The Impact of Sorting on Cell Function

Cell purification by FACS has grown to become a mainstay of biomedical research since its invention in the early 1970s. FACS technology was initially designed and utilized to purify lymphoid populations, and lymphocytes survived the purification process with high viability. The promise of FACS was therefore realized since, after purification, the purified cells remained viable and functioned as anticipated. When FACS became utilized for more diverse cell types, such as cardiomyocytes or dendritic cells, these cells ( and others ) were observed to be sensitive to the FACS process, with either significant loss of viability or loss of function after FACS purification. Post-sorting cell-viability concerns were amplified in the early ’90s as high-speed commercial FACS systems were introduced, which utilized higher pressures, such as the Becton-Dickinson FACSVantage TurboSort and the Cytomation MoFlo cell sorter. Functional deficits of FACS-purified cells are now described as SICS or sorter-induced cellular stress. While there is a myriad of SICS manifestations, many being specific functional deficits relative to specific cell types, it has been observed that a common SICS manifestation is the global loss of cellular metabolites. This SICS metabolic phenotype appears to be the expected outcome of cell purification using traditional droplet-deflection FACS technology, regardless of the cell type or the cell sorter manufacturer. As cells purified by FACS may be a critical component in the generation of cellular therapeutics, this common post-purification depletion of cellular metabolites must be appreciated, and its impact on the downstream application of these purified cells must be considered.

 

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