Primary cell donor variability

Human hepatocytes, for example, are considered invaluable for testing hepatotoxicity and also the activities of drug transporters and the metabolism of xenobiotics by CYP450 enzymes. At present, ready-to-use frozen homogeneous preparations of human hepatocytes are commercially available for these purposes. Since primary human liver cells rapidly lose their functional properties when cultured in vitro, their usefulness relies on repeated sourcing, which raises the clear limitation of sample consistency due to donor-donor variability (Rodriguez-Antona, 2002). 

A further obstacle to more widespread use of primary cells is donor-to-donor variability, particularly for large compound collections. Differences can arise from variability in the isolation and preparation of the cells or from intrinsic differences among individual donors (e.g., age, gender, genetic background, and disease state). Standardization and automation of as many passages as... 

The majority of the cell-based assays use established cell lines. The cell line of choice would naturally express receptors of interest that respond to the therapeutic protein product, and can be obtained from commercial sources, American Type Culture Collection (ATCC), for example. Alternatively, if an appropriate commercially sourced cell line cannot be found, one can be engineered to respond to a therapeutic protein (see b.Reporter Gene Assay). Most frequently the cells are stably transfected with a vector containing the desired receptor gene or responsive element of a gene of interest. In rare instances when the cell lines are not available, primary cells separated from blood or tissues (human or animal) can be used to develop bioassays. Primary cells are the last resort because of donor-to-donor variability, accessibility of material, and limited practicality of such assays. 

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