The study looked at two proteins, MMP‑9 (which helps cells invade) and kisspeptin‑10 (which blocks invasion), in normal and abnormal pregnancies. Early in pregnancy MMP‑9 is high and kisspeptin is low, then they swap as the pregnancy progresses. In preeclampsia both are low, while in abnormal growths like molar pregnancies MMP‑9 stays high and kisspeptin stays low, and in the most aggressive cancer (choriocarcinoma) kisspeptin isn’t detectable at all. The balance between these two proteins seems to control how much the placenta cells can invade tissue.

To explore the role of metastasis-related gene KiSS-1 and matrix metalloproteinase (MMP)-9 in regulation of invasion of trophoblasts. RT-PCR and Western blotting were used to detect the MMP-9 and KiSS-1 expression levels in the placental tissues obtained from 90 cases of normal pregnant women undergoing artificial abortion, induction of labor with water bag or selective cesarean section among which 30 cases were in the first trimester, 30 in second-trimester and 30 cases of term pregnancy, and in the placental tissues of 40 cases of preeclampsia (15 cases of mild and 25 cases of severe preeclampsia) undergoing cesarean section, and tissues of 90 cases of hydatidiform mole, 9 cases of invasive mole and 8 cases of choriocarcinoma, all undergoing surgery. The expression levels of MMP-9 mRNA and protein were higher in first-trimester [A value 0.391 +/- 0.215, (36 +/- 7) microg/100 microg total protein] and then decreased gradually with the progress of gestation. The expression levels of MMP-9mRNA and protein in the term placental samples were significantly lower than those of first-trimester (both P < 0.01). The expression levels of KiSS-1mRNA and metastin in normal placenta increased along with the progress of gestation (both P < 0.01). The KISS-1 mRNA expression level and MMP-9 protein expression level in the placental tissue of preeclampsia were 0.09 +/- 0.06 (A value) and (9.6 +/- 4.3) microg/100 microg total protein respectively, both significantly lower than those of the term placenta (both P < 0.01). The expression levels of MMP-9 mRNA and protein in the tissues of gestational trophoblastic disease were significantly higher than those in the first-trimester placenta (both P < 0.01). The expression level of KISS-1 mRNA and metastin in the tissues of hyddatidiform mole and invasive mole were both significantly lower than those in the first trimester placenta (P < 0.05, P < 0.01). The expression of KiSS-1mRNA and metastin in the tissues of choriocarcinoma could not be detected. The expression of the invasion-related gene, MMP-9, is positively related with, while the invasion suppressor gene, KiSS-1, is negatively related with the invasive ability of trophoblasts. The interaction of these two genes plays an important role in regulation of the invasion of trophoblasts.