Decreased risk of cholangiocarcinogenesis following repeated cycles of Opisthorchis viverrini infection-praziquantel treatment: Magnetic Resonance Imaging (MRI) and histopathological study in a hamster model

Abstract

It has been suggested that repeated infection of Opisthorchis viverrini followed by repeated treatment with praziquantel (PZQ) increases risk of development of cholangiocarcinoma (CCA). Evidence for the prediction has accumulated based on findings of indirect approaches involving molecular changes and epidemiological trends. By contrast, here we directly monitored the impact of repeated liver fluke infection and treatment with PZQ on cholangiocarcinogenesis in a rodent model of human opisthorchiasis, using magnetic resonance imaging (MRI) and histopathology. Twenty five Syrian golden hamsters were assigned to five treatment groups: 1) infection with O. viverrini (OV group), 2) treatment with the carcinogen N-nitrosodimethylamine (NDMA) at 12.5ppm (DMN), 3) O. viverrini infection in tandem with NDMA (OD), 4) O. viverrini infection, NDMA, and treatment with PZQ (ODP), and 5) uninfected, untreated control. The repeated infections were established by intragastric inoculation of 50 metacercariae of O. viverrini to the OV, OD and ODP hamsters at weeks 0, 5 and 10. PZQ at 300mg/kg body weight was given to each hamster of the ODP group on weeks 4, 9 and 13 (four weeks after each infection). Imaging by MRI was undertaken on weeks 5, 10 and 14 (i.e. one week after each PZQ treatment). MRI revealed that the ODP hamsters did not develop CCA, whereas necropsy at week 40 revealed CCA in hamsters of the OD and DMN groups. Findings for histopathology and for proliferating cell nuclear antigen index conformed to the MRI findings. In overview, and notwithstanding that the immune response of individual hosts may play roles in cholangiocarcinogenesis, three cycles of the infection with O. viverrini followed treatment of the infection with PZQ did not increase the risk of bile duct cancer in this hamster model of liver fluke infection-induced CCA.

Keywords: Cholangiocarcinoma; Hamster; MRI; Opisthorchis; Praziquantel; Repeated infection.

Fig. 1

Necropsy and histopathological findings of the livers from the OV (C), OD (A, D), DMN (E) and ODP groups (B, F). CCA (T) was protruding from the middle lobe of the OD liver. The ODP liver contained multiple cysts. Periductal fibrosis and lymphoid aggregation were predominant lesions in the OV hamsters. Histopathology of cholangiocarcinoma (CCA) was shown in the OD and DMN livers. Dead worms were seen often in bile ducts of the liver of hamsters of the ODP group. Original magnification C = 10×, D = 20×, E = 20×, and F = 10×.

Fig. 2

Axial T2 weighed images of hamsters in the OV, DMN, OD and ODP groups. Experimental weeks (W) and order of MRI examination (T#) are labeled on the left and right sides of the figure, respectively. The first MRI (T#1) applied at week five (5W) being shown in the first row could reveal different degrees of hepatobiliary lesions. The animals in the OD group showed the most progressive appearance. Arrows indicated periductal fibrosis and duct dilatation, which increased in the OD hamsters. Hamsters of the ODP group exhibited less severe lesions compared to hamsters in the DMN and OV groups. Progression of the hepatobiliary lesions is in accordance with number of cycles of infections with O. viverrini and treatment with PZQ treatment: the higher number, the more progress.

Fig. 3

Three coronal planes of MRI scans (T#1, T#2, T#3) at weeks 5, 10, 15 and 20 (5W, 10W, 15W and 20W) after infection for the treatment groups, OV, DMN, OD and ODP. These T2 weighed images documented pathological changes similar to those revealed in Fig. 1. The lesional changes in the ODP livers in the final MRI scan (T#3) were not as markedly progressive as those in the OD liver.