Introduction: A leap in modeling early human development
University of Cambridge scientists have created three-dimensional, embryo‑like structures from human stem cells that self‑organize and mimic aspects of very early human development. Named hematoids, these models reproduce the formation of blood stem cells and beating heart cells in a lab setting, offering a window into the processes that shape our first weeks of life.
What are hematoids and why do they matter?
Hematoids are self‑organizing, stem cell–based structures designed to emulate certain stages of embryogenesis. While they resemble embryos in their organization, they lack essential embryonic tissues and supporting structures such as the yolk sac and placenta, so they cannot develop into a fetus. Yet they recapitulate a critical portion of development—the formation of blood stem cells (hematopoietic stem cells) and early cardiovascular cells—within the first two weeks of lab culture.
How the model mirrors early blood formation
In the study, researchers observed the hematoids progressing through three germ layers by day two, a foundational step in body plan formation. By day eight, beating heart cells emerged, and by day thirteen, red and white blood cell precursors formed within the structures. Importantly, the team demonstrated that hematopoietic stem cells within the hematoids could differentiate into a range of blood cell types, including specialized immune cells such as T cells.
Why this work stands apart
Traditional lab methods to generate blood stem cells in vitro often rely on supplying external growth factors and proteins. The Cambridge approach pushes the formation of blood cells to occur in a way that resembles the embryo’s own developmental cues, driven by the intrinsic properties of the cells and their microenvironment. This self‑organizing strategy is a key advance, as it reduces the need for a cocktail of added signals and more closely mirrors natural embryogenesis.
Potential applications: medicine, research, and ethics
The hematoid model offers multiple promising avenues. It provides a platform to study early blood and immune development, screen drugs for impacts on hematopoiesis, and model blood disorders such as leukemia. They also hold potential for generating long‑lasting blood stem cells that could be compatible with a patient’s own tissue, advancing personalized regenerative therapies.
Researchers emphasize that this is an early stage of a complex field. The hematoids, while informative, cannot replace studies on real embryos and are governed by strict ethical and regulatory frameworks. Ethics approvals, peer review, and responsible oversight guide this line of inquiry, reflecting the scientific community’s commitment to safety and transparency.
What the scientists say
Dr. Jitesh Neupane, first author from the Gurdon Institute, highlighted the practical and conceptual significance of the work, noting the visible, red‑coloured blood cells appearing in the dish as a milestone. Senior author Professor Azim Surani described the model as a powerful tool for studying early blood development and a potential stepping stone toward regenerative therapies using a patient’s own cells. Co‑author Dr. Geraldine Jowett pointed to the hematoids’ ability to capture the second wave of hematopoiesis, opening paths to model healthy and cancerous blood development.
Looking ahead
As the field advances, researchers aim to refine the hematoid system to more precisely model later stages of blood and immune system development, while ensuring ethical compliance and safety. The Cambridge team has also patented their approach through Cambridge Enterprise, reflecting a commitment to translating this knowledge into real-world benefits while maintaining robust oversight.
