D.E. Clark

Expression and localization of the Th2-type cytokine interleukin-13 and its receptor in the placenta during human pregnancy

PROBLEM: To investigate the expression of the Th2‐type cytokine interleukin (IL)‐13 and its receptor in human placenta during gestation.

Angiogenic growth factor expression in placenta

New blood vessel growth is generally a rare event in the healthy adult. However, a notable exception to this is the female reproductive tract where cyclic angiogenesis occurs. Striking new vessel growth and remodeling also occurs during placentation; thus angiogenesis is essential for reproductive success. Vascular endothelial growth factor is a potent stimulator of this process and its production and action is tightly regulated. Indeed the placenta is a rich source of a soluble variant of the flt-1 receptor which seems to protect the placenta from the effects of excess vascular endothelial growth factor. The balance between new vessel growth (in the placental villi for example) and endothelial cell loss in the spiral arteries within the decidua is a delicate one. This is influenced by the local production of promotors and inhibitors of endothelial cell activation. Perturbation of this may lead to maternal pathology during pregnancy.

Hepatocyte growth factor levels during normal and intra-uterine growth-restricted pregnancies

Hepatocyte growth factor (HGF), also known as scatter factor, binds the c-met receptor. It has been shown to be involved in mesenchyme-epithelial interactions. HGF is produced by the villous mesenchyme of the placenta throughout pregnancy and its receptor located on the villous cytotrophoblast cells. In this study the levels of HGF were measured in consecutive samples of plasma taken from pregnant women. Normal pregnancies were compared with intrauterine growth restricted (IUGR) pregnancies (below the third centile). In both groups, the levels of HGF were found to increase significantly as pregnancy progressed and then fall post partum. There was a considerable amount of variation found between individual women but no significant difference (P=0.65) between the normal and IUGR pregnancies.

PGE2 and TXA2 Production by Isolated Macrophages from Human Placenta

In earlier studies we have investigated the eicosanoid production of placenta in short-term tissue culture where thromboxane A2 (TXA2) was the main cyclooxygenase (COX) product of arachidonic acid.1 Immunohistochemically, the strongest positive staining for COX 1 and 2 and thromboxane synthase (TXS) could be located to placental macrophages (Hofbauer cells).2, 3 These tissue macrophages of the placenta are located close to trophoblast cells and fetal capillaries which makes them ideal candidates for involvement in regulatory processes. Recent studies suggested a role for Hofbauer cells in angiogenesis4, 5 and immunological reactions6.