Matrix metalloproteinase-9 expression in alveolar extraction sockets of Zoledronic acid-treated rats.

PURPOSE: The use of nitrogen-containing bisphosphonates (n-bis) is associated with necrosis of the jaws, also known as bisphosphonate-related osteonecrosis of the jaws (BRONJ); however, the pathophysiology is unknown. Matrix metalloproteinase-9 (MMP-9) expression is essential for normal bone healing and is also required for angiogenesis. N-bis alters MMP-9 expression in vitro and in vivo; therefore, we hypothesized that n-bis alters MMP-9 expression during oral wound healing after tooth extraction. MATERIALS AND METHODS: A total accumulated dose of 2.25 mg/kg (n = 20) of Zoledronic acid (ZA) Zometa or saline (control, n = 20) was administered to Sprague-Dawley male rats. Next, both groups had maxillary molar teeth extracted. Rats were sacrificed at postoperative day 1, 3, 7, or 21. Western blotting or multiplex ELISA was used to evaluate proteins of interest. Real-time polymerase chain reaction was used to assess the relative quantities of target gene mRNA. MMP-9 enzymatic activity was assessed by zymography. RESULTS: The ZA group showed a statistically significant reduction in bone mineralization rate 21 days after tooth extraction compared with the control group (Student t test, P = .005). Moreover, ZA-treated animals showed a statistically significant increase in MMP-9-specific mRNA at postoperative days 3 (P = .003), 7 (P < .0001), and 21 (P < .0001) and protein on postoperative days 3 (P = .005) and 7 (P < .0001). MMP-9 enzymatic activity was also increased in ZA-treated rats compared with control animals (Student t test, P = .014). We also evaluated the extraction sockets for the presence of tissue inhibitor of MMP-1 (TIMP1), which is an inhibitor of MMP-9 enzymatic activity. TIMP1-specific mRNA and protein were not significantly altered by ZA treatment at the times tested (P > .05). Receptor of NF-κB ligand (RANKL) is known to regulate the expression of MMP-9; we therefore assessed the RANKL expression in our experimental oral wound-healing model. The ZA-treated animals had significantly increased RANKL mRNA at postoperative days 3 (P = .02) and 21 (P = .004), while the protein expression was significantly increased at postoperative days 1 (P < .0001), 7 (P = .02), and 21 (P = .03) compared with the control group. CONCLUSIONS: ZA reduced bone mineralization within tooth extraction sockets, suggesting aberrant bone healing. ZA increases the amount and enzymatic activity of MMP-9, while apparently not altering the amount of TIMP1 within extraction sockets. RANKL is increased in ZA-treated rats, which suggests that increased MMP-9 expression is due, in part, to augmented RANKL expression.

Bisphosphonate-related osteonecrosis of the jaw: clinical features, risk factors, management, and treatment outcomes of 26 patients.

PURPOSE: To report the clinical features, risk factors, management, and treatment outcomes of nitrogen-containing bisphosphonate (n-BIS)-related osteonecrosis of the jaw (BRONJ). PATIENTS AND METHODS: Patients with suspected BRONJ were referred to the School of Dentistry for evaluation and treatment. RESULTS: A total of 26 patients (9 men and 17 women, mean age 64 years) were diagnosed with BRONJ. Of the 26 patients, 23 had received n-BIS therapy for cancer and 3 for osteoporosis. BRONJ lesions were noted more frequently in the mandible and in the posterior sextants. Of the 26 patients, 16 had developed BRONJ after dentoalveolar procedures, and 10 had developed it spontaneously. The mean interval to development of BRONJ was shorter in the patients with cancer receiving intravenous n-BIS than in the patients with osteoporosis receiving oral n-BIS (37.1 versus 77.7 months, P = .02). Using the American Association of Oral and Maxillofacial Surgeons staging system, 2 patients were diagnosed with stage I lesions, 19 with stage II, and 5 with stage III lesions. The initial management of BRONJ was nonsurgical, with debridement performed at subsequent visits, if needed. The BRONJ lesions healed completely in 4 patients, healed partially in 8, remained stable in 7, and progressed in 7. The spontaneous lesions responded favorably to BRONJ management compared with lesions that developed after dentoalveolar procedures (P = .01). No significant difference was found in response to BRONJ management between patients who had continued or discontinued n-BIS therapy after the BRONJ diagnosis (P = .54). CONCLUSIONS: Long-term n-BIS therapy and recent dental procedures are consistent findings in patients with BRONJ. Spontaneous BRONJ lesions respond favorably to current BRONJ treatment strategies.