Erythroblast-derived lipid mediators program neutrophil development and function

Area of Science:

• Hematology
• Immunology
• Cell Biology

Background:

• Granulopoiesis, the production of neutrophils, is crucial for host defense but its regulation is not fully understood.
• Neutrophil effector functions require balanced regulation during their development in the bone marrow.

Purpose of the Study:

• To investigate the role of bone marrow-resident erythroblasts in regulating granulopoiesis and neutrophil function.
• To identify the mechanisms by which erythroblasts influence neutrophil development and effector responses.

Main Methods:

• Conditional erythroblast-specific depletion of 12/15-lipoxygenase (Alox15).
• Analysis of neutrophil phenotypes, including reactive oxygen species release, extracellular trap formation, and migration.
• Assessment of bacterial clearance and inflammatory responses in vivo.
• Reconstitution experiments with Resolvin D5 (RvD5n-3 DPA) and depletion of the SPM receptor Gpr101.

Main Results:

• Erythroblasts were identified as a key source of specialized pro-resolving mediators (SPMs).
• Depletion of Alox15 in erythroblasts reduced bone marrow SPM levels, leading to altered neutrophil phenotypes (increased ROS, NETs, migration).
• This resulted in peripheral neutropenia, impaired bacterial clearance, and exacerbated colitis, which were partially reversible by RvD5n-3 DPA.

Conclusions:

• Erythroblasts play a critical role in instructing granulopoiesis through SPM production, ensuring balanced neutrophil function.
• The macrophage niche may mediate SPM effects on granulopoiesis via the Gpr101 receptor.
• These findings reveal a novel mechanism for regulating neutrophil immunity originating from erythroblasts.