Intravenous ibandronate rapidly reduces pain, neurochemical indices of central sensitization, tumor burden, and skeletal destruction in a mouse model of bone cancer.

Over half of all chronic cancer pain arises from metastases to bone and bone cancer pain is one of the most difficult of all persistent pain states to fully control. Currently, bone pain is treated primarily by opioid-based therapies, which are frequently accompanied by significant unwanted side effects. In an effort to develop nonopioid-based therapies that could rapidly attenuate tumor-induced bone pain, we examined the effect of intravenous administration of the bisphosphonate, ibandronate, in a mouse model of bone cancer pain. Following injection and confinement of green fluorescent protein-transfected murine osteolytic 2472 sarcoma cells into the marrow space of the femur of male C3H/HeJ mice, ibandronate was administered either as a single dose (300 microg/kg), at Day 7 post-tumor injection, when tumor-induced bone destruction and pain were first evident, or in three consecutive doses (100 microg/kg/day) at Days 7, 8, and 9 post-tumor injection. Intravenous ibandronate administered once or in three consecutive doses reduced ongoing and movement-evoked bone cancer pain-related behaviors, neurochemical markers of central sensitization, tumor burden, and tumor-induced bone destruction. These results support limited clinical trials that suggest the potential of ibandronate to rapidly attenuate bone pain and illuminate the mechanisms that may be responsible for limiting pain and disease progression.

Nerve growth factor sequestering therapy attenuates non-malignant skeletal pain following fracture.

Current therapies to treat skeletal fracture pain are extremely limited. Some non-steroidal anti-inflammatory drugs have been shown to inhibit bone healing and opiates induce cognitive dysfunction and respiratory depression which are especially problematic in the elderly suffering from osteoporotic fractures. In the present report, we developed a closed femur fracture pain model in the mouse where skeletal pain behaviors such as flinching and guarding of the fractured limb are reversed by 10mg/kg morphine. Using this model we showed that the administration of a monoclonal antibody against nerve growth factor (anti-NGF) reduced fracture-induced pain-related behaviors by over 50%. Treatment with anti-NGF reduced c-Fos and dynorphin up-regulation in the spinal cord at day 2 post-fracture. However, anti-NGF treatment did not reduce p-ERK and c-Fos expression at 20 and 90 min, respectively, following fracture. This suggests NGF is involved in maintenance but not the acute generation of fracture pain. Anti-NGF therapy did not inhibit bone healing as measured by callus formation, bridging of the fracture site or mechanical strength of the bone. As the anti-NGF antibody does not appreciably cross the blood-brain barrier, the present data suggest that the anti-hyperalgesic action of anti-NGF therapy results from blockade of activation and/or sensitization of the CGRP/trkA positive fibers that normally constitute the majority of sensory fibers that innervate the bone. These results demonstrate that NGF plays a significant role in driving fracture pain and that NGF sequestering therapies may be efficacious in attenuating this pain.

Effects of a monoclonal antibody raised against nerve growth factor on skeletal pain and bone healing after fracture of the C57BL/6J mouse femur.

UNLABELLED: A closed femur fracture pain model was developed in the C57BL/6J mouse. One day after fracture, a monoclonal antibody raised against nerve growth factor (anti-NGF) was delivered intraperitoneally and resulted in a reduction in fracture pain-related behaviors of approximately 50%. Anti-NGF therapy did not interfere with bone healing as assessed by mechanical testing and histomorphometric analysis. INTRODUCTION: Current therapies to treat skeletal fracture pain are limited. This is because of the side effect profile of available analgesics and the scarcity of animal models that can be used to understand the mechanisms that drive this pain. Whereas previous studies have shown that mineralized bone, marrow, and periosteum are innervated by sensory and sympathetic fibers, it is not understood how skeletal pain is generated and maintained even in common conditions such as osteoarthritis, low back pain, or fracture. MATERIALS AND METHODS: In this study, we characterized the pain-related behaviors after a closed femur fracture in the C57BL/6J mouse. Additionally, we assessed the effect of a monoclonal antibody that binds to and sequesters nerve growth factor (anti-NGF) on pain-related behaviors and bone healing (mechanical properties and histomorphometric analysis) after fracture. RESULTS: Administration of anti-NGF therapy (10 mg/kg, days 1, 6, and 11 after fracture) resulted in a reduction of fracture pain-related behaviors of approximately 50%. Attenuation of fracture pain was evident as early as 24 h after the initial dosing and remained efficacious throughout the course of fracture pain. Anti-NGF therapy did not modify biomechanical properties of the femur or histomorphometric indices of bone healing. CONCLUSIONS: These findings suggest that therapies that target NGF or its cognate receptor(s) may be effective in attenuating nonmalignant fracture pain without interfering with bone healing.