Passage and save the cell lines in the cell bank
introduction:
To properly maintain cell lines in culture (primary culture or subculture), it is essential to regularly assess cell morphology and periodically replace the culture medium.
Cell Morphology:
Cells in culture should be examined regularly to evaluate their health status, check for contamination, and assess other factors (such as toxins in the medium, inadequate nutrients, etc.).
Replacement of Culture Medium:
To sustain cultured cell lines, whether the cells are in a proliferative or non-proliferative state, periodic replacement of the culture medium is necessary. For proliferating cells, the medium must be changed more frequently compared to non-proliferating cells. The time interval for medium replacement depends on the growth rate and metabolism of the cells.
For instance, for rapidly growing transformed cells (e.g., HeLa), the culture medium should be replaced twice a week, while for slowly growing non-transformed cells (e.g., IMR-90), the medium may be changed once a week. Additionally, for rapidly proliferating cells, subculturing should be performed more frequently than for slow-growing cells.
When replacing the culture medium, the following factors should be considered:
Cell Concentration:
Cultures with high cell concentrations utilize nutrients from the medium more rapidly than those with lower concentrations. Therefore, it is necessary to change the culture medium more frequently.
pH Reduction:
A drop in pH indicates changes in the culture medium. Most cells can grow well at a pH of 7.0, and their growth typically stops when the pH decreases to approximately 6.5. With further reduction of pH (between 6.5 and 6.0), cells may die. The rate of pH decline is generally estimated for each cell line with the selected culture medium. If the decline is less than 0.1 pH units per day, cells will not be harmed even if the medium is not immediately replaced. However, if the decline reaches 0.4 pH units per day, the medium should be replaced immediately.
Cell Type:
Embryonic cells, transformed cells, and immortal cell lines grow rapidly and require continuous subculturing and medium replacement. In contrast, normal cells grow more slowly.
Morphological Changes:
Regular examination of cell morphology is crucial in culture techniques. Any abnormalities in cell morphology may lead to irreversible damage to the cells. Medium replacement should be performed to prevent the risk of cell damage.