Proinflammatory signaling regulates hematopoietic stem cell emergence

Area of Science:

• Developmental biology
• Immunology
• Stem cell biology

Background:

• Hematopoietic stem cells (HSCs) are essential for lifelong blood and immune cell production.
• HSCs originate from hemogenic endothelium during a specific embryonic window, a process not yet replicated in vitro.
• The precise signaling cues required for in vitro HSC generation remain incompletely understood.

Purpose of the Study:

• To elucidate the signaling pathways and cellular interactions involved in embryonic HSC generation.
• To identify the specific molecular triggers necessary for replicating HSC development in vitro.
• To investigate the role of inflammatory signaling in establishing HSC fate.

Main Methods:

• Utilized in vitro models to study HSC generation from pluripotent precursors.
• Investigated the function of Tumor Necrosis Factor Receptor 2 (TNFR2) and its ligand TNFα.
• Analyzed the activation of Notch and Nuclear Factor-kappa B (NF-κB) signaling pathways.
• Identified the cellular source of TNFα during HSC development.

Main Results:

• TNFR2 activation by TNFα is essential for establishing HSC fate.
• Notch and NF-κB signaling pathways are activated by TNFα to promote HSC generation.
• Primitive neutrophils were identified as the primary source of TNFα.
• Demonstrated that pro-inflammatory signaling, independent of infection, drives HSC generation.

Conclusions:

• Inflammatory signaling is a critical, previously underappreciated, component of embryonic HSC generation.
• The interplay between innate immunity (neutrophils) and developmental signaling (TNFR2, Notch, NF-κB) is key to establishing the hematopoietic system.
• These findings provide a foundation for in vitro replication of HSC development, with implications for regenerative medicine.