The cell cycle in normal human chorionic and placental villi. A study using flow cytometry

The amount of DNA in cells obtained from chorionic and placental villi by collagenase digestion was analyzed by flow cytometry. 15 cases ranging from 7th to 40th gestational weeks were analyzed. Approximately 1 X 10(4) cell nuclei were measured in each specimen. At 7th gestational week, 16-18.4% of cells were at S-phase, and 16.5-20.6% of cells at G2 + M phase. During midpregnancy, about 6.2-13.2% of cells were at S-phase and 5.3-9.1% of cells at G2 + M phase. At full term, in placentas from 40th gestational week 6.0-8.6% of cells were at S-phase and 3.0-5.0% of cells at G2 + M phase. The results suggest, that at term still 11% of placental cells are able to enter mitosis. Using flow cytometry, the DNA content in cell nuclei can be measured in specimens obtained by CVS A.