Defining mesenchymal stem/stromal cell-induced myeloid-derived suppressor cells using single-cell transcriptomics.

Area of Science:

• Immunology
• Cell Biology
• Stem Cell Research

Background:

• Mesenchymal stem/stromal cells (MSCs) are known to modulate immune responses.
• Previous work showed MSCs alleviate ocular autoimmune inflammation by altering myeloid cell differentiation.
• The specific immune cell types and markers involved in MSC-mediated immunosuppression require further elucidation.

Purpose of the Study:

• To analyze the immune cell types generated by MSCs.
• To compare the transcriptional profiles of MSC-induced CD11b^midLy6C^mid cells with pro-inflammatory CD11b^hiLy6C^hi cells.
• To identify key markers for detecting and potentially enriching MSC-induced immunosuppressive cells.

Main Methods:

• Single-cell RNA sequencing was employed to analyze MSC-induced CD11b^midLy6C^mid cells and compare them with CD11b^hiLy6C^hi cells.
• Flow cytometry and functional assays were used to characterize cell populations and their effects on T cells.
• A mouse model of experimental autoimmune uveoretinitis was utilized for in vivo validation.

Main Results:

• MSC-induced CD11b^midLy6C^mid cells comprised seven distinct immune cell types, including myeloid-derived suppressor cells (MDSCs).
• These MDSCs exhibited high expression of Retnlg, Cxcl3, Cxcl2, Mmp8, Cd14, Csf1r, and Arg1.
• CSF-1R^hiCD11b^midLy6C^mid cells displayed monocyte morphology, produced interleukin-10, inhibited CD4⁺ T cell proliferation, and promoted Treg expansion, unlike CSF-1R^lo cells.
• Resistin-like molecule (RELM)-γ did not directly impact T cell proliferation or Treg expansion.

Conclusions:

• MSC-induced MDSCs possess a distinct transcriptional profile.
• CSF-1R serves as a crucial cell-surface marker for identifying and therapeutically enriching these immunosuppressive MDSCs.
• These findings offer insights into MSC-based immunomodulation strategies for autoimmune diseases.