Determination of critical quality attributes of mesenchymal stem cell by defining critical process parameters and efficacy of the product

Abstract

Background & Aim Today, despite thousands of MSC clinical trials conducted, we have not reached any conclusion on what are the Critical Quality Attribute's (CQA's) for MSC. MSC is generated from various mesodermal tissues and can differentiate to mesoderm lineage cells or secret immuno-modulatory cytokines after transplant, which makes the definition of CQA vague. To resolve this, we propose to specify the origin of the cell, the mechanism and scope of indication, and then consider to name the tissue specific-stem cell instead of ‘MSC’. Methods, Results & Conclusion We select immuno-suppression as an indication of tissue specific-stem cells to define the CQA easily. In this case, it will be defined mainly by two major events: having proliferative potential as a process parameter and expecting anti-inflammatory effect as an efficacy. Tissue stem cells cease to proliferate after certain number of mitosis, which relates to the “aging” process. “Aged” cells can be described by increased production of ROS, hyperpolarization of mitochondrial membrane, decreased Rho activity related to spindle shape of cell and low mobility, decrease serine uptake and increase kynurenine secretion that could relate to the loss of intracellular anti-oxidization mechanism. The above parameters can explain the status of exponential cell growth, non-senescence stage in a real time manner via in process monitoring, and can be used as critical process parameters (CPPs) to verify the CQA of the product. As process parameters may vary depending on the culture condition, it is essential to define an optimized culture condition first to address CPPs and CQA. CPPs are used as monitoring points during manufacturing (quality by design) and are well matched to automated mass culturing systems with sensors, not manual manufacturing that verifies the quality of final product only at the release stage (quality by testing) due to lack of information on material and process variability. Efficacy of the final product also constitutes a CQA of the product. We propose to set up a simple immuno-modulation assay such as measuring INF-g or IL-4 secreted from PBMC in Th1 or Th2 induction conditions in the presence of tissue stem cells to address immunosuppressant effect of the product, such an assay needs further refinement in a future study. We hope our approach to define CQA can contribute to find the answer of a decades-long question “what is MSC” and will pave the way to commercial manufacturing of cell products.