Evidence for prion protein expression in enteroglial cells of the myenteric plexus of mouse intestine.

Transmissible spongiform encephalopathies (TSEs) are slowly progressive and fatal neurodegenerative diseases affecting man and animals. They are caused by pathological isoforms (PrP(Sc)) of the host-encoded cellular prion protein (PrP(C)). There are two crucial factors for the initiation of infection, namely host cells PrP(C) expression and sufficient sequence homology between the PrP(Sc) to which the animal is exposed and its own PrP(C). In acquired TSEs, the gastrointestinal tract (GIT) is the main prion entry site. Hence, it is of paramount importance to an understanding of the early pathogenesis of prion infections, to characterize the GIT cell types constitutively expressing PrP(C). Twenty-three mice were utilized, including wild-type (WT), Prnp knock-out (KO), and PrP(C)-overexpressing (tga20/tga20) animals, of 20-30 g in weight and of either sex. In all three groups of mice, PrP(C)-immunoreactivity (IR), along with glial fibrillary acidic protein (GFAP)-IR and synaptophysin (Syn)-IR were investigated by means of indirect immunofluorescence in wholemount preparations from several gut regions, from duodenum to rectum. In WT mice, PrP(C)-IR and GFAP-IR co-localization was observed in enteric glial cells (EGCs) from all intestinal segments. PrP(C)-overexpressing mice showed a stronger PrP(C)-IR in EGCs, whereas the same cells exhibited no PrP(C)-IR in Prnp-KO mice. Our findings clearly indicate that EGCs of the mouse intestine constitutively express PrP(C); thus they could be a potential target for infectious prions.