Cell culture is the process of growing plant, insect, animal, or human cells in an artificial, controlled environment. These cells can be taken directly from organisms or an existing cell line can be utilized. Cells are grown in dishes or flasks and are supplied with media containing important nutrients, growth factors, and hormones to promote their growth and survival. These dishes and flasks are then stored in incubators kept at optimal growth temperatures. Mammalian cells, for example, grow best at near body temperature (~37℃) in a humid environment.

At Sanford Research, scientists utilize cell culture to study cellular and molecular biology. Jazmine Yaeger PhD, a postdoctoral fellow in the Francis Lab, enjoys culturing cells for her experiments studying the rare cholesterol deficiency disease Smith-Lemli-Opitz Syndrome (SLOS). Yaeger states there are many benefits to using cell models in biomedical research. Cell models help to relieve some of the ethical issues of using animal models for experiments. “If you are going to use an animal, you want to make sure that you are using it for the right purposes and are not just sacrificing animals for no reason,” says Yeager. Cells are different in that “there are less ethical and regulatory concerns; cells can be thrown away.” Studying cells outside their natural environment also allows scientists to focus on specific cellular processes with less noise and interference from other processes. “If you can focus in on that [system], you might be able to answer a question that you wouldn’t otherwise be able to,” says Yaeger .

Although cell culture has many advantages and has helped in the process of studying numerous diseases, it has its disadvantages. “All cells are a little needy in a sense,” Dr. Yaeger explains, “you really have to be familiar with the cell that you are working with.” No two cell types are the same, so special attention needs to be given to a cell type’s optimal growing conditions. If the media ingredients or the incubator temperatures are off, the cells will not grow as they should and could die. Stem cells, a special type of cell that has the potential to differentiate into other cell types, are particularly troublesome to culture. “When you’re talking about growing finicky things like stem cells that you're working to differentiate into other cells, getting the media ingredients can become pretty expensive,” says Yaeger. No matter the cell type, there is always the risk of the cells becoming contaminated by viruses, microbes, and chemicals. Contamination is never a good thing. Yaeger and other scientists find contamination to be “a bummer, especially when you have cells that you have been growing for a long, long time.”

When studying complex diseases like SLOS, it is useful to look at cells derived from SLOS patients and mice models of the disease. This is where primary cell culture comes in. Primary cell culture is the growing of cells freshly obtained from multicellular organisms. These cells are removed from the organism, purified, and transferred to flasks with an appropriate media where they are grown under controlled conditions. Since primary cultures come directly from patients or mice, they can provide a more biologically accurate representation of diseases. Unfortunately, primary cell cultures have a limited lifespan and will die or stop growing after a certain number of divisions. This is called senescence. For primary cell lines to become immortal and grow indefinitely, genetic modifications need to occur. Once immortalization has happened, these cells can be subcultured indefinitely.

Secondary cell cultures, or cell lines, are primary cell cultures that have been passaged. Passaging cell lines occurs when a portion of cells are transferred from one dish to another, allowing the cells more room to grow and multiply, providing more cells for additional experiments. Passaging, or splitting, cells sometimes involves enzymatically destroying the junctions between cells and the surface they grow on, while other cells may float in the media and do not require removal from a flask or dish. These cells are then washed and resuspended in media, where they can be added to a fresh plate or frozen in liquid nitrogen. Frozen cell lines have the capability to be stored for years after the initial experiment, aiding in researchers’ ability to reproduce or continue previous experiments.

Cell culture is an invaluable tool used by biomedical researchers to study complex biology. Cell culturing provides consistent, reproducible model systems for studying cellular processes, allowing scientists to dive deeper into topics such as disease modeling, drug development, and vaccine production.

For more information on how cells grow, divide, and differentiate, check out our unit called Immortal Cells.