Though a great deal of attention is typically paid to optimizing the conditions and reagents used in cell-based assays, quality control of the cells themselves is frequently overlooked. Human errors such as mislabeling or cross contaminating cell lines can lead to researchers working with cells of unintended identity.
Moreover, even in the absence of errors/contamination, the inherent genetic instability of many cell lines and the epigenetic modifications resulting from culture conditions/passage number can have an effect on cellular phenotype – confounding fundamental research or drug screening efforts. Genotyping methods such as short tandem repeat profiling can verify cellular identity but do not exhaustively prove the absence of genetic modification and cannot elucidate changes in cell behavior resulting from epigenetic modification. By providing information about phenotype (cell-substrate attachment quality, cell size and morphology, and the kinetics of cell proliferation) xCELLigence® real-time cell analysis (RTCA™) using impedance measurement provides a quick, easy, and cost effective means of validating cell identity and health.
As proof of principle consider the below impedance traces for three different cell lines. A549 (adenocarcinomic human alveolar basal epithelial cell line), GTL16 (gastric carcinoma cell line), and SHSY5Y (neuroblastoma cell line) cells display markedly different real-time impedance traces for cell attachment and growth (Figure 1) – validating xCELLigence as a means of differentiating between cell types.
As a more subtle RTCA analysis requiring quantitative comparison between different cell sources, an xCELLigence® instrument was used to monitor the real time growth of HeLa cell lines obtained from the American Type Culture Collection (ATCC), three academic labs, and two biotech labs. Though visual inspection revealed some morphological heterogeneity within and between these six cell lines, “none showed morphologies that were unambiguously outside the range of normal HeLa cells” (Figure 2A). Despite this, real-time impedance curves revealed the cell line from lab 5 to have attachment and growth characteristics dramatically different from the other cell lines (Figures 2B and C).
For a more thorough examination of how xCELLigence® can be used for cell quality control, and why this is superior to other methods, please see the following Application Note and the publications listed at the bottom of this page.
Key Benefits of xCELLigence®
- Cell identity validation: Using the RTCA trace of a reference cell type, the identity of new stocks of the same cell type can be readily validated.
- Cell quality assessment: The health of cells subjected to different culture conditions or passage number can be evaluated by comparing their substrate/surface attachment quality, size/morphology, and growth properties to naïve/young reference cells. Cell quality issues – including cell line mix-ups, genetic and epigenetic changes, contamination, and passage number effects – result in distinct impedance profile changes.
- Ease of use: Cellular properties/phenotype can be rapidly and quantitatively assessed with minimal hands-on time or effort by the researcher. Once cells have been plated and data acquisition initiated no further involvement is required.