In vitro assays for investigating the immunomodulatory properties of human mesenchymal stromal cells

TL;DR

This review evaluates in vitro assays used to study how human mesenchymal stromal cells modulate the immune system, aiming to improve research consistency and effectiveness.

Contribution

The paper proposes a standardized reporting checklist and multi-assay workflows to enhance transparency and comparability in MSC immunomodulation studies.

Findings

Common assays include characterization, proliferation, and polarization using flow cytometry and ELISA.

MSC priming and inclusion of immune cells like T cells and macrophages are frequently used strategies.

Variability in study design highlights the need for standardized reporting and combined assay approaches.

Abstract

Mesenchymal stromal cells (MSCs) are widely recognized for their immunomodulatory properties, which underpin their therapeutic potential in inflammatory and immune-mediated diseases. Although MSC therapies have consistently proven safe, clinical efficacy remains inconclusive, maybe due to incomplete understanding of MSC interactions with the immune environment. This review evaluates current trends in MSC immunomodulation research, based on 318 studies published since 2019 until medio 2024. The most frequently used assays included characterization, proliferation, and polarization, employing methods such as flow cytometry, enzyme-linked immunosorbent assays and colorimetric assays, and polymerase chain reaction. Many studies incorporated strategies for priming of MSCs or included immune cells, most commonly peripheral blood mononuclear cells, T cells, and macrophages. We identify key sources of variability and propose a minimum reporting checklist including MSC source, priming conditions, assay design, and immune cell characteristics. We further recommend implementation of multi-assay workflows combining phenotypic characterization with at least one functional assay. These measures may improve transparency, comparability across studies, and guide robust assay design.

The online version contains supplementary material available at 10.1186/s13287-026-04920-x.

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