Cell Cycle Analysis of Cultured Porcine Mammary Cells

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Abstract
One of the major points of debate in determining the effectiveness of nuclear transfer technology has been the phase of the cell cycle of the donor cell at the time of nuclear transfer. Here, a primary mammary cell line has been isolated and various treatments for synchronization of the cell cycle have been tested. The cells were then simultaneously stained for DNA content and protein content and the percentages of cells in G1, G0, S, and G2 + M were estimated. In the first experiment, cells were either cycling, grown to confluence, or serum-starved for 5 days. Serum starvation increased (p < 0.05) the percentage of cells in G0 compared to confluent or cycling cells from 3% to 8% to 22%. By using forward scatter to determine the size of the cells it was determined that if small cells (7-15 μm) were selected from the serum-starved group 43.9% will be in G0 as compared to 4.5% of cycling cells and 9.9% of confluent cells. Dimethyl sulfoxide (DMSO) treatment (0%, 0.5%, or 1.0%) for 72 hours (shown to synchronize some cell types in G0) had no effect on the percentage of cells in G0, G1, S, or G2 + M. Treatment with mimosine (0 μM, 0.4 μM, 0.8 μM or 1.2 μM), a compound that should synchronize the cells in G1, increased (p < 0.05) the percentage of cells in G1 from 66.7% (0 μM mimosine) to 79.0% to 82.0%. Finally, treatment with colchicine for 24 hours (shown to synchronize some cell types in G2 + M) increased (p < 0.05) the percentage of cells in G2 + M (0 μM colchicine) from 13.3% to 27.2% to 31.6%. It is concluded that many cell cycle synchronization techniques are effective in porcine mammary cell lines, but none of the techniques are 100% effective. Such results should help elucidate the mechanisms involved in nuclear transfer.