In Vitro Maintenance of Clonorchis sinensis Adult Worms

Clonorchis sinensis is a biological carcinogen inducing human cholangiocarcinoma, and clonorchiasis is one of the important endemic infectious diseases in East Asia. The present study investigated survival longevity of C. sinensis adult worms in various in vitro conditions to find the best way of keeping the worms longer. The worms were maintained in 0.85% NaCl, 1${\times}$PBS, 1${\times}$Locke's solution, RPMI-1640, DMEM, and IMDM media, and in 1${\times}$Locke's solution with different supplements. All of the worms died within 3 and 7 days in 0.85% NaCl and 1${\times}$PBS, respectively, but survived up to 57 days in 1${\times}$Locke's solution. The worms lived for 106 days in DMEM, and 114 days in both RPMI-1640 and IMDM media. The survival rate in RPMI-1640 medium was the highest (50%) compared to that in DMEM ($20{\pm}10%$) and in IMDM ($33.3{\pm}25.2%$) after 3 months. The 1${\times}$Locke's solution with 0.005% bovine bile supplement showed increased duration of maximum survival from 42 days to 70 days. Higher concentration of bile supplements than 0.005% or addition of glucose were disadvantageous for the worm survival. The worms died rapidly in solutions containing L-aspartic acid, L-glutamic acid, and adenine compared to L-arginine, L-serine, and L-tryptophan. In conclusion, the 1${\times}$Locke's solution best supports the worms alive among inorganic solutions for 57 days, and the RPMI-1640 medium maintains living C. sinensis adults better and longer up to 114 days in vitro than other media.