SMAD3 and Hepatic fibrosis: Specifically, (a) a large number of novel miRNA-33 molecules from egg-derived exosomes of S. japonicum are present in the liver and serum of hosts infected with S. japonicum, (b) the novel miRNA-33 participates in the activation of HSCs and the occurrence of liver fibrosis in the host, (c) the novel miRNA-33 from S. japonicum regulates post-transcriptional processes in the host in a cross-species manner, (d) the novel miRNA-33 promotes liver fibrosis through the TGF-β/Smad3 signaling pathway.