Hematopoietic stem cells (HSCs) reside in the bone marrow within niches that provide microenvironmental signals in the form of biophysical cues, bound and diffusible biomolecules, and heterotypic cell–cell interactions that influence HSC fate decisions. This study seeks to inform the development of a synthetic culture platform that promotes ex vivo HSC expansion without exhaustion. A library of methacrylamide‐functionalized gelatin (GelMA) hydrogels is used to explore remodeling and crosstalk from mesenchymal stromal cells (MSCs) on the expansion and quiescence of murine HSCs. The use of a degradable GelMA hydrogel enables MSC‐mediated remodeling, yielding dynamic shifts in the matrix environment over time. An initially low‐diffusivity hydrogel for co‐culture of hematopoietic stem and progenitor cells to MSCs facilitates maintenance of an early progenitor cell population over 7 days. Excitingly, this platform promotes retention of a quiescent HSC population compared to HSC monocultures. These studies reveal MSC‐density–dependent upregulation of MMP‐9 and changes in hydrogel mechanical properties (Δ
Hematopoietic stem cells (HSCs) are capable of entering the cell cycle to replenish the blood system in response to inflammatory cues; however, excessive proliferation in response to chronic inflammation can lead to either HSC attrition or expansion. The mechanism(s) that limit HSC proliferation and expansion triggered by inflammatory signals are poorly defined. Here, we show that long-term HSCs (HSCLT) rapidly repress protein synthesis and cell cycle genes following treatment with the proinflammatory cytokine interleukin (IL)-1. This gene program is associated with activation of the transcription factor PU.1 and direct PU.1 binding at repressed target genes. Notably, PU.1 is required to repress cell cycle and protein synthesis genes, and IL-1 exposure triggers aberrant protein synthesis and cell cycle activity in PU.1-deficient HSCs. These features are associated with expansion of phenotypic PU.1-deficient HSCs. Thus, we identify a PU.1-dependent mechanism triggered by innate immune stimulation that limits HSC proliferation and pool size. These findings provide insight into how HSCs maintain homeostasis during inflammatory stress.
more » « less- PAR ID:
- 10222297
- Author(s) / Creator(s):
- ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »
- Publisher / Repository:
- DOI PREFIX: 10.1084
- Date Published:
- Journal Name:
- Journal of Experimental Medicine
- Volume:
- 218
- Issue:
- 6
- ISSN:
- 0022-1007
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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