Hematoids Created from Human Stem Cells Model Early Blood Development

Scientists at the University of Cambridge have created hematoids—three-dimensional, embryo-like structures derived from human stem cells—that replicate crucial stages of early blood development seen in human embryos. These hematoids are unique in their ability to self-organize and emulate the process through which blood stem cells, or hematopoietic stem cells, first arise during embryogenesis.

The development of hematoids begins with human pluripotent stem cells, which have the capacity to become any cell type in the body. Within the first two days of culture, these cells self-assemble into three germ layers—ectoderm, mesoderm, and endoderm—laying the foundation for all tissue and organ formation, including the blood system. This organization is a critical early event in human development and is faithfully recapitulated within the hematoids.

By day eight, the hematoids develop beating heart cells, demonstrating advanced organ-like features. Progressing further, by day thirteen, red patches indicating blood formation become visible. These blood cells arise without the addition of external protein factors, highlighting the intrinsic cellular environment that supports differentiation. Laboratory analysis showed that the blood stem cells produced within hematoids can differentiate into multiple types of blood cells, including specialized immune cells such as T cells.

The findings were published in Cell Reports. Jitesh Neupane, first author of the study, described the moment blood appeared in the cultures: “It was an exciting moment when the blood red color appeared in the dish—it was visible even to the naked eye.” He added, “Our new model mimics human fetal blood development in the lab. This sheds light on how blood cells naturally form during human embryogenesis, offering potential medical advances to screen drugs, study early blood and immune development, and model blood disorders like leukemia.” 

While hematoids replicate important features of early human embryonic development, they differ from natural embryos by lacking certain tissues, such as the yolk sac and placenta, and thus cannot develop into complete embryos. The structures instead provide a controlled model to study early blood formation, which occurs after the embryo implants and is normally inaccessible for direct observation. 

The use of human stem cells allows for potential personalized applications, as these cells can be derived from any cell in the human body. Professor Azim Surani, senior author of the paper, “This model offers a powerful new way to study blood development in the early human embryo... the ability to produce human blood cells in the lab marks a significant step towards future regenerative therapies.”