AdipocytesPerilipin+

Caveolin+

Stromal cellsHaematopoietic cells

LEPR+

+

SCA1+

Periarteriolar Perisinusoidal

CD45–

CD31–PDGFRA+

PDGFRB+CD105+ CD51+

TER119–

Prx1 Gli1

Ng2Nestin–GFP (high)

Cxcl12ScfNestin–GFP (dim)Foxc1

MSCs

Gremlin

Lineage–

SCA1+

KIT+

CD48–

CD105+

FLT3–

CD150+

PROCR+

CD34–

α-catulinHoxB5Tie2

HSCs

Protein expression

Genetic labelling

Osteoprogenitors

OsterixNestinCxcl12

CD31–

CD45–

TER119–

CD51+

PDGFRA+

SinusoidsVEGFR3+

CD144low

TJP1low

CD31+

MECA32+

VEGFR2+

Laminin+

Endothelialcells

Capillaries

Arterioli

SCA1+

TJP1hi

CD144hi

Tie2

Nestin

Osteoblasts

Collagen 1OsterixOsteocalcin

ALCAM+

SCF

IL-1

G-CSF

CXCL12

ANGPT1

Monocyte

Quiescent HSC

Cycling HSC

Quiescent HSC

Cycling HSC Quiescent HSC

Cycling HSC

Mobilized HSC

T cell

NK cell

Myeloid cells

Myeloid cells

TLR

IFNα/β IFNγ

IFNγ

IL- 1 G-CSF

Viral infection Bacterial infection Malignancy

Inflammation

OsteoclastsTRAP+

CD169+

F4/80+

CD115int

GR1–

Macrophages

Macrophage Leukocytes

Fibroblast

Apoptotic HSC

Megakaryocyte

IFNα/β

CD61+ VWF+ CXCL4+ CD41+ Clec2

Megakaryocytes

Notchligand

SinusoidCXCL12

HSC mobilizationVCAM1CXCL12

–

TGFβ1 TPOCXCL4SCF CXCL12ANGPT1

–

+

HSC quiescence and maintenance

E-selectin

+

HSC cycling and differentiation

IL-7EPONotch ligands FGF1

SCF

Latent TGFβ1

Active TGFβ1

Noradrenaline

FGF1

Macrophage

Endothelial cell

Non-myelinating Schwann cell

Sympathetic nerve

Sinusoid

Sinusoid

Perisinusoidal MSC

Bone Central bone marrow

Arteriole

Sinusoid

MSC

Osteoclast

Osteoblast

Sinusoid

Periarteriolar MSC

Perisinusoidal MSC

CXCL12

IL-7

EPO

TNF

ANGPT1

CXCL12

SCF

LatentTGFβ1

TPO CXCL4

Adiponectin

OsteoprogenitorAdipocyte

Macrophage

Arteriole

VCAM1

E-selectin

Endosteum

Arteriole

Endothelial cell

Megakaryocyte

IL-1

IL1

CCL3 TPO

CXCL12

Malignant myeloid cellsMalignant

myeloid cells

Loss of NG2+ MSC

Non-functional osteoprogenitor

Neuropathy

Neuropathy

Inflammation

Transformation

HSCNestin+ MSC

Loss of nestin+ MSC

Loss of nestin+ MSC

Impaired differentiation

MLL–AF9blasts

Niche-driven malignancies

Haematopoietic cell-driven malignancies

MLL–AF9-driven AMLJAK2V617F-driven MPN

Primary driver mutation

Sinusoid

ArterioleOsteoprogenitors

Endosteal collagen 1 fibrosis

Remodelled endosteal MSC

Leukaemicstem cell

BCR–ABL-driven CML

HSC

Leukaemicstem cell

SCF

CXCL12

ANGPT1

Endomucin+

Arteriole

Bone marrow niches and HSC fatesEvgenia V. Verovskaya, Timothy B. Campbell and Emmanuelle Passegué

Self-renewing and multipotent haematopoietic stem cells (HSCs) generate all mature blood cells. Adult HSCs exist in highly specialized bone marrow niches. These niches have crucial roles in regulating the fate of HSCs in terms of quiescence, mobilization into the peripheral blood and differentiation in response to steady-state and emergency cues. HSC fate is influenced by diverse types of stromal and haematopoietic cells that make up the bone marrow niche and provide signals in the form of soluble factors, direct cell–cell contact and cell-surface ligands. In stress conditions, such as

during an inflammatory response, bone marrow niches respond by regulating the balance of downstream HSC fates. In the case of myeloid malignancies, bone marrow niches can be remodelled to create an environment that supports malignant stem cells but impairs the maintenance of normal HSCs. Understanding the signalling pathways of the bone marrow niche will aid the therapeutic use and targeting of HSCs, as well as provide more general insights into stem cell regulation and the function and composition of stem cell niches.

STEMCELL Technologies — Your Ideas. Our Tools.Having the right tools for the isolation, culture and analysis of haematopoietic stem and progenitor cells (HSPCs) is essential for increasing our understanding of the mechanisms controlling HSPC behaviour and fate decisions. This knowledge furthers the development of cell therapies to treat haematological disorders. STEMCELL supports every step of your HSPC research with products for:

Document #27038 | Version 1.0.0

Expansion & Differentiation• Serum-free media and supplements for culture,

expansion and lineage-specific differentiation ofHSPCs (www.StemSpan.com)

• Media and detection reagents for long-termculture of HSPCs in the presence of stromal cells(www.MyeloCult.com)

• Cytokines and small molecules for completeflexibility in the design of experimental cultureconditions

Analysis• Semi-solid methylcellulose-based (www.MethoCult.com) and

collagen-based (www.MegaCult.com) media to quantitateprogenitor cells of different lineages in haematopoieticcolony assays

• Antibodies for immunophenotyping and sorting of HSPCs andmature blood cell subsets (www.STEMCELL.com/Antibodies)

To see our full portfolio of products for HSPC research visit www.STEMCELL.com/HSPCworkflow

Cell Sourcing & Isolation • Fresh and frozen primary haematopoietic cells

isolated from human donors(www.STEMCELL.com/PrimaryCells)

• Column-free isolation of HSPCs(www.EasySep.com & www.RosetteSep.com)

• Instruments for fully automated, walk-away cellisolation (www.RoboSep.com)

Abbreviations ALCAM, activated leukocyte cell adhesion molecule; AML, acute myeloid leukaemia; ANGPT1, angiopoietin 1; Clec2, C-type lectin domain family 2; CML, chronic myeloid leukaemia; CXCL, CXC-chemokine ligand; EPO, erythropoietin; FGF1, fibroblast growth factor 1; FLT3, Fms-related tyrosine kinase 3; Foxc1, Forkhead box c1; GFP, green fluorescent protein; G-CSF, granulocyte colony- stimulating factor; IL, interleukin; LEPR, leptin receptor; MPN, myeloproliferative neoplasm; PDGFRA, platelet-derived growth factor receptor A; PROCR, protein C receptor; SCF, stem cell factor;

TGFβ1, transforming growth factor β1; TJP1, tight junction protein 1; TLR, Toll-like receptor; TNF, tumour necrosis factor; TPO, thrombopoietin; TRAP, tartrate-resistant acid phosphatase; VCAM1, vascular cell adhesion molecule 1; VEGFR, vascular endothelial growth factor receptor; VWF, von Willebrand factor.

AffiliationsEvgenia V. Verovskaya, Timothy Campbell and Emmanuelle Passegué are at the Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California San Francisco,

California 94143, USA. Evgenia V. Verovskaya and Emmanuelle Passegué are relocating to the Columbia Stem Cell Initiative, Columbia University Medical Center, New York 10032, USA.Correspondence to E.P. e-mail: ep2828@cumc.columbia.eduThe authors declare no competing interests.

Edited by Kirsty Minton; designed by Caio Bracey.© 2017 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.http://www.nature.com/posters/hsc

Stress signals alter HSC fatesDiverse stressors and insults to the bone marrow, such as bacterial and viral infection and malignancy, create an inflammatory milieu that controls HSC fate via cell-surface receptors. Inflammatory factors can act on HSCs and their downstream progenitors through various mechanisms that are illustrated by the prototypical examples of type I and type II interferons (IFNs; IFNα/β and IFNγ, respectively), IL-1 and G-CSF. IFNs are produced preferentially by haematopoietic cells and act directly on HSCs to direct downstream differentiation and proliferation. IL-1 is produced under stress conditions by stromal and haematopoietic cells and acts directly on HSCs to drive an emergency myeloid response. G-CSF is produced by stromal and haematopoietic cells and acts indirectly on HSCs by downregulating the production of stromal cell-derived factors, which affects HSC quiescence and mobilization, and by the induction of TLR signalling, which leads to HSC proliferation.

The active roles of bone marrow niches in malignancyBone marrow niches have an active role in the initiation and progression of myeloid malignancies. In BCR–ABL-driven CML, remodelled endosteal MSCs differentiate to osteoblast lineage cells that deposit collagen I at the endosteal surface, creating a hostile environment for normal HSCs. In JAK2V617F-driven MPN, neuropathy and loss of nestin+ MSCs are hallmarks of disease progression, mediated by IL-1-driven inflammation. In MLL–AF9-driven AML, sympathetic neuropathy leads to the depletion of periarteriolar NG2+ MSCs but expands the population of remodelled osteoblast-primed nestin+ MSCs through a mechanism dependent on β-adrenergic signalling. Primary driver mutations in bone marrow niche cells, particularly osteoprogenitor cells, can initiate myeloid malignancies within the haematopoietic compartment by establishing an inflammatory milieu.

Identification of bone marrow niche cell types in miceBone marrow niche cells have been characterized by protein expression (cell-surface and intracellular), by genetic labelling and by lineage tracing. Expression patterns often correlate with specialized locations of niche cells in vascular bone marrow niches (capillaries, arterioli or sinusoids), particularly for MSCs and endothelial cells.

Diverse bone marrow niches influence HSC fateThe bone marrow contains a dense neurovascular network that is innervated by sympathetic nerves and includes an enrichment of arterioles and capillaries in the endosteum, as well as large sinusoids located throughout the endosteum and central bone marrow cavity. Cellular bone marrow niches are closely associated with this neurovascular network and contain stromal elements including perivascular mesenchymal stromal cells (MSCs), endothelial cells (of arterioles, capillaries and sinusoids), differentiated osteoprogenitors and adipocytes. Haematopoietic cells of the bone marrow niche include megakaryocytes, macrophages and osteoclasts. These diverse cell types provide crucial signals to HSCs in the form of soluble factors, direct cell–cell contact and cell-surface ligands that influence fates such as mobilization, quiescence and differentiation.

Central bone marrow

Bone

Endosteum

Nutrient artery

Nutrientvein

Articular cartilage

Central artery

Central vein/sinusoid

Sympathetic nerve

Periostial capillary

Sinusoid

Arteriole

marrow niches are closely associated with this neurovascular network and contain stromal elements including perivascular mesenchymal stromal cells (MSCs), endothelial cells (of

Central vein/sinusoidCentral vein/sinusoid

Periostial capillary

Sinusoid

Arteriole

Nutrient artery

Periostial capillary

Sinusoid

Arteriole

cells (MSCs), endothelial cells (of

adipocytes. Haematopoietic cells of the bone marrow niche

macrophages and osteoclasts.

Nutrient artery

NutrientveinNutrientNutrientNutrientNutrientNutrientveinveinveinveinvein

cells (MSCs), endothelial cells (of cells (MSCs), endothelial cells (of cells (MSCs), endothelial cells (of

cells of the bone marrow niche

macrophages and osteoclasts.

cells (MSCs), endothelial cells (of