Self-maintenance ability of circulating hemopoietic stem cells.

In adult mice, circulating hemopoietic stem cells (CFUs) and their progeny that repopulate an ectopic hematopoietic site possess a self-maintenance potential that is less than that of resident stem cells. This is manifested by a decrease in the content of daughter CFUs in 11-day spleen colonies produced by circulating CFUs, compared to those produced by resident CFUs. Study of the CFUs content in 139 individual spleen colonies showed that circulating CFUs produce the entire spectrum of colonies, both those with a low and those with a high CFUs content. However, the proportion of colonies that contained 10 or fewer CFUs was much higher among the colonies produced by circulating CFUs (60-70%) than by the resident CFUs (less than 10%). The lower self-maintenance of circulating CFUs, compared to that of resident CFUs, is also confirmed by direct comparison of the overall regeneration of hemopoietic populations derived from blood and bone marrow by means of chromosome markers. The embryonal circulating and resident CFUs (from the liver) do not differ in self-maintenance. In adult mice, intravenously infused circulating CFUs leave the circulation no more slowly than do the resident CFUs.