Human mesenchymal stromal cells (MSC) are multipotent adult progenitor cells of perivascular origin identified in nearly all tissues including the bone marrow, adipose tissue, and cord blood. MSC have emerged as attractive candidates for cell therapy promoting an immunosuppressive and immunomodulatory environment via multifactorial mechanisms. Production of human multipotent MSC as a form of cell therapy require a GMP-compliant manufacturing process as well as a quality control recognized and accepted by authorities.

MSCs were generated from bone marrow from healthy donors. GMP-compliant manufacturing process took place in a Quantum® cell expansion system, a functionally closed and automated Bioreactor-System. Analysis of purity of MSC cell population was performed by detection of MSC positive markers and absence of cellular impurities using antibody staining followed by flow cytometry. Detection of absence of ACE2 (SARS-CoV2 entry receptor) expression was executed by flow cytometry using antibody staining of MSCs. Assessment of immunosuppressive potential of MSCs on proliferation of stimulated T-cells was done by using CFSE-Assay. Fibroblastoid colony forming ability of the produced MSCs were examined by using CFU-f assays.

Characterization of produced MSCs generated from expanded human bone marrow showed a purity greater than 95%. MSCs do not show ACE2 receptor expression compared to control cell line. Using CFSE assay significant inhibition of the proliferation of stimulated T-cells greater than 60% could be detected, regarding co-cultivated PBMCs with MSCs compared to the control, stimulated PBMCs in absence of MSCs. Furthermore MSC-derived fibroblastoid colony forming units were verified.

The established methods for the quality control of MSC were appropriate. The characterization of the cell surface expression proved the purity of the final product. Additionally, the absence of ACE2 receptor on MSC could be detected in comparison to ACE2 receptor-carrying cell line. The biological activity of MSC could be demonstrated using the CFSE assay. The results of CFU-f assay showed the proliferation and differentiation ability of the manufactured MSCs.

I declare there is no conflict of interest