Abstract

Background: Placental mRNA in maternal plasma is suitable for quantitative analysis regardless of fetal gender and genetic polymorphism status.

Methods: We obtained 155 blood samples from pregnant women to compare human placental lactogen (hPL) and β-subunit of human chorionic gonadotropin (βhCG) mRNA and protein levels between the cellular and plasma components of maternal blood. To assess clearance of hPL mRNA expression, we obtained blood samples from nine women immediately before and after delivery by caesarean section. mRNA was extracted from the cellular and plasma components of all samples, and hPL and βhCG mRNA expression was analysed by reverse transcription-PCR assay.

Results: The concentration of βhCG mRNA in the cellular component positively correlated with the plasma concentration of βhCG protein and βhCG mRNA (p = 0.001 for both). The concentration of hPL protein in the plasma correlated with the hPL mRNA concentration of the cellular component (p<0.05). For both hPL and βhCG, the mRNA concentration of the cellular component was greater than that of the plasma component (22.9-fold higher for hPL and 4.3-fold higher for βhCG). The half life of hPL mRNA clearance was significantly longer for the cellular fraction (mean half life = 203.8 min, range 150–3465 min) than for the plasma fraction (mean half life = 32.2 min, range 15–385 min) (p = 0.008).

Conclusion: The present findings indicate that the concentration of hPL and βhCG mRNA is significantly higher in the cellular component of maternal blood samples than in the plasma component. Cellular mRNA in maternal blood is useful for non-invasive evaluation of placental function.