Serum, Serum-Free Media, and Growth Factors
Most cell culture media procedures include the addition of serum products, such as Fetal Bovine Serum (FBS). Serum is a biological product that naturally contains many growth factors and other components. When scientists want better control of the media, they often remove or reduce the level of serum. Then, individual growth factors can be added back into the serum-free or serum-reduced media to promote cell growth and viability for specific cell lines and experiments.
It can also be useful to add growth factors in media that contains the usual level of serum. "In some circumstances, researchers want a higher success rate from the sample, so they may use serum in the medium, but they may also have to add some growth factors to maintain the cells' status or keep the cells stable," Dr. Zhu said.
How Should Scientists Choose What Cell Culture Media Growth Factors to Use?
"First and foremost, it depends on the cell type," Dr. Zhu explained. "There are different families of growth factors. Each family will have an effect on specific cell types. For example, nerve growth factors will mainly affect nerve cells."
The choice of growth factors may also depend on the goals of the experiment. For example, "There are some commonly used growth factors, like fibroblast growth factor or epidermal growth factor (EGF); these are widely used in media recipes and are commonly used in protein expression or cell differentiation induction."
What Distinguishes Growth Factors and Cytokines for Cell Culture Media?
Cytokines and growth factors are both natural signaling molecules that act by binding to receptors on the surfaces of cells, but they derive from different sources and have different functions in the body. Cytokines derive mainly from immune cells and send signals to other immune cells, controlling processes like immune cell development, survival, and activity, while growth factors derive from and signal to a wide variety of cell types.
Despite having different sources and functions within living organisms, both types of signaling molecules can help regulate cell proliferation, differentiation, and viability.
In cell cultures, both types of signaling molecules "can be used in large-scale protein expression or even some therapies." However, "We mainly use cytokines when we want to culture immune cells or conduct some research in inflammation."
Examples of Growth Factors and Their Uses
Human- and animal-derived as well as recombinant growth factors have many roles in cell culture and bioproduction. A few examples are:
- Basic fibroblast growth factor is a mitogenic peptide that induces DNA synthesis and proliferation in a variety of cell lines. It also has uses in mesenchymal stem cell (MSC) culture.
- Epidermal growth factor binds to the receptor EGFR and stimulates mitosis in a variety of cell types. It is widely used in cell culture media and has uses in MSC culture.
- Nerve growth factor is often used in nerve cell cultures or to induce iPSC to become neurons.
- Granulocyte colony-stimulating factor (GCSF) and stem cell factor (SCF) are regulators of hematopoietic cell differentiation and proliferation. Both GCSF and SCF can be used to induce patient-derived blood and bone marrow cells to differentiate to a specific type of immune cell.
- Insulin has uses as a growth factor in bioprocessing applications, such as improving yields from industrial Chinese Hamster Ovary (CHO) cell cultures.
