The protozoan parasite Giardia duodenalis is the etiological agent for the intestinal diarrheal disease giardiasis. Infections are acquired via the fecal-oral route, mostly via uptake of cysts from contaminated drinking water. Taken up cysts transform into the trophozoite stage, which is the parasite’s motile and vegetative life stage. The colonization of the hosts’ duodenum and upper jejunum and the attachment of Giardia trophozoites onto the epithelium is the cause of a variety of gastrointestinal complaints but the exact pathomechanisms are unknown. Furthermore, the outcome of Giardia infections varies greatly between individuals, ranging from self-limiting to chronic, and asymptomatic to severe enteritis. One proposed mechanism for the pathogenesis is the breakdown of intestinal barrier function, e.g. by tight junction impairment or induction of cell death.
In this work, effects of G. duodenalis on in vitro models of the human small intestinal epithelium were investigated by studying mainly barrier-related properties and changes of widely used Caco-2 cells as well as newly established human small intestinal organoid-derived monolayers (ODMs).
It could be shown that several isolates of G. duodenalis, some described as highly virulent, fail to induce barrier dysfunction or any other investigated pathological effect on two Caco-2 cell lines under various infection and culturing conditions. On the other side, by developing a new organoid-based model system and the use of luminal mock medium TYI-S-33, considerable epithelial disruption (including loss of cells), cell death (apoptosis and non-apoptotic), tight junction impairment (degradation and dislocation of claudins and ZO-1), and microvilli depletion reproducibly induced by G. duodenalis trophozoites between one and two days after infection could be observed. Moreover, emergence of ClCa-1 positive cells with ongoing parasite infections suggest epithelial differentiation or metaplasia towards goblet cells, which is furthermore not associated to tissue damage.
Those findings, which were not achieved or even impossible to detect by the popular Caco-2 approach, indicate the advantage of organoid-based models over such traditional carcinoma-derived cell systems. It becomes clear that those advanced in vitro models are required to gain robust data from complex and elusive diseases like giardiasis and future research may build upon findings and the developed ODM system of this work.
|Advisor:||Aebischer , Anton , Matuschewski , Kai , Schulzke , Jörg-Dieter|
|School:||Humboldt Universitaet zu Berlin (Germany)|
|Source:||DAI-C 81/8(E), Dissertation Abstracts International|
|Keywords:||Protozoan parasites, Duodenum|
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