by Abby Poff
Fun Rating: 4/5
Difficulty Rating: 4/5
What is the general purpose?
Primary cell culture is an in vitro technique which refers to growing and maintaining cells collected directly from an organism.
Why do we use it?
Primary cells from patients or animal models are often the closest comparator we can use in the lab to what really happens in the body. Primary refers to the fact that these cells are directly extracted from an organism, as compared to immortalized cell lines that are derived from a single common ancestor cell. These cells grow and develop in their normal environment, and then they are placed in culture dishes for experiments that can’t be easily done in vivo. For example, we can use primary cells isolated from cancer tissue to test different medications at various concentrations to understand how that individual’s specific tumor might be treated.
Figure 1: Workflow of primary cell culture. Made by the author with images from Servier Medical Art, provided by Servier, and licensed under a Creative Commons Attribution 3.0 unported license.
How does it work?
First, the cell source of interest must be ethically obtained by methods like biopsy or surgical removal. In order to protect both humans and animals, important regulations govern who can collect and use primary tissues and cells for research.
Then, the removed piece of tissue must be dissociated, or broken down into individual cells using enzymatic or mechanical digestion. This involves adding enzymes called proteases that chew away at the proteins that tether the cells to one another. Triturating the sample, or mixing it up and down with a pipette or syringe, also helps to physically separate the individual cells.
Next, these cells must be counted with a hemocytometer and added to the culture dishes. Cells can be very sensitive to their plating density, or how close together or far apart they are from their neighboring cells in the plate. Therefore, it’s important to add the right number of cells at the outset, which might involve diluting the cell solution.
Finally, these cells must be maintained under the appropriate conditions until the end of your experiment. This can include changing the liquid they grow in (cell culture media) to ensure the cells have the appropriate nutrients to stay healthy, or moving them to a new plate if they outgrow the original plate over time. It also includes ensuring that the cells have the right temperature and humidity in their growth incubator. One important downside of using primary cells is that they can only grow in culture for a limited amount of time before they enter senescence, a state in which they no longer divide. This means it’s important to give them the best growth conditions possible to keep them healthy longer!
Importantly, all of the steps of this procedure have to be performed using aseptic technique, or common laboratory methods to reduce the likelihood of microbes like bacteria and fungi infecting the primary cell culture. These techniques should include thoroughly cleaning and sterilizing all tools and equipment before working with the cells. In addition, all steps should be carried out within a designated laminar flow hood, a partially enclosed sterile lab bench specially designed for sterile cell culture.
