Transepithelial Transport of Folic Acid in Human Trophoblastic BeWo Cells

Abstract

Transport of folate across the placental interface may be an important determinant of availability of maternal folate for proper embryonic development. The present aim was to develop a method for studying transepithelial folate transport across monolayers of human trophoblastic BeWo cells. To ensure the suitability of BeWo cells as a model for folate transport, we determined the expression of folate transport-related genes using real time PCR-based reverse transcription-PCR detection and found that transcripts for Folate Receptors α, β and γ and also Reduced Folate Carrier-1 were expressed. For transport studies, the apical surface of 14 day old BeWo cell monolayers maintained on (12 well dish) permeable membrane supports were exposed to transport buffer consisting of 200 nM of folic acid conjugated to rhodamine dye and equimolar concentration of sodium fluorescein (paracellular marker) dissolved in Hanks’ Balanced Salt Solution (HBSS) while the monolayer's basolateral side was bathed in HBSS, followed by sampling at various time points from basolateral chamber for fluorescence quantitation. The rate of transcellular transport of folic acid, calculated by subtracting the paracellular component from total folic acid-rhodamine transported, was 185 ± 24 femtomoles/minute/well in the apical (maternal) to basolateral (fetal) direction. Support: Young Investigator Award 2005, Spina Bifida Association of America.