Animal free alternatives to the study of nutrition in early pregnancy

Why did we fund this project?

This award aims to further develop a 3D organoid model of the fallopian tube to replace the use of pregnant mice in early developmental studies.

A wide range of diseases such as cardiovascular disease and diabetes can affect conception and subsequently embryonic development through changes in gene expression. Understanding how these diseases cause changes in gene expression and the impacts of these on the health of the offspring is a key focus in developmental research. Experiments are typically performed in mice by exposing the animals to a challenge, such as a specific diet, and culling them during pregnancy. Embryos are extracted and the fallopian tubes assessed to determine how the challenge impacted developmental conditions. Professor Roger Sturmey and colleagues have developed an organoid model using human tissue that produces a fluid-filled sphere similar to that in the fallopian tube. The student, with Roger, will now build confidence in the organoid model by characterising how accurately the organoid replicates human tissue and demonstrate the model’s utility for understanding how disease can affect the cells and conditions within the fallopian tube.

The key events of conception are when the sperm and egg meet and form the embryo. This normally occurs inside the female body, in a structure called the oviduct, also called the Fallopian tubes. After fertilisation, the embryo spends about 5 days in the Fallopian tube. During this time, the embryo completes a remarkable series of processes, during which time it begins to express its own genes, make its own proteins and make choices about the which cells will form key parts of the fetus, placenta and ultimately the whole body. Importantly, we can now say with confidence that events during conception are uniquely sensitive to subtle disruption. Disruptions in the environment in which the embryo forms can lead to changes in the expression of key genes or proteins, leading to modest changes in the developmental programme. However, what initially seem to be subtle changes can have notable impact, because they can change development in ways that can affect the health of the offspring that arises from the embryo. Major diseases such as cardiovascular disease and diabetes have been linked to the conditions around conception. Crucially, the discoveries that have led us to this understanding have been usually carried out using mice and other small animals. In the case of mice, animals will be exposed to a challenge; for example a poor quality diet, and then mated to become pregnant. After about 3.5 days, the pregnant mice are culled and the embryos extracted to allow researchers to study how the conditions in the fallopian tube were modified as a result of the challenge and how this in turn affects the development of the embryos. Mice have been used because they are easy to house, produce lots of embryos and have a short generation interval. However, this use is not sustainable: 1) from a welfare perspective it is not justifiable to use large numbers of mice in this way,  and 2) from a scientific outlook, the physiology of mice differs significantly from humans. Moreover, maintaining colonies of mice for such work is expensive. It is therefore a responsibility for scientists to seek better models of the early reproductive environment.

We have advanced a new model of the Fallopian tube, which we call organoids. Organoids are small 3-dimensional structures in which cells self-assemble into an arrangement that resembles the organ under investigation. In our model, the cells of the Fallopian tube that are responsible for creating the environment for development can be collected from tissue removed from women undergoing hysterectomy. These cells, which are called epithelial cells, are placed into a controlled and specific panel of nutrients and growth factors, then embedded in a biological gel. After about 5 days, the cells create a fluid-filled sphere, similar to the space within the Fallopian tube. We have been able to extract the fluid from within these spheres and study the environment that the cells of the Fallopian tube create. We are confident that this environment is very close to what the cells would create if they were inside the body. Importantly, we have been able to grow embryos in this liquid, proving that the cells are doing the task that they would if they were still in the Fallopian tube. These exciting results suggests that we can use this model to explore how the cells of the Fallopian tube change their behaviour, altering the environment in which development occurs.

We now wish to train a new researcher of outstanding quality to demonstrate and validate our Fallopian tube model as a way to study how the environment of the Fallopian tube affects early development. This model is completely free of animal tissue, meaning that it is a more faithful representation of human reproduction. Crucially, this model can be maintained easily and inexpensively and lead to a significant reduction in the reliance of animals in the study of early human reproduction.