Abstract
Background Schistosoma japonicum is a parasitic flatworm that causes human schistosomiasis. Secreted extracellular vesicles (EVs) play a key role in pathogen-host interfaces. Previous studies have shown that S. japonicum adult worms can release microRNA (miRNA)-containing EVs, which can transfer their cargo to mammalian cells and regulate gene expression in recipient cells. Tissue-trapped eggs are generally considered the major contributor to the severe pathology of schistosomiasis; however, the interactions between the host and parasite in this critical stage remain largely unknown.MethodsThe culture medium for S. japonicum eggs in vitro was used to isolate EVs. Transmission electron microscopy (TEM) analysis was used to confirm that vesicles produced by the eggs were EVs based on size and morphology. Total RNA extracted from EVs was analyzed by Solexa technology to determine the miRNA profile. The in vitro internalization of the EVs by mammalian cells was analyzed by confocal microscopy. The presence of EVs associated miRNAs in the primary hepatocytes of infected mice was determined by quantitative real-time PCR (qRT-PCR).ResultsEVs were isolated from the culture medium of in vitro cultivated S. japonicum eggs. TEM analysis confirmed that nanosized vesicles were present in the culture medium. RNA-seq analysis showed that the egg-derived EVs contained small non-coding RNA (sncRNA) populations including miRNAs, suggesting a potential role in host manipulation. This study further showed that Hepa1-6, a murine liver cell line, internalized the purified EVs and their cargo miRNAs that were detectable in the primary hepatocytes of mice infected with S. japonicum.Conclusions Schistosoma japonicum eggs can release miRNA-containing EVs, and the EVs can transfer their cargo to recipient cells in vitro. These results demonstrate the regulatory potential of S. japonicum egg EVs at the parasite-host interface.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-016-1845-2) contains supplementary material, which is available to authorized users.
Highlights
Schistosoma japonicum is a parasitic flatworm that causes human schistosomiasis
Schistosoma japonicum egg isolation, culture and culture medium collection For collection of S. japonicum egg secretion products, New Zealand rabbits were percutaneously infected with approximately 1,200 S. japonicum cercariae that were shed from lab-infected snails (Oncomelania hupensis) obtained from the National Institute of Parasitic Disease, Chinese Center for Disease Control and Prevention
extracellular vesicles (EVs) isolation from schistosomal eggs and small RNA analysis The schistosomal eggs were incubated for 24 h in standard culture conditions, and vesicles were purified from the culture medium and evaluated by Transmission electron microscopy (TEM)
Summary
Schistosoma japonicum is a parasitic flatworm that causes human schistosomiasis. Secreted extracellular vesicles (EVs) play a key role in pathogen-host interfaces. Exosomes are a subtype of small (30–150 nm in diameter), membrane-enclosed vesicles, released by various types of mammalian cells in both normal and pathological conditions [9,10,11]. The cargo of exosomes is complex and variable, containing bioactive proteins, functional mRNAs, miRNAs and other small non-coding RNA (sncRNA) species [9, 10, 15]. These vesicles can “horizontally” transfer signals to neighboring cells and serve as mediators of intercellular communication [15,16,17,18,19,20]. Based upon the increasing realization that EVs facilitate intercellular communication in eukaryotes, we speculate that they contribute to maintenance of the long-term host-parasite interactions during schistosomiasis
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