Challenges for Standardization of Cell Lines

Despite the fact that cell lines usually appear to be quite monomorphic when examined microscopically, they are inherently prone to variation and contamination and can be difficult to control. In some cases they may contain a variety of subpopulations representing different states of differentiation. Thus, standardization is a critical activity to obtain reliable data or products from tissue and cell-based systems [7, 10, 21].

Microbial contamination can have dramatic effects on cell cultures. In most cases, a bacterial or fungal contamination will cause death of the cell culture. Contamination with organisms such as Mycoplasma and viruses can become established as persistent infections of the cells, without causing overt cytotoxic effects. However, these persistent infections may substantially alter the characteristics of the cell line. In the case of Mycoplasma there may be irreversible changes including genetic effects, physiological changes, and transformation [22]. Effects can also be quite subtle, including increased chromosomal abnormality [23], induction of cytokines in the infected cells [24, 25], and interference with the selection of hybrids [26]. The eradication of viral infection is not generally feasible, while treatment with antibiotics for Mycoplasma infections is not routinely successful and may lead to deleterious effects on the cells themselves.

Genetic stability is also a key issue, and cell lines may show evidence of genetic change through a shift in karyotype (Table 9.3) which may be reflected in a change of culture characteristics. Furthermore, other subtle genetic changes that do not affect the gross chromosomal structure of the cells may yet have dramatic effects on cell function.

Cells will also vary in their response to environmental factors and treatments depending on their particular phase of growth (i.e., lag phase, exponential growth phase versus stationary or plateau phase) or the proportion of cells in a particular part of the cell cycle (i.e., G0, Gj, S G2, M). Standardizing the status of cells prior to use in a cell-based assay is central to assuring the reproducibility and quality of data from cell-based assays [7, 11], and will require investigation for each assay and cell type.

0 0

Post a comment