The use of Caco-2 cells as an in vitro method to study bioavailability of iron.

Iron absorption is essential for the maintenance of iron levels in the body, since excretion is poorly regulated. Dietary factors can influence iron absorption including low molecular weight substances such as ascorbic acid which has been shown to enhance iron transport across mucosal cell monolayers. Both in vivo and in vitro work may be carried out to study iron absorption. Studies in vivo have the drawback of dealing with a complex system in which it is difficult to determine the relative importance of different factors. In vitro cell culture models could overcome this difficulty but attempts to establish differentiated enterocyte cell lines in culture have not been successful. However the Caco-2 line, derived from a colon carcinoma, is able to differentiate spontaneously when grown in standard culture conditions. The differentiated cells polarized, formed microvilli and T-junctions associated with the duodenal enterocytes brush border. This cell line thus represents an appropriate model for the study of transport mechanisms related to the intestinal barrier and can be used to study the absorption of nutrients especially iron in relation to dietary intake in particular pertaining to dietary factors that may affect absorption. In this work we have therefore used differentiated Caco-2 cells grown in bicameral chambers as a intestinal cell model to study the absorption of iron from different sources and compared it with INT 407 cells. Transfer of iron across the monolayers in the apical-to-basolateral direction has been found to be greater from feric lactoferrin than from iron citrate, while very little transport occurred from Fe-transferrin. It is concluded that in this in vitro study lactoferrin but not transferrin enhances mucosal iron transport. More importanty this study has also shown that Caco-2 can be used as an in vitro method to investigate not only iron bioavailability but can be applied to other minerals as well.