The effect of mild agitation on in vitro erythroid development.

The cultivation of erythroid cells at large scale would have to be performed in suitable bioreactors which would most likely employ some mode of agitation to ensure optimal mass and gas transfer and prevent culture inhomogeneity. The effect of low agitation at 15-20 rpm on ex vivo erythropoiesis of PB CD34+ derived cultures was investigated and found to have significant impact on erythroid development. Agitated cultures showed a reduced lag phase and increased cell expansion during the early stages of culture. Additionally, agitation accelerated erythroid differentiation as seen by the loss of early development markers, acquisition of late erythroid markers and premature cell cycle arrest, although not yielding higher fractions of terminally differentiated cells in comparison to stationary culture. However, agitation at 20 rpm led to significantly increased loss of cell viability after day 15 in culture, an effect that could be reduced by decreasing the agitation rate to 15 rpm. On the one hand these results imply that agitation may improve cell yields and reduce expensive cytokine-dependent early culture stages but on the other hand it might introduce the risk of increased cell death in large scale culture.