Compromised integrity of excised porcine intestinal epithelium obtained from the abattoir affects the outcome of in vitro particle uptake studies.

Excised porcine intestinal tissue obtained from the local abattoir was studied for its suitability to examine the uptake and transport of poly(lactic-co-glycolic acid) (PLGA) nanoparticles in Peyer's (PP) and non-Peyer's patch (NPP) tissue in vitro. Incubation of such tissue with fluorescent PLGA and polystyrene particles revealed negligible uptake into the intercellular space with no noticeable difference between PP and NPP tissue. Similarly, yeast cells, which were used as a positive control for selective uptake into PP tissue, were found in the subepithelial area of both PP and NPP tissue. Therefore we examined the morphological integrity of the tissue for the duration of the experiments. For this purpose, excised intestinal tissue from the abattoir transported to the laboratory was examined for morphological changes by light microscopy and compared to intestinal tissue from freshly slaughtered piglets. Already after 25 min postmortem, we observed lysis and defoliation of the epithelial cell layer followed by a complete loss of villus architecture and, consequently, resulting in a complete loss of the integrity of the intestinal tissue. This may explain the limited and non-selective particle uptake when using excised intestinal tissue from the abattoir. It is suggested to avoid small intestine obtained from the abattoir and to use tissue from freshly sacrificed animals within a few minutes postmortem. Experiments should then be performed under adequate oxygenation of the excised intestinal tissue.