Interferon-Gamma Primed Human Clonal Mesenchymal Stromal Cell Sheets Exhibit Enhanced Immunosuppressive Function

Mesenchymal stromal cells (MSCs) represent a promising treatment for immune-related diseases due to their diverse immunomodulatory paracrine functions. However, progress of culture-expanded MSCs is hindered by inconsistent cell function, poor localization, and insufficient retention when administered as suspended cell injections, thus placing spatiotemporal dosing constraints on therapeutic functions. To address these limitations, we introduce the combination of in vitro interferon-gamma (IFN-gamma) priming, a key stimulator of MSC immunosuppressive potency, and thermoresponsive cultureware to harvest cultured MSCs as directly transplantable scaffold-free immunosuppressive cell sheets. Here, we demonstrate that MSC sheets produced with IFN-gamma priming upregulate expression of immunosuppressive factors indoleamine 2,3-dioxygenase (IDO-1), interleukin-10 (IL-10), programmed death ligand-1 (PD-L1), and prostaglandin E2 (PGE2) in both dose- and duration-dependent manners. In addition, IFN-gamma primed MSC sheets showed increased ability to inhibit T-cell proliferation via indirect and direct contact, specifically related to increased IDO-1 and PGE2 concentrations. Furthermore, this study's use of human clinical-grade single-cell-derived clonal bone marrow-derived MSCs, contributes to the future translatability and clinical relevancy of the produced sheets. Ultimately, these results present the combination of IFN-gamma priming and MSC sheets as a new strategy to improve MSC-mediated treatment of localized inflammatory diseases.