Bisphosphonate-related osteonecrosis induced change in alveolar bone architecture in rats with participation of Wnt signaling.

Objective: This work aimed to study the role of inflammation in medication-related osteonecrosis of the jaw (MRONJ) in rats with focus on Wnt signaling.

Methods: A total of 36 female Wistar rats (12 weeks ± 200 g) were divided into 2 groups (n = 6) in 3 experiments: saline (SAL) and zoledronic acid (ZOL). For MRONJ induction, rats received 0.1 mg/kg of ZOL (ip) 3×/week for 9 weeks. Animals from the SAL group received 0.1 mg/kg of 0.9% SAL, ip 3×/week for 9 weeks. On the 8th week, 3 left upper molars were extracted, and on the 11th week, they were euthanized. Maxillae were evaluated by macroscopic and histopathological analyses; scanning electron microscopy (SEM); immunohistochemistry for DKK-1, Wnt 10b, and caspase-3; and Raman spectrometry. Gingiva was also collected for TNF-α e IL-1β quantification.

Results: Bone necrosis was confirmed by healing impairment, reduced number of viable osteocytes, increased caspase-3 immunoexpression, and increased number of empty lacunae (p < 0.05). ZOL enhanced inflammation and increased gingival levels of IL-1β and TNF-α (p < 0.05). Irregular indentations were seen on bone after ZOL administration. Bone necrosis was marked by reduced amount of total and type I collagen. ZOL reduced the mineral/matrix ratio and increased carbonate/phosphate ratio. It was observed a significant reduction on Wnt10b and beta-catenin immunolabeling in the bone tissue of ZOL group.

Conclusion: In summary, MRONJ model caused bone necrosis due to intense inflammation. Wnt signaling seems to play an important role in this process.

Clinical Relevance: New therapeutic strategies focusing on Wnt pathway can provide an interesting approach for future treatments.