Intermittent parathyroid hormone therapy to increase bone formation

Calcium Deficiency Decreases Bone Mass without Affecting Adiposity in Ovariectomized Rats Fed a High-Fat Diet

Obesity induced by a high-fat (HF) diet increases bone resorption and/or decreases bone formation, resulting in reduced bone mass and strength in various animal models. Studies showed that Ca intake is a modifiable factor for osteoporosis and obesity. This study investigated whether Ca deficiency affects bone structure and adiposity in ovariectomized (OVX) rats fed a HF diet. We hypothesized that Ca deficiency further decreases bone mass and increases fat mass in HF-fed OVX rats. Forty-seven OVX at 6-month-old were randomly assigned to four groups in a 2 × 2 factorial design: normal-fat (NF, 10% fat as energy) or HF (45% fat as energy) diet with either low Ca (LC, 1 g/4057 kcal) or normal Ca (NC, 6 g/4057 kcal). In addition, 12 sham-operated rats at 6 months old were fed a NFNC diet as a control for the OVX procedure. Rats were fed the respective diet for 4 months. Dietary Ca content did not affect body weight, fat mass, lean mass, food intake, energy intake, and serum cytokines. Compared to NC, LC resulted in lower tibial bone volume/total volume (BV/TV, p < 0.01), connectivity density (p < 0.01), trabecular number (Tb.N, p = 0.01), bone mineral density (BMD, p < 0.01), and femur weight (p < 0.01), femur content of Ca (p < 0.01), Cu (p = 0.03), Zn (p < 0.01), and greater trabecular separation (Tb.Sp, p < 0.01) at proximal tibia indicating bone structure deterioration. Compared to rats on the NF diet, animals fed the HF had lower BV/TV (p = 0.03) and Tb.N (p < 0.01) with greater body weight (p < 0.01), fat mass (p < 0.01), Tb.Sp (p = 0.01), the content of Ca, Cu, and Zn in the femur, and serum leptin (p < 0.01). There were no significant interactions between Ca and fat for body composition and bone structural parameters. Compared to Sham, OVX resulted in greater body weight and fat mass. The trabecular bone structure of the tibia, but not the cortical bone, was significantly impaired by the OVX procedure. These data indicate that inadequate Ca intake and a high-fat diet have independent negative effects on bone structure and that Ca deficiency does not affect adiposity in OVX rats.

The effect of intermittent parathyroid hormone on bone lengthening: current evidence to inform future effective interventions

PURPOSE

Recent studies have demonstrated the positive effects of parathyroid hormone (PTH) on bone healing, and findings support the use of PTH to accelerate bone healing following distraction osteogenesis. The goal of this review was to compile and discuss the mechanisms potentially underlying the effects of PTH on newly formed bone following a bone-lengthening procedure incorporating all relevant evidence in both animal and clinical studies.

METHODS

This review summarized all evidence from in vivo to clinical studies regarding the effects of PTH administration on a bone-lengthening model. In addition, a comprehensive evaluation of what is currently known regarding the potential mechanisms underlying the potential benefits of PTH in bone lengthening was presented. Some controversial findings regarding the optimal dosage and timing of administration of PTH in this model were also discussed.

RESULTS

The findings demonstrated that the potential mechanisms associated with the action of PTH on the acceleration of bone regeneration after distraction osteogenesis are involvement in mesenchymal cell proliferation and differentiation, endochondral bone formation, membranous bone formation, and callus remodeling.

CONCLUSIONS

In the last 20 years, a number of animal and clinical studies have indicated that there is a prospective role for PTH treatment in human bone lengthening as an anabolic agent that accelerates the mineralization and strength of the regenerated bone. Therefore, PTH treatment can be viewed as a potential treatment to increase the amount of new calcified bone and the mechanical strength of the bone in order to shorten the consolidation stage after bone lengthening.

Factors associated with bone response to teriparatide in young postmenopausal women with osteoporosis

INTRODUCTION

To investigate the factors associated with changes in vertebral bone mineral density during teriparatide treatment.

MATERIALS AND METHODS

Single centre, longitudinal study involving 145 osteoporotic postmenopausal women treated with teriparatide. Clinical evaluation, bone mineral density (BMD) measurements assessment and laboratory analyses were performed at baseline then after 12 and 18 months of treatment. Bone non-response to treatment was defined as no significant increase in BMD at 18 months as compared to baseline.

RESULTS

Of the 145 women initially included, 109 completed the 18-month course of the treatment. 75% of them had a history of prior osteoporotic treatment. Baseline mean age was 60 ± 8 years. Mean baseline vertebral T-score was - 3.7 ± 0.7 and 83 (76%) women had suffered at least one vertebral fracture. At the end of treatment, 18 women (17%) were classified as non-responders. In the responder group (n = 91), vertebral BMD increased by 0.091 ± 0.04 g/cm2 (12.2 ± 5.3%). Clinical characteristics, baseline BMDs and the percentage of women previously treated with bisphosphonates as well as the duration of prior treatment did not significantly differ between the two groups of responders and non-responders. At baseline, non-responders had significant mean lower C-terminal fragment of type 1 collagen (CTX) values than responders (p < 0.01). Only baseline CTX values (r = 0.30 p < 0.01) were independently correlated to vertebral BMD changes during teriparatide treatment.

CONCLUSION

A minority of treated women had no vertebral densitometric gain after 18 months of teriparatide therapy. Low levels of baseline bone remodeling were the main factor associated with poor response to treatment.

The Osteocyte as the New Discovery of Therapeutic Options in Rare Bone Diseases

Osteocytes are the most abundant (~95%) cells in bone with the longest half-life (~25 years) in humans. In the past osteocytes have been regarded as vestigial cells in bone, since they are buried inside the tough bone matrix. However, during the last 30 years it has become clear that osteocytes are as important as bone forming osteoblasts and bone resorbing osteoclasts in maintaining bone homeostasis. The osteocyte cell body and dendritic processes reside in bone in a complex lacuno-canalicular system, which allows the direct networking of osteocytes to their neighboring osteocytes, osteoblasts, osteoclasts, bone marrow, blood vessels, and nerves. Mechanosensing of osteocytes translates the applied mechanical force on bone to cellular signaling and regulation of bone adaptation. The osteocyte lacuno-canalicular system is highly efficient in transferring external mechanical force on bone to the osteocyte cell body and dendritic processes via displacement of fluid in the lacuno-canalicular space. Osteocyte mechanotransduction regulates the formation and function of the osteoblasts and osteoclasts to maintain bone homeostasis. Osteocytes produce a variety of proteins and signaling molecules such as sclerostin, cathepsin K, Wnts, DKK1, DMP1, IGF1, and RANKL/OPG to regulate osteoblast and osteoclast activity. Various genetic abnormality-associated rare bone diseases are related to disrupted osteocyte functions, including sclerosteosis, van Buchem disease, hypophosphatemic rickets, and WNT1 and plastin3 mutation-related disorders. Meticulous studies during the last 15 years on disrupted osteocyte function in rare bone diseases guided for the development of various novel therapeutic agents to treat bone diseases. Studies on genetic, molecular, and cellular mechanisms of sclerosteosis and van Buchem disease revealed a role for sclerostin in bone homeostasis, which led to the development of the sclerostin antibody to treat osteoporosis and other bone degenerative diseases. The mechanism of many other rare bone diseases and the role of the osteocyte in the development of such conditions still needs to be investigated. In this review, we mainly discuss the knowledge obtained during the last 30 years on the role of the osteocyte in rare bone diseases. We speculate about future research directions to develop novel therapeutic drugs targeting osteocyte functions to treat both common and rare bone diseases.

Forecasting the critical role of intermittent therapies for the control of bone resorption

BACKGROUND

Osteoporosis is a chronic metabolic disease characterized by an imbalance of bone resorption and formation, leading to bone fragility and increased susceptibility to fracture. Parathyroid hormone is approved therapy for the treatment of osteoporosis.

METHODS

The intermittent therapy of parathyroid hormone requires accurate administration. Meta-analysis is conducted to draw a clear picture of the impact of intermittent therapy and dose rates relative to time, on the osteoporotic patients. A novel mathematical model is presented in this article synchronised with the parametric values, depicted from meta-analysis.

FINDINGS

Results obtained from the mathematical model are in close agreement with the results obtained from the clinical trials. The model can be used to forecast the drug potency and dosage rates, to control the vicious cycle of osteoporosis.

INTERPRETATIONS

The intermittent administration of parathyroid hormone, rather than the continuous administration, is more effective, furthermore it is also concluded that a mathematical model, linked with the extensive literature of clinical trials, using meta-analysis can help in drug administration and future clinical studies of drug development.

Update on the impact of type 2 diabetes mellitus on bone metabolism and material properties

The prevalence of type 2 diabetes mellitus (T2DM) is increasing worldwide, especially as a result of our aging society, high caloric intake and sedentary lifestyle. Besides the well-known complications of T2DM on the cardiovascular system, the eyes, kidneys and nerves, bone strength is also impaired in diabetic patients. Patients with T2DM have a 40-70% increased risk for fractures, despite having a normal to increased bone mineral density, suggesting that other factors besides bone quantity must account for increased bone fragility. This review summarizes the current knowledge on the complex effects of T2DM on bone including effects on bone cells, bone material properties and other endocrine systems that subsequently affect bone, discusses the effects of T2DM medications on bone and concludes with a model identifying factors that may contribute to poor bone quality and increased bone fragility in T2DM.

Interaction among Calcium Diet Content, PTH (1-34) Treatment and Balance of Bone Homeostasis in Rat Model: The Trabecular Bone as Keystone

The present study is the second step (concerning normal diet restoration) of the our previous study (concerning the calcium-free diet) to determine whether normal diet restoration, with/without concomitant PTH (1-34) administration, can influence amounts and deposition sites of the total bone mass. Histomorphometric evaluations and immunohistochemical analysis for Sclerostin expression were conducted on the vertebral bodies and femurs in the rat model. The final goals are (i) to define timing and manners of bone mass changes when calcium is restored to the diet, (ii) to analyze the different involvement of the two bony architectures having different metabolism (i.e., trabecular versus cortical bone), and (iii) to verify the eventual role of PTH (1-34) administration. Results evidenced the greater involvement of the trabecular bone with respect to the cortical bone, in response to different levels of calcium content in the diet, and the effect of PTH, mostly in the recovery of trabecular bony architecture. The main findings emerged from the present study are (i) the importance of the interplay between mineral homeostasis and skeletal homeostasis in modulating and guiding bone's response to dietary/metabolic alterations and (ii) the evidence that the more involved bony architecture is the trabecular bone, the most susceptible to the dynamical balance of the two homeostases.

Dose-dependent effect of parathyroid hormone on fracture healing and bone formation in mice

BACKGROUND

Parathyroid hormone (PTH) is the only clinically approved osteoanabolic drug for osteoporosis treatment. However, PTH is not established for the treatment of fracture healing, and doses of PTH diverge significantly between different studies. We hypothesized that the effect of PTH on promoting fracture healing and bone formation is dose dependent.

MATERIALS AND METHODS

In vivo, mice were treated with PTH (10, 40, and 200 μg/kg) in a closed femoral fracture model. Fracture healing was analyzed after 4 weeks. The fourth lumbar vertebra was analyzed to assess systemic effects. In addition, osteoblasts from calvaria of mice were treated in vitro with PTH doses of 10^-5-50 nM, and their differentiation was analyzed after 26 days.

RESULTS

In vivo, PTH dose-dependently stimulated bone formation in the fracture callus and the vertebral body. However, PTH treatment did not increase biomechanical stiffness of the fractured femora in a dose-dependent manner. The increased bone formation in the 200 μg/kg group was associated with a depletion of osteoclasts, indicating diminished bone remodeling. Of interest, in vitro, we observed diminished mineralization with the highest doses of PTH in osteoblast cultures.

CONCLUSIONS

PTH dose-dependently stimulates bone formation in vivo. However, during fracture healing, this did not result in a dose-dependent increase of the mechanical stiffness of the fracture callus. Taken together, our in vivo and in vitro data indicate that the dose-dependent effects of PTH during fracture healing are based on the actions on multiple cell types, thereby influencing not only bone formation but also osteoclastic callus remodeling.

PTH(1-34) effects on repairing experimentally drilled holes in rat femur: novel aspects - qualitative vs. quantitative improvement of osteogenesis

The timetable of effects on bone repair of the active fraction-parathyroid hormone, PTH(1-34), was analytically investigated from the morphometric viewpoint in 3-month-old male Sprague-Dawley rats, whose femurs were drilled at mid-diaphyseal level (transcortical holes). The animals were divided into groups with/without PTH(1-34) administration, and sacrificed at different times (10, 28, 45 days after surgery). The observations reported here need to be framed in the context of our previous investigations regarding bone histogenesis (Ferretti et al. Anat Embryol. 2002; 206: 21-29) in which we demonstrated the occurrence of two successive bone-forming processes during both skeletal organogenesis and bone repair, i.e. static and dynamic osteogenesis: the former (due to stationary osteoblasts, haphazardly grouped in cords) producing preliminary bad quality trabecular bone, the latter (due to typical polarized osteoblasts organized in ordered movable laminae) producing mechanically valid bone tissue. The primary function of static osteogenesis is to provide a rigid scaffold containing osteocytes (i.e. mechano-sensors) for osteoblast laminae acting in dynamic osteogenesis. In the present work, histomorphometric analysis revealed that, already 10 days after drilling, despite the holes being temporarily filled by the same amount of newly formed trabecular bone by static osteogenesis independently of the treatment, the extent of the surface of movable osteoblast-laminae (covering the trabecular surface) was statistically higher in animals submitted to PTH(1-34) administration than in control ones; this datum strongly suggests the effect of PTH(1-34) alone in anticipating the occurrence of dynamic osteogenesis involved in the production of good quality bone (with more ordered collagen texture) more suitable for loading. This study could be crucial in further translational clinical research in humans for defining the best therapeutic strategies to be applied in recovering severe skeletal lesions, particularly as regards the time of PTH(1-34) administration.

A novel therapeutic strategy for adolescent idiopathic scoliosis based on osteoporotic concept

Adolescent idiopathic scoliosis (AIS) is a complex three dimensional spinal deformity which occurs mostly in prepubertal and pubertal girls. Although bracing and surgery have been the mainstays of treatment for AIS, because of the complications and poor compliance, many patients with this disorder continue to experience significant residual symptoms. The etiology and pathogenesis of AIS is unclear, but recent studies show the association between osteopenia and AIS and imply that osteopenia play a causative role in the development of AIS. Anti-osteoporosis treatment can improve bone strength, prevent osteoporosis and rebalance the OPG-RANK-RANKL system, which may help to prevent curve progression in AIS. This report proposes that anti-osteoporosis treatment may be an effective treatment for AIS.

Complex dynamics of transcription regulation

Transcription is a tightly regulated cellular function which can be triggered by endogenous (intrinsic) or exogenous (extrinsic) signals. The development of novel techniques to examine the dynamic behavior of transcription factors and the analysis of transcriptional activity at the single cell level with increased temporal resolution has revealed unexpected elements of stochasticity and dynamics of this process. Emerging research reveals a complex picture, wherein a wide range of time scales and temporal transcription patterns overlap to generate transcriptional programs. The challenge now is to develop a perspective that can guide us to common underlying mechanisms, and consolidate these findings. Here we review the recent literature on temporal dynamics and stochastic gene regulation patterns governed by intrinsic or extrinsic signals, utilizing the glucocorticoid receptor (GR)-mediated transcriptional model to illustrate commonality of these emerging concepts. This article is part of a Special Issue entitled: Chromatin in time and space.

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

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

Transcriptional regulation of BMP2 expression by the PTH-CREB signaling pathway in osteoblasts

Intermittent application of parathyroid hormone (PTH) has well established anabolic effects on bone mass in rodents and humans. Although transcriptional mechanisms responsible for these effects are not fully understood, it is recognized that transcriptional factor cAMP response element binding protein (CREB) mediates PTH signaling in osteoblasts, and that there is a communication between the PTH-CREB pathway and the BMP2 signaling pathway, which is important for osteoblast differentiation and bone formations. These findings, in conjunction with putative cAMP response elements (CREs) in the BMP2 promoter, led us to hypothesize that the PTH-CREB pathway could be a positive regulator of BMP2 transcription in osteoblasts. To test this hypothesis, we first demonstrated that PTH signaling activated CREB by phosphorylation in osteoblasts, and that both PTH and CREB were capable of promoting osteoblastic differentiation of primary mouse osteoblast cells and multiple rodent osteoblast cell lines. Importantly, we found that the PTH-CREB signaling pathway functioned as an effective activator of BMP2 expression, as pharmacologic and genetic modulation of PTH-CREB activity significantly affected BMP2 expression levels in these cells. Lastly, through multiple promoter assays, including promoter reporter deletion, mutation, chromatin immunoprecipitation (ChIP), and electrophoretic mobility shift assay (EMSA), we identified a specific CRE in the BMP2 promoter which is responsible for CREB transactivation of the BMP2 gene in osteoblasts. Together, these results demonstrate that the anabolic function of PTH signaling in bone is mediated, at least in part, by CREB transactivation of BMP2 expression in osteoblasts.

Bone mineral density in pseudohypoparathyroidism type 1a

CONTEXT

The biochemical hallmark of pseudohypoparathyroidism type 1a (PHP1a) is resistance to PTH, but based on tissue-specific imprinting of GNAS, PTH resistance may be limited to the renal cortex. Some studies have shown that bone is responsive to PTH, suggesting that PHP1a patients with chronically elevated PTH levels may have low bone mineral density (BMD).

SETTING

This observational study was conducted at the Institute of Clinical and Translational Research, Johns Hopkins Medical Institutions.

SUBJECTS

Twenty-two children and adults with PHP1a were studied.

MAIN OUTCOME MEASURE

The main outcome measure was BMD Z-score at the lumbar spine (LS), total hip, femoral neck, and total body using dual-energy x-ray absorptiometry, relative to height, weight, and pubertal status.

RESULTS

The mean (+/-SD) Z-score for height was 0.77 +/- 1.66 and 1.85 +/- 1.15 for BMI. The BMD Z-score at each of the four sites studied was as follows: LS, 0.29 +/- 1.08; total hip, 0.27 +/- 1.24; femoral neck, 0.02 +/- 1.26; and total body, 0.98 +/- 1.50. Only two subjects (9%) had BMD Z-scores less than -2, and each had additional risk factors for low BMD. BMD in total body and LS spine corrected for height-for-age Z-score was significantly greater than normal. There was no correlation between PTH level and BMD Z-score or between body mass index and BMD Z-score.

CONCLUSIONS

Despite secondary hyperparathyroidism, region-specific BMD is not reduced in patients with PHP1a, and total body BMD is significantly greater than normal.

Elevated serum IGF-1 levels synergize PTH action on the skeleton only when the tissue IGF-1 axis is intact

There is growing evidence that insulin-like growth factor 1 (IGF-1) and parathyroid hormone (PTH) have synergistic actions on bone and that part of the anabolic effects of PTH is mediated by local production of IGF-1. In this study we analyzed the skeletal response to PTH in mouse models with manipulated endocrine or autocrine/paracrine IGF-1. We used mice carrying a hepatic IGF-1 transgene (HIT), which results in a threefold increase in serum IGF-1 levels and normal tissue IGF-1 expression, and Igf1 null mice with blunted IGF-1 expression in tissues but threefold increases in serum IGF-1 levels (KO-HIT). Evaluation of skeletal growth showed that elevations in serum IGF-1 in mice with Igf1 gene ablation in all tissues except the liver (KO-HIT) resulted in a restoration of skeletal morphology and mechanical properties by adulthood. Intermittent PTH treatment of adult HIT mice resulted in increases in serum osteocalcin levels, femoral total cross-sectional area, cortical bone area and cortical bone thickness, as well as bone mechanical properties. We found that the skeletal response of HIT mice to PTH was significantly higher than that of control mice, suggesting synergy between IGF-1 and PTH on bone. In sharp contrast, although PTH-treated KO-HIT mice demonstrated an anabolic response in cortical and trabecular bone compartments compared with vehicle-treated KO-HIT mice, their response was identical to that of PTH-treated control mice. We conclude that (1) in the presence of elevated serum IGF-1 levels, PTH can exert an anabolic response in bone even in the total absence of tissue IGF-1, and (2) elevations in serum IGF-1 levels synergize PTH action on bone only if the tissue IGF-1 axis is intact. Thus enhancement of PTH anabolic actions depends on tissue IGF-1.

Parathyroid hormone PTH(1-34) increases the volume, mineral content, and mechanical properties of regenerated mineralizing tissue after distraction osteogenesis in rabbits

BACKGROUND AND PURPOSE

Parathyroid hormone (PTH) has attracted considerable interest as a bone anabolic agent. Recently, it has been suggested that PTH can also enhance bone repair after fracture and distraction osteogenesis. We analyzed bone density and strength of the newly regenerated mineralized tissue after intermittent treatment with PTH in rabbits, which undergo Haversian bone remodeling similar to that in humans.

METHODS

72 New Zealand White rabbits underwent tibial mid-diaphyseal osteotomy and the callus was distracted 1 mm/day for 10 days. The rabbits were divided into 3 groups, which received injections of PTH 25 microg/kg/day for 30 days, saline for 10 days and PTH 25 microg/kg/day for 20 days, or saline for 30 days. At the end of the study, the rabbits were killed and the bone density was evaluated with DEXA. The mechanical bone strength was determined by use of a 3-point bending test.

RESULTS

In the 2 PTH-treated groups the regenerate callus ultimate load was 33% and 30% higher, absorbed energy was 100% and 65% higher, BMC was 61% and 60% higher, and callus tissue volume was 179% and 197% higher than for the control group.

INTERPRETATION

We found that treatment with PTH during distraction osteogenesis resulted in substantially higher mineralized tissue volume, mineral content, and bending strength. This suggests that treatment with PTH may benefit new bone formation during distraction osteogenesis and could form a basis for clinical application of this therapy in humans.

A bicistronic expression strategy for large scale expression and purification of full-length recombinant human parathyroid hormone for osteoporosis therapy

Parathyroid hormone (PTH) contributes to the increase of trabecular connectivity and is a candidate medication for effective treating osteoporosis. PTH is a protein of 84 amino acids and some studies have suggested that the active site lies within the range from amino acid (aa) 1 to 34. However, a few reports have indicated a causal relationship between PTH (aa 1-34) and osteogenic sarcoma in rats, while some less obvious but important roles of the carboxyl-terminus of PTH were also found. Unfortunately, it is difficult to obtain the active integrated PTH (1-84) in vitro, due to the instability of both the protein and its mRNA. Because an alternative translation start site is located at +25 nucleotides downstream of the true start site, a truncated PTH can be translated. We constructed a rhPTH bicistronic expression plasmid (pTrepth) that could highly express non-fusion soluble rhPTH proteins in Escherichia coli. The BL-21(DE3) containing pTrepth was cultured on a small scale until satisfactory expression and purification results were obtained. We then amplified the transformed cells in a 15-L fermentor and harvested 27g/L cells (wet weight). Extensive rhPTH purification was achieved by a three step chromatography process. Activity tests demonstrated that our purified protein could dramatically increase cAMP in osteosarcoma cells in vitro.

Global burden of trauma: Need for effective fracture therapies

Orthopedic trauma care and fracture management have advanced significantly over the last 50 years. New developments in the biology and biomechanics of the musculoskeletal system, fixation devices, and soft tissue management have greatly influenced our ability to care for musculoskeletal injuries. Many therapies and treatment modalities have the potential to transform future orthopedic treatment by decreasing invasive procedures and providing shorter healing times. Promising results in experimental models have led to an increase in clinical application of these therapies in human subjects. However, for many modalities, precise clinical indications, timing, dosage, and mode of action still need to be clearly defined. In order to further develop fracture management strategies, predict outcomes and improve clinical application of newer technologies, further research studies are needed. Together with evolving new therapies, the strategies to improve fracture care should focus on cost effectiveness. This is a great opportunity for the global orthopedic community, in association with other stakeholders, to address the many barriers to the delivery of safe, timely, and effective care for patients with musculoskeletal injuries in developing countries.

Teriparatide (1-34 human PTH) regulation of osterix during fracture repair

Based on remarkable success of PTH as an anabolic drug for osteoporosis, case reports of off-label use of teriparatide (1-34 PTH) in patients with complicated fractures and non-unions are emerging. We investigated the mechanisms underlying PTH accelerated fracture repair. Bone marrow cells from 7 days 40 microg/kg of teriparatide treated or saline control mice were cultured and Osx and osteoblast phenotypic gene expression assessed by real-time RT-PCR in these cells. Fractured animals injected daily with either saline or 40 microg/kg of teriparatide for up to 21 days were X-rayed and histological assessment performed, as well as immunohistochemical analyses of the Osx expression in the fracture callus. Osx, Runx2 and osteoblast or chondrocyte phenotypic gene expression was also assessed in fracture calluses. Our data shows that Osx and Runx2 are up-regulated in marrow-derived MSCs isolated from mice systemically treated with teriparatide. Furthermore, these MSCs undergo accelerated osteoblast maturation compared to saline injected controls. Systemic teriparatide treatments also accelerated fracture healing in these mice concomitantly with increased Osx expression in the PTH treated fracture calluses compared to controls. Collectively, these data suggest a mechanism for teriparatide mediated fracture healing possibly via Osx induction in MSCs.

Sequential changes of bone metabolism in normal and delayed union of the spine

Time-dependent changes in bone markers in delayed or nonunion of vertebral fracture were compared with those of normal union. Thirty-three patients with a fresh vertebral fracture were enrolled. Urinary Type I collagen C-terminal telopeptide, pyridinoline, deoxypyridinoline, serum C-terminal telopeptide, and N-midportion of osteocalcin (OC(N-mid)) were determined at the time of hospital admission (within 24 hours after the fracture event in all cases) and at 2, 4, 12, 24, and 48 weeks thereafter. Subjects were divided into two groups according to the results of MR images taken 48 weeks after fracture. Twenty-four were normally united (Group N) and nine had delayed or nonunion (Group D) of the spine. No differences between values of bone resorption markers in Group N and Group D were observed at any time. Serum OC(N-mid) in Group N started to increase at 2 weeks and reached the peak value at 24 weeks (180%); however, serum OC(N-mid) in Group D increased at most 120% from baseline to 4 weeks. Values of serum OC(N-mid) in Group N were higher at 24 and 48 weeks than those in Group D. Impairment of fracture healing was strongly associated with a deficit in the increase of osteocalcin in the later stage of fracture repair.

LEVEL OF EVIDENCE

Level II, prognostic study. See the Guidelines for Authors for a complete description of levels of evidence.

Critical analysis of the evidence for current technologies in bone-healing and repair

Substances that enhance fracture-healing and bone regeneration have valuable clinical application and merit future research. Advances in these technologies will enhance our ability to heal fractures in a more effective and expedient manner. This review provides a brief description of the different techniques and technologies and their respective clinical utility. This paper also reviews the available literature on gene therapy, tissue engineering, growth factors, osteoconductive agents, and physical forces and assesses the evidence regarding the current status of these techniques of healing and regenerating bone. Only twenty-seven articles met our guidelines for studies containing Level-I evidence. We were able to determine that atrophic nonunions and pseudarthrosis led to poorer outcomes, and the results were uniformly poor irrespective of the technique used. Although the literature contains a large number of studies on the effects of different agents and modalities on bone repair and healing, it still is not clear how these agents work or in what circumstances they should be used. Many of the treatment modalities of interest are still at an experimental stage, so good evidence to support clinical practice is lacking. Additional multicenter, prospective randomized studies are needed to define the indications, specifications, dosage, limitations, and contraindications in the treatment of nonunions. Studies are also needed to address the full clinical feasibility of the role of each modality in fracture-healing and repair.

Two-year changes in bone mineral density and T scores in patients treated at a pharmacist-run teriparatide clinic

STUDY OBJECTIVES

To determine changes in bone mineral density (BMD) and T scores of patients after 2 years of teriparatide therapy, and to determine the number of fractures that occurred during therapy.

DESIGN

Prospective, observational study.

SETTING

Pharmacist-run teriparatide clinic in a private-practice endocrinology group.

PATIENTS

Sixty patients with osteoporosis who experienced fractures or adverse events while receiving antiresorptive therapy and were referred by the endocrinologists to the clinic between January 1, 2002, and January 1, 2004.

INTERVENTION

After a 1-hour counseling and training session with a clinical pharmacist, patients self-administered subcutaneous teriparatide 20 microg/day for the next 2 years.

MEASUREMENTS AND MAIN RESULTS

Primary outcome measures were dual x-ray absorptiometry-determined BMDs and T scores for the total hip, spine, and wrist at baseline and at 1 and 2 years. Patients' BMDs for the hip significantly increased by 3.5% at 1 year and by 3.9% at 2 years. In addition, BMD for the spine significantly increased by 7.2% at 1 year and 10.9% at 2 years. In 56 (93%) patients, BMD for the spine increased after 2 years of treatment. For the wrist, BMD decreased by 0.75% at 1 year and by 2.4% at 2 years, but the change was only significant at 2 years (p=0.011). At both 1 and 2 years, T scores for the total hip and spine significantly improved from baseline (p< or =0.019), whereas T scores for the wrist significantly declined after 2 years of therapy (p<0.003). No new fractures were documented in any of the patients.

CONCLUSION

In patients with osteoporosis, the use of teriparatide in a pharmacist-run clinic significantly increased BMD at the total hip and spinal sites and significantly decreased BMD in the wrist.

Roles of epidermal growth factor family in the regulation of postnatal somatic growth

Ligands of the epidermal growth factor receptor (EGF-R), known to be important for supporting tissue development particularly in the gut and brain, have also been implicated in regulating postnatal somatic growth. Although optimal levels of both milk-borne and endogenous EGF-R ligands are important for supporting postnatal somatic growth through regulating gastrointestinal growth and maturation, supraphysiological levels of EGF-R ligands can cause retarded and disproportionate growth and alter body composition because they can increase growth of epithelial tissues but decrease masses of muscle, fat, and bone. Apart from their indirect roles in influencing growth, possibly via regulating levels of IGF-I and IGF binding proteins, EGF-R ligands can regulate bone growth and modeling directly because they can enhance proliferation but suppress maturation of growth plate chondrocytes (for building a calcified cartilage scaffold for bone deposition), stimulate proliferation but inhibit differentiation of osteoblasts (for depositing bone matrix), and promote formation and function of osteoclasts (for resorption of calcified cartilage or bone). In addition, EGF-like ligands, particularly amphiregulin, can be strongly regulated by PTH, an important regulatory factor in bone modeling and remodeling. Finally, EGF-R ligands can regulate bone homeostasis by regulating a pool of progenitor cells in the bone marrow through promoting proliferation but suppressing differentiation of bone marrow mesenchymal stem cells.