Deciphering transcriptome alterations in bone marrow immune cells at single-cell resolution under denosumab treatment

Area of Science:

• Immunology
• Bone Biology
• Pharmacology

Background:

• Denosumab (anti-RANKL antibody) inhibits bone resorption but may cause immune imbalances.
• Bone marrow is critical for immune cell development, making it a key site to study these effects.
• Understanding denosumab's impact on the bone marrow osteoimmune microenvironment is crucial.

Purpose of the Study:

• To evaluate alterations in the bone marrow osteoimmune microenvironment induced by denosumab treatment.
• To characterize cell-type-specific changes in bone marrow following anti-RANKL antibody administration.
• To identify potential mechanisms behind denosumab-induced immune modulation.

Main Methods:

• Adult female mice received denosumab (10 mg/kg) twice weekly for 4 weeks.
• Single-cell RNA sequencing (scRNA-seq) analyzed bone marrow cell populations.
• Flow cytometry and immunofluorescence validated observed cellular shifts.

Main Results:

• Denosumab treatment led to distinct bone marrow cell clusters, including expanded Mmp8high mNeu neutrophils.
• Increased proportions of neutrophils and B lymphocytes, with decreased T lymphocytes, were observed.
• Activated neutrophil extracellular trap (NET) formation and THBS1-CD36 mediated neutrophil-macrophage interactions were identified.

Conclusions:

• Denosumab significantly alters the bone marrow osteoimmune microenvironment, affecting immune cell composition.
• Mmp8high mNeu expansion and neutrophil-macrophage interactions are key findings requiring further study.
• These alterations highlight potential therapeutic targets for mitigating denosumab's immune-related adverse effects in osteoporosis.