Damage-free sorting of iPSC-derived cells
In the field of regenerative medicine, differentiated somatic cells from embryonic stem cells or iPSCs are transplanted to patients. However, any remaining undifferentiated cells can become tumorous once they are implanted, obstructing the advancement in patient treatment. The removal of undifferentiated cells has been a challenge, and thus there is a need to efficiently remove the undifferentiated cells prior to transplantation. On-chip Sort effectively and efficiently removes rare undifferentiated cells present in the sample by a method called ‘multi-step negative sorting’.
Fig. 1. (a) Principle of multi-step negative sorting. Red dots are undifferentiated cells and blue dots are differentiated cells. (b) Removal of undifferentiated cells from a sample of differentiated neural stem cells by multi-step negative sorting. The results are obtained in conjunction with Dr. Chuma from Institute for Frontier Medical Sciences, Kyoto University, Japan.
Multi-step negative sorting with On-chip Sort works by loading the sample (differentiated cells mixed with a rare population of undifferentiated cells) to the sample reservoir of the chip. Undifferentiated cells (non-target cells) are removed by formation of the pulse flows into the collection reservoir, while differentiated cells (target cells) flow into the waste reservoir located downstream of the chip. Differentiated cells are recovered and reloaded to the sample reservoir for further purification. This process is repeated until all the undifferentiated cells are removed (Fig. 1a). Fig. 6b shows the removal of ~4% of undifferentiated cells remaining in the sample containing cells that were differentiated to neural stem cells. Undifferentiated cells were fluorescently labeled with FITC-conjugated anti-TRA-1-60, and the fluorescence signals were used for the detection. We confirmed that all undifferentiated cells were removed after three sorts. We also cultured the sorted differentiated cells and found them viable (Fig. 1b).