High-Dimensional Spatiotemporal Single-Cell and 3D Atlas of the Bone Marrow Microenvironment during Leukemic...

Area of Science:

• Hematology
• Immunology
• Cancer Biology
• Microscopy
• Single-cell analysis

Background:

• The bone marrow microenvironment (BMME) is critical for blood cell formation and immune function.
• Understanding cellular dynamics within the BMME during leukemia development is crucial but technically challenging.
• Spatiotemporal single-cell analysis provides a powerful approach to dissect these complex interactions.

Purpose of the Study:

• To create a detailed spatiotemporal single-cell atlas of the BMME during chronic myeloid leukemia (CML) progression.
• To identify cellular and spatial alterations in the BMME that support leukemogenesis.
• To investigate mechanisms of immune evasion and niche reprogramming by leukemia cells.

Main Methods:

• Highly multiplexed imaging (CODEX) and 3D microscopy were used to analyze mouse femurs at multiple time points post-leukemia induction.
• A 54-marker panel was employed to profile over 2 million cells, enabling identification of 41 distinct cell types.
• Unsupervised clustering and supervised annotation were used for cell type identification, complemented by spatial mapping.

Main Results:

• Leukemic progression led to myeloid and progenitor cell expansion, increased PD-L1 on leukemia cells, PD-1 upregulation on T cells, and loss of B cells, plasma cells, and bone cells.
• Advanced CML showed disorganized vasculature, impacting hematopoietic stem/progenitor cell niches and positioning.
• Spatial analysis revealed leukemia-specific neighborhoods with exhausted T cells and altered megakaryocyte morphology and function, observed also in CML patients.

Conclusions:

• Leukemic cells actively reprogram the BMME to facilitate their expansion and immune evasion.
• The study provides a comprehensive spatiotemporal atlas of BMME changes during CML.
• Understanding these niche alterations offers potential therapeutic targets for leukemia treatment.