Poly(I:C)-Stimulated Exosomes Mitigate Cholesterol-Induced Hepatic Fibrosis by Modulating the TGF-β/Smad3 Signal Transduction Pathway

Background: Hepatic fibrosis, primarily driven by the activation of hepatic stellate cells (HSCs), results in excessive deposition of extracellular matrix (ECM) and subsequent liver scarring. Exosomes derived from mesenchymal stem cells (MSCs) play a key role in tissue repair by modulating the inflammatory environment — specifically through the suppression of pro-inflammatory cytokines and the enhancement of anti-inflammatory signals. This immunomodulatory function, along with their regenerative potential, positions MSC-derived exosomes as a promising acellular therapeutic approach and a compelling alternative to conventional cell-based therapies. Objectives: This study aimed to explore the therapeutic capability of exosomes originating from human umbilical cord Wharton’s jelly mesenchymal stem cells (WJ-MSCs), stimulated with polyinosinic: Polycytidylic acid (poly I:C), to reduce hepatic fibrosis by targeting the SMAD3 pathway and modulating oxidative stress levels. Methods: The LX2 cell line was cultured in Dulbecco’s modified Eagle medium (DMEM) containing 10% fetal bovine serum (FBS) and allowed to interact with 100 μM cholesterol for 24 hours. Exosomes produced by MSCs derived from human umbilical cords, treated with 10 μg/mL poly(I:C), were applied to evaluate Smad3 protein levels and the expression of transforming growth factor-beta (TGF-β) messenger RNA, alpha-smooth muscle actin (α-SMA), and alpha-1 collagen genes. This study was not a randomized trial, and the methods used were based on cell culture models rather than in vivo trials. Results: The upregulation of TGF-β gene expression, along with the phosphorylation of Smad3 protein, collagen 1α, NADPH oxidases (NOXs), and α-SMA in LX2 cells following cholesterol treatment, indicates cholesterol's involvement in liver fibrosis progression. In contrast, the reduced phosphorylation of Smad3 protein and decreased expression of these genes suggest that exosomes exert a therapeutic effect by inhibiting hepatic stellate cell (HSC) activation. Conclusions: Stimulating WJ-MSC-derived exosomes with poly(I:C) reduces stellate liver cell activation and inhibits the signaling pathway involving Smad3, effectively limiting liver fibrosis progression. Therefore, activating exosomes in WJ-MSCs with poly(I:C) offers a promising therapeutic strategy for hepatic scarring treatment. Future studies should focus on in vivo validation and exploration of the long-term therapeutic potential of these exosomes in clinical models of liver fibrosis.