CD317-Positive Immune Stromal Cells in Human "Mesenchymal Stem Cell" Populations

Area of Science:

• Immunology
• Cell Biology
• Regenerative Medicine

Background:

• Heterogeneity in bone marrow mesenchymal stromal cells (MSCs) complicates their biological understanding and clinical applications.
• A specific MSC subtype expressing CD317 (CD317^pos) exhibits a constitutive interferon signature, potentially linked to human diseases.

Purpose of the Study:

• To characterize the functional differences between CD317-positive (CD317^pos) and CD317-negative (CD317^neg) MSCs.
• To investigate the role of these MSC subtypes in inflammatory responses and tissue regeneration.

Main Methods:

• Analysis of MSC subtypes based on CD317 expression.
• Assessment of MSC effects on skin explants in an inflammation model.
• Evaluation of MSCs' impact on human T cell proliferation and polarization in vitro.
• In vivo studies using a peritonitis model and MSC-loaded scaffolds in mice.

Main Results:

• CD317^pos MSCs induced tissue damage in skin explants, while CD317^neg MSCs did not.
• Only CD317^neg MSCs suppressed T cell proliferation; CD317^pos MSCs promoted pro-inflammatory Th1 cell polarization.
• Both MSC subtypes reduced leukocyte recruitment in vivo, but only CD317^neg MSCs suppressed macrophage numbers.
• CD317^neg MSCs promoted tissue generation and vascularization in scaffolds, unlike CD317^pos MSCs.

Conclusions:

• The study identifies CD317^pos MSCs as a distinct immune-related stromal cell population.
• CD317^pos MSCs contribute to pathological inflammation and tissue damage, contrasting with the regenerative potential of CD317^neg MSCs.
• Distinguishing MSC subtypes is crucial for understanding their physiological roles and optimizing clinical therapeutic outcomes.