Characteristics of peri-implantation porcine concepti population and maternal milieu influence the transcriptome profile

Authors: Blomberg, Le Ann; Schreier, Lori; Li, Robert

Submitted to: Journal of Molecular Reproduction and Development
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/20/2010
Publication Date: 11/20/2010
Citation: Blomberg, L., Schreier, L.L., Li, R.W. 2010. Characteristics of peri-implantation porcine concepti population and maternal milieu influence the transcriptome profile. Journal of Molecular Reproduction and Development. 77:978-989.

Interpretive Summary: The pre-implantation period is extended in swine to enable the conceptus to undergo a rapid, dramatic morphological change i.e. an expansion or elongation of primordial placental tissue, between gestational days 11 and 12 in preparation for implantation. In a litter-bearing animal like the pig, this rapid elongation of the primordial placenta is considered to be essential for conceptus survival; however asynchrony in the elongation process is often observed between concepti. The goal of the current study was to determine the extent to which messenger ribonucleic acid (mRNA) may be altered in the conceptus in response to developmental delay as well as the physiological implications. Concepti with the same morphology, oval-shaped and 7-8 mm, were isolated and designated as normal or developmentally delayed if collected from a homogenous oval-shaped conceptus population or a heterogeneous conceptus population (oval-shaped to thread-like), respectively. Whole cell RNA containing mRNA was prepared from 4 distinct normal and 4 distinct developmentally delayed concepti, and mRNA levels were measured for ~ 39,000 genes by microarray analysis. The mRNA levels for 209 genes were found to be different between normal and developmentally delayed concepti. Functional analysis of these genes indicated that a significant number of the genes regulate signaling inside the cell/mRNA production, organism development, metabolism, and cell adhesion and/or, were regulated by an important growth factor, transforming growth factor beta 1. Ten genes were selected, based on their known role in promoting interaction between the maternal tissue and and specific placental cell types in preparation for implantation, for validation of their mRNA levels by quantitive polymerase chain reaction technology. The microarray results were confirmed. Based on gene expression, our findings suggested that developmentally delayed concepti are distinct from their morphologically similar counterparts and, highlighted potential developmental factors that can be interrogated further to determine if, and how, they affect/regulate conceptus survival during the elongation phase of the primordial placenta.

Technical Abstract: Asynchrony of trophectoderm elongation, gestational days 11-12, is evident in porcine concepti and rapid progression through this phase has been associated with conceptus competency. The goal of the current study was to determine the extent of transcriptomic responses of concepti to developmental delay and their physiological implications. Concepti with the same morphology, ovoid and 7-8 mm, were isolated and designated as normal or developmentally delayed if collected from a homogenous ovoid conceptus population or a heterogeneous conceptus population (ovoid to filamentous), respectively. Total RNA prepared from 4 distinct normal and 4 distinct developmentally delayed concepti, was analyzed using an Agilent high-density porcine custom microarray. Two hundred-nine transcripts were found differentially expressed between normal and developmentally delayed concepti. Functional analysis of these genes indicated that a significant number of the genes regulate signal transduction/transcription, organismal development, metabolism, and cell adhesion and/or, can be modulated by transforming growth factor ß1. Ten genes were selected for real-time PCR validation of differential expression based on a known role in steroid synthesis, endometrium receptivity, and modulation of trophoblast differentiation/growth or interaction with transforming growth factor ß1. As in the microarray, all except one, achaete-scute complex homolog 2, were preferentially up-regulated in delayed concepti. The findings suggested developmentally delayed concepti are distinct from their morphologically similar counterparts and, highlighted the potential effects of the conceptus’ microenvironment as well as developmental factors that can be interrogated further to determine if, and how, they affect embryo competency/elongation.