Interferon Gamma Mediates Hematopoietic Stem Cell Activation and Niche Relocalization through BST2

Area of Science:

• Immunology
• Stem Cell Biology
• Hematopoiesis

Background:

• Chronic infection triggers inflammation, with interferon gamma (IFNγ) impairing hematopoietic stem cells (HSCs).
• IFNγ disrupts HSC quiescence and promotes differentiation, but the underlying mechanism remains unclear.
• The HSC niche, particularly interactions with CXCL12-abundant reticular (CAR) cells, is crucial for stem cell regulation.

Purpose of the Study:

• To elucidate the mechanism by which IFNγ hinders HSC quiescence.
• To identify key molecules involved in IFNγ-mediated HSC activation and relocation within the bone marrow niche.
• To investigate the role of BST2 in IFNγ-induced HSC responses.

Main Methods:

• Intravital 3-dimensional microscopy to observe HSC-niche interactions.
• Analysis of BST2 expression in HSCs following IFNγ stimulation.
• Assessment of HSC quiescence and depletion in wild-type and BST2-deficient mice during chronic infection.
• Evaluation of E-selectin binding and bone marrow homing.

Main Results:

• IFNγ disrupts close interactions between HSCs and CAR cells in the HSC niche.
• IFNγ stimulation upregulates BST2 on HSCs, which is essential for IFNγ-dependent HSC relocalization and activation.
• BST2 mediates increased E-selectin binding and bone marrow homing of HSCs upon IFNγ stimulation.
• HSCs lacking BST2 exhibit enhanced quiescence and resistance to depletion during chronic infection compared to wild-type HSCs.

Conclusions:

• This study identifies BST2 as a critical regulator of HSC quiescence and activation.
• BST2 mediates IFNγ-induced disruption of HSC-niche interactions, leading to HSC activation and relocation.
• BST2 represents a key molecular player in the inflammatory damage to HSCs during chronic infection, impacting stem cell pool maintenance.