Bisphosphonates (BPs) are successfully used to cure a number of diseases characterized by a metabolic reduction in bone density, such as Osteoporosis, or a neoplastic destruction of bone tissue, such as multiple myeloma and bone metastases. These drugs exert their therapeutic effect by causing a systemic osteoclast depletion that, in turn, is responsible for reduced bone resorption. Unfortunately, in addition to their beneficial activity, BPs can also determine a frightening side effect known as osteonecrosis of the jaw (ONJ). It is generally believed that the inability of osteoclasts to dispose of inflamed/necrotic bone represents the main physiopathological aspect of ONJ. In principle, a therapeutic strategy able to elicit a local re-activation of osteoclast production could counteract ONJ and promote the healing of its lesions. Using an experimental model of Vitamin D3-dependent osteoclastogenesis, we have previously demonstrated that Magnesium is a powerful inducer of osteoclast differentiation. Here we show that, surprisingly, this effect is greatly enhanced by the presence of Zoledronate, chosen for our study because it is the most effective and dangerous of the BPs. This finding allows us to hypothesize that Magnesium might play an important role in the topical therapy of ONJ.

Bisphosphonates (BPs) are successfully used to cure a number of bone diseases characterized by metabolic osteopenia, such as Osteoporosis, or neoplastic osteolysis, such as Multiple Myeloma and Bone Metastases. These drugs exert their therapeutic effect inducing a systemic osteoclast depletion that, in turn, is responsible for a reduced bone resorption. Unfortunately, in addition to their beneficial activity, BPs can also determine a frightening side effect known as Osteonecrosis of the Jaw (ONJ). It is generally believed that the inability of osteoclasts to get rid of inflamed / necrotic bone tissue represents the main physio-pathological aspect of ONJ. In principle, a therapeutic strategy able to elicit a local re-activation of osteoclast production could counteract ONJ and promote the healing of its lesions. We have previously demonstrated that Magnesium (Mg) is a powerful inducer of osteoclast differentiation. Using a model of Vitamin D3 – dependent osteoclastogenesis, based on the U937 cell line, here we show that, surprisingly, this property of Mg is greatly enhanced by the presence of Zoledronic Acid (ZA), chosen for our study because it is the most effective among BPs. This finding allow us to hypothesize that Mg might play an important role in the topical therapy of ONJ.

Bisphosphonates (BPs) are drugs used to cure metabolic diseases like osteoporosis and oncological conditions, such as multiple myeloma and bone metastases. The pharmacological activity of these compounds is mediated by their capacity to induce a systemic osteoclast depletion, finally resulting in reduced bone resorption. In spite of their efficacy, the clinical application of BPs is sometimes associated with a frightening side effect known as osteonecrosis of the jaw (ONJ). In principle, a therapeutic approach able to elicit the local re-activation of osteoclast production could counteract the onset of ONJ and promote the healing of its lesions. Using a vitamin D3-dependent model of osteoclast differentiation, it has been previously demonstrated that when used at supra-physiological concentrations, magnesium strongly favors the process under consideration, and its effect is furtherly enhanced by the presence of a BP called zoledronate. Here, we show that similar results can be obtained in a RANKL-dependent model of osteoclast differentiation, suggesting that a topical therapy based on magnesium may be also suitable for ONJ determined by denosumab in light of the ability of this monoclonal antibody to target RANKL.