Transferrin expression by placental trophoblastic cells

Transferrin (TF), a 76-80 kDa glycoprotein, is responsible for the transport of iron to cells within both the fetal and maternal systems, but it does not cross the multiple cell layer barrier of the placenta. Recent findings that both rat and human placental cells produce TF indicated that placental TF may function in some manner to transport or regulate iron passage across this barrier. However, placental production of TF was brought into question because the cell preparations used to identify TF were obtained using dispersed tissue and may have contained non-placental contaminating elements. In this study, cultures of phenotypically distinct cell types containing only placental cells were used to firmly establish whether or not TF is expressed, and if so to begin to identify the cell(s) associated with its synthesis. Utilizing RT-PCR, in situ hybridization, and Western blot analysis, we identified TF mRNA and protein in three trophoblast cell types, HRP-1 (rat), Rcho-1 (rat), and BeWo (human) cells. Additionally, TF mRNA and protein were found in Giant cells, the differentiated form of Rcho-1 cells. When taken together, these results demonstrate clearly that TF is expressed by both differentiated and non-differentiated placental cells, and when viewed in light of previous findings, strengthen the possibility that placental TF may be central to the passage of iron from the mother to the fetus during development.