The risky business of cell culture

The process of cell culture is one which can be beneficial for modelling health and disease but is not without its risks — risks which many scientists are often willing to take.

Cultured cells — ie, those removed from an animal or plant for growth in an artificial environment — retain many of the properties of the parental tissue or cell type, including disease-specific changes. This similarity means that cell-based screening platforms can be used effectively to test new therapeutic approaches.

However, cell culture also carries risks. Without proper handling, cultured cells may change in behaviour as they are transferred to new medium formulations, become contaminated with microorganisms or become cross-contaminated by cells from another culture. This could place the safety of the scientist at risk and/or negatively impact any subsequent research. However, many laboratories are not aware of common cell culture problems and do not manage these risks effectively.

In order to assess cell culture risks and their management, not-for-profit cell line repository CellBank Australia conducted what is claimed to be the first survey to look at cell culture practice in Australia and New Zealand. The 250 eligible survey respondents were typically Australian biomedical scientists with at least 12 months' experience who handle multiple cell lines on a weekly basis. The results of the survey were published in the International Journal of Cancer by University of Sydney researchers, led by CellBank Australia General Manager Mark Shannon.

When asked about the sources of cell lines that entered their laboratories during the previous year, 76% of respondents indicated that they had obtained cell lines from either research laboratories or originators — sources where mycoplasma and authentication testing are often not performed — as opposed to official cell line repositories. In addition, more than half (54%) had gifted their cell lines to other research laboratories.

The researchers acknowledged that the sharing of reagents is often seen in the scientific community as a form of collaboration. “However," they wrote, “sharing of cell lines contravenes Material Transfer Agreements, which usually state that material should not be distributed to third parties. Sharing of cell lines without testing also means that contamination is not detected and is an important reason why it continues to be a widespread problem.

“To address this risk, scientists should obtain their cell lines from a source that performs mycoplasma and authentication testing. We encourage scientists to deposit published cell lines in a repository, where the necessary testing is performed to detect contamination before cell lines are widely distributed."

Respondents were further quizzed on their own laboratories' testing and quality assurance practices. When asked about mycoplasma, 75% of respondents indicated that testing was typically performed — others said their laboratory did not test for mycoplasma (16%) or had not decided (9%). Laboratories most commonly performed their own testing (32%), though some used in-house services or went to external providers.

Meanwhile, 46% of respondents said that authentication testing was typically performed in their laboratory — others stated that authentication testing was typically not performed (18%), that they were unsure (18%) or that a decision had not been made regarding testing (16%). Laboratories that tested for authenticity most commonly used an external provider (40%), with others performing their own testing or using in-house services.

“When testing is performed, 18–20% of scientists detect contamination in at least one sample," the authors noted. And yet, “A large minority of the scientists surveyed still do not test for mycoplasma or authenticity." This is particularly worrying in the case of those respondents who do not conduct testing when gifting to, or obtaining from, other laboratories.

Finally, respondents were asked about practices regarding banking, storage and shipping of cell culture. Around 6% indicated that frozen stocks were lost in the last year due to failure of an on-site liquid nitrogen storage container, while a further 10% had lost cell line stocks while in transit from an overseas source. When asked whether their laboratory typically uses a master bank approach for its cell lines — an approach which minimises the risks associated with prolonged passaging and enables testing of stocks for authenticity and contamination — approximately half (47%) responded in the affirmative and 20% in the negative. The rest were either unsure or undecided.

The researchers concluded that there are many measures which could help combat cell culture risks, including more standardised and accessible methods for testing contamination, guidelines to improve the reporting of preclinical research and improved training.

“[But] while training is part of the solution, it does not address the risk that scientists may decide not to test their cell lines for contamination," the authors stressed. “To address this risk, it is essential for publications to report on a cell line's source and its mycoplasma and authentication testing status."

According to Shannon, the study has been very worthwhile.

“Now the research community has a better sense of both its strengths and its weaknesses when it comes to managing common risks in everyday cell culture practice,” he said. “To me, this is a great step forward as we now have a benchmark to work from — one that I expect will be very helpful to individual laboratories and institutions as they strive to achieve more credible, reproducible and translatable research from cultured cells.”