The use of stem cells in regenerative medicine is continuing to gather pace with a large number of new clinical trials starting every year with cell therapy at their heart. The generation and expansion of cells for use in these models is an important factor that is often overlooked, but is critical. There is ample evidence that cells grown in different culture conditions have different potency and therefore, consideration of the culture conditions is important. To this end, many consider using 3D methods of cell growth to be a sensible step-forward in this process. The generation of cell spheroids has been suggested by a number of authors as a method for the expansion of stem cells for use in therapeutic contexts.
In this paper, the authors describe the effect that cluster size has on gene expression, both in conditions of normoxia and hypoxia. A number of important differences (and important non-differences!) are identified using the genes BMP, Map-2 and Nestin. In addition, the authors have added additional information to their study by using cells deficient for HIF-1a, a common hypoxia response gene. The authors show that cluster size impacts on the expression of genes within the cell cluster, particularly in the case of large clusters, when compared to cells grown in 2D culture.
This study has important observations and, as a whole, should go some way to highlighting the importance that researchers should place on knowing the impact of their culture methods on the phenotype of the cells that come out of the other end.