Development of characterisation and quality potency assays for human mesenchymal stem cells

Regenerative medicine and cell therapies hold great potential to treat a variety of medical conditions. Product characterisation of these therapies is particularly difficult as they pose regulatory challenges due to donor heterogeneity and the lack of standardised lot release tests that can reliably predict in vivo function. Human mesenchymal stem cells (hMSCs), also called multipotent stem cells or mesenchymal stromal cells, are a viable option in cell therapies due to their immunosuppressive and pro-angiogenic functions. Currently there are no standardised methods or potency assays to quantify these properties. To address this, five individual hMSCs lines from different donors were created and characterised based upon growth rate, differentiation capability and extracellular surface protein expression. A novel multiparameter flow cytometry method to characterise the cells based upon extracellular surface markers was developed that supports high-throughput and high-content analyses. Three candidate lines were taken forward and assessed in multiple in vitro bioassays that examined the hMSC immunosuppressive response to a defined inflammatory environment, effect on T-cell proliferation, and effect on a mixed lymphocyte population. Next, the angiogenic properties were assessed using human umbilical vein endothelial cells (HUVECs) tube formation as a model for cardiac regeneration. This involved utilising automated time lapse microscopy techniques coupled with image analysis software to quantify endothelial to tube formation. Further analysis of the hMSC secretome revealed differences in the levels of pro-angiogenic cytokines such as vascular endothelial growth factor, hepatocyte growth factor and IL-8. Significant differences in angiogenic potency were found between the hMSC lines. This thesis highlights the need to develop specific assays that reflect the intended clinical action. Taken together, these quantitative approaches provide valuable tools to measure hMSC quality and potency, and supports continued efforts to improve characterisation strategies for cellular therapies.