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Toxicity mechanisms regulating bone differentiation and development defects following abnormal expressions of miR-30c
Weiwei Wang1, Danting Wang2, Xin Li1
1Zhejiang Provincial Key Laboratory of Medical Genetics, Key Laboratory of Laboratory Medicine, Ministry of Education, China, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou 325035, China.
Abstract:
As a ubiquitous environmental estrogen-disrupting chemical, triclosan (TCS) can induce severe osteotoxicity; however, the underlying molecular mechanisms remain uncertain. Herein, we evaluated the toxic effects of TCS on the development of cartilage and osteogenesis in 5-dpf zebrafish. Under TCS exposure from 62.5 to 250 μg/L, several osteodevelopmental malformations were observed, such as defect of craniofacial cartilage, pharyngeal arch cartilage dysplasia, and impairments on skeletal mineralization. Further, the morphology of mature chondrocytes became swollen and deformed, their number decreased, nucleus displacement occurred, and most immature chondrocytes were crowded at both ends of ceratobranchial. SEM observation of larval caudal fin revealed that, the layer of collagen fibers and the mineralized calcium nodules were significantly decreased, with the collagen fibers becoming shorter upon TCS exposure. The activity of bone-derived alkaline phosphatase significantly reduced, and marker functional genes related to cartilage and osteoblast development were abnormally expressed. RNA-seq and bioinformatics analysis indicated, that changes in marker genes intimately related to the negative regulation of miR-30c-5p overexpression targeted by TCS, and the up-regulation of miR-30c induced bone developmental defects by inhibiting the bone morphogenetic protein (BMP) signaling pathway. These findings were confirmed by artificially intervening the expression of miR-30c and using BMP pathway agonists in vivo. In sum, TCS induced osteototoxicity by targeting miR-30c up-regulation and interfering in the BMP signaling pathway. These findings enhance mechanistic understanding of TCS-induced spontaneous bone disorders and bone metastatic diseases. Further research is necessary to monitor chronic TCS-exposure levels in surrounding environments and develop relevant safety precautions based on TCS environmental risk.
Insights
Triclosan (TCS) exposure causes bone defects in zebrafish by upregulating miR-30c, which inhibits the bone morphogenetic protein (BMP) signaling pathway, leading to osteotoxicity.
Area of Science:
- Environmental toxicology
- Developmental biology
- Molecular mechanisms of bone development
Background:
- Triclosan (TCS) is a widespread environmental chemical with known estrogenic and endocrine-disrupting properties.
- TCS exposure has been linked to various toxic effects, including potential impacts on skeletal development, but the precise molecular pathways are not fully understood.
Purpose of the Study:
- To investigate the toxic effects of triclosan (TCS) on cartilage and osteogenesis in zebrafish.
- To elucidate the molecular mechanisms underlying TCS-induced osteotoxicity, focusing on the role of microRNAs and signaling pathways.
Main Methods:
- Exposure of 5-day post-fertilization (dpf) zebrafish to varying concentrations of TCS (62.5–250 μg/L).
- Assessment of skeletal and cartilage development using morphological analysis and scanning electron microscopy (SEM).
- Analysis of gene expression, alkaline phosphatase activity, RNA sequencing, bioinformatics, and in vivo functional interventions (miR-30c and BMP pathway agonists).
Main Results:
- TCS exposure led to craniofacial and pharyngeal cartilage defects, impaired skeletal mineralization, and altered chondrocyte morphology.
- SEM revealed decreased collagen fibers and mineralized calcium nodules in zebrafish caudal fins exposed to TCS.
- TCS induced osteotoxicity by upregulating miR-30c, which inhibited the bone morphogenetic protein (BMP) signaling pathway, confirmed by in vivo interventions.
Conclusions:
- Triclosan (TCS) exposure induces significant osteotoxicity and developmental defects in zebrafish cartilage and bone.
- The mechanism involves the upregulation of miR-30c, leading to the inhibition of the crucial BMP signaling pathway.
- Findings provide mechanistic insights into TCS-induced bone disorders and highlight the need for environmental risk assessment.
