The secretome of UC‐MSC reprogrammed to a glycolytic metabolism promotes Treg generation and naive CD4 T cells stability in PBMC from rheumatoid arthritis patients

Objective Rheumatoid arthritis (RA) is characterized by persistent inflammation and dysregulated T cell responses. Mesenchymal stromal cells (MSCs) have immunomodulatory properties, but their clinical efficacy remains variable. We investigated whether metabolic reprogramming of umbilical cord–derived MSCs (UC‐MSCs) toward glycolysis enhances their immunoregulatory function and the underlying mechanisms. Methods UC‐MSCs were reprogrammed toward glycolysis by pharmacologic inhibition of oxidative phosphorylation using oligomycin. Their immunomodulatory capacity was assessed in coculture with activated peripheral blood mononuclear cells (PBMCs) from 21 RA patients under direct‐contact and conditioned‐medium conditions. T cell proliferation, phenotype, and cell cycle were analyzed by flow cytometry. Anti‐inflammatory effects were evaluated in a delayed‐type hypersensitivity (DTH) murine model, and the contribution of the UC‐MSC secretome and its protein fraction was investigated. Results Glycolysis‐reprogrammed UC‐MSCs exhibited enhanced immunosuppressive activity compared with unmodified UC‐MSCs, suppressing proinflammatory T cell responses, promoting Treg expansion, and preserving CD4 + CD45RA + naïve T cells. These effects were associated with T cell cycle arrest in G0. Conditioned‐medium experiments showed that these effects were largely mediated by the MSC secretome, increasing Treg frequency from 16.5% to 30.2% and enriching the CD4 + CD45RA + naïve T‐cell compartment from 9.7% to 29.1%, with the protein fraction accounting for most of this immunomodulatory activity. In vivo, the >3 kDa protein‐enriched fraction attenuated DTH‐associated inflammation and promoted an anti‐inflammatory immune response. Conclusion Metabolic reprogramming of UC‐MSCs toward glycolysis enhances their immunomodulatory capacity through secretome‐dependent mechanisms, primarily mediated by proteins within the >3 kDa fraction, supporting metabolism‐based and cell‐free strategies for MSC‐based therapy in RA.