Cell kinetic behaviour of a synchronized population of erythroid precursor cells in vitro.

Erythropoiesis in vitro was studied with practically pure erythroid progenitor cells: CFU-E (colony-forming-units-erythroid). The isolation of CFU-e from spleens of thiamphenicol pretreated anaemic mice with the combined methods of centrifugal elutriation and Percoll density gradient centrifugation was monitored by flow cytometry. The ultimate CFU-e preparation with a density of 1.070 g/ml contained a high percentage of cells in the S phase of the cell cycle (80%). CFU-e occasionally found at a lower density of 1.065 g/ml were predominantly in the G2 + M and G1 phases. When CFU-e were cultured, the number of cells in the distinctive phases of the cell cycle changed periodically, so the cells were partly synchronized. Four periods up to 27 hr were observed by flow cytometrical screening of the cultured cells at hourly intervals. Cell-cycle times between 6 and 7 hr were found for all erythroid cell divisions. This was in agreement with results obtained from colony growth curves. Without the addition of erythropoietin cells start to degenerate after the second cell division. This experimental approach can be used for the cell kinetic modelling of erythropoiesis.