BACH1 orchestrates macrophage state transitions to coordinate regenerative inflammation

Area of Science:

• Immunology
• Molecular Biology
• Regenerative Medicine

Background:

• Efficient tissue regeneration hinges on coordinated inflammatory and regenerative processes, primarily driven by monocyte-derived macrophages.
• The intricate transcriptional and epigenomic mechanisms governing macrophage subtype specification and state transitions remain largely unknown.

Purpose of the Study:

• To identify critical regulators of monocyte-derived macrophage specification during skeletal muscle regeneration.
• To elucidate the role of the transcriptional repressor BACH1 in controlling macrophage fate and function.

Main Methods:

• Utilized a myeloid-specific BACH1 knockout mouse model.
• Performed single-cell RNA-sequencing (scRNA-seq) to profile macrophage populations.
• Analyzed transcriptional networks, including Nfkb1, Cebpb, and interferon signaling.

Main Results:

• BACH1 deficiency disrupted the temporal coordination of monocyte-to-macrophage differentiation, creating aberrant macrophage subsets with mixed inflammatory profiles.
• BACH1 loss altered core macrophage identity, sustaining inflammatory programs (e.g., Il1b upregulation) and hindering tissue remodeling.
• Immune alterations due to BACH1 deficiency compromised the regenerative paracrine landscape and impaired muscle stem cell differentiation.

Conclusions:

• BACH1 acts as a crucial cell-intrinsic regulator of macrophage specification in skeletal muscle regeneration.
• BACH1 integrates innate immune signaling with regenerative outcomes, influencing immune cell fate and tissue repair.
• Targeting BACH1 may offer therapeutic strategies for enhancing tissue repair processes.