Evaluation of biodistribution by local versus systemic administration of 99mTc-labeled pamidronate

Local application of an ibandronate/collagen sponge improves femoral fracture healing in ovariectomized rats

Non-union is a major clinical problem in the healing of fractures, especially in patients with osteoporosis. The systemic administration of drugs is time consuming and large doses are demanding and act slowly, whereas local release acts rapidly, increases the quality and quantity of the bone tissue. We hypothesize that local delivery demonstrates better therapeutic effects on an osteoporotic fracture. The aim of this paper is to investigate the effect of the local application of ibandronate loaded with a collagen sponge on regulating bone formation and remodeling in an osteoporotic rat model of fracture healing. We found that the local delivery of ibandronate exhibited excellent effects on improving the bone microarchitecture and suppressed effects on bone remodeling. At 4 weeks, more callus formation and improvement of mechanical character and microstructure were observed in a local delivery via μCT, mechanical test, histological research and serum analysis. The suppression of bone remodeling was compared with a systemic treatment at 12 weeks, and the structural mechanical properties and microarchitecture were also improved with local delivery. This research identifies an earlier, safer and integrated approach for local delivery of ibandronate with collagen and provides a better strategy for the treatment of osteoporotic fracture in rats.

Local administration of zoledronic acid for giant cell tumor of bone

Giant cell tumor of bone is a locally aggressive tumor with a high local recurrence rate. Several adjuvant therapies have been employed to reduce the recurrence rate, but their effectiveness remains controversial. The authors attempted local administration of zoledronic acid, a nitrogen-containing bisphosphonate that strongly inhibits bone resorption, as an adjuvant treatment for histologically proven giant cell tumor of bone in 5 patients at their institution. After biopsy, 4 patients were treated with local administration of zoledronic acid with artificial bone and 1 was treated with zoledronic acid without artificial bone. Histologic response to the treatment was evaluated with surgically resected specimens. The 4 patients treated with artificial bone showed local control, with histologic tumor necrosis rates of 90%, 90%, 50%, and 10%. Magnetic resonance imaging showed poor gadolinium enhancement, and histologic examination after local zoledronic acid treatment showed tumor necrosis. One patient without artificial bone showed no histologic tumor necrosis and had local recurrence in soft tissue 18 months after tumor resection. A 3-week waiting period between biopsy and zoledronic acid treatment appears reasonable from the histological study. Complication of this therapy was delayed wound healing and it occurred in 2 cases. Taken together, this case series suggests that local administration of zoledronic acid with artificial bone is a potential adjuvant therapy for giant cell tumor of bone. On the other hand, effective local administration of zoledronic acid requires some bone matrix, including artificial bone. Campanacci's grading is important for predicting the effect of local administration of zoledronic acid.

An aromatase polymorphism (g.132810C>T) predicts risk of bisphosphonate-related osteonecrosis of the jaw

Background: Bisphosphonate (BP)-related osteonecrosis of the jaw (ONJ) is an unpredictable, debilitating adverse effect. Recently, genetic polymorphisms have arisen as promising tools to identify patients with a higher risk of drug-related adverse events. Aim: We aimed to examine the association between the aromatase polymorphism g.132810C>T, and the estrogen receptor polymorphisms g.156705T>C and g.156751A>G, and the risk of BP-related ONJ. Methods: Eighty-three subjects were included in the study. A clinical and radiological examination was conducted on oncologic subjects treated with zoledronic acid. Subjects with histologically confirmed ONJ were included in the test group (n = 30) whereas subjects with good oral health were included in control group (n = 53). Aromatase and estrogen receptor polymorphisms from blood samples were analyzed. Results: The aromatase g.132810C>T polymorphism displayed an over-representation of the TT genotype in the test group (36.67 vs 16.98%; p < 0.05). There was no significant difference in either estrogen receptor polymorphism genotype frequency between the test and control groups. Conclusion: Our data suggest a role for the g.132810C>T polymorphism in predicting ONJ risk. These results can pave the way to the personalization of BP therapy, based on individual genotype.

Bisphosphonates in orthopedic applications

Bisphosphonates (BPs) exert potent effects on the skeleton. As such, there are important questions relating to how treatment with BPs for metabolic disorders might affect outcomes of orthopedic problems. A further question is what role, if any, might BPs play as adjunctive therapeutics for orthopedic problems. This article outlines the research thus far in the application of BPs to the management of osteonecrosis, bone repair, and joint arthroplasty. Many animal studies show a benefit to decreasing bone resorption in models of osteonecrosis. These include studies in both small and large animals, backed up by limited human data. Further clinical trials are underway for this indication. In bone repair, again, multiple studies exist. There are concerns that BPs could interfere with the normal processes of healing. Some of the controversy about benefits or adverse effects of BPs in this context can be distilled down to effects of dosing and administration. With some exceptions, longer intervals between dosing seem to be more beneficial while not producing adverse healing effects in animal studies. In joint arthroplasty, animal studies suggest a role for topical or systemic BPs for enhancing bone on-growth to implant surfaces and strength of mechanical fixation, although these are yet to be confirmed in clinical studies. Clinical studies show that BPs inhibit periprosthetic bone loss due to strain-adaptive remodeling and after impaction bone grafting, although an efficacy in inhibiting inflammatory bone loss due to wear particle-induced osteolysis has not been confirmed. Lastly, as anabolic drugs have become available, there is increasing interest in their combined use with BPs. From experimental data, manipulation of both the anabolic and catabolic responses is a powerful approach in models of bone repair.

Current and future treatments of bone metastases

Bone metastases contribute to a significant degree of morbidity in patients with common cancers through the development of skeletal related events (SRE) such as bone pain and pathological fracture. Traditional therapy has relied on surgical removal of lesions and, with the advent of adjuvant therapies, has been combined with radiotherapy, chemotherapy, and more recently osteoclast inhibiting agents like bisphosphonates. Although these therapeutic combinations can achieve a degree of local control, and rarely cure, across the vast majority of metastatic cancers they provide only palliation. Newer molecular agents currently under investigation, combined with innovations in surgery and radiation therapy offer a more targeted approach to bone metastasis. These utilise our understanding of key steps in the metastatic cascade including chemotactic attraction to bone, secretion of proteases, the cancer supporting microenvironment of bone matrix and the RANK-RANKL interaction for osteoclast activation. Direct inhibition of metastasis progression and osteolysis with less reliance on cytotoxic agents and invasive therapy should result in improved metastatic control, longer survival and less overall morbidity.

Bisphosphonate delivery to tubular bone allografts

Large structural allografts used for reconstruction of bone defects after revision arthroplasty and tumor resection fracture up to 27% of the time from osteolytic resorption around the fixation screw holes and tendon or ligament attachment sites. Treating structural allografts before implantation with bisphosphonates may inhibit local osteoclastic processes and prevent bone resorption and the development of stress risers, thereby reducing the long-term fracture rate. Taking advantage of allografts' open-pore structure, we asked whether passive soaking or positive-pressure pumping was a more efficient technique for delivering bisphosphonates. We treated matched pairs of ovine tibial allografts with fluids containing Tc-99m pamidronate and toluidine blue stain to facilitate indicator distribution analysis via microSPECT-microCT imaging and light microscopy, respectively. Surfactants octylphenoxy polyethoxy ethanol or beractant were added to the treatment fluids to reduce flow resistance of solutions pumped through the allografts. Indicator distribution after 1 hour of soaking produced a thin ring around periosteal and endosteal surfaces, while pumping for 10 minutes produced a more even distribution throughout the allograft. Flow resistance was reduced with octylphenoxy polyethoxy ethanol but unaffected with beractant. Pumped allografts displayed a more homogeneous indicator distribution in less time than soaking while surfactants enhanced fluid movement.

Optimal timing of a single dose of zoledronic acid to increase strength in rat fracture repair

We hypothesized that ZA treatment would bolster fracture repair. In a rat model for closed fracture healing, a single dose of ZA at 0, 1, or 2 wk after fracture significantly increased BMC and strength of the healed fracture. Delaying the dose (1 or 2 wk after fracture) displayed superior results compared with dosing at the time of fracture.

INTRODUCTION

Bisphosphonates are known to increase bone strength and thus the resistance to fracture by decreasing osteoclastic bone resorption. These properties may enable bisphosphonates to also increase the strength of fracture repair. Zoledronic acid (ZA) is a potent bisphosphonate with a high affinity for bone mineral, allowing bolus intravenous dosing in a range of indications. In this study, we examined the application of bolus dose ZA in endochondral fracture repair.

MATERIALS AND METHODS

Carbon-14 labeled ZA was used in a closed rat fracture model. Rats were divided into five treatment groups (n = 25 per group): saline control, local ZA (0.01 mg/kg), and three systemic bolus ZA groups (0.1 mg/kg) with different administration times: at fracture, 1 wk after fracture, and 2 wk after fracture. Rats were killed 6 wk postoperatively. Postmortem analyses included radiography, QCT, microCT, biomechanical testing, scintillation counting, autoradiography, and histology.

RESULTS

Single-dose systemic ZA administration significantly increased callus volume, callus BMC, and mechanical strength. Perioperative treatment increased mechanical strength by 30% compared with controls (p < 0.05). Administering the systemic dose at 1 or 2 wk after fracture further increased mechanical strength compared with controls by 44% and 50%, respectively (p < 0.05). No significant differences in mechanical parameters were seen with local injection at the dose studied. Autoradiographic analysis indicated that ZA binds significantly to bone that is present at the time of administration. ZA quantification indicated that delayed administration significantly increased the uptake efficiency in the callus. Histological and microCT analysis showed that ZA treated calluses had a distinctive internal structure consisting of an intricate network of retained trabecular bone.

CONCLUSIONS

The timing of a single systemic dose of ZA plays an important role in the modulation of callus properties in this rat fracture model; delaying the single dose produces a larger and stronger callus.