Preclinical ex vivo expansion of peripheral blood CD34+ selected cells from cancer patients mobilized with combination chemotherapy and granulocyte colony-stimulating factor

Design and Validation of an Automated Process for the Expansion of Peripheral Blood-Derived CD34+ Cells for Clinical Use After Myocardial Infarction

We previously demonstrated that intracardiac delivery of autologous peripheral blood‐derived CD34⁺ stem cells (SCs), mobilized by granulocyte‐colony stimulating factor (G‐CSF) and collected by leukapheresis after myocardial infarction, structurally and functionally repaired the damaged myocardial area. When used for cardiac indication, CD34⁺ cells are now considered as Advanced Therapy Medicinal Products (ATMPs). We have industrialized their production by developing an automated device for ex vivo CD34⁺‐SC expansion, starting from a whole blood (WB) sample. Blood samples were collected from healthy donors after G‐CSF mobilization. Manufacturing procedures included: (a) isolation of total nuclear cells, (b) CD34⁺ immunoselection, (c) expansion and cell culture recovery in the device, and (d) expanded CD34⁺ cell immunoselection and formulation. The assessment of CD34⁺ cell counts, viability, and immunophenotype and sterility tests were performed as quality tests. We established graft acceptance criteria and performed validation processes in three cell therapy centers. 59.4 × 10⁶ ± 36.8 × 10⁶ viable CD34⁺ cells were reproducibly generated as the final product from 220 ml WB containing 17.1 × 10⁶ ± 8.1 × 10⁶ viable CD34⁺ cells. CD34⁺ identity, genetic stability, and telomere length were consistent with those of basal CD34⁺ cells. Gram staining and mycoplasma and endotoxin analyses were negative in all cases. We confirmed the therapeutic efficacy of both CD34⁺‐cell categories in experimental acute myocardial infarct (AMI) in immunodeficient rats during preclinical studies. This reproducible, automated, and standardized expansion process produces high numbers of CD34⁺ cells corresponding to the approved ATMP and paves the way for a phase I/IIb study in AMI, which is currently recruiting patients. stem cells translational medicine2019;8:822&832

A stromal-free, serum-free system to expand ex vivo hematopoietic stem cells from mobilized peripheral blood of patients with hematologic malignancies and healthy donors

BACKGROUND AIMS

The number of hematopoietic stem cells (HSCs) is critical for transplantation. The ex vivo expansion of mobilized peripheral blood (MPB) HSCs is of clinical value for reconstitution to meet clinical need.

METHODS

This study proposed a simple, defined, stromal-free and serum-free culture system (SF-HSC medium) for clinical use, which is composed of Iscove's modified Dulbecco's medium, cytokine cocktails and serum substitutes. This study also characterized the cellular properties of expanded MPB CD133(+) HSCs from patients with hematologic malignancies and healthy donors by surface antigen, colony-forming cell, long-term culture-initiating cell, gene expression and in vivo engraftment assays.

RESULTS

The expanded fold values of CD45(+) white blood cells and CD34(+), CD133(+), CD34(+)CD38(-), CD133(+)CD38(-), CD34(+)CD133(+), colony-forming and long-term culture-initiating cells at the end of 7-day culture from CD133(+) MPB of hematologic malignancies were 9.4-fold, 5.9-fold, 4.0-fold, 35.8-fold, 21.9-fold, 3.8-fold, 11.8-fold and 6.7-fold, and values from healthy donor CD133(+) MPB were 20.7-fold, 14.5-fold, 8.5-fold, 83.8-fold, 37.3-fold, 6.2-fold, 19.1-fold and 14.6-fold. The high enrichment of CD38(-) cells, which were either CD34(+) or CD133(+), sustained the proliferation of early uncommitted HSCs. The expanded cells showed high levels of messenger RNA expression of HOBX4, ABCG2 and HTERT and had the in vivo ability to re-populate NOD/SCID mice.

CONCLUSIONS

Our results demonstrated that an initial, limited number of MPB CD133(+) HSCs could be expanded functionally in SF-HSC medium. We believe that this serum-free expansion technique can be employed in both basic research and clinical transplantation.