Leukemia Inhibitory Factor Receptor Signaling Directs Development of the Maternal-Placental Interface

Leukemia Inhibitory Factor Receptor Signaling Directs Development of the Maternal-Placental Interface

Savannah L. Speckhart¹, Khursheed Iqbal¹, and Michael J. Soares^1,2,3

< !1. Institute for Reproductive and Developmental Sciences, Department of Pathology and Laboratory Medicine, Kansas City, KS, USA

< !2. Department of Obstetrics and Gynecology, University of Kansas Medical Center, Kansas City, KS, USA

< !3. Center for Perinatal Research, Children’s Mercy Research Institute, Children’s Mercy, Kansas City, MO, USA

 

Abstract Text:

The placenta controls nutrient and waste flow between maternal and fetal compartments. Central to these transfer properties of the placenta is a trophoblast lineage termed syncytiotrophoblast. Syncytiotrophoblast arise from the fusion of trophoblast cell progenitors creating a multi-nucleated cell barrier. Both human and rat have trophoblast barriers comprised of syncytiotrophoblast; however, the positioning of trophoblast progenitor cells and syncytiotrophoblast exhibit species differences. In the human, syncytiotrophoblast are located at the maternal interface with proximally situated progenitors at the fetal interface. In contrast, in the rat, trophoblast progenitor cells, referred to as sinusoidal trophoblast cells, are positioned within the labyrinth zone at the maternal interface with two proximal syncytiotrophoblast layers at the fetal interface. Failures in syncytiotrophoblast development are associated with pregnancy loss. A connection between a cytokine, leukemia inhibitory factor (LIF) and its receptor (LIFR), and reproduction is well established; however, involvement of LIF/LIFR signaling in trophoblast barrier development is poorly understood. Our research investigation had two objectives: 1) evaluate LIF/LIFR signaling in human syncytiotrophoblast development, and 2) assess the role of LIFR signaling in establishing the maternal-placental barrier. In-situ hybridization of 8-week-old human placentation sites revealed strong expression of LIFR in syncytiotrophoblast lining villi and the maternal blood space. Human trophoblast stem (TS) cells were used to evaluate the actions of LIF/LIFR signaling on syncytiotrophoblast development. We observed a 12-fold increase in LIFR transcript expression as TS cells transitioned from the stem state to syncytiotrophoblast. Addition of exogenous LIF negatively influenced syncytiotrophoblast development. LIF treatment caused a decrease in the acquisition of syncytiotrophoblast-specific transcripts and instead a retention of elevated TS cell stem state-specific transcripts as determined by RNA-sequencing. Next, we examined expression and action of LIFR within the rat placentation site. In-situ hybridization revealed Lifr expression within sinusoidal trophoblast cell progenitors and sinusoidal trophoblast giant cells, which line the maternal blood space. Localization was confirmed via co-localization of Lifr transcripts with transcripts specific to each cell lineage within the labyrinth zone. A global Lifr null rat was generated to interrogate LIF/LIFR signaling in placentation. Lifr disruption was lethal after gestation day (gd) 15.5 in the rat. At gd 15.5, disruption of LIFR was associated with placental and fetal growth restriction. Transcriptomes of gd 15.5 labyrinth zones from Lifr null and wild type placentation sites were compared by RNA-sequencing. Lifr null labyrinth zones exhibited disruptions in the expression of genes specific to sinusoidal trophoblast cells and to syncytiotrophoblast layer 1 (SynT1) and syncytiotrophoblast layer 2 (SynT2). The labyrinth zones of Lifr null and wild type placentation sites were next interrogated for the expression of monocarboxylate transporter 1 (MCT1, a protein specific to SynT1, and to monocarboxylate transporter 4 (MCT4, a protein specific to SynT2). Immunolocalization of MCT1 and MCT4 revealed severe disorganization of SynT1 and SynT2 layers in LIFR disrupted gd 15.5 labyrinth zones. Collectively, these results indicate that our model systems (i.e., human TS cells and the rat) are useful for understanding LIF/LIFR actions on the maternal-placental interface where LIF/LIFR acts on trophoblast cells lining the maternal blood space. In humans, syncytiotrophoblast development is directly impacted by the actions of LIF, whereas syncytiotrophoblast development is indirectly affected in the rat via LIF/LIFR actions on sinusoidal trophoblast cells. [This work is supported by GM103418 (SLS), Lalor Foundation (SLS), HD116506 (SLS), NIH-LRP (SLS), HD020676, HD105734, HD112559, and the Sosland Foundation]