Abstract
BackgroundMesenchymal stem cells (MSCs) have entered the clinic as an Advanced Therapy Medicinal Product and are currently evaluated in a wide range of studies for tissue regeneration or in autoimmune disorders. Various efforts have been made to standardize and optimize expansion and manufacturing processes, but until now reliable potency assays for the final MSC product are lacking. Because recent findings suggest superior therapeutic efficacy of freshly administered MSCs in comparison with frozen cells, we sought to correlate the T-cell suppressive capacity of MSCs with their metabolic activity.MethodsHuman MSCs were obtained from patients’ bone fragments and were employed in coculture with peripheral blood mononuclear cells (PBMCs) in an allogeneic T-cell proliferation assay to measure immunosuppressive function. Metabolic activity of MSCs was measured in real time in terms of aerobic glycolysis quantified by the extracellular acidification rate and mitochondrial respiration quantified by the oxygen consumption rate.ResultsWe show that MSC-induced suppression of T-cell proliferation was highly dependent on individual healthy donors’ lymphocytes. Moreover, coculture with PBMCs increased the glycolytic and respiratory activity of MSCs considerably in a PBMC donor-dependent manner. The twofold to threefold enhancement of cell metabolism was accompanied by higher T-cell suppressive capacities of MSCs. The cryoprotectant dimethyl sulfoxide decreased metabolic and immunosuppressive performances of MSCs while valproic acid (VPA) increased their glycolytic, respiratory and T-cell suppressive capacity.ConclusionsFunctional fitness of MSCs can be determined by measuring metabolic activity and can be enhanced by exposure to VPA. Pretesting the increment of metabolic activity upon interaction of donor MSCs with patient T-cells provides a rational approach for an individualized potency assay prior to MSC therapy.
Highlights
Mesenchymal stem cells (MSCs) have entered the clinic as an Advanced Therapy Medicinal Product and are currently evaluated in a wide range of studies for tissue regeneration or in autoimmune disorders
Variation of MSC-induced T-cell suppression of lymphocytes from healthy individuals In order to determine the capability of MSCs to suppress the proliferation of CD3/CD28 antibody-stimulated Tcells, every MSC batch was tested in a coculture assay with peripheral blood mononuclear cell (PBMC) from three different healthy donors in parallel
Broad testing of 29 MSC and 65 PBMC batches revealed that immunosuppression was highly variable between different PBMC as well as MSC donor samples
Summary
Mesenchymal stem cells (MSCs) have entered the clinic as an Advanced Therapy Medicinal Product and are currently evaluated in a wide range of studies for tissue regeneration or in autoimmune disorders. Because recent findings suggest superior therapeutic efficacy of freshly administered MSCs in comparison with frozen cells, we sought to correlate the T-cell suppressive capacity of MSCs with their metabolic activity Because of their high ex-vivo expansion potential and their immunomodulatory capacity, the therapeutic benefits of mesenchymal stem cells (MSCs) are currently assessed in numerous clinical trials [1, 2]. While most studies on MSCs as an immunosuppressive cellular therapy product raised new hope for treatment of otherwise refractory patients [5, 8], outcomes of other studies were below expectations [9, 10] These differences could be explained by the highly varying manufacturing protocols employed for MSC expansion in different studies. An in-vitro potency assay that reliably determines the immunomodulatory capabilities of MSCs is still lacking [15]
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