The expression and role of integrin-linked kinase during human trophoblast differentiation

Elustondo, Pia Alejandra (2012) The expression and role of integrin-linked kinase during human trophoblast differentiation. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

A critical phase of placental development is the differentiation of cytotrophoblasts into invasive extravillous trophoblasts. Alterations of this process can lead to serious pregnancy pathologies such as preeclampsia and intrauterine growth restriction. Unfortunately it is poorly understood which physiological and molecular mechanisms are involved in the regulation of trophoblast differentiation. -- lntegrin-Linked Kinase (ILK) is a ubiquitous protein able to regulate outside-inside signaling by binding to integrins. Since ILK is overexpressed in tumors that become invasive, it was hypothesized that ILK is expressed in human placenta and that it is necessary for the differentiation of trophoblasts into invasive cells. To test the hypothesis, spatial and temporal patterns of ILK expression were studied in normal human and mouse placentas by immunohistochemistry, immunofluorescence analysis, and immunoblot analysis. In human placenta, ILK was present in cytotrophoblast and extravillous trophoblast in the first trimester (n=17), early second trimester (n=6) and at term (n=10). By comparison, ILK was present in the three layers of the mouse placenta: labyrinth, junctional zone, and trophoblast giant cells. -- HTR8-SVneo cells were also used to determine the role of ILK in migration and invasion. When ILK function was impaired in HTR8-SVneo cells with a dominant negative form of ILK, migration and invasion were inhibited. Furthermore, HTR8-SVneo and human chorionic villous explant cultures were utilized to study the effect of the oxygen environment on ILK expression and activity. Exposure of HTR8-SVneo cells to a low oxygen environment produced a transient increase in the expression of ILK mRNA, but did not affect the level of protein expression nor its kinase activity. In contrast to these results, placental explants showed lower expression of ILK under 3% O₂ environment compared to placental ex plants exposed to 8% and 20% O₂ . Placentas from preeclamptic patients also showed lower detection of ILK in the fetal capillaries compared to age-matched controls. -- In total these novel results showed that ILK is present in human and mouse placenta in cells that invade the maternal uterus during pregnancy and that it plays a critical role in the migration and invasion of trophoblasts. -- The results contribute to a better understanding of the mechanisms involved in the control of placental invasion and could assist in the production of future tools to improve the early diagnosis and treatment of gestational trophoblastic diseases such as preeclampsia.

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