Ectopic FOXP3 Expression Preserves Primitive Features Of Human Hematopoietic Stem Cells While Impairing Functional T...

Area of Science:

• Immunology
• Hematology
• Gene Therapy

Background:

• FOXP3 is crucial for regulatory T cell function and immune tolerance.
• Mutations in FOXP3 cause IPEX autoimmune syndrome.
• FOXP3 acts as a cell-cycle inhibitor and onco-suppressor.

Purpose of the Study:

• Investigate ectopic FOXP3 expression's effect on HSC differentiation.
• Assess FOXP3-expressing HSCs as a potential gene therapy for IPEX.
• Explore FOXP3's role in HSC biology and clinical applications.

Main Methods:

• Cultured FOXP3-expressing HSCs in vitro (liquid and OP9-ΔL1 co-cultures).
• Transplanted FOXP3-expressing HSCs into immunodeficient mice.
• Assessed HSC engraftment, repopulating ability (extreme limiting dilution assay), and gene expression.
• Analyzed peripheral T cell development and function in humanized mice.

Main Results:

• FOXP3-expressing HSCs exhibited reduced proliferation and increased primitive marker maintenance in vitro.
• Transplanted FOXP3-expressing HSCs showed significantly enhanced engraftment and repopulating ability.
• FOXP3-expressing HSCs displayed increased expression of stemness-related genes.
• Peripheral T cells in FOXP3-humanized mice were reduced in number and hyporesponsive.

Conclusions:

• Ectopic FOXP3 expression profoundly impacts HSC biology, enhancing stemness and engraftment.
• Reduced T cell function in FOXP3-humanized mice indicates potential therapeutic limitations.
• Endogenous FOXP3 regulation is essential for successful HSC-based gene therapy for IPEX syndrome.