Histopathological alterations of the intrinsic tongue muscles following zoledronic acid treatment in a rat model

Bisphosphonates (BPs) are widely used as anti-bone-resorptive agents. Despite the great benefits of BPs, they may cause local and systemic adverse side effects. The aim of this study was to evaluate the histopathological effect zoledronic acid (ZA), which belongs to BPs, has on the intrinsic tongue muscles in a rat model. A total of 30 adult male albino rats were divided into 3 groups (10 rats each): group I served as a control; group II was given an intraperitoneal (i.p.) injection of 0.2 mg/kg of ZA once per week for 3 weeks; and group III received the same dosage of ZA, but for 8 weeks. After the animals were euthanized, the tongue tissue was dissected and examined histologically, histochemically and immunohistochemically. Histologically, a normal architecture of the muscle fascicles was observed in the control group. Group II showed degenerated muscle fibers with an indistinct sarcolemma. In group III, the muscle fibers were degenerated with severe sarcoplasmic dissolution. The histochemical examination using Masson's trichrome (MT) demonstrated a significant increase in collagen fibers in groups II and III as compared to the control group. The immunohistochemical results revealed a statistically significantly higher expression of nuclear factor kappa B (NF‑κB) in the ZA-treated groups (II and III) as compared to the control group, with the highest mean value recorded in group III. Zoledronic acid induced histopathological changes to the intrinsic tongue muscles, and this effect was exaggerated with a longer duration of administration.