Endocrine Abstracts

Pregnancy complications such as pre-eclampsia and intrauterine growth restriction are associated with abnormal placental cell (cytotrophoblast; CT) proliferation and apoptosis. The mechanisms regulating these events are unclear however altered levels of IGFs have also been reported in these conditions. Using an explant model of human first trimester placenta we have shown that both IGF-I and –II act through IGF1R mediated signalling pathways to enhance CT proliferation, differentiation and survival. We have also shown that non-specific inhibition of protein tyrosine phosphatases (PTPs) inhibits IGF-mediated signalling in trophoblast. In other systems the PTP, SHP-2, regulates IGF signalling but the role of SHP-2 in the human placenta is unknown. In this study we have used siRNA mediated knockdown of SHP-2 to examine its role in regulating IGF effects in the placenta.

Amaxa Nucleofector technology was used to deliver SHP-2 or scrambled siRNA (100 nM) to BeWo choriocarcinoma cells or first trimester villous tissue fragments. Following transfection cells and tissue were maintained in culture for 72 h, then treated with IGF-I or IGF-II (10 nM) for a further 24 h. Western blot analysis revealed a 95% reduction in SHP-2 expression in BeWo cells and immunohistochemical (IHC) analysis for cell proliferation (Ki67, BrdU) demonstrated that IGF-induced proliferation was reduced from 67.3±3.5% to 41.9±2.4% (P<0.001, n=5). In placental tissue IHC analysis revealed that SHP-2 is localised to CT. Following knockdown (93% decrease by Q-PCR), IGF-I- and IGF–II-induced CT proliferation was decreased by 60.02±7.4% and 55.9±9.6% respectively (P<0.001, n=4). Furthermore, the ability of IGF-I- and IGF–II to prevent CT apoptosis (M30 staining) was reduced by 48.3±10.1% and 39.1±7.9% respectively (P<0.05, n=4) following SHP-2 knockdown.

In summary, this study demonstrates that SHP-2 positively regulates IGF stimulation of CT proliferation. Exogenous IGF rescues CT from apoptosis, and this pathway is also SHP-2-dependent.