Enhanced hematopoietic recovery in irradiated mice pretreated with interleukin-1 (IL-1)

Data in this report compare the number of colony-forming cells (CFC) in bone marrow from irradiated and pre-irradiated C57Bl/6J mice injected with saline or recombinant interleukin-1-alpha (rIL-1). Eight to 12 days after sublethal or lethal irradiation, there were more CFU-E (colony-forming units-erythroid), BFU-E (burst-forming units erythroid), GM-CFC (granulocyte-macrophage colony-forming cells), and day 8 CFU-S (colony-forming units-spleen) in bone marrow from rIL-1 injected mice than from saline injected mice. Prior to irradiation, there was no increase in number of CFC in bone marrow from rIL-1 injected mice. However, as determined by sensitivity to hydroxyurea, rIL-1 injection stimulated GM-CFC into cell cycle. These results demonstrate that rIL-1 injection increases the number of CFC that survive in irradiated mice and may be a consequence of the stimulation of CFC into cell cycle prior to irradiation.

The kinetics of hematopoietic stem cells during and after hypoxia. A model analysis

A previously described mathematical model of the hematopoietic stem cell system has been extended to permit a detailed understanding of the data during and after hypoxia. The model includes stem cells, erythroid and granuloid progenitors and precursors. Concerning the intramedullary feedback mechanisms two basic assumptions are made: 1) The fraction "a" of CFU-S in active cell cycle is regulated. Reduced cell densities of CFU-S, progenitors or precursors lead to an accelerated stem cell cycling. Enlarged cell densities suppress cycling. 2) The self renewal probability "p" of CFU-S is also regulated. The normal steady state is described by p = 0.5, indicating that on statistical average each dividing mother stem cell is replaced by one daughter stem cell, while the second differentiates. Diminished cell densities of CFU-S or enlarged densities of progenitors and precursors induce a more intensive self renewal (p greater than 0.5), such that the stem cell number increases. The self renewal probability declines (p less than 0.5) if too many CFU-S or too few progenitors and precursors are present. The model reproduces bone marrow data for CFU-S, BFU-E, CFU-C, CFU-E, 59 Fe-uptake and nucleated cells in hypoxia and posthypoxia. Although the ratio of differentiation into the erythroid and granuloid cell lines is kept constant in the model, a changing ratio of CFU-E and CFU-C results. The model suggests that stem cells and progenitor cells are regulated by a regulatory interference of erythropoiesis and granulopoiesis.

A comprehensive mathematical model of stem cell proliferation which reproduces most of the published experimental results

On the basis of experimental knowledge about haemopoietic stem cells a catalogue of fundamental statements is formulated. From this a simple mathematical model of haemopoietic regulation mechanisms is developed. The functional net effects of regulatory processes which are still unknown or unmeasurable are estimated using evolution arguments. The model is developed in three steps. It allows description of the self-replication of stem cells after direct destruction as well as their reaction to increased or reduced needs in the erythropoietic system. The most important experimental data about changes in CFUs, BFUe and CFUe after acute or chronic irradiation, anaemia, hypoxia, hypertransfusion or direct erythropoietic stimulation can be reproduced within the model. The model allows us to understand most of the results of experimental stem cell research. Furthermore, it can be applied for a more precise analysis of the existing data. Predictions about the results of certain experiments can be made.