Kinetic differences between fed and starved Chinese hamster ovary cells

Area of Science:

• Cell Biology
• Biophysics

Background:

• Chinese hamster (CHO-K1) cells in monolayer cultures reach a plateau phase with no net cell increase.
• Understanding the cell kinetics of aged cells in plateau phase is crucial for interpreting their behavior.

Purpose of the Study:

• To investigate the cell cycle kinetics of Chinese hamster cells in nutritionally deprived (starved) versus density-inhibited (fed) plateau-phase cultures.
• To compare the proliferative potential and cell cycle distribution of cells under different plateau conditions.

Main Methods:

• Cell viability and reproductive integrity assessed via clonogenic assays and dye exclusion.
• Cell cycle analysis using time-lapse microscopy, [3H]thymidine ([3H]TdR) autoradiography, and nucleoside incorporation assays.
• Monitoring DNA synthesis rates using liquid scintillation and gamma counters after labeling with [3H]TdR or [125I]UdR.

Main Results:

• Starved plateau-phase cells primarily arrested in G1 or G2 phases, with <2% in S phase.
• Fed plateau-phase cultures showed approximately 50% of cells in S phase, fluctuating with medium replacement.
• Both starved and fed cells exhibited highly synchronized DNA synthesis upon reculturing, maintaining synchrony for over three generations.

Conclusions:

• Nutritionally deprived plateau-phase cells arrest predominantly in G1 or G2.
• Periodically fed plateau-phase cultures maintain a significant fraction of cycling cells in S phase.
• The distinct kinetic profiles of starved and fed plateau-phase cells suggest differential responses to extracellular stimuli.