Hepatic Stellate Cell Exosomes Resolve Fibrosis in Mice Livers via Enriched Metabolic and Regenerative Signaling Molecules
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Background
Hepatic stellate cells (HSC) are Vitamin A storing non-parenchymal cells of the liver. During injury and inflammation, HSCs are the major contributors of excessive extracellular matrix (ECM) leading to Liver Fibrosis (LF). Emerging evidence suggests a fibrosis-independent role of these cells as key regulators of liver homeostasis and liver regeneration, emphasising on the dual role of HSCs in liver. HSCs are known to secrete several growth factors through which they largely execute their functions. However, the role of secretome (exosomes) from early activated or undifferentiated HSCs in a fibrotic milieu nor its composition are completely understood.
Methods
LX-2 cells were cultured in low to no serum conditions and their isolated exosomes were transplanted into fibrotic severe combined immune deficient (SCID) mice livers, followed by post-transplantation analysis of the liver tissue and compared to the untreated controls. Total proteomic profiling of cell and exosomal cargo was performed using mass spectrometry and the data analysed and compared with the total HSC cell proteome.
Results
Significant reduction in collagen in the transplanted mice livers compared to untreated fibrotic controls was observed with both the cells and exosomes transplantation. Comparative analysis revealed distinct enrichment of proteins and signaling pathways associated with extracellular matrix regulation, cellular communication, and metabolism in exosomes. Notably, these pathways are prominently represented in the exosomal fraction, suggesting a selective packaging of functional mediators.
Conclusion
This study suggests the potential role of HSCs in regulating the complex liver homeostasis via exosomal network of proteins that contribute significantly to liver repair by ECM remodelling and growth factor-mediated signalling to regulate metabolism, fibrosis and liver regeneration.
