Background: Fetal growth restriction is associated with an increased risk of perinatal mortality and morbidity as well as an increased risk of chronic disease in later life. Placental amino acid transport to the fetus is essential for optimal fetal growth. The gene expression of specific amino acid transporters in the human placenta, including the facilitated transporters LAT3, LAT4 and TAT1, has been positively linked with fetal growth. The mechanisms controlling the expression of these transporters within the placenta are not currently known; we have previously shown the HEK293 cell line is a suitable model to study placental amino acid transporters. This study aimed to investigate whether mRNA expression of placental amino acid transporters is regulated by DNA methylation.Methods: Human embryonic kidney (HEK) 293 cells were plated at 2 x 10^5 per 32 mm well. Cells were cultured with 7 µM of the demethylating agent 5-Aza-2′-deoxycytidine (AZA) or media control for 48 h. RNA was extracted and converted to cDNA. Quantitative real-time PCR was used to measure amino acid transporter mRNA expression; normalized to housekeeping genes. One way analysis of variance (ANOVA) was used to determine whether AZA treatment significantly (p<0.05) altered amino acid transporter mRNA expression.Results: AZA treatment significantly increased mRNA expression of the amino acid exchangers ASCT1 (p=0.000) and ASCT2 (p=0.000), the facilitated transporters LAT3 (p=0.000) and LAT4 (p=0.000) and the accumulative transporters SNAT1 (p=0.000) and SNAT2 (p=0.000). TAT1 mRNA expression (p=0.712) did not differ significantly with AZA treatment. Conclusion: The gene expression of specific placental amino acid transporters is regulated by methylation. Further studies are required to determine whether these methylation effects are direct, i.e within the genes promoter region, or indirect i.e via changes in transcription factor methylation. These results suggest that altered methylation status could regulate expression of placental amino acid transporters, and therefore influence placental amino acid transport to the fetus. Furthermore, DNA methylation may provide a mechanism by which the early environment can influence placental function throughout gestation, which in turn can influence fetal growth.