To investigate the factors that may jeopardize the success of pregnancy in cattle, researchers at the University of São Paulo (USP) in Brazil used a kind of chip to mimic the environment of the endometrium, the tissue that covers the inside of the uterus.
The study was conducted by biologist Tiago Henrique Camara de Bem, a postdoctoral fellow at the Faculty of Animal Sciences and Food Engineering at the University of São Paulo (FZEA-USP), in collaboration with four researchers from the University of Leeds. in the United Kingdom. His findings are reported in a journal article Endocrinology.
The researchers focused on analyzing alterations in insulin and glucose levels in the maternal epithelium and stroma. cells, and the possible consequences for the initial development of the pregnancy. Epithelial cells are the outermost of the endometrium. They interface with light and are in direct contact with the embryo. Stromal cells lie deeper, acting as support cells that guide the growth, differentiation, and development of epithelial cells, among other functions.
The group found that high glucose levels altered 21 genes encoding proteins epithelial cells and 191 in stromal cells, in addition to causing quantitative changes in the secretoma protein (proteins secreted into the culture medium, which in this case mimicked the endometrial fluid). “By changing the amount of glucose and insulin in the culture medium, stressing the cells, we were able to turn genes on or off, determining whether they were expressed or not,” Camara de Bem said.
Changes in insulin levels altered the quantitative secretion of 196 proteins, but resulted in limited alteration of gene transcription. “The key factor may be the protein composition of the uterine fluid, in which these cells secrete proteins into the embryo,” he explained. “We found that this group of proteins is associated with signaling pathways that play an important role in the success of early pregnancy in cattle, related to metabolism, cell matrix, and other factors. All of these findings demonstrate a mechanism by which alterations in maternal glucose and insulin can affect the functioning uterus. “
Camara de Bem received the support of FAPESP through a postdoctoral fellowship for a project carried out in the Laboratory of Morphophysiology and Molecular Development under the supervision of Professor Flávio Vieira Meirelles, and a fellowship for a research practice abroad (BEPE ).
According to Camara de Bem, Brazil is a world leader in the production of bovine embryos, but nevertheless has a high rate of pregnancy loss. “A large proportion of our embryos are produced by in vitro fertilization. Oocytes are collected, matured, fertilized, cultured and transferred to synchronized receptors. However, 40% of pregnancies are lost in the third or fourth week. “, he said, recalling that a bovine pregnancy lasts about nine months, as in humans.
Reproductive success depends on several conditions. “Pregnancy is an interaction between the mother and the embryo that develops in the mother’s womb,” Camara de Bem said. “It involves cross-conversations between the cells of the embryo and those of the mother. This communication is influenced by multiple processes. Loss of pregnancy can occur when communication is not correct, when the embryo cannot signal its presence or the mother does not recognize the developing embryo. “
Stress from environmental or nutritional problems or even from the production process itself can lead to instability in maternal-embryonic communication and alter pregnancy, he continued. In the case of cattle, pregnancy in high-yield dairy cows is the main problem, as the initial postpartum period often involves metabolic stress due to a negative energy balance in the prey.
“Glucose, for example, is a basic substrate for cellular metabolism,” Camara de Bem said. “Cells need glucose to perform their functions. Dairy cows experience a metabolic challenge to produce milk. They consume a lot of energy because they need to maintain the body’s basic functions and all the functions involved in milk production. “Mother’s metabolism status significantly influences reproduction. Therefore, we focus on understanding the factors that cause metabolic stress in the environment that the embryo receives.”
Endometrium on a chip
Camem de Bem stressed that the study was conducted in collaboration with the group led by Niamh Forde, a professor at the University of Leeds School of Medicine and the last author of the article. “She’s researching maternal pregnancy recognition in cattle. I’m interested in researching the signals the embryo sends to the mother. We thought it would be a good collaboration and we had this idea of developing an ‘endometrium on a chip.’ “It could be used for multicellular culture, that is, growing more than one cell type from the endometrium,” he said.
The chip resembles a histology slide, except that it is divided into chambers, compartments in which scientists seeded two types of cells. The partitions are formed by a porous membrane that allows information to be exchanged between the two cell types grown in the different chambers, but does not allow the cell types to change position. The device can be considered a commercial chip adapted to simulate an endometrium.
“Epithelial cells were seeded in the upper chamber, stromal cells at the bottom, “said Camara de Bem.” Both types of cells are abundant in the endometrium. The upper chamber culture medium was enriched with factors produced and secreted by epithelial cells, which represent the endometrial secretoma. “
The chip allowed scientists to constantly infuse the cells with one culture medium. “We cultured the cells for three days, injecting medium all the time [one microliter per minute for 72 hours] “With three different concentrations of glucose or two different concentrations of insulin,” he said. “The nutrients were administered very slowly, in a flow that mimics the best physiology of the environment. This ensured that the cells were exposed to the same levels of glucose and insulin during the experiment.”
The method was innovative and had never been used before to mimic bovine endometrium. Conventional cell culture is too simple to simulate all endometrial conditions. “The endometrium is three-dimensional, with various types of cells and glands that produce factors and nutrients to sustain pregnancy,” Camara de Bem recalled. “In vitro embryo culture using the traditional method is static and involves a single cell type in an environment that does not reflect the richness of the animal organism. You can grow cells, transfer embryos to a receptor. and produce healthy animals, but we aim to recreate the process in a way that is as close as possible to physiological reality. ”
Bem’s camera noted that its partners at the University of Leeds are developing other types of chips for embryonic insertion. “The methodology opens up a lot of opportunities, and in the future we hope to be able to grow cells and embryos together to know exactly what happens when there are changes in the environment and in communication with stem cells. This is an opening for more applied research, ”he said.
The group’s work also offers a potential model for the study of pregnancy in mammals, including humans. “Except for non-human primates, mice are the main model for studying humans. Placenta formation in mice is the most similar to the process in humans. In contrast, unlike us, mice have many offspring. In cattle bovine placenta is very different from humans, but the gestational period is similar and cows also have only one offspring by pregnancy.There will never be an ideal model, due to differences between species, but this may be one more model, ”he said.
Tiago HC De Bem et al, Endometrium On-a-Chip reveals insulin and glucose induced alterations in transcriptome and proteomic secretoma, Endocrinology (2021). DOI: 10.1210 / endocr / bqab054
Citation: Beef Endometrium Imitating Chips Used in Study of Factors That May Endanger Pregnancy (2021, June 7) Retrieved June 7, 2021 at https://medicalxpress.com/news/2021-06-chip -mimicking-bovine-endometrium-factors.html
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