Evaluation of a cell-banking strategy for the production of clinical grade mesenchymal stromal cells from Wharton's jelly.

BACKGROUND AIMS: Umbilical cord (UC) has been proposed as a source of mesenchymal stromal cells (MSCs) for use in experimental cell-based therapies provided that its collection does not raise any risk to the donor, and, similar to bone marrow and lipoaspirates, UC-MSCs are multipotent cells with immuno-modulative properties. However, some of the challenges that make a broader use of UC-MSCs difficult include the limited availability of fresh starting tissue, time-consuming processing for successful derivation of cell lines, and the lack of information on identity, potency and genetic stability in extensively expanded UC-MSCs, which are necessary for banking relevant cell numbers for preclinical and clinical studies. METHODS: Factors affecting the success of the derivation process (namely, time elapsed from birth to processing and weight of fragments), and methods for establishing a two-tiered system of Master Cell Bank and Working Cell Bank of UC-MSCs were analyzed. RESULTS: Efficient derivation of UC-MSCs was achieved by using UC fragments larger than 7 g that were processed within 80 h from birth. Cells maintained their immunophenotype (being highly positive for CD105, CD90 and CD73 markers), multi-potentiality and immuno-modulative properties beyond 40 cumulative population doublings. No genetic abnormalities were found, as determined by G-banding karyotype, human telomerase reverse transcriptase activity was undetectable and no toxicity was observed in vivo after intravenous administration of UC-MSCs in athymic rats. DISCUSSION: This works demonstrates the feasibility of the derivation and large-scale expansion of UC-MSCs from small and relatively old fragments of UC typically discarded from public cord blood banking programs.

Clinical-scale expansion of CD34+ cord blood cells amplifies committed progenitors and rapid scid repopulation cells.

Umbilical cord blood (UCB) transplantation is associated with long periods of aplastic anaemia. This undesirable situation is due to the low cell dose available per unit of UCB and the immaturity of its progenitors. To overcome this, we present a cell culture strategy aimed at the expansion of the CD34+ population and the generation of granulocyte lineage-committed progenitors. Two culture products were produced after either 6 or 14days of in vitro expansion, and their characteristics compared to non-expanded UCB CD34+ controls in terms of phenotype, colony-forming activity and multilineage repopulation potential in NOD-scid IL2Rγnull mice. Both expanded cell products maintained rapid SCID repopulation activity similar to the non-expanded control, but 14-day cultured cells showed impaired long term SCID repopulation activity. The process was successfully scaled up to clinically relevant doses of 89×106 CD34+ cells committed to the granulocytic lineage and 3.9×109 neutrophil precursors in different maturation stages. Cell yields and biological properties presented by the cell product obtained after 14days in culture were superior and therefore this is proposed as the preferred production setup in a new type of dual transplant strategy to reduce aplastic periods, producing a transient repopulation before the definitive engraftment of the non-cultured UCB unit. Importantly, human telomerase reverse transcriptase activity was undetectable, c-myc expression levels were low and no genetic abnormalities were found, as determined by G-banding karyotype, further confirming the safety of the expanded product.