**1. Introduction**

The placenta is a unique temporary organ and the central regulator of maternal-fetal environment [1]. It is a complex organ that needs to adapt constantly to maternal and fetal requirements during the progression of the pregnancy. The placenta is composed of several varieties of cells including trophoblasts, mesenchymal and endothelial cells and immune cells [2]. It is essential for materno-fetal exchange enabling the transfer of regulatory molecules to the fetus and fetal molecules to the maternal circulation [3]. The placenta is also involved in hormonal regulation [4, 5] and immunological defense of mother [6] and fetus [7]. The placenta synthetizes and secretes large number of molecules necessary for its development, metabolism

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

of mother and fetus growth [8]. These factors including placental hormones and growth factors lead to the regulation of gene expression critical for placenta plasticity and functions including angiogenesis, immune response, decidua invasion, endocrine regulation and fetal nutrition and growth [9].

**2. Placenta transcriptome in normal pregnancy**

**2.1. Gene expression and anatomic organization of placenta**

parts of placenta tissue are functionally different.

**Species Placenta and** 

Human At term placentas

Human At term placenta

(amnion, chorion and decidua part)

RNAsequencing

**Table 1.** Transcriptomic analysis of tissue component of the placenta.

**gestational age**

(amnion, chorion, umbilical cord and section of villus parenchyma)

Human placenta is a feto-maternal organ composed of the fetal part (also known as chorion) and the maternal part (also known as decidua). The chorion is composed of trophoblasts, cytotrophoblasts and syncytiotrophoblasts, whereas the decidua contains enlarged endometrial stromal cells (epithelium) and leukocytes populations, thus suggesting that these two

Few studies have investigated the transcriptomic profile of the different areas of the placenta tissue (**Table 1**). As shown in **Table 1**, two studies have investigated gene expression in amnion, chorion, decidua and villus parenchyma of at term placenta using microarray or RNA-sequencing. A core of gene expression patterns was observed in the different areas of the placenta; they are related to histology categories [10]. Microarray analysis revealed major differences among amnion, chorion and villus parenchyma. It showed that the gene encoding

**Technique Results References**

Gene Expression Profiling of Placenta from Normal to Pathological Pregnancies

http://dx.doi.org/10.5772/intechopen.80551

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with placental trophoblast secretion, signal transduction, metabolism, immune regulation, [10]

[11]

• Inter-individual differences are observed in gene expression between the mother and the fetal

• The expression of a set of genes is related to the

• 938, 865 and 944 genes are modulated in amnion, chorion and decidua tissues, respectively • 216 genes were commonly modulated among the

• Common genes were associated with placenta abnormalities including prolactin receptor, insulin-like growth factor 2 and a set of genes enriched with interleukin-1 pathway

• Amnion: genes associated with cell adhesion and

• Chorion: genes associated with angiogenesis, cell proliferation and Wnt receptor signaling • Decidua: genes associated with female preg-

Microarray • Differentially modulated genes are associated

cell adhesion and structure

section of the placenta

three placenta tissues

epidermal cell differentiation

nancy and wound healing

sex of the fetus

The investigation of a complex organ such as placenta requires an approach without *a priori* that can be provided by high throughput methods such as microarray, ribonucleic acidsequencing (RNA-Seq) and/or quantitative reverse transcription-polymerase chain reaction (qRT-PCR) technologies, which markedly changed our analysis of tissue physiology and pathophysiology. This field is expanding since the investigation of keywords including placenta, transcriptomic and gene expression on PubMed database revealed a progression of the number of publications per years from 1 in 2001 to 55 in 2017 (**Figure 1**). The transcriptomic studies have enabled identification of specific genes involved in the progression of the gestation and the outcome of complications. These gene signatures may be used as new biomarkers for maternal and fetal complications of pregnancy.

In this chapter, we will review the literature focusing on the gene expression profiling of placenta tissue and isolated cells during the progression of the gestation and pathological pregnancies.

**Figure 1.** Number of publications associated with "placenta, transcriptome and gene expression".
