic effects on bone in osteoporosis patients, recombinant parathyroid hormone (PTH(1-34)) has been evaluated as a potential therapy for skeletal repair. In animals, the effect of PTH(1-34) has been investigated in various skeletal repair models such as fractures, allografting, spinal arthrodesis and distraction osteogenesis. These studies have demonstrated that intermittent PTH(1-34) treatment enhances and accelerates the skeletal repair process via a number of mechanisms, which include effects on mesenchymal stem cells, angiogenesis, chondrogenesis, bone formation and resorption. Furthermore, PTH(1-34) has been shown to enhance bone repair in challenged animal models of aging, inflammatory arthritis and glucocorticoid-induced bone loss. This pre-clinical success has led to off-label clinical use and a number of case reports documenting PTH(1-34) treatment of delayed-unions and non-unions have been published. Although a recently completed phase 2 clinical trial of PTH(1-34) treatment of patients with radius fracture has failed to achieve its primary outcome, largely because of effective healing in the placebo group, several secondary outcomes are statistically significant, highlighting important issues concerning the appropriate patient population for PTH(1-34) therapy in skeletal repair. Here, we review our current knowledge of the effects of PTH(1-34) therapy for bone healing, enumerate several critical unresolved issues (e.g., appropriate dosing regimen and indications) and discuss the long-term potential of this drug as an adjuvant for endogenous tissue engineering.

Effects of intermittent parathyroid hormone treatment on new bone formation during distraction osteogenesis in the rat mandible

OBJECTIVE

The effect of intermittent parathyroid hormone (PTH[1-34]) treatment on bone regeneration in a rat model of mandibular distraction was evaluated using microcomputed tomography.

STUDY DESIGN

After a 5-day latency period, mandibles of 18 rats were distracted at 0.2 mm/12 hours for 10 days, and rats in the PTH and control groups received subcutaneous injections of PTH(1-34) at a dosage of 60 μg/kg body weight or a vehicle only, respectively, 3 times a week. The animals were humanely killed after 10 days of distraction and after 1 week and 3 weeks of consolidation.

RESULTS

In reconstructed 3-dimensional images of the distracted mandible, mean bone volumes of the desired region of interest in the PTH group were significantly larger than those in the control group at all time points.

CONCLUSIONS

Intermittent PTH(1-34) treatment enhances new bone formation during mandibular distraction in a rat model, and it may be effective for shortening the consolidation period.

Delayed short-course treatment with teriparatide (PTH(1-34)) improves femoral allograft healing by enhancing intramembranous bone formation at the graft-host junction

Clinical management of critical bone defects remains a major challenge. Despite preclinical work demonstrating teriparatide (PTH(1-34)) effectiveness in small animals, inconclusive data from clinical trials have raised questions of dose and regimen. To address this, we completed a comprehensive study in the murine femoral allograft model, to assess the effects of dose (0.4, 4, and 40 µg/kg/day) and various treatment regimens on radiographic, histologic, and biomechanical healing at 2, 4, and 9 weeks. Only the high dose (40 µg/kg) of PTH(1-34) demonstrated significant effects when given daily over 9 weeks. Remarkably, equivalent biomechanical results were obtained with delayed, short treatment from 2 to 6 weeks that did not induce a significant increase in endochondral bone formation and callus volume. In contrast, PTH(1-34) treatment from 1 to 5 weeks postop demonstrated similar osteogenic effects as immediate daily treatment for 9 weeks, but failed to achieve a significant increase in biomechanics at 9 weeks. MicroCT and histologic analyses demonstrated that the 2-week delay in treatment allowed for timely completion of the endochondral phase, such that the prominent effects of PTH(1-34) were enhanced intramembranous bone formation and remodeling at the graft-host junction. These findings support the potential use of PTH(1-34) as an adjuvant therapy for massive allograft healing, and suggest that there may be an ideal treatment window in which a short course is administered after the endochondral phase to promote osteoblastic bone formation and remodeling to achieve superior union with modest callus formation.

Choosing a treatment for patients at the time a fracture is presented

The occurrence of a fragility fracture is an opportunity to recognize osteoporosis and begin treatment to reduce the risk of another fracture. However, selecting the treatment may have an impact on the incident fracture and this requires careful consideration of the patient and the treatment choices. There is no consensus regarding the management of osteoporosis at the time of an incident fracture. This review will consider the treatment options after a fragility fracture.

Osteoporotic fracture and parathyroid hormone

Osteoporosis and age-related bone loss is associated with changes in bone remodeling characterized by decreased bone formation relative to bone resorption, resulting in bone fragility and increased risk of fractures. Stimulating the function of bone-forming osteoblasts, is the preferred pharmacological intervention for osteoporosis. Recombinant parathyroid hormone (PTH), PTH(1-34), is an anabolic agent with proven benefits to bone strength and has been characterized as a potential therapy for skeletal repair. In spite of PTH's clinical use, safety is a major consideration for long-term treatment. Studies have demonstrated that intermittent PTH treatment enhances and accelerates the skeletal repair process via a number of mechanisms. Recent research into the molecular mechanism of PTH action on bone tissue has led to the development of PTH analogs to control osteoporotic fractures. This review summarizes a number of advances made in the field of PTH and bone fracture to combat these injuries in humans and in animal models. The ultimate goal of providing an alternative to PTH, currently the sole anabolic therapy in clinical use, to promote bone formation and improve bone strength in the aging population is yet to be achieved.

Teriparatide Therapy as an Adjuvant for Tissue Engineering and Integration of Biomaterials

Critically sized large bone defects commonly result from trauma, radical tumor resections or infections. Currently, massive allografting remain as the clinical standard to treat these critical defects. Unfortunately, allograft healing is limited by the lack of osteogenesis and bio-integration of the graft to the host bone. Based on its widely studied anabolic effects on the bone, we have proposed that teriparatide [recombinant parathyroid hormone (PTH(1-34))] could be an effective adjuvant for massive allograft healing. In support of this theory, here we review studies that have demonstrated that intermittent PTH(1-34) treatment enhances and accelerates the skeletal repair process via a number of mechanisms including: effects on mesenchymal stem cells (MSC), angiogenesis, chondrogenesis, bone formation and remodeling. We also review the current literature on the effects of PTH(1-34) therapy on bone healing, and discuss this drug's long term potential as an adjuvant for endogenous tissue engineering.

The effect of vitamin D receptor BsmI genotype on the response to osteoporosis treatment in postmenopausal women: a pilot study

AIM

The purpose of our study was to investigate the possible effect of BsmI vitamin D receptor (VDR's) polymorphism on changes in bone mineral density (BMD) and bone turnover markers in postmenopausal women receiving different treatments.

MATERIAL AND METHODS

This pilot study included 42 postmenopausal women with elevated fracture risk, randomized into 1-year treatment with weekly oral alendronate or daily subcutaneous teriparatide. Both groups received daily supplements of 1000 mg calcium and 800 IU vitamin D. Blood samples were obtained for biochemical evaluation and genotyping. BMD at the lumbar spine and femoral neck were assessed with dual energy X-ray absorptiometry. Baseline, follow-up BMD and markers of bone turnover were assessed according to the BsmI genotype.

RESULTS

BMD at the lumbar spine increased in patients carrying at least one b allele, while it decreased in patients with the BB genotype (P = 0.041). Whereas no gene-treatment interaction was observed in teriparatide-receiving patients, women with the BB genotype receiving alendronate resulted in negative BMD (-0.056 ± 0.032 g/m(2) ) and T-score (-0.295 ± 0.190) gradient, compared to carriers of the b allele (BMD: +0.020 ± 0.017 g/m(2) , P = 0.054; T-score: +0.217 ± 0.100, P = 0.030). No effect of genotype was apparent with respect to gradients of biochemical bone markers.

CONCLUSIONS

These preliminary results indicate that alendronate has a differential effect on BMD, depending on the VDR genotype. Carriers of the b allele may be more responsive to treatment compared to patients with the BB genotype. The interaction of VDR's BsmI polymorphism with the efficacy of the anti-osteoporotic treatment needs further investigation by larger prospective studies.

Per-1 is a specific clock gene regulated by parathyroid hormone (PTH) signaling in osteoblasts and is functional for the transcriptional events induced by PTH

Per-1 is one of the clock genes and is known to regulate various biological events including bone mass determination. Parathyroid hormone is anabolic to bone while the mechanism of its action is not fully understood. Here, we examined the role of PTH on Per-1 gene expression under osteoblast specific PTH signaling. Constitutively active PTH receptor (caPPR) expressed specifically in osteoblasts in transgenic mice activates Per-1 gene expression in bone. This is specific as expression of other clock gene Bmal-1 is not affected by caPPR over-expression. Per-1 is also expressed in osteoblastic cell line. Interestingly, Per-1 expression is required for PTH signaling-induced CRE dependent transcription. This is forming a positive feed back loop in the anabolic action of PTH signaling and Per-1 in bone. These data indicate that PTH singling in osteoblasts activates Per-1 gene expression in vivo in association with its anabolic action in bone at least in part through the regulation of transcriptional events.

Side chain cyclization based on serine residues: synthesis, structure, and activity of a novel cyclic analogue of the parathyroid hormone fragment 1-11

The N-terminal region of the parathyroid hormone (PTH) is sufficient to activate the G-protein-coupled PTH receptor 1 (PTHR1). The shortest PTH analogue displaying nanomolar potency is the undecapeptide H-Aib-Val-Aib-Glu-Ile-Gln-Leu-Nle-His-Gln-Har-NH(2) that contains two helix-stabilizing residues (Aib(1,3)). To increase the helical character and proteolytic stability of this linear peptide, we replaced Gln(6,10) with (a) Lys(6) and Glu(10) to introduce a lactam bridge and (b) Ser(6,10) to form a diester bridge upon cross-linking with adipic acid. These cyclopeptides were, respectively, 468-fold less and 12-fold more potent agonists than the linear analogue. Despite their different potencies, all three analogues adopted similar α-helix structures, as shown by NMR and molecular dynamics studies. However, the diester bridge could better mimic the orientation and chemical properties of the side chains of Gln(6) and Gln(10) in the linear PTH analogue than the lactam moiety. This is apparently important for efficient receptor activation and provides further insights into the receptor-bound ligand conformation.