Hematopoietic cells

Abstract

Hematopoiesis represents a dynamic example of tissue homeostasis in which cells undergo constant cell proliferation and death. In the normal physiological condition, a small fraction of blood cells are steadily removed from the body and replaced by new cells generated from the bone marrow, the site of human hematopoiesis. This normal turnover is maintained by a balance between the rates of proliferation and renewal of progenitor cells and the rate of death of more differentiated cells. With the loss of mature blood cells the number of functional cells decreases and pluripotent progenitors supply their replacements through proliferation and differentiation into mature cells. In certain “stress” conditions, the bone marrow can expand a specific sub-population of hematopoietic cells to more than ten times of its normal level. When such an increased physiological demand exists, specific cell types have “unbalanced” rates of proliferation and death, such that the death rate is decreased relative to the proliferation rate and expansion of the specific population results. As the expanding cell population reaches the point of meeting the increased demand, the drive for expansion subsides. Then the death rate is increased relative to the proliferation rate until the cell number returns to that of the normal basal homeostasis. The balance between proliferation and death is partially regulated by availability of soluble hematopoietic growth factors. Because blood cells can mediate various inflammatory reactions, extensive turnover and expansion of hematopoietic cells occur during inflammatory states.KeywordsHematopoietic CellTrophic FactorErythroid Progenitor CellMature Blood CellReactive ThrombocytosisThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.