Umbilical cord blood stem cells (UCB-SCs) have been used in a variety of clinical trials and treatments. Their use in treatment bone marrow-based conditions is very well-known, but they have also been used in other experimental treatments as well.
Treatments with UCB-SCs suffer from inconsistent results that stem from a variable number of viable cells in UCB-SC samples. Establishing high numbers of viable cells in UCB-SC samples is not easy, and there is a great interest in being able to grow UCB-SCs in culture and expand them. However, even though UCB-SCs can be grown in culture, the effects of culturing UCB-SCs is presently unclear.
To address this question in a rigorous fashion, Miguel Alaminos at the University of Granada and his colleagues grew UCB-SCs in culture and analyzed cell viability and gene expression at every passage.
What they discovered was astounding. When UCB-SCs were passaged two or three times, the cells showed signs of cells death, and gene expression studies revealed that many of the cells expressed genes associated with programmed cell death. Cells passaged eight, nine, or ten times also showed extensive cell death. However, cells passaged five or six times showed the highest viability.
This suggests that different studied have used cells that were grown for different periods of time and probably had different viabilities. This explains why UCB-SCs have performed so variably in experiments and clinical trials. This suggests that therapies that utilize UCB-SCs should use them after they are passaged for the fifth or sixth time in order to ensue the highest levels of viability.