Culture models to study leukocyte trafficking across the choroid plexus

Background: A critical point during the course of central nervous system infection is the influx of leukocytes from the blood into the brain across the blood-brain barrier (BBB) and the blood-cerebrospinal fluid barrier (BCSFB). However, experimental in vitro models to investigate leukocyte transmigration across cultured choroid plexus epithelial cells have been lacking so far. Methods: We have developed a porcine and human inverted culture insert system that enables leukocyte transmigration specifically from the physiologically relevant basolateral side. The models use primary porcine choroid plexus epithelial cells (PCPEC) and human choroid plexus papilloma cells (HIBCPP). As a prerequisite for a functional barrier, we optimized culture conditions in which cells are maintained in serum-containing medium until high barrier function is reached. Leukocyte transmigration through the plexus epithelial cells is analysed by three-dimensional Apotome (R)-imaging and electron microscopy, and the route of transmigration through the plexus epithelial cells, i. e. transcellular as well as paracellular, can be determined. Discussion: As a functionally relevant porcine and human BCSFB model, PCPEC and HIBCPP respectively, offer a wide range of options for analysis of disease-related mechanisms at the choroid plexus epithelium, especially involving human pathogens. Moreover, our in vitro models facilitate the investigation of leukocyte entry into the CNS via the blood-CSF barrier.