Strontium ranelate: new data on fracture prevention and mechanisms of action

Strontium Ranelate Elevates Expression of Heme Oxygenase-1 and Decreases Alveolar Bone Loss in Rats

Objectives

The purpose of this study was to determine the effects of strontium ranelate on ligature-induced periodontitis in rats and assess the putative involvement of heme oxygenase-1 (HO-1) pathway in these effects.

Material and Methods

Male Wistar rats underwent nylon ligature placement around maxillary molars and were treated (v.o.) with strontium ranelate (20 or 100 mg/kg) for 7 days. After that, rats were euthanized and histomorphometric/histopathological analyses and RT-PCR for HO-1 expression were performed.

Results

Strontium ranelate (20 or 100 mg/kg) prevented bone resorption by 28% and 38%, respectively. Strontium ranelate treatment (100 mg/kg) up-regulated (P < 0.05) heme oxygenase-1 mRNA levels in the gingival tissues in comparison to control groups.

Conclusions

Strontium ranelate prevented periodontal bone loss in experimental periodontitis in rats while heme oxygenase-1 mRNA levels increased after treatment.

Effects of strontium ranelate treatment on osteoblasts cultivated onto scaffolds of trabeculae bovine bone

Blocks of Bovine bone have shown promising results as implantable scaffolds to promote bone regeneration. Strontium ranelate (SrR) is both an antiresorptive and an anabolic drug that has been indicated for oral administration to treat osteoporosis. Few studies, however, have investigated the local effects of SrR and its use in association with biomaterials thus far. In this work, we investigated SrR effects in cultures of primary osteoblasts (PO, from Wistar rats calvaria) and immortalized osteoblasts (IO, from MC3T3-E1 cell line) cultivated as a monolayer or in association with scaffolds of bovine bone in mineralized (MBB) and demineralized (DBB) forms. The optimum dose to induce SrR effects on cell viability was established as 0.1 mM. Our results suggested that the local administration of SrR is biocompatible and non-cytotoxic. In addition, SrR appeared to accelerate primary osteoblast cell differentiation by enhancing alkaline phosphatase activity, the expression of osteogenic differentiation markers, the synthesis of the organic matrix, and a decrease of Ca²⁺ ions in mineralized nodules. DBB was found to be a better scaffold material to promote PO and IO cell proliferation. Exposing the proteins of the demineralized bone matrix might improve scaffold osteoconductive properties. Our results indicated the importance of further investigation of the administration of SrR at sites of bone repair. The association of SrR and bone grafts suggests the possibility of using SrR as a co-adjuvant for bone tissue bioengineering and in bone regeneration therapies.

Uses and misuses of statistics: the case of strontium ranelate and the number needed to treat

In the last 15 years, several pharmacological agents for the prevention of fractures have been developed and commercialized. Most of them showed to be effective in reducing fracture risk. The enhanced availability of drugs to prevent fractures has generated a fierce competition among pharmaceutical companies to conquer a share of the potential market, often with claims of superiority of a drug over another without direct comparisons. The definitive way to compare different treatments would require randomized head to head trials. These trials are expensive, need large samples and are unlikely to be ever performed. Therefore, it has become a common practice to compare pharmacological agents through observational studies on administrative databases or by the indirect comparison of the results of individual randomised-controlled trials (RCT) and their meta-analyses. These studies may produce evidence of clinical value, complementary to that given by RCT. However, without a proper and complete analysis, they may result in a biased picture of effectiveness and be completely misleading. In this article, we critically disclose how such competition may produce biased and misleading picture of evidence, by reviewing the significance of the number needed to treat, absolute risk reduction and relative risk reduction in relation to vertebral fractures prevention with available drugs.

Antifracture efficacy of currently available therapies for postmenopausal osteoporosis

Osteoporosis is a systemic bone disease characterized by low bone mass and bone mineral density, and deterioration of the underlying structure of bone tissue. These changes lead to an increase in bone fragility and an increased risk for fracture, which are the clinical consequences of osteoporosis. The classical triad for consideration in osteoporosis is morbidity, mortality and cost. Vertebral fracture is an important source of morbidity in terms of pain and spinal deformity. On the other hand, hip fracture is associated with the worst outcomes and is widely regarded as a life-threatening event in the elderly; it is the source of the bulk of the cost of the disease in contemporary healthcare. The prevention of osteoporosis-associated fracture should include fall prevention, calcium supplementation and lifestyle advice, as well as pharmacological therapy using agents with proven antifracture efficacy. The most commonly used osteoporosis treatments in Europe are the bisphosphonates alendronate, risedronate, ibandronate and zoledronic acid; the selective estrogen receptor modulator (SERM) raloxifene; teriparatide; and strontium ranelate. Recent additions include the biological therapy denosumab and the SERM bazedoxifene. In this review, we explore the antifracture efficacy of these agents with the aim of simplifying treatment decisions. These treatments can be broadly divided according to their mode of action. The antiresorptive agents include the bisphosphonates, the SERMs and denosumab, while the bone-forming agents include parathyroid hormone and teriparatide. Strontium ranelate appears to combine both antiresorptive and anabolic activities. We collated data on vertebral and hip fracture efficacy from the pivotal 3-year phase III trials, all of which had a randomized, double-blind, placebo-controlled design. The relative reductions in risk in the osteoporosis trials range from 30% to 70% for vertebral fracture and 30% to 51% for hip fracture. This translates into 3-year number needed to treat values of between 9 and 21 for vertebral fracture and from 48 upwards for hip fracture. International guidelines agree that agents that have been shown to decrease vertebral, nonvertebral and hip fractures should be used preferentially over agents that only demonstrate vertebral antifracture efficacy. This is the case for alendronate, risedronate, zoledronic acid, denosumab and strontium ranelate. Finally, therapeutic decisions should be based on a balance between benefits and risks of treatment, which must be carefully considered in each particular case both by the physician and the patient. Indeed, no single agent is appropriate for all patients and, therefore, treatment decisions should be made on an individual basis, taking into account all measures of treatment effect and risk before making informed judgments about the best individual treatment option.