Transferrin Receptor 1 protein expression and localization in human IntraUterine Growth Restriction placentas

The mechanisms involved in Intrauterine Growth Restriction (IUGR) remain to be fully understood but a significant reduction in placental nutrient transport is clearly involved. Iron (Fe) deficiency in pregnancy leads to low birth weight and premature delivery. The Transferrin Receptor 1 (TfR1) is a Fe transporter located in the placental plasma membranes linearly related to the fetal liver Fe. We previously demonstrated a lower TfR1 mRNA expression in IUGR compared to control placentas, but no differences were found in relation to severity. Here, we measured the TfR1 protein expression levels and localization in IUGR and control placentas. 3 IUGR severity groups were identified depending on the umbilical artery pulsatility index and fetal heart rate. Western Blotting analysis was performed on 17 IUGR and 11 control term placentas, whereas 20 IUGR and 18 control term placentas were analysed by immunohistochemistry, to assess TfR1 protein expression and localization, respectively. TfR1 protein expression was significantly lower in IUGR compared to control placentas (p=0.03). Among the three severity groups TfR1 protein expression was significantly decreased in the most severe IUGR3 group (p=0.007). Protein localization was similar for all the analysed samples. Controversial results have been reported in vitro and in vivo about TfR1 expression in tissues under cellular hypoxic conditions, which is an important characteristic of IUGR placentas. However, no data are available about TfR1 expression in human IUGR compared to control placentas. We confirmed and expanded our previous results demonstrating lower TfR1 protein levels in IUGR. It is conceivable that the decrease in TfR1 expression is related to hypoxic conditions, which increase with severity in IUGR, although the protein localization does not change. Further data are needed to confirm these preliminary results.