Scientists from the Terumo Research Institute (TRI) recently achieved a noteworthy first in cell expansion. With a monoculture protocol that used a hollow-fiber bioreactor and a novel cytokine coating to create a bone marrow-like niche, they reached a clinically relevant number of undifferentiated CD34+ cells from a low seeding density with minimal lymphocyte residual.
"It's the first time that we've seen a manufacturing process take a seed of 2 million cells into a clinically relevant dose range using this novel cocktail of soluble and immobilized factors in monoculture," said lead author Mark Jones, Laboratory Scientist at Terumo Blood and Cell Technologies. "The protocol has the potential to help to move cell therapies from the research stage into manufacturing." Moreover, this perfusion CD34+ cell seeding approach has the potential to expand the range of cord blood source units with 2 million cells and above.
The study, published in Stem Cell Reports and presented at the American Society of Gene & Cell Therapy 2023 annual meeting, shows the promise of this protocol to simplify the expansion of cord blood-derived progenitor cells, while improving the overall efficiency for cell therapy developers and manufacturers.
To meet the need for CD34+ cells in suitable quantities, the TRI initially developed a successful protocol to coculture them with mesenchymal stem cells (MSCs) on the Quantum® Cell Expansion System. The next goal was to reduce complexity, and therefore time and cost, with a monoculture protocol. That meant coating the hollow-fiber membrane of the Quantum bioreactor with a novel cytokine cocktail of soluble and immobilized factors that included fibronectin-stromal-cell-derived factor-1 (SDF-1), a signaling molecule that helps CD34+ cells remain in an undifferentiated state as they expand in the bone marrow.
That coating allowed the monoculture to mimic the successful coculture by using MSCs, which express SDF-1. In the monoculture study, a seed of 2 million CB-derived CD34+ cells resulted in 100 million cells with 95.5% viability after 8 days of expansion, and the mean frequency of the CD45+CD34+ immunophenotype was 54.3%.
Jones added that CD34+ expansion was initially developed as a method to reconstitute the immune system, and it continues to be used in that way, but an increasing number of applications include differentiation into chimeric antigen receptor (CAR) T cells, NK cells, and more.
Dalip Sethi, Scientific Affairs Director at Terumo Blood and Cell Technologies, noted, "The perfusion-based hollow-fiber technology enabled the monoculture protocol for the expansion of cord blood-derived CD34 cells. It is exciting to think about the potential applications of this protocol. Our Quantum Flex automated cell expansion system allows users to customize the protocol to their specific needs. In addition, it can support expansion of various adherent and suspension cells. The system can also be used for exosome and viral vector production."
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