External signals regulate continuous transcriptional states in hematopoietic stem cells.

Eva M Fast,David Scadden,Fernando Camargo,Margot Manning,Nikolaos Barkas,Leonard I Zon,Audrey Sporrij,Yi Zhou,Song Yang,Jimin Guo,Edroaldo Lummertz Rocha,Ninib Baryawno

doi:10.7554/elife.66512

Abstract

Hematopoietic stem cells (HSCs) must ensure adequate blood cell production following distinct external stressors. A comprehensive understanding of in vivo heterogeneity and specificity of HSC responses to external stimuli is currently lacking. We performed single-cell RNA sequencing (scRNA-Seq) on functionally validated mouse HSCs and LSK (Lin-, c-Kit+, Sca1+) progenitors after in vivo pharmacological perturbation of niche signals interferon, granulocyte colony-stimulating factor (G-CSF), and prostaglandin. We identified six HSC states that are characterized by enrichment but not exclusive expression of marker genes. External signals induced rapid transitions between HSC states but transcriptional response varied both between external stimulants and within the HSC population for a given perturbation. In contrast to LSK progenitors, HSCs were characterized by a greater link between molecular signatures at baseline and in response to external stressors. Chromatin analysis of unperturbed HSCs and LSKs by scATAC-Seq suggested some HSC-specific, cell intrinsic predispositions to niche signals. We compiled a comprehensive resource of HSC- and LSK progenitor-specific chromatin and transcriptional features that represent determinants of signal receptiveness and regenerative potential during stress hematopoiesis.

Highlights

Stem cell therapy holds promises for numerous indications, including blood diseases, autoimmune diseases, neurodegeneration, and cancer (Blau and Daley, 2019)
To encompass a wide variety of different transcriptional responses, we evaluated three different signaling pathways: an inflammatory pathway through stimulation or inhibition of prostaglandins by 16,16-d imethyl prostaglandin E2 and indomethacin, a host-d efense immune signaling pathway mediated by activating of TLR and interferon signaling with poly(I:C), and a cellular mobilization pathway stimulated by the growth factor granulocyte colony-stimulating factor (G-C SF)
After the respective drug treatments, hematopoietic stem cells (HSCs) and multipotent progenitors (MPPs) populations comprising the entire LSK compartment were isolated via fluorescence-activated cell sorting (FACS) (Figure 1—figure supplement 1A)

Summary

Introduction

Stem cell therapy holds promises for numerous indications, including blood diseases, autoimmune diseases, neurodegeneration, and cancer (Blau and Daley, 2019). Despite being used in the clinic for over 30 years, hematopoietic stem cell (HSC) transplants remain a highly risky procedure. To better understand HSC regeneration, recent efforts have used single-cell RNA sequencing (scRNA-Seq) to discover novel markers to further enrich for functional HSCs (Chen et al, 2016; Cabezas-Wallscheid et al, 2017; Wilson et al, 2015; Rodriguez-F raticelli et al, 2020). No consensus exists on the optimal marker combination to obtain the most purified HSCs in part because extensive functional. Stem Cells and Regenerative Medicine eLife digest Most organs in the human body are maintained by a type of immature cells known as adult stem cells, which ensure a constant supply of new, mature cells. Adult stem cells monitor their environment through external signalling molecules and replace damaged cells as needed

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