Final Report Summary - MACE (Maternal Communication with embryo)
Project context and objectives
Reproductive fitness and offspring heath are major players in determining the economic profitability of the livestock industry. Both parameters are highly complex and are deeply influenced by a wide array of physiological and environmental variables. Maternal communication with embryos stands at the base of early embryonic development, implantation and maintenance of the pregnancy. This maternal-embryo interaction not only underpins pregnancy but also influences the future health of the offspring. Therefore, understanding the mechanisms involved in the communication between the maternal tract and the embryos in terms of the molecules involved and their function is of major scientific, economic and heath importance. Increasing our knowledge regarding maternal interaction with embryos will lead to the creation of novel molecular markers of fertility that will help to improve the fertility of the livestock population by genomic selection and thus provide unique competitive advantages to the animal breeding industry. Knowledge of the embryo-maternal interactome will facilitate novel approaches for improving the efficiency and safety of assisted reproduction techniques. Finally, this knowledge has cross-disciplinary applications in human health and is of immense importance for future public health.
The maternal tract plays a critical role in the success of early embryonic development providing an optimal environment for the 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. The present project was aimed at understanding the signals involved in the maternal communication with embryos in pigs. The information obtained has been used in an in silico computational model to gain a more comprehensive understanding of the interactions between the maternal tract and the embryo.
We hypothesised that the presence of the embryo at the very early stages of pregnancy induces a local response in the maternal tract that supports embryo development during the early pregnancy. Therefore, the specific objectives of the study were:
- to determine the local response of the maternal tract in terms of alterations of the uterine trancriptome and proteome to the presence of the embryo at the very early stages of development compared to the presence of oocytes;
- to determine when the uterus recognises the presence of the embryo;
- to describe how the uterus alters its environment in response to the embryo at key stages of development in order to allow the refractory uterus to tolerate the embryo and support its development.
Work performed
In the current project we identified the signals involved in the maternal communication with embryos at the transcriptomic and the proteomic level. We used a novel in vivo experimental model in pigs that eliminated genetic variability and individual differences to identify the signals involved in this embryo-maternal dialogue together with high-throughput technologies. 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.
Holistic transcriptomic analyses of the uterine samples in response to the embryo, as the embryo develops from two cells to the blastocyst stage, were performed using microarrays analysis. The results of the present project revealed that the embryo-induced changes in the uterine transcriptome profile during the first week of embryonic development occur in a complex and dynamic manner. The local response of the uterine horn in terms of genes altered towards the embryo was dependent on the embryonic stage, showing a different transcriptome profile for each embryonic stage analysed. Surprisingly, changes in the uterine transcriptome profile became evident as soon as the embryo reaches the two-cell stage, when the embryo was still in the oviduct. This different gene expression pattern of the uterine horn implies an early maternal recognition of the embryo at the two-cell stage.
In addition, the proteomic profile of the uterine horn in response to the presence of the embryo at the blastocyst stage was analysed using Isobaric tag for relative and absolute quantitation (iTRAQ) technology. We hypothesised that the presence of the embryo in the uterus also alters the local uterine proteomic profile and induces the production of proteins during the very early stages of pregnancy. The proteomic analysis revealed 26 differentially expressed proteins in the presence of the blastocyst in the uterine horn when compared to the oocyte. Interestingly, a high number of these proteins altered in the uterine horn in the presence of the embryo have been previously reported to play a role during pregnancy.
Bioinformatics analysis revealed that most of the genes and proteins altered in the uterine horn in response to the embryo at different stages of development were involved in metabolism and immunity. This data may reflect the metabolic needs of the embryo at the very early stages of development. In addition, our findings implied that the presence of the embryo in the maternal tract regulated local immune responses and potentially reduced the local activity of the innate immune system within the maternal tract at the site of implantation. Furthermore, 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. Our data implies that the embryo might play a role as a modulator of the metabolism and immune system in the maternal tract, inducing the up and down-regulation of genes and proteins in the uterus to allow the refractory uterus to tolerate the embryo and support its development.
Main results
The work carried out during this project firmly demonstrated the local effect of the embryo in the uterus. Our data provides a worthwhile addition to the present literature, focusing on the existence of local responses of the uterus towards the embryo at the very early stages of development. Until now, most studies have compared transcriptomic and proteomic profiles of pregnant and non-pregnant animals during implantation time, pointing to major differences in transcriptional activities that were mainly under hormonal control. We reported a holistic view of the local changes in the uterine horn at the transcriptomic and proteomic level in response to the embryo during pre-implantation stages. Particularly interesting is the fact that changes in the uterine transcriptome profile in response to the embryo become evident as soon as the embryo reaches the two-cell stage. This response reveals a maternal recognition of the embryo occurring much earlier than has been reported before.
Reproductive fitness and offspring heath are major players in determining the economic profitability of the livestock industry. Both parameters are highly complex and are deeply influenced by a wide array of physiological and environmental variables. Maternal communication with embryos stands at the base of early embryonic development, implantation and maintenance of the pregnancy. This maternal-embryo interaction not only underpins pregnancy but also influences the future health of the offspring. Therefore, understanding the mechanisms involved in the communication between the maternal tract and the embryos in terms of the molecules involved and their function is of major scientific, economic and heath importance. Increasing our knowledge regarding maternal interaction with embryos will lead to the creation of novel molecular markers of fertility that will help to improve the fertility of the livestock population by genomic selection and thus provide unique competitive advantages to the animal breeding industry. Knowledge of the embryo-maternal interactome will facilitate novel approaches for improving the efficiency and safety of assisted reproduction techniques. Finally, this knowledge has cross-disciplinary applications in human health and is of immense importance for future public health.
The maternal tract plays a critical role in the success of early embryonic development providing an optimal environment for the 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. The present project was aimed at understanding the signals involved in the maternal communication with embryos in pigs. The information obtained has been used in an in silico computational model to gain a more comprehensive understanding of the interactions between the maternal tract and the embryo.
We hypothesised that the presence of the embryo at the very early stages of pregnancy induces a local response in the maternal tract that supports embryo development during the early pregnancy. Therefore, the specific objectives of the study were:
- to determine the local response of the maternal tract in terms of alterations of the uterine trancriptome and proteome to the presence of the embryo at the very early stages of development compared to the presence of oocytes;
- to determine when the uterus recognises the presence of the embryo;
- to describe how the uterus alters its environment in response to the embryo at key stages of development in order to allow the refractory uterus to tolerate the embryo and support its development.
Work performed
In the current project we identified the signals involved in the maternal communication with embryos at the transcriptomic and the proteomic level. We used a novel in vivo experimental model in pigs that eliminated genetic variability and individual differences to identify the signals involved in this embryo-maternal dialogue together with high-throughput technologies. 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.
Holistic transcriptomic analyses of the uterine samples in response to the embryo, as the embryo develops from two cells to the blastocyst stage, were performed using microarrays analysis. The results of the present project revealed that the embryo-induced changes in the uterine transcriptome profile during the first week of embryonic development occur in a complex and dynamic manner. The local response of the uterine horn in terms of genes altered towards the embryo was dependent on the embryonic stage, showing a different transcriptome profile for each embryonic stage analysed. Surprisingly, changes in the uterine transcriptome profile became evident as soon as the embryo reaches the two-cell stage, when the embryo was still in the oviduct. This different gene expression pattern of the uterine horn implies an early maternal recognition of the embryo at the two-cell stage.
In addition, the proteomic profile of the uterine horn in response to the presence of the embryo at the blastocyst stage was analysed using Isobaric tag for relative and absolute quantitation (iTRAQ) technology. We hypothesised that the presence of the embryo in the uterus also alters the local uterine proteomic profile and induces the production of proteins during the very early stages of pregnancy. The proteomic analysis revealed 26 differentially expressed proteins in the presence of the blastocyst in the uterine horn when compared to the oocyte. Interestingly, a high number of these proteins altered in the uterine horn in the presence of the embryo have been previously reported to play a role during pregnancy.
Bioinformatics analysis revealed that most of the genes and proteins altered in the uterine horn in response to the embryo at different stages of development were involved in metabolism and immunity. This data may reflect the metabolic needs of the embryo at the very early stages of development. In addition, our findings implied that the presence of the embryo in the maternal tract regulated local immune responses and potentially reduced the local activity of the innate immune system within the maternal tract at the site of implantation. Furthermore, 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. Our data implies that the embryo might play a role as a modulator of the metabolism and immune system in the maternal tract, inducing the up and down-regulation of genes and proteins in the uterus to allow the refractory uterus to tolerate the embryo and support its development.
Main results
The work carried out during this project firmly demonstrated the local effect of the embryo in the uterus. Our data provides a worthwhile addition to the present literature, focusing on the existence of local responses of the uterus towards the embryo at the very early stages of development. Until now, most studies have compared transcriptomic and proteomic profiles of pregnant and non-pregnant animals during implantation time, pointing to major differences in transcriptional activities that were mainly under hormonal control. We reported a holistic view of the local changes in the uterine horn at the transcriptomic and proteomic level in response to the embryo during pre-implantation stages. Particularly interesting is the fact that changes in the uterine transcriptome profile in response to the embryo become evident as soon as the embryo reaches the two-cell stage. This response reveals a maternal recognition of the embryo occurring much earlier than has been reported before.