Prednisolone suppresses collagen-encoding gene expression causing cartilage defects in zebrafish larvae

Molecular structure of Fgfbp1 protein and its regulation of zebrafish cartilage development and homeostasis: Implications for Wnt signaling and ECM stability

The role of Wnt signaling pathway in the regulation of chondrodevelopment has received extensive attention. The role and molecular mechanism of Fgfbp1 protein, which interacts with extracellular matrix, in the development of zebrafish cartilage are not fully understood. The aim of this study was to investigate the molecular structure of Fgfbp1 protein and its regulatory role in the development and homeostasis of zebrafish cartilage, especially its effects on the stability of Wnt signaling pathway and ECM. The amino acid sequence of Fgfbp1 protein was predicted by bioinformatics analysis and molecular cloning, and its three-dimensional structure model was constructed. Using zebrafish embryo as experimental model, the role of Fgfbp1 protein in the development of zebrafish cartilage was studied by gene knock-down and overexpression techniques. The expression pattern and localization of Fgfbp1 protein in zebrafish embryos were analyzed by immunofluorescence staining and confocal microscopy. In order to explore the effect of Fgfbp1 protein on Wnt signaling pathway, the expression of genes related to Wnt signaling pathway was also analyzed in this study. The changes of ECM components were detected by biochemical methods to evaluate the role of Fgfbp1 protein on ECM stability. The study found that the Fgfbp1 protein has a unique molecular structure, and its three-dimensional model revealed multiple potential binding sites for interacting with ECM components. In zebrafish embryos, Fgfbp1 protein is mainly expressed in the chondrogenic region, and its expression level is closely related to the differentiation and maturation of chondrocytes. Gene knock-down experiments have shown that deletion of the Fgfbp1 protein leads to chondrodysplasia, which is characterized by reduced number and abnormal morphology of chondrocytes. On the contrary, overexpression of Fgfbp1 protein promoted the proliferation and differentiation of chondrocytes. Further analysis showed that Fgfbp1 protein can regulate the expression of key genes in the Wnt signaling pathway, such as Wnt3a and β-catenin, thereby affecting the proliferation and differentiation of chondrocytes. The loss of Fgfbp1 protein leads to decreased expression levels of ECM components such as collagen and fibranexin, suggesting that Fgfbp1 protein plays an important role in the stability of ECM.

Modulation of the gut-bone axis: Lacticaseibacillus paracasei LC86 improves bone health via anti-inflammatory metabolic pathways in zebrafish models of osteoporosis and cartilage damage

Aim

Osteoporosis and cartilage injury are major health concerns with limited treatment options. This study investigates the therapeutic effects of Lacticaseibacillus paracasei LC86 (LC86) on osteoporosis and cartilage damage in a zebrafish (Danio rerio) model, focusing on its modulation of the gut-bone axis and its potential mechanisms for enhancing bone health.

Methods

A Dexamethasone-induced zebrafish model was used to mimic osteoporosis and cartilage injury. Zebrafish were divided into control, model, and LC86 treatment groups (3×107 CFU/mL). Bone and cartilage health were assessed using Alizarin red staining and fluorescence microscopy. Bone marker expression (sp7, runx2a, bmp2a, bmp4, and col2a1a) was quantified via qPCR. Metabolic alterations were analyzed using untargeted metabolomics, and changes in gut microbiota were examined through 16S rRNA gene sequencing.

Results

LC86 treatment significantly improved bone and cartilage health, as evidenced by increased fluorescence intensity in the skull, hard bone, and cartilage (p < 0.01, p < 0.05). qPCR results showed upregulation of key bone-related genes (sp7, runx2a, bmp2a, bmp4, and col2a1a), indicating enhanced bone and cartilage structure. Metabolomics analysis revealed alterations in over 300 metabolites, with changes in anti-inflammatory and energy pathways. Gut microbiota analysis demonstrated an increase in beneficial bacteria and a decrease in pathogenic genera.

Conclusions

LC86 significantly improved bone health, cartilage structure, and gut microbiota composition in a Dexamethasone-induced zebrafish model, supporting its potential as a therapeutic strategy for osteoporosis and cartilage injury via modulation of the gut-bone axis.

Exposure effects of synthetic glucocorticoid drugs on skeletal developmental and immune cell function in zebrafish

Synthetic glucocorticoids (GCs) are used to treat a wide range of human health conditions and as such are frequently detected in the aquatic environment. This, together with the highly conserved nature of the glucocorticoid system across vertebrates means that the potential for biological effects of GCs in fish is relatively high. Here, we found that exposure of zebrafish (Danio rerio) to environmentally relevant concentrations of 4 of the most widely used synthetic GCs (beclomethasone dipropionate, budesonide, fluticasone propionate, and prednisolone), from 0 to 4 days post fertilisation (dpf), resulted in no effects on embryo-larval development or bone and cartilage formation. However, after exposure to equivalents of human therapeutic plasma levels, developmental abnormalities were observed that included pericardial oedema, blood pooling and alterations in jaw cartilage. Furthermore, using a double transgenic zebrafish osteoblast and chondrocyte reporter line, exposure up to 10 dpf resulted in alterations to lower jaw cartilage and bone development for all compounds at, and above, human therapeutic plasma concentrations. In the case of beclomethasone dipropionate, a reduction in lower jaw intercranial distance was observed at the environmentally relevant concentration of 0.1 μg/L. Using further transgenic reporter lines with fluorescently tagged neutrophils and macrophages, we also show exposure of embryo-larvae (0-4 dpf) to the GCs tested resulted in altered immune cell migration, but only at relatively high exposure concentrations. Collectively, our findings show GC exposure impacts embryo-larval zebrafish development, immune function, and skeletal formation, but predominantly at concentrations greater than those currently reported for the aquatic environment. Despite this, however, it is suggested that studies with longer exposure times, and to mixtures of multiple GCs (many GCs act via the same mechanism of action) are warranted before we can confidently assert that these commonly detected contaminants do not pose a risk to fish in the wild.

Zebrafish models for glucocorticoid-induced osteoporosis

Glucocorticoid-induced osteoporosis (GIOP) is the most common form of secondary osteoporosis due to excessive or long-term glucocorticoid administration, disturbing the homeostasis between bone formation and bone resorption. The bone biology of zebrafish shares a high degree of similarities with mammals. In terms of molecular level, genes and signaling pathways related to skeletogenesis are also highly correlated between zebrafish and humans. Therefore, zebrafish have been utilized to develop multiple GIOP models. Taking advantage of the transparency of zebrafish larvae, their skeletal development and bone mineralization can be readily visualized through in vivo staining without invasive experimental handlings. Moreover, the feasibility of using scales or fin rays to study bone remodeling makes adult zebrafish an ideal model for GIOP research. Here, we reviewed current zebrafish models for GIOP research, focused on the tools and methods established for examining bone homeostasis. As an in vivo, convenient, and robust model, zebrafish have an advantage in performing high-throughput drug screening and could be used to investigate the action mechanisms of therapeutic drugs.

Are synthetic glucocorticoids in the aquatic environment a risk to fish?

The glucocorticosteroid, or glucocorticoid (GC), system is largely conserved across vertebrates and plays a central role in numerous vital physiological processes including bone development, immunomodulation, and modification of glucose metabolism and the induction of stress-related behaviours. As a result of their wide-ranging actions, synthetic GCs are widely prescribed for numerous human and veterinary therapeutic purposes and consequently have been detected extensively within the aquatic environment. Synthetic GCs designed for humans are pharmacologically active in non-mammalian vertebrates, including fish, however they are generally detected in surface waters at low (ng/L) concentrations. In this review, we assess the potential environmental risk of synthetic GCs to fish by comparing available experimental data and effect levels in fish with those in mammals. We found the majority of compounds were predicted to have insignificant risk to fish, however some compounds were predicted to be of moderate and high risk to fish, although the dataset of compounds used for this analysis was small. Given the common mode of action and high level of inter-species target conservation exhibited amongst the GCs, we also give due consideration to the potential for mixture effects, which may be particularly significant when considering the potential for environmental impact from this class of pharmaceuticals. Finally, we also provide recommendations for further research to more fully understand the potential environmental impact of this relatively understudied group of commonly prescribed human and veterinary drugs.