High-Dose Zoledronic Acid Impacts Bone Remodeling with Effects on Osteoblastic Lineage and Bone Mechanical Properties

Abstract

Purpose: The increasing incidence of osteonecrosis of the jaw and its possible association with high cumulative doses of bisphosphonate led us to study the effects of high doses of zoledronic acid (ZA) on bone remodeling. Experimental Design: Five-week-old C57BL6 mice were treated with saline or ZA weekly for 3 weeks at increasing doses (0.05-1 mg/Kg). Effects of ZA on bone remodeling were studied using standard assays. Results: We observed an increase in bone mineral density and content in treated animals at doses of 0.05 mg/Kg, which was not further enhanced at higher doses of ZA. Trabecular bone volume at the proximal tibia and the distal femur assessed by histomorphometry and microCT, respectively, increased significantly in ZA-treated groups. There was however no difference between 0.5 and 1 mg/kg, suggesting a ceiling effect for ZA. ZA led to decreased numbers of osteoclasts and osteoblasts per bone perimeter that paralleled a significant reduction of serum levels of TRAC5b and osteocalcin in vivo. Effects on osteoblasts were confirmed in in vitro assays. Mechanical testing of the femur showed increased brittleness in ZA-treated mice. Conclusions: High doses of ZA inhibit both osteoclast and osteoblasts function and bone remodeling in vivo interfering with bone mechanical properties. No dose response was noted beyond 0.5 mg/kg suggesting that lower doses of ZA may be adequate in inhibiting bone resorption. Our data may help inform future studies of ZA use with respect to alternate and lower doses in the treatment of patients with cancer bone disease. (Clin Cancer Res 2009;15(18):5829-39)

Severe compromise of preosteoblasts in a surgical mouse model of bisphosphonate-associated osteonecrosis of the jaw

“…Interestingly, the number of empty lacunae in the submucosal bone significantly increased after long-term treatment, suggesting that this finding may be associated with the cumulative doses fixed in the alveolar bone. This fact is in agreement with previous clinical and experimental reports (Ruggiero et al 2009;Marx et al 2005;Allen 2008;Aguirre et al 2012), supporting the hypothesis that long-term exposure to high doses of aminobisphosphonates determines their accumulation in alveolar BMUs, inducing local changes and constituting a potential first step in the development of osteonecrosis of the jaw (Allen 2008;Hoff et al 2008;Daubiné et al 2007;Pozzi et al 2009). …”

“…The same study showed that the suppression of bone formation markers was most pronounced in BONJ patients (Raje et al 2008). In addition, a decrease in osteoblasts number was observed in the long bones after 3 weeks of systemic treatment with increasing doses of ZOL (Pozzi et al 2009). Moreover, the absence of woven bone in the alveolar socket after tooth extraction in mice treated with bisphosphonate and denosumab, two agents associated with osteonecrotic-lesions, has recently been demonstrated (Williams et al 2014).…”

“…The drug tolerance of the mice was assessed daily by clinical examination. The total dose of ZOL administered was the equivalent of a lifetime dose of the drug over 4 years of therapy in a 70 kg adult multiple myeloma patients (Pozzi et al 2009). At the end of the third week, the first left maxillary molar was surgically extracted from all the animals (Supplementary appendix 1).…”

“…At the end of the third week, the first left maxillary molar was surgically extracted from all the animals (Supplementary appendix 1). After 6 weeks of treatment with ZOL (or saline solution), and 3 weeks after the molar extraction, 50 % of the animals were sacrificed to assess the situation at an intermediate time point (the equivalent of 2 years according to Pozzi et al, 2009). The remaining 50 % of the animals was sacrificed at the end of the protocol, after 12 weeks of treatment with ZOL (or saline solution) (the equivalent of 4 years according to Pozzi et al, 2009) and 9 weeks after the molar extraction, for long-term assessment.…”

“…These findings confirm the compromise of the entire osteoblastic lineage including preosteoblasts, osteoblasts, and osteocytes (Koch et al 2011;Manzano-Moreno et al 2015). On another hand, in vitro studies report cytotoxic effects of bisphosphonates on osteoblastic cells, decreasing their viability and osteogenic ability in a dose-dependent manner (Pozzi et al 2009;Basso et al 2013). …”