Development of endometrial/myometrial organoids to study disorders of pregnancy and parturition

Approximately 15% of all clinically recognised pregnancies end in miscarriage, mostly before 12 weeks of gestation. Apart from physical trauma (pain, bleeding, and infection), each miscarriage compounds the risk of significant psychological morbidity (depression, post-traumatic stress disorder, and suicide) and obstetrical complications in a future ongoing pregnancy, foremost preterm birth. Globally, preterm birth, defined as delivery of a baby before 37 completed weeks' gestation, affects 5-18% of live births, although the incidence varies dependent on ethnicity and socioeconomic factors. Preterm birth is the single most important cause of neonatal morbidity and mortality, especially in "very preterm" infants (those born before 32 weeks' gestation). To date, there are no effective preventative treatments for either miscarriage or preterm birth. Clinical management is largely confined to progesterone, a hormone discovered > 90 years ago, but its effectiveness remains contentious. These important reproductive disorders, together with others, remain unresolved largely as a consequence of scientific animal models failing to accurately represent human specific traits. Although animal models, such as mice, are widely used, they do not approximate human pregnancy, nor have they yielded sufficient mechanistic insights to impact demonstrably on clinical practice. Most model organisms such as the mouse, rat and guinea pig, have fundamentally different reproductive strategies when compared to humans, as well as anatomically distinct uteri. Primates, and more specifically Old-World monkeys, are an exception but these models are expensive, ethically contentious, and require specialised facilities. To address the knowledge gap in human uterine diseases, we recently established endometrial assembloids, consisting of lab assembled cultures that contain the main cells of the lining of the uterus.These assembloids can be manipulated to mimic different pathological states associated with reproductive failure, exemplified by co-culturing with human research embryos. This model does not yet contain the main muscle of the uterus the myometrium. Human embryo implantation is deep and involves disruption of the inner myometrial layer, also termed the junctional zone (JZ). Studies have demonstrated that the JZ is important for implantation and fertility and that it is a crucial component of the uterine response to pregnancy. The aim of this proposal is to improve our assembloid model further by the addition of this muscle layer to create a new model of human pregnancy. In doing so we should be able to replace animal experiments by offering a scientifically superior model when considering studies in early human pregnancy and associated diseases. We will also create a new, annual virtual conference, for scientific groups around the world currently attempting to replace animal experiments by using organoid technologies. We will exchange valuable state-of-the-art methods as this productive area of research makes advances and document these methods in a form that can be readily used by researchers interested in adopting these techniques. We already have agreement from over ten of the worlds leading groups to participate in this initiative and we will endeavour to recruit further groups as the conferences become more established.

Approximately 15% of all clinically recognised pregnancies end in miscarriage, mostly before 12 weeks of gestation. Apart from physical trauma (pain, bleeding, and infection), each miscarriage compounds the risk of significant psychological morbidity (depression, post-traumatic stress disorder, and suicide) and obstetrical complications in a future ongoing pregnancy, foremost preterm birth. Globally, preterm birth, affects 5-18% of live births, although the incidence varies dependent on ethnicity and socioeconomic factors. Preterm birth is the single most important cause of neonatal morbidity and mortality, especially in "very preterm" infants (those born before 32 weeks' gestation). The main roadblock in developing effective strategies for miscarriage and preterm birth prevention is the lack of suitable model systems that recapitulate human-specific reproductive traits. Although animal models, which can vary from mild to severe are widely used, they do not approximate human pregnancy, and have not yielded effective treatments. We have had success in pioneering an assembloid model of the human endometrium that recapitulates the peri implantation endometrium. However, implantation in the human is deeply interstitial, and involves disruption of the inner myometrial layer, also termed the junctional zone (JZ). Successful placentation depends on trophoblast invasion of the JZ, which forms the placental bed. Importantly, a spectrum of obstetrical disorders, including preterm birth, is caused by failure of invading trophoblast to sufficiently remodel the JZ and its vessels. This project involves creating a JZ by the addition of myometrial cells to our lab grown assembloids, creating a superior model to parse the mechanisms of prevalent pregnancy disorders. Importantly, if validated, a whole series of animal experiments in species including mice, rats, guinea pigs and non-human primates could be replaced when undertaking studies of human pregnancy and implantation.