How Does Cell Culture Work? – Serene’s Synopsis 104
Cell cultures grow an organism’s cells in a growth medium, rather than through the original animal. Although some sources disagree, the term “cell culture” typically applies only to animal cells, while plant, fungal, and microbial cultures are specified as such.
Once cells are extracted from the organism of focus, they are immersed in substrate, making up the primary culture. The cells of the primary culture go through a lag phase, exponential/log phase, then plateau phase, and divide until they saturate their environment, which is limited by the amount of substrate. This point is called confluence, at which point the cells are subcultured, where they are transferred to new growth media with more room. Since normal cells are limited in the number of times they can divide, the subculture is called the subclone or cell line to distinguish itself from the primary culture. The point at which the cells can no longer divide is called senescence, and it isn’t experienced in one type of subclone called a continuous cell line, which can include cancerous or transformed cells that can replicate indefinitely. The cell line is cultured until the cells with the highest growth capacity outcompete the others, resulting in uniformity throughout the sample. Since cell cultures are a free-floating mix of cells that aren’t separated by distinct animals, genetic drift from the source organism can occur, resulting in distinct cell strains.
Cell cultures can be used to directly produce molecules or other cellular products, farming individual cells in a laboratory environment, opposed to growing the entire source organism. Tissue cell cultures are how lab-grown meat is produced, will be covered in an upcoming Synopsis. Beyond harvesting cellular products, though, cell cultures can be used for pharmaceutical testing and other research, like the hamster cell cultures mentioned previously. The population doubling time can be determined during the log and plateau phase, which can be compared with experimental cultures to determine the effect of variables. This is likely how a change in growth rate was determined in the cell cultures with added chloroplasts in that previous article.
Talking about limited cell divisions prompted me to research something I’ve been wondering for a while: why do we die of old age? In AP bio, I learned about telomeres, the end segments of chromosomes, and how the structure of DNA polymerase causes them to shorten with each replication. Then why are babies young? In gen bio last spring, I learned about telomerase, an enzyme that lengthens telomeres with junk DNA that isn’t important, so it doesn’t matter if it’s cut off. I learned that telomerase levels decrease as we age, but why?
Turns out telomerase is active in germ and stem cells, but not somatic cells. This is because high telomerase activity means that cancer cells could divide indefinitely, which is definitely not favorable. Between aging and cancer, I’d definitely take aging, and evolution would, too. So this is the combination we get, which is fascinating! Makes me wonder if, in the distant future when we have far more tools to fight cancer, people chasing immortality would choose to stimulate telomerase activity in body cells. Or perhaps more immediate and useful, we could do that to our cell cultures. If it develops cancer, wouldn’t that kind of be good, since they’d be more prolific? Although it might be risky considering the genetic drift that may occur with a high mutation rate. Interesting stuff, and I hope to learn more about this sort of thing when I start taking upper division classes this fall! Stay tuned to learn with me!
https://pmc.ncbi.nlm.nih.gov/articles/PMC7325846/