Characterization of cellular signalling pathways involved in the regulation of trophoblast cell functions
This publication based doctoral thesis comprises six manuscripts covering the intracellular signaling pathways activated by LIF and OSM and the functional analysis of miR-21 in trophoblastic cells. The aim of this thesis was to elucidate the signaling pathways activated by the cytokines LIF and OSM as well as the role of specific miRNAs in the control of trophoblast cell functions. The results demonstrate that LIF and OSM have similar functions in activating STAT3 and ERK1/2 by changing their phosphorylation status in four trophoblastic cell lines. However, LIF but not OSM significantly increases invasion of trophoblastic cell lines. Inhibition of STAT3 decreases the invasiveness of trophoblastic cell lines by inhibiting the secretion of matrix metalloproteinases (MMPs). These results suggest that LIF shares STAT3 and ERK1/2 activation with OSM but their resulting responses are cell type dependent. The second part of this dissertation is focused on placenta-specific miRNAs and their function on trophoblast cells. The miRNA profile of primary cells includes the expression of at three clusters which are specifically expressed in placenta tissue: C19MC, C14MC and the miR-371-3 cluster. C19MC is highly expressed in third trimester trophoblast cells and in choriocarcinoma cell lines. C14MC is highest expressed in first trimester trophoblast cells as well as in HTR-8/SVneo cells and its plasma concentration decreases with the gestational age. Both miRNA clusters are evolutionary related to the appearance of placenta and their dysregulation can be associated with pregnancy pathologies. In conclusion, this work describes the intercellular signaling pathways activated by OSM and LIF, as well as the function of miR-21 in trophoblastic cells. Moreover, it may provide novel information on their involvement in the pathogenesis of pregnancy-related disorders which may be useful for the design of future non-invasive diagnostic tools or for the development of new therapeutic approaches.