Objectives: To compare the distribution of placental protein 13 (PP13) in fetal and maternal blood and amnionic fluid and to correlate it with PP13 protein and mRNA in the placenta.
Methods: Umbilical arterial serum, amnionic fluid, maternal venous serum and placental tissues were collected from normal outcome pregnancies (N = 63) (GA>37), early onset preeclampsia (PE) (N = 12, GA: 26-33), and HELLP syndrome (N = 5, GA: 27-29). Because PE and HELLP cases delivered preterm, cases of preterm delivery (PTD) (N = 6, GA: 31-36) served as additional control. PP13 was determined by ELISA, Western blot, and immunohistochemistry. PP13 mRNA was measured by PCR (RT-PCR). Continuous parameters were compared by t-test, P < 0.05 was considered significant.
Results: In women with normal pregnancy outcome significantly higher PP13 levels were found in maternal serum compared to amnionic fluid and negligible amount was found in fetal serum. A similar pattern was identified in cases of PTD with concentrations similar to term control. In PE and HELLP cases PP13 levels in amnionic fluid level were more than twice compared to maternal serum (P < 0.001). Umbilical cord level was negligible in PE but high in HELLP corresponding to the much higher level of PP13 in this patient group compared to all others. In the placenta PP13 level in term controls was higher compared to PTD. In PE and HELLP (similar early delivery time as PTD) the level was significantly higher (P < 0.01) compared to PTD or term controls. PP13 mRNA levels in term control and PTD were similar while PP13 mRNA levels in PE and HELLP placentas were significantly lower compared to term controls or PTD or the two combined. Syncytiotrophoblast labeling appeared stronger in PE and HELLP compared to term controls and PTD.
Conclusions: In all cases but HELLP, PP13 in fetal blood is very low indicating that routing of PP13 to fetal blood is limited and that the fetus is unlikely to generate PP13. PP13 mRNA is lower in the third trimester at the time of disease while protein level accumulates and become higher creating an unparallel change in the level of the mRNA and the corresponding protein.
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