Foetal bovine serum is a nutrient-rich additive widely used for in vitro cell culture studies. However, harvesting the serum involves inhuman methods, calling for replacing or reducing its use in experiments. Here is a report on one such ethical step by a team of researchers who found a novel technique to grow skin cells by drastically reducing bovine serum use.
A team of researchers led by Karishma Kaushik, Assistant Professor from the Savitribai Phule Pune University (SPPU), Pune, has developed a new method to grow and study skin cells. This method uses at least five times lesser concentrations of foetal bovine serum (FBS), a central component of cell growth media. FBS is widely used in experiments to grow cells that mimic physiological conditions in the lab.
FBS is a cocktail of growth hormones, vitamins, proteins, fatty acids, and lipids. It facilitates the growth, survival, and proliferation of many human and animal cells in the laboratory. It is also preferred routinely in cell culture studies due to low levels of antibodies, which ensures minimum unwanted immune response when used in experiments. Usually, 10% vol/vol of FBS is added to the cell culture medium for experiments.
However, FBS is extracted from unborn foetuses of pregnant cows, raising numerous ethical concerns. Moreover, procuring FBS poses several economic challenges as it is a byproduct of slaughterhouses. “There is an increasing impetus to reduce and eventually replace the use of animals and animal products in advanced research,” says Kaushik. While this is a tall order per se, the development of cell culture methods that can reduce the use of animal serum is a viable place to start, she adds.
In the present study, the team developed two new methods with which two types of skin cells, fibroblasts and keratinocytes, could grow in a cell culture medium with only 1 – 2% FBS.
Keratinocytes are the cells that make up the dermis or the outermost layer of our skin. Fibroblasts reside in a layer just below the keratinocytes.
The major hurdle faced by the team was in growing the skin cells together (co-culture). “Fibroblast skin cells love serum-containing media. Keratinocytes, on the other hand, typically grow poorly in the presence of serum,” explains Kaushik. So, the researchers attempted to tweak the growth media components for the two cell types to overcome the hurdle.
They achieved a ‘sweet spot’ by (1) using cell-specific growth media, (2) by adding cell-specific additives in addition to the primary minimum cell growth media. They used commercially available and accessible cell growth media called Minimum Essential Medium (MEM), all-inclusive fibroblast and keratinocyte growth media (known commercially as FGM and KGM), and a ready-made cocktail of growth supplements for their experiments. MEM is a growth media containing minimum constituents required for the growth of animal or human cells in laboratories.
In the first protocol, the researchers added 1% FBS to fibroblast and keratinocyte specific growth media. In the second method, they combined 2% FBS with MEM; to this, they added supplements like proteins and vitamins to enhance cell growth. The combined approach resulted in a healthy proliferation of both keratinocytes and fibroblasts.
“Research is often constrained by resources and time. Hence, we tend to use tried and tested methods and don’t play as much with the methodology as we like. A study like this is filling the gap there,” says Joey Shepherd, Senior lecturer in Microbiology, University of Sheffield, United Kingdom. She was not involved in this study.
The team has also tested the applicability of their new growth media to study wound healing under laboratory conditions. They found that keratinocytes and fibroblasts show normal healing behaviour even with reduced FBS concentrations. The study opens avenues for further research and application in wound healing studies.