Donor Pooling as an Effective Method to Increase MSC EV Production Without Compromising Therapeutic Potential.

Mesenchymal stromal cell extracellular vesicles (MSC EVs) hold great therapeutic potential. Their immunomodulatory abilities make them suitable candidates to treat autoimmune diseases, such as rheumatoid arthritis. However, MSC EV production must be reproducibly scaled to meet the demand of research and therapeutics. To achieve this, four human umbilical cord MSC (UC-MSC) donors were pooled, a method known to generate a large cell source, that averages heterogeneous cell attributes. Upon generating MSC EV enrichments, donor pooling proved advantageous by increasing EV yield, both by increasing particle number and the presence of EV defining characteristics. Protein analysis suggests this could be due to an upregulation of protein transport mechanisms but requires further work to confirm. When applied to an inflammatory model of arthritis, pooled UC-MSC EV enrichments surpassed their parental cells and single donor UC-MSC EV enrichments, in alleviating arthritic pathophysiology, albeit the particle input was doubled since this was normalised by cell number. Therefore, we propose donor pooling as a simple and effective method to generate MSC EV enrichments, with potential to increase EV production without compromising therapeutic efficacy.