Optimizing an immunomodulatory potency assay for Mesenchymal Stromal Cell

Area of Science:

• Cellular immunology
• Regenerative medicine
• Biotechnology

Background:

• Mesenchymal Stromal Cells (MSC) show therapeutic promise, but variations in potency due to production methods and tissue origin necessitate standardized assays.
• Existing methodologies for assessing MSC immunomodulatory potential vary significantly, hindering reliable comparisons between cell products.

Purpose of the Study:

• To establish and optimize a flow cytometry-based assay for quantifying the immunomodulatory potency of Adipose tissue-derived Stromal Cells (ASC).
• To evaluate different mitogens and donor combinations for maximizing lymphocyte proliferation and ASC-mediated inhibition for robust assay development.

Main Methods:

• Utilized flow cytometry to analyze lymphocyte proliferation inhibition by ASC using cryopreserved peripheral blood mononuclear cells.
• Evaluated technical aspects of fluorescent staining and cryopreservation for optimal results.
• Tested specific (anti-CD3/CD28) and unspecific mitogens (PHA, Concanavalin A, Pokeweed mitogen) and multi-donor mixed lymphocyte reactions.

Main Results:

• Antibody-mediated CD3/CD28 stimulation and phytohemagglutinin (PHA) effectively induced lymphocyte proliferation, which was significantly inhibited by ASC.
• Phytohemagglutinin (PHA) emerged as the most suitable mitogen among those tested.
• Combining 4 or more donors in mixed lymphocyte reactions maximized proliferation, enabling efficient suppression by ASC.

Conclusions:

• Optimized flow cytometry assays using cryopreserved cells and specific mitogens like PHA provide a robust method for assessing MSC immunomodulatory potency.
• Standardized functional metrics are crucial for comparing MSC therapeutic products and advancing their clinical application.
• The detailed methodological framework aids others in establishing reliable potency assays for MSC-based therapies.