A placenta model is a scientific tool used to study the human placenta outside of the body. It represents a controlled environment that mimics various aspects of the placenta’s structure and function. These models allow researchers to observe and manipulate processes that would be impossible or unethical to study directly in pregnant individuals. By recreating the placental environment, scientists can gain insights into its complex biology and how it interacts with the maternal and fetal systems.
Why Placenta Models Are Essential
Studying the human placenta directly during pregnancy presents significant challenges due to ethical considerations and the organ’s inaccessibility. Despite its fundamental role in fetal development and maternal health, much about its function and dysfunction remains unknown.
Direct in vivo studies in humans, especially for drug testing or manipulating placental function in real-time, are often impossible due to concerns for the safety of the mother and fetus. The dynamic changes in placental structure throughout pregnancy also make in vivo investigation challenging. Therefore, placenta models provide a necessary alternative to overcome these limitations and advance scientific understanding.
Diverse Types of Placenta Models
Scientists employ various approaches to create placenta models, each offering unique advantages for studying different aspects of placental biology. These models range from simple cell cultures to complex bioengineered systems that replicate the organ’s intricate architecture.
In Vitro Models
Cell cultures are a foundational in vitro approach, often using trophoblast cells, the main placental cell type. These two-dimensional cultures allow for the study of basic cellular processes like hormone secretion and invasion.
Organoids represent a more advanced in vitro model, consisting of three-dimensional cell cultures that mimic placental structure and function, including villous structures. These trophoblast organoids provide a platform to study early placental development and cell differentiation.
Microfluidic systems, such as “placenta-on-a-chip” devices, recreate the dynamic microenvironment of the placenta. These devices involve culturing placental cells, such as trophoblasts and human umbilical vein endothelial cells, on opposite sides of a porous membrane. This mimics the maternal-fetal interface and allows for the study of blood flow and nutrient exchange.
Ex Vivo Models
Ex vivo models involve the use of human placentas shortly after birth, keeping them viable for research.
The dual perfusion system is a prominent ex vivo method, where a cotyledon (a functional unit) is cannulated on both maternal and fetal sides and connected to reservoirs. This setup allows researchers to study maternal-fetal transfer, hemodynamics, and vascular reactivity in the intact organ.
While technically complex, this model preserves the functional integrity of the placenta, offering insights into its physiology and pathology without risk to pregnancy.
Animal Models
Animal models, such as rodents, guinea pigs, sheep, and non-human primates, are utilized to study placental development and function.
Mice are often used due to their accessibility and the ability to create gene-knockout models, despite differences in placental structure and gestation length compared to humans.
Guinea pigs are considered a good alternative to other rodents because of similarities to human placentation.
However, significant interspecies differences in placental anatomy, metabolism, and transport mean that findings from animal models are approximations and may not fully translate to humans.
3D Bioprinting
An emerging technology, 3D bioprinting, involves printing biological tissue by layering living cells while preserving their function.
This technique has been used to create bioengineered placenta models that mimic the placenta’s complex cellular structure. These bioprinted models allow for the study of specific cellular behaviors, such as trophoblast migration. They can also be used to investigate conditions like preeclampsia.
How Placenta Models Advance Research
Placenta models are used to study the intricate processes of normal placental development and function. Researchers investigate how the placenta transports nutrients, such as glucose, amino acids, and fatty acids, from the mother to the fetus, often by examining the activity of specific transport proteins. The models also facilitate research into the placenta’s role in hormone production, which is crucial for maintaining pregnancy and supporting fetal growth.
These models are instrumental in investigating the causes and mechanisms of various pregnancy complications. For instance, they help scientists understand conditions like preeclampsia, which involves abnormal trophoblast migration and can lead to hypertension and other issues. Placenta models are also used to explore fetal growth restriction and gestational diabetes, examining how altered nutrient transport or placental changes contribute to these conditions. These models allow for the testing of new drugs during pregnancy, assessing their safety and efficacy without posing risks. They also help in understanding the impact of environmental factors and infections on placental health, observing how pathogens or toxins affect the placental barrier.
Looking Ahead: Innovations and Impact
The field of placenta model research continues to evolve, with advancements aiming to provide more accurate insights into placental biology. Organ-on-a-chip models are becoming increasingly complex, incorporating multiple cell types and dynamic flow conditions to better mimic the maternal-fetal interface. Personalized placenta models are also emerging, utilizing patient-specific cells to create models that reflect individual variations in placental function and disease susceptibility.
Artificial intelligence (AI) is another significant innovation, enabling automated analysis of placental images and pathology reports to identify abnormalities linked to conditions like infection and neonatal sepsis. These AI tools can potentially make placental examination more accessible by providing rapid assessments from simple photographs. These innovations collectively aim to enhance our understanding of placental biology, ultimately improving maternal and fetal health outcomes through earlier diagnosis, more targeted interventions, and safer therapies.