Proteomic analysis of perfusate from in situ rat placenta perfusion

Background: The placenta is the most important organ for the development of the embryo and fetus because of its transport functions. Over the past several decades, a small number of proteins were tested that can cross the placenta, however, there have been no high throughput and comprehensive studies of protein crossing of the placenta. Methods: To evaluate the in situ perfused placenta model and applicate it to investigate the protein transfer functions of the placenta, the rat placenta was perfused in situ and the proteome of the perfusate was analyzed by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) in the present study. Results: To eliminate the effects of remnants of fetal plasma in the perfusate, a two-tailed t-test of relative quantitation based on spectral counts was performed between the perfusate and fetal plasma. Twenty two proteins in the perfusate were significantly enriched (p<0.05) in comparison to the fetal plasma. Most enriched proteins were located in the cytoplasma, membrane, or matrix. There were few plasma proteins that were obviously enriched in the perfusate when we examined alpha fetal protein as the indicator of fetal plasma remnants. Conclusions: We generated no definite evidence that plasma proteins cross the placenta. The placenta acts as a protein barrier in perfused condition. However, some of the proteins identified in the perfusate may be useful as biomarkers of the integrity of placenta barrier and the degree of placental injury.