Villous trophoblasts cultured on semi-permeable membranes form an effective barrier to the passage of high and low molecular weight particles.

An effective in vitro model of the placental villous syncytium cultured on semi-permeable substrata is essential for studies of infectious pathogen transmission from mother to fetus. Current models using amniotic membranes or thinner artificial membranes show significant leakage, suggesting disruption of tight junctions or the presence of gaps between syncytial units. Such disruption and discontinuity of trophoblast cultures are probably the result of high stromal cell contamination, poor viability and lack of proliferation in culture. We have successfully cultured confluent layers of tight-junctioned syncytium on semi-permeable insert membranes using highly viable purified cytotrophoblasts and an alternating multiple seeding and differentiation technique. Using criteria including transepithelial diffusion of high and low molecular weight substances, electrical resistance and directional secretion of the matrix metalloproteinase, MMP-9, we demonstrate that these cultures form effective and functional physical barriers that can be maintained for up to 1 month. Copyright 2001 Harcourt Publishers Ltd.