Fisetin modulates fluoride induced osteochondral toxicity in zebrafish larvae

Excessive fluoride (F⁻) exposure, particularly during early development, poses a significant risk to skeletal integrity by disrupting bone homeostasis through oxidative stress and altered mineralization. While F⁻ induced oxidative stress is well documented, studies investigating the role of natural antioxidants in mitigating F⁻ induced osteochondral toxicity remain limited. Hence, the present study investigated the osteomodulatory effect of fisetin (Fis) against F⁻ toxicity in zebrafish larvae. Fis (15 μM) was exposed to zebrafish larvae at 3 days post fertilization (dpf) for 24 h, followed by 72 h exposure to 25 ppm sodium fluoride (NaF). F⁻ accumulation, oxidant (ROS, LPO, NO, PCC) and antioxidant (SOD, CAT, GSH) levels, cartilage (alcian blue staining), skeletal (alizarin red staining, hydroxyproline content, ALP activity) markers, and expression of osteochondral genes (sox9b, runx2b, ocn, osx, col1a1, alp, rankl, and opg) were assessed in control and treated larvae. F⁻ exposure significantly elevated oxidative stress, disrupted craniofacial cartilage morphology, and induced premature ossification, alongside altered expression of osteogenic and resorptive markers. Remarkably, Fis pretreatment effectively reduced F⁻ accumulation, restored redox homeostasis, preserved cartilage architecture, and normalized mineral deposition. Gene expression analysis further confirmed that Fis modulated key regulators of osteogenesis, chondrogenesis, and bone resorption, underscoring its osteoprotective role. Collectively, these findings demonstrate that Fis confers protection against F⁻ induced osteochondral toxicity by attenuating oxidative stress, supporting bone matrix development, and regulating genes essential for bone homeostasis.