Senescence markers in the placenta (JSAM 2021, MD project Theresa Forndran)

Senescence markers in the placenta - Premature aging as a consequence of or cause of pregnancy pathologies.

The placenta develops, grows, differentiates, and ages during the 9 to 10 months of pregnancy. Physiologically, the functionality of the placenta decreases markedly after 40 weeks of gestation and it begins to fail altogether, which is clinically evident in an increased intrauterine mortality rate of human fetuses after 38 weeks of gestation.

Accelerated and premature aging of the placenta represents a pathological condition (Fabiana 2020) and is a hallmark of several placenta-associated pregnancy complications, such as fetal growth restriction (FGR) (Paules 2019) and preeclampsia (PE) (Farladansky-Gershnabel 2019)-the two leading causes of maternal and neonatal morbidity and mortality. Understanding the physiologically occurring placental aging processes and how they are disrupted is therefore of enormous clinical importance especially to develop clinical approaches to treatment.

The cellular phenotype of aging is senescence, in which irreversible cell cycle arrest occurs (Yosef 2016). In this process, the cyclin kinase inhibitors p21, p16, and p53 are increasingly expressed in the cell (Kruiswijk 2015, Childs 2014). Senescent cells produce proinflammatory cytokines called "senescence-associated secretory proteins" (SASP) that accelerate aging processes in neighboring cells (Herranz 2015, Laberge 2015). The composition of SASP varies depending on the cell, with IL-6 (interleukin-6) and TNF-α (tumor necrosis factor-alpha) as markers. At the cellular level, placental aging is seen through the expression of these senescence markers (Higuchi 2019).

There is a causal relationship between oxidative stress leading to the production of ROS (reactive oxygen species) and cell senescence (Passos 2010, Cindrova Daviesa 2018), suggesting that oxidative stress contributes to premature aging. ROS induce oxidation of polyunsaturated fatty acids, leading to increased aldehyde synthesis such as that of 4-hydroxy-2-nonenal (HNE). ROS production is counteracted by antioxidants such as superoxide dismutase (SOD) (Stadtman and Levine 2003, Panieri 2013, Forman 2008). Microarray and proteomic analyses of human placentas of different gestational ages have shown that the expression of p21, p53, and SASP, as well as HNE and SOD activity, is increased early in placentas from patients with PE and FGR (Guerby 2021).

Cell fusion, an essential physiological process for the establishment and expansion of the syncytiotrophoblast (outer cell layer of the placental barrier), has recently been identified as a trigger of cell senescence (Cox and Redman 2017, Redman 2020). The syncytiotrophoblast shows, the high expression of the cyclin kinase inhibitors p16, p21, and p53 characteristic of senescent cells, as well as the secretion of SASP, which induces labor toward the end of pregnancy (Menon 2016a, Menon 2016b, Phillippe 2015). In cases where fusion is restricted, the syncytiotrophoblast is hypofunctional. As a result, the mother may develop preeclampsia and the fetus may develop growth restriction. Premature senescence in placental membranes may result in preterm labor and delivery (Cox and Redman 2017).

The goal of this project is to immunohistochemically analyze the expression of several known senescence markers, such as p21, p16, and p53, markers of oxidative stress, and SASP, in placentas from patients with PE and/or FGR.

To functionally characterize the affected placental cell populations and their interactions, we will use spatial phenotyping to assign cell type and cell senescence status after multiplex immunofluorescence labeling (multiplex IF) and thus draw conclusions about their role in placental senescence in the different pregnancy pathologies.

After establishing multifluorescence-based immunodetection using control placentas from healthy pregnant women with term births, comparative evaluation with retrospectively collected placental blocks from clinically diagnosed PE and FGR pregnancies will be performed. Finally, the influence of PETN (pentaerythritol tetranitrate), a drug investigated in recent years in the PETN study for the treatment of pregnant patients at risk for developing FGR and/or PE (Groten 2019), on the expression patterns of placental senescent markers will be analyzed.