Effects of Perfluorobutane Sulfonate (PFBS) on Development and Bone Mineralization in Zebrafish Larvae

Perfluorobutane sulfonate (PFBS), a short-chain perfluoroalkyl substance (PFAS) and a common substitute for legacy PFAS, has been detected in human cord serum, raising concerns about its potential developmental toxicity. However, its effects on skeletal development remain inadequately characterized. Zebrafish embryos were exposed to environmentally relevant concentrations of PFBS (0.05, 0.2, and 0.8 ng/mL) until 8 days postfertilization (dpf). A dexamethasone (DEX, 10 μg/mL) group served as a positive control for osteotoxicity. Developmental endpoints were monitored, and bone mineralization was assessed via calcein staining. The expression of osteogenesis-related (alp, runx2, and bmp2b) and osteoclastogenesis-related (acp5, ctsk, and mmp9) genes was analyzed by qRT-PCR. PFBS exposure did not significantly affect survival or hatching rates but induced subtle morphological abnormalities, including tail curvature and pericardial edema in a small subset of larvae. A significant, dose-dependent decrease in heart rate was observed at 72 hpf. Calcein staining revealed that PFBS significantly reduced cranial bone mineralization area and vertebral bone mineral density (BMD) in a concentration-dependent manner. Gene expression analysis demonstrated that PFBS exposure downregulated key osteogenic markers (alp, runx2, and bmp2b) and upregulated osteoclastogenic markers (acp5, ctsk, and mmp9), suggesting a disruption of the bone remodeling balance. Environmental levels of PFBS can induce cardiotoxicity and disrupt bone mineralization in developing zebrafish larvae. The underlying mechanism may involve the inhibition of osteogenesis and promotion of osteoclastogenesis. These findings highlight the potential skeletal developmental risks associated with PFBS exposure.