What are the growth phases of culture cells?

There are four main phases in the growth curve of normal cultured cells, which typically displays a sigmoid pattern of proliferation.

• Lag phase: At this stage cells do not divide. It is the period when cells are adjusting to the culture condition and preparing for the cell division.
• Log phase: It is also called logarithmic phase or exponential phase, when cells actively proliferate and the cell density increases exponentially. It is recommended to assess cellular function at this stage since the cell population is most viable. Cells are also generally passaged at late log phase, because passaging cells too late can lead to overcrowding, apoptosis and senescence.
• Stationary phase (or plateau phase): Cell proliferation slows down due to a growth-limiting factor such as the depletion of an essential nutrient and/or the formation of an inhibitory product, resulting in a situation in which growth rate and death rate are equal. Cells are most susceptible to injury at this stage.
• Death phase (or decline phase): Cell death predominates at this phase and the number of viable cells reduces.