Pregnancy

Spatio-Temporal Expression of Matrix Metalloproteinase-26 in Human Placental Trophoblasts and Fetal Red Cells During Normal Placentataion

Abstract
The processes of implantation and placentation involve the degradation and remodeling of extracellular matrix, cellular proliferation, apoptosis, and differentiation. Evidence indicates that members of the matrix metalloproteinase (MMP) family play crucial roles in these processes. In the present study, we identified the expression and localization of MMP-26/endometase/matrilysin-2 in human placentae at different stages of gestation using methods of reverse transcriptase-polymerase chain reaction, in situ hybridization and immunohistochemistry. MMP-26 was widely localized to villous cytotrophoblast cells, syncytiotrophoblast cells, and the column trophoblasts during early pregnancy. The mRNA and protein level of MMP-26 in chorionic villi was highest at week 6-7, and decreased thereafter, reaching its lowest level at the second trimester. The mRNA level was significantly up-regulated in term placenta, while the immunoreactivity remained undetectable. Notably, intense expression of MMP-26 was found in fetal nucleated red cells inside the villous capillaries during gestational weeks 6-9. Strong expression of MMP-26 mRNA was also demonstrated in fetal red cells isolated from the whole blood of fetuses at mid pregnancy. The expression patterns of MMP-26 in human placenta suggests complicated roles for MMP-26 during the processes of placentation and hematopoiesis, perhaps working in concert with other members of the MMP family, such as MMP-9.

Key words: Pregnancy • Implantation • Placenta • Trophoblast

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