Stem cell research is an up an coming field of study. Like all cell types, stem cells require specific growth factor signals for proper functionality. One of which is FGF2. So, what is FGF2 (Fibroblast Growth Factor 2) and how does it work?
Basics about growth factors and FGF2
Let’s start with the second half of the name, growth factor (GF), as this is a bit more general and easier to explain. GFs are naturally occurring substances that stimulate cellular growth, division, and/or differentiation. Most of the time, GFs are proteins that are secreted from a cell and bind to receptors on other cells to bring about their effects. The term GF is sometimes used interchangeably with the term cytokine, which is a general term for a small signaling molecule. While GFs, a lot of the time, do exactly what the name implies—help cells grow and expand—certain GFs can do the exact opposite and stop cells from growing. It is important to remember that growth factors are signaling molecules to “turn on” or “turn off” different cellular actions.
Fibroblast Growth Factors make up a large family of growth and differentiation factors. In humans, there are 22 members of the FGF family which all share similar structures. Like most GFs, FGFs are secreted proteins that bind to a receptor to bring about their function. There are four different FGF receptors, FGFRs 1-4. In this article, we will focus on FGF2, which binds FGFR1. When FGF2 binds FGFR1, the most common pathway activated is the mitogen-activated protein kinase pathway, otherwise known as the MAPK pathway.
How FGF2 Works
FGF2 regulates the Mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) pathway. This pathway is critical for cell signaling cascades, including those that regulate cell proliferation, differentiation, and cellular stress. In the case of stem cell culture, the addition of FGF2 triggers these pathways to start and its absence triggers these pathways to stop. Maintenance of these pathways at the most efficient level promotes proliferation and reduces unwanted spontaneous differentiation to keep stem cells from beginning to transition into other cell types.
A recent study discovered that FGF2 is incredibly unstable in the culture medium due to its heat lability. This requires a daily feeding schedule and creates fluctuations in the amount of FGF2 that is available to the cells. The stem cells then get mixed signals, don’t differentiate, differentiate, don’t differentiate, etc. over the course of a few days. This stressful signaling results in negative outcomes for scientist’s experiments. Stabilizing growth factor levels eliminates the fluctuations in growth factor levels, preventing mixed signaling and promoting the most efficient growth.
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