Biologicals in osteoporosis: teriparatide and parathyroid hormone in women and men

PTH/PTHrP in controlled release hydrogel enhances orthodontic tooth movement by regulating periodontal bone remodaling

OBJECTIVE

This study aimed to evaluate the effects of local application of parathyroid hormone (PTH) or parathyroid hormone-related protein (PTHrP) on osteogenesis and osteoclastogenesis during orthodontic tooth movement (OTM).

BACKGROUND

Periodontal bone remodeling is the crucial biological process in the OTM that involves both bone resorption and formation, with the former more important as the initiator. PTH or PTHrP both play dual roles in bone remodeling regulation, and the balance may shift to the bone resorption side when they are given continuously, suggesting them as potential candidate medicine for OTM acceleration.

METHODS

A total of 40 rats underwent orthodontic mesialization of the maxillary first molars and received no micro-perforation (MOP), or MOP followed by injection of temperature-sensitive hydrogel containing PTH, PTHrP, or normal saline. The rats were sacrificed after 2-week OTM, except for the relapse groups, which had one more week of observation after removal of the force appliances. The amount of tooth movement, rate of relapse after OTM, and effects on the bone remodeling were assessed through micro-computed tomography (μCT) analysis, alkaline phosphatase (ALP) assay, alizarin red staining, tartrate-resistant acid phosphatase (TRAP) staining, immunohistochemistry (IHC) analysis, Western blot (WB), and quantitative real-time polymerase chain reaction (qRT-PCR). The effects of PTHrP on the osteogenic differentiation of human periodontal ligament cells (hPDLCs) were explored in vitro.

RESULTS

The cumulative release of PTH or PTHrP from PECE hydrogels was beyond 75% at 14 days in a sustained manner. After the intervention in vivo, the distance of OTM in the PTH (0.78 ± 0.06 mm) or PTHrP (0.81 ± 0.04 mm) group was significantly larger than that of the MOP only (0.51 ± 0.04 mm) or the no MOP (0.46 ± 0.05 mm) group. Moreover, PTH injection significantly reduced the rate of relapse after OTM (25.7 ± 4.3%) compared to the control (69.6 ± 6.1%). μCT analysis showed decreased BV/TV, BS/BV, and Tb.N, while increased Tb.Sp of alveolar bone in the PTH or PTHrP group. There were also more TRAP-positive osteoclasts in the PTH or PTHrP group with a significantly enhanced ratio of receptor activator of nuclear factor-κB ligand (RANKL)/osteoprotegerin (OPG). The protein expressions of PTH/PTHrP type 1 receptor (PTHR1), alkaline phosphatase (ALP), osteocalcin (OCN), runt-related transcription factor 2 (RUNX2), and β-catenin were significantly increased in the PTH or PTHrP group, as well as the gene expressions of Pth1r, Bglap, and Alpl. There was no significant difference between the effects of PTH and PTHrP. Nevertheless, inhibition of PTHrP on the osteogenic differentiation of hPDLCs was detected in vitro with decreased expression of OCN, RUNX2, COL-1, and ALP.

CONCLUSION

Local injection of either PTH or PTHrP carried by controlled release PECE hydrogel similarly enhances OTM in rats through regulating periodontal bone remodeling, which deserves further study for potential clinical application.

Management of chronic pain in osteoporosis: challenges and solutions

Osteoporosis (OP) is a pathological condition that manifests clinically as pain, fractures, and physical disability, resulting in the loss of independence and the need for long-term care. Chronic pain is a multidimensional experience with sensory, affective, and cognitive aspects. Age can affect each of these dimensions and the pain that is experienced. In OP, chronic pain appears to have sensory characteristics and properties of nociceptive and neuropathic pain. Its evaluation and treatment thus require a holistic approach that focuses on the specific characteristics of this population. Pain management must therefore include pharmacological approaches, physiotherapy interventions, educational measures, and, in rare cases, surgical treatment. Most rehabilitative treatments in the management of patients with OP do not evaluate pain or physical function, and there is no consensus on the effects of rehabilitation therapy on back pain or quality of life in women with OP. Pharmacological treatment of pain in patients with OP is usually insufficient. The management of chronic pain in patients with OP is complicated with regard to its diagnosis, the search for reversible secondary causes, the efficacy and duration of oral bisphosphonates, and the function of calcium and vitamin D. The aim of this review is to discuss the most appropriate solutions in the management of chronic pain in OP.

Efficacy of weekly teriparatide does not vary by baseline fracture probability calculated using FRAX

The aim of this study was to determine the efficacy of once-weekly teriparatide as a function of baseline fracture risk. Treatment with once-weekly teriparatide was associated with a statistically significant 79 % decrease in vertebral fractures, and in the cohort as a whole, efficacy was not related to baseline fracture risk.

INTRODUCTION

Previous studies have suggested that the efficacy of some interventions may be greater in the segment of the population at highest fracture risk as assessed by the FRAX® algorithms. The aim of the present study was to determine whether the antifracture efficacy of weekly teriparatide was dependent on the magnitude of fracture risk.

METHODS

Baseline fracture probabilities (using FRAX) were computed from the primary data of a phase 3 study (TOWER) of the effects of weekly teriparatide in 542 men and postmenopausal women with osteoporosis. The outcome variable comprised morphometric vertebral fractures. Interactions between fracture probability and efficacy were explored by Poisson regression.

RESULTS

The 10-year probability of major osteoporotic fractures (without BMD) ranged from 7.2 to 42.2 %. FRAX-based hip fracture probabilities ranged from 0.9 to 29.3 %. Treatment with teriparatide was associated with a 79 % (95 % CI 52-91 %) decrease in vertebral fractures assessed by semiquantitative morphometry. Relative risk reductions for the effect of teriparatide on the fracture outcome did not change significantly across the range of fracture probabilities (p = 0.28). In a subgroup analysis of 346 (64 %) participants who had FRAX probabilities calculated with the inclusion of BMD, there was a small but significant interaction (p = 0.028) between efficacy and baseline fracture probability such that high fracture probabilities were associated with lower efficacy.

CONCLUSION

Weekly teriparatide significantly decreased the risk of morphometric vertebral fractures in men and postmenopausal women with osteoporosis. Overall, the efficacy of teriparatide was not dependent on the level of fracture risk assessed by FRAX in the cohort as a whole.

Osteoporosis - a current view of pharmacological prevention and treatment

Postmenopausal osteoporosis is the most common bone disease, associated with low bone mineral density (BMD) and pathological fractures which lead to significant morbidity. It is defined clinically by a BMD of 2.5 standard deviations or more below the young female adult mean (T-score =−2.5). Osteoporosis was a huge global problem both socially and economically – in the UK alone, in 2011 £6 million per day was spent on treatment and social care of the 230,000 osteoporotic fracture patients – and therefore viable preventative and therapeutic approaches are key to managing this problem within the aging population of today. One of the main issues surrounding the potential of osteoporosis management is diagnosing patients at risk before they develop a fracture. We discuss the current and future possibilities for identifying susceptible patients, from fracture risk assessment to shape modeling and in relation to the high heritability of osteoporosis now that a plethora of genes have been associated with low BMD and osteoporotic fracture. This review highlights the current therapeutics in clinical use (including bisphosphonates, anti-RANKL [receptor activator of NF-κB ligand], intermittent low dose parathyroid hormone, and strontium ranelate) and some of those in development (anti-sclerostin antibodies and cathepsin K inhibitors). By highlighting the intimate relationship between the activities of bone forming (osteoblasts) and bone-resorbing (osteoclasts) cells, we include an overview and comparison of the molecular mechanisms exploited in each therapy.

Mixed-treatment comparison of anabolic (teriparatide and PTH 1-84) therapies in women with severe osteoporosis

PURPOSE

The recent development of compounds with anabolic action on bone have increased the range of therapeutic options for the treatment of osteoporosis and the prevention of fractures. Two major PTH analogs, the synthetic full-length 1-84 PTH molecule and the recombinant 1-34 N-terminal fragment (teriparatide), are available for the treatment of osteoporosis in many countries. There have bee no comparative trials on the bone anabolic effects of these compounds.

MATERIALS AND METHODS

In this study we applied a mixed treatment comparison (MTC) to compare the efficacy of teriparatide versus PTH 1-84 for the prevention of vertebral and non-vertebral fractures in women with severe osteoporosis. With this approach the relative treatment effect of one intervention over another can be obtained in the absence of head-to-head comparison. Among the candidate papers selected for analysis, two randomized controlled trials investigating the effects of teriparatide and PTH 1-84 met the selection criteria and underwent MTC analysis.

RESULTS

Based on a fixed-effect MTC model analysis of data from two RCTs, teriparatide (20 µg/day) showed a 70% and 94% probability of being the best treatment for the prevention of vertebral and non-vertebral fractures, respectively. Together with a lack of statistical significance, this study has additional limitations. Some differences in trial procedures and populations exist; another limitation concerns the impossibility of carrying out a randomized-effect model MTC, due to sample exiguity. Furthermore, in order to consider unknown or unmeasured differences of covariates across trials, a random-effects approach would be preferred in order to assess the presence of heterogeneity across comparisons. In contrast, in our analysis a fixed-effect MTC model only was used.

CONCLUSIONS

Teriparatide is expected to provide a greater efficacy over PTH 1-84 with both vertebral and non-vertebral fracture prevention in postmenopausal women with severe osteoporosis.

Effect of parathyroid hormone on hypogonadism induced bone loss of proximal femur of orchiectomized rat

Purpose

Management of hypogonadism-induced osteoporosis in elderly men is still a challenge. We investigated the short-term effects of parathyroid hormone (PTH) treatments on strength, micro-architecture, and mineral density of trochanteric region of orchiectomized rat femur.

Methods

Eight-month-old male Sprague–Dawley rats (n = 44) were divided into two groups: (1) orchiectomized (ORX) and (2) sham group. Twelve weeks after orchiectomy, half of the orchiectomized animals were treated with daily subcutaneously injected PTH (0.040 mg/kg/BW) (ORX-PTH) for 5 weeks. The other half remained untreated (ORX). The sham-operated group was divided and treated in the same way (sham, sham-PTH). After 5 weeks, both femurs were excised for biomechanical and histomorphometric analysis, trabecular measurements, mineral content assessment, and immunofluorescence analysis.

Results

The femoral trochanteric strength after PTH treatment was enhanced in the breaking test (ORX-F_max = 158.7 N vs. ORX + PTH-F_max = 202 N). Stiffness of treated ORX animals reached nearly the levels observed in untreated sham rats. PTH therapy improved the trabecular connectivity, width, and area (ORX-Tb.Ar = 47.79% vs. ORX + PTH-Tb.Ar = 68.47%, P < 0.05) in the proximal femur. The treated rats showed significantly improved mineral content in ashed femurs (ORX-mineral content = 43.73% vs. ORX + PTH-mineral content = 49.49%) when compared to the untreated animals. A comparison of widths of fluorescence bands in cortical bone of the subtrochanteric cross-sections showed a significant increase in oppositions after the PTH therapy.

Conclusions

Our finding supports the hypothesis that PTH therapy seems to be a rational therapy in patients with hypogonadism induced bone loss and improves the bone strength of trochanteric region of rat femur.