Curative effect of radiotherapy at various doses on subcutaneous alveolar echinococcosis in rats.

BACKGROUND: Alveolar echinococcosis (AE) is a disease in human and animals, and the cure rate is unsatisfactory. This study aimed to investigate the curative efficacy of different doses of locally applied radiotherapy on alveolar echinococcosis in rats. METHODS: Rats infected with Echinococcus multilocularis were randomly divided into 4 groups of 15 rats each: low-, middle-, and high-irradiation groups and a control group. Rats in the control group underwent no treatment, while rats in the irradiation groups received 6-MeV radiotherapy at 20 Gy/8 f, 40 Gy/8 f, and 60 Gy/8 f respectively, once every 3 days for a total of 8 times. One month after radiotherapy, wet weight and AE vesicle inhibitory rate were detected in rats of each group. Histopathologic and ultrastructural observations of tissues with AE lesions were performed. RESULTS: In the treatment groups, an obvious inhibitory effect was found in AE rats; the inhibitory rates were 50%, 72%, and 82%, respectively. There were also statistical differences in pathological changes and average wet weight of the lesions compared with the control group (P < 0.05). In the treatment groups, injuries of various degrees were found in the ultrastructure of the laminated and germinal layers in the capsular wall of AE, and injury was most severe in the high-dose group. CONCLUSION: Radiotherapy has a dose-dependent inhibitory effect on the growth of AE.

Echinococcus multilocularis: the impact of ionizing radiation on metacestodes.

Alveolar echinococcosis is caused by the metacestode stage of the fox tapeworm Echinococcus multilocularis. Current chemotherapeutical options for the treatment of echinococcosis are not satisfactory, and novel drugs and/or other potential means of therapy are needed. E. multilocularis metacestodes are characterized by almost potentially unlimited growth, and also display other features of cancerous tumours. In this study, we exposed metacestodes that were generated in vitro to 50-100 Gy ionizing irradiation, and subsequently investigated the short-term (10-12 days post-treatment) and long-term (14 weeks post-treatment) effects. We found, that in the short-term, no release of alkaline phosphatase (EmAP) activity as a measure for potentially induced damage and loss of viability could be detected, and that the protein expression pattern and protease activities in vesicle fluids and medium supernatants did not alter dramatically following irradiation. However, irradiation was associated with distinct morphological and ultrastructural alterations in the tissue of metacestodes, affecting most notably cell-cell contacts, mitochondrial shape, glycogen-storage cells and lipid droplet formation. These could be detected already at 10 days following treatment and remained as such also in the long-term. In addition, as determined after 14 weeks of culture, irradiation affected the proliferation and the growth of E. multilocularis metacestodes. Thus, we demonstrate that radiotherapy does not have a clear-cut parasitocidal effect, but can lead to metabolic impairment of E. multilocularis metacestodes, as reflected by the distinct morphological and structural alterations induced by irradiation treatment.