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Embryonic development of the human hematopoietic system.
1INSERM U506, Hôpital Paul Brousse, Villejuif, France. tavian@infobiogen.fr
The International Journal of Developmental Biology
|May 21, 2005
Summary
Human hematopoiesis begins in the yolk sac and embryo. Embryonic hematopoietic stem cells, emerging from vessel walls, are multipotent, initiating definitive hematopoiesis.
Area of Science:
- Developmental Biology
- Hematology
- Stem Cell Biology
Background:
- Human hematopoiesis initiates early in development.
- The precise origin of definitive hematopoietic stem cells is debated.
Purpose of the Study:
- To investigate the origin and hierarchy of early human blood-forming tissues.
- To understand the role of embryonic vessel walls in hematopoiesis.
Main Methods:
- Observational studies of human embryonic development.
- Analysis of hematopoietic stem cell emergence and differentiation.
Main Results:
- Hematopoietic stem cells emerge from embryonic vessel walls around day 27.
- Yolk sac progenitors are limited; embryonic progenitors are multipotent (myeloid, erythroid, lymphoid).
- This pathway precedes liver hematopoiesis and suggests a conserved vertebrate mechanism.
Conclusions:
- A novel hierarchy of human blood development is proposed.
- Definitive hematopoiesis originates from embryonic vessel walls, not solely the yolk sac.
- This finding supports a conserved, ancestral blood production route in vertebrates.