Early Developing Pig Embryos Mediate Their Own Environment in the Maternal Tract

et al. (2012) Early Developing Pig Embryos Mediate Their Own Environment in the Maternal Tract. PLoS ONE 7(3): e33625. doi:10.1371/journal.pone.0033625 Early Developing Pig Embryos Mediate Their Own Environment in the Maternal Tract Carmen Almin ana 0 Paul R. Heath 0 Stephen Wilkinson 0 Jonatan Sanchez-Osorio 0 Cristina Cuello 0 Inmaculada Parrilla 0 Maria A. Gil 0 Jose L. Vazquez 0 Juan Maria Vazquez 0 Jordi Roca 0 Emilio A. Martinez 0 Alireza Fazeli 0 Reiner Albert Veitia, Institut Jacques Monod, France 0 1 Academic Unit of Reproductive and Developmental Medicine, Department of Human Metabolism, The University of Sheffield , Sheffield , United Kingdom , 2 Sheffield Institute for Translational Neuroscience (SITraN) , Sheffield , United Kingdom , 3 Chemical and Biological Engineering , The University of Sheffield , Sheffield , United Kingdom , 4 Department of Medicine and Animal Surgery, Veterinary Faculty, University of Murcia , Murcia , Spain The maternal tract plays a critical role in the success of early embryonic development providing an optimal environment for establishment and maintenance of pregnancy. Preparation of this environment requires an intimate dialogue between the embryo and her mother. However, many intriguing aspects remain unknown in this unique communication system. To advance our understanding of the process by which a blastocyst is accepted by the endometrium and better address the clinical challenges of infertility and pregnancy failure, it is imperative to decipher this complex molecular dialogue. The objective of the present work is to define the local response of the maternal tract towards the embryo during the earliest stages of pregnancy. We used a novel in vivo experimental model that eliminated genetic variability and individual differences, followed by Affymetrix microarray to identify the signals involved in this embryo-maternal dialogue. Using laparoscopic insemination one oviduct of a sow was inseminated with spermatozoa and the contralateral oviduct was injected with diluent. This model allowed us to obtain samples from the oviduct and the tip of the uterine horn containing either embryos or oocytes from the same sow. Microarray analysis showed that most of the transcripts differentially expressed were down-regulated in the uterine horn in response to blastocysts when compared to oocytes. Many of the transcripts altered in response to the embryo in the uterine horn were related to the immune system. We used an in silico mathematical model to demonstrate the role of the embryo as a modulator of the immune system. This model revealed that relatively modest changes induced by the presence of the embryo could modulate the maternal immune response. These findings suggested that the presence of the embryo might regulate the immune system in the maternal tract to allow the refractory uterus to tolerate the embryo and support its development. - Funding: This work was supported by Marie Curie IEF (236708), Minister of Science and Innovation (MICINN; AGL2009-12091), Seneca Foundation (GERM04543/ 07), COST ACTION FA0702 and Centre for the Development of Industrial Technology (CDTI; 2008/0268). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. Despite many advances in assisted reproductive technologies (ART) in humans, to date the incidence of pregnancy failure remains high [1]. Pregnancy loss also affects livestock breeding and has economical implications for the livestock industry [2]. The high rate of pregnancy failure has been attributed mainly to asynchronous embryo development in the maternal tract and inappropriate communication between the mother and the developing embryo(s) [3,4,5]. In addition, with the recent emergence of the field of Developmental Origins of Health and Disease (DOHaD), it is becoming increasingly evident that a greater understanding of the milieu of the female reproductive tract and the potential effect that disturbances of this milieu may have on the offspring is needed [6]. The maternal tract hosts a crucial cross-talk between the mother and the embryo at a very early stage of life and it seems that this cross talk may have long term consequences which extend into adulthood [7,8,9,10]. Hence, understanding the complex molecular dialogue between the maternal tract and the embryo is essential for solving infertility problems, reducing pregnancy loss and even identifying the factors that may influence the developmental potential of offspring into adulthood, in human and livestock. The response of the endometrium towards the embryo(s) at very early stages of pregnancy is poorly understood. A number of genes and proteins have already been described to be activated in the endometrium when the embryo arrives in the maternal tract [5,11]. It is apparent that precise recognition of the embryo in the maternal tract is critical for preparation of a suitable environment for implantation, embryonic development and pregnancy [12]. However, exactly when the oviduct and the uterus recognize the presence of embryo(s) and how the maternal tract alters its environment in response to embryo(s) is not completely understood. In the past, it has been generally assumed that maternal-embryo communication and the environment of the womb are mainly controlled by the endocrine system [13,14]. Many studies have compared genomic and proteomic profiles of pregnant and nonpregnant animals, pointing to major differences in transcriptional activities that are mainly under hormonal control (mouse: [10,15]; bovine: [16,17,18]; pig [19,20,21]; human: [1,22]). Paracrine and autocrine signals from the embryo and the maternal tract are also involved in this important process [23,24,25]. This complex network of signals is reflected in alteration of uterine transcriptome, leading to morphological, biochemical and also immunological changes in the uterine environment. Little is known about the potential local signalling molecules involved in cell-to-cell interactions in embryo-maternal communication. In literature, only one study has provided evidence of transcriptional changes in the oviduct in response to the embryo that can be regarded as maternal tract responses to the local signals received from embryo and not related to the hormones released during pregnancy [10]. Technological, experimental and ethical issues make it very difficult to define a clear picture of the local maternal tract responses that are produced due to exactly local signalling by embryo(s) and its arrival in the female reproductive tract. In the current investigation, we aimed to define the local response(s) of the maternal tract towards the embryo during the very earliest stages of pregnancy. We used a novel porcine in vivo experimental model in which each sow was subjected to laparoscopic insemination procedures (...truncated)