Hematopoietic stem cells proliferate until after birth and show a reversible phase-specific engraftment defect
Michelle B. Bowie, … , Pamela A. Hoodless, Connie J. Eaves
Michelle B. Bowie, … , Pamela A. Hoodless, Connie J. Eaves
Published October 2, 2006
Citation Information: J Clin Invest. 2006;116(10):2808-2816. https://doi.org/10.1172/JCI28310.
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Research Article Hematology

Hematopoietic stem cells proliferate until after birth and show a reversible phase-specific engraftment defect

Abstract

The regulation of HSC proliferation and engraftment of the BM is an important but poorly understood process, particularly during ontogeny. Here we show that in mice, all HSCs are cycling until 3 weeks after birth. Then, within 1 week, most became quiescent. Prior to 4 weeks of age, the proliferating HSCs with long-term multilineage repopulating activity displayed an engraftment defect when transiting S/G2/M. During these cell cycle phases, their expression of CXC chemokine ligand 12 (CXCL12; also referred to as stromal cell–derived factor 1 [SDF-1]) transiently increased. The defective engrafting activity of HSCs in S/G2/M was reversed when cells were allowed to progress into G1 prior to injection or when the hosts (but not the cells) were pretreated with a CXCL12 antagonist. Interestingly, the enhancing effect of CXCL12 antagonist pretreatment was exclusive to transplants of long-term multilineage repopulating HSCs in S/G2/M. These results demonstrate what we believe to be a new HSC regulatory checkpoint during development. They also suggest an ability of HSCs to express CXCL12 in a fashion that changes with cell cycle progression and is associated with a defective engraftment that can be overcome by in vivo administration of a CXCL12 antagonist.

Authors

Michelle B. Bowie, Kristen D. McKnight, David G. Kent, Lindsay McCaffrey, Pamela A. Hoodless, Connie J. Eaves

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Figure 4

Hst/Py-sorted HSCs display an absolute but transient S/G2/M engraftment defect.

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Hst/Py-sorted HSCs display an absolute but transient S/G2/M engraftment ...
(A) Ter119– 14.5-dpc FL cells in G1/S/G2/M were fractionated into their component G1 and S/G2/M subsets, leaving a slight separation between them. Aliquots of the sorted subsets were then stained with PI as well as with Hst/Py (data not shown). The sorted cells were cultured for 6 hours and then stained again with PI. We found that during this 6-hour culture period, approximately one-third of the cells originally in G1 had progressed into S/G2/M, and a similar proportion of the cells originally in S/G2/M had progressed into G1. (B) CRUs per 105 initial Ter119– FL cells for G1 and S/G2/M fractions before and after 6 hours in culture. There was a 3.5-fold loss of CRUs when G1 cells were cultured for 6 hours, but no loss when the cultured cells were re-sorted for G1 cells (P = 0.36). Conversely, we detected a greater than 65-fold increase in the number of CRUs detected when CRUs in S/G2/M were cultured and a greater than 128-fold increase when the cultured cells were sorted for G1 cells. IF, intrafemoral. Values are mean ± SEM of results from at least 3 experiments. *P < 0.01, **P < 0.001 versus respective cell types before culture.