Hematopoietic stem cells and transdifferentiati o n

Manifestation of Novel Social Challenges of the European Unionin the Teaching Material ofMedical Biotechnology Master’s Programmesat the University of Pécs and at the University of DebrecenIdentification number: TÁMOP-4.1.2-08/1/A-2009-0011

HEMATOPOIETIC STEM CELLS ANDTRANSDIFFERENTIATION

Dr. Péter Balogh and Dr. Péter EngelmannTransdifferentiation and regenerative medicine – Lecture 6

Manifestation of Novel Social Challenges of the European Unionin the Teaching Material ofMedical Biotechnology Master’s Programmesat the University of Pécs and at the University of DebrecenIdentification number: TÁMOP-4.1.2-08/1/A-2009-0011

TÁMOP-4.1.2-08/1/A-2009-0011

Issues of hemopoietic differentiation• Development of hemopoietic system

EmbryonicPostnatal

• Regenerating hemopoiesis• Use of HSCs in non-hemopoietic regenerative

medicine

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Ontogeny of embryonic hemopoietic tissues

Pro-definitivePrimitive Meta-definitiveMeso-definitive Adult-definitive

E10.5E7.5 E9.0E8.25

Hemangioblast Hemogenic Endothelium

Myeloid Lymphoid-Myeloid CFU-sNeonatal HSC

HSC

Yolk sacAllantois Chorion

Allantois

YS blood islands

Placenta

AGM

Liver

Placenta

AGM

LiverYolk sacEmbryo pSP

Umbilicalartery

Vitellineartery

Umbilicalartery

Vitellineartery

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Evolution of hemopoietic tissues in rodents

Yolk sac

Onset of circulation

ProPrimitive MetaMeso Adult

E7.5 E8.5 E9.5 E10.5 E11.5 E12.5 E15E13.5 E14.5 birthE11

Para-aorticSplanchnopleura

Allantois

Liver

Thymus

Spleen

Bone marrow

AGM

Aortic clusters

Placenta

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Characteristics of murine embryonic HSCs (AGM/YS/FL)• Leukocyte surface markers: Ly-6A(Sca-1), c-

kit+, CD34+, CD45+, • Shared endothelial markers: CD31+, VE-

cadherin+• TF: Runx1+ SCL+ Gata-2+

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Transcriptional induction of eHSCsIntrinsic signals: TF• Runx1: promotes fetal transition of

hemogenic endothelium into hemopoietic cells

• GATA-2: sequential promotion of mesodermal specification, hemangioblast formation and erythroid differentiation

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Extrinsic regulation of eHSCs

Extrinsic signals: interactions with other germ layer elements

• Yolk sac (endoderm and mesoderm)• The chorio-allantoic placenta (mesoderm and

trophectoderm) • AGM region (dorsal ectoderm, mesoderm and ventral

endoderm)– Ventralizing factors – promote hemopoiesis (VEGF,

bFGF, TGFβ and BMP4)– Dosalizing factors – antagonize hemopoiesis (EGF

and TGFα)

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Hemopoietic differentiation modelsClassic dichotomy model

Modified classic model

Myeloid-based model

Myeloid potentialMErythroid potentialE

Megakaryocyte potentialm

T-cell potentialTB-cell potentialB

(CMLP)

M E m

T BMT B

E m

B

M

T

M

(CLP)

(CMEP)

M E m T B

E m

B

M

T

M E m

T B

(CLP)

(CMEP)

BM

M E m T B

M E m

T BM

E m

B

M

T

M

M

M

M

TM

(CMLP)

(CMEP)

M E m T B

TÁMOP-4.1.2-08/1/A-2009-0011Transcriptional regulation of early hemopoietic commitment

Hemangioblasts Hemogenic endothelium

Apoptosis

SCLAML-1GATA-2Lmo

PU.1/GATA-3/IkarosPU.1/GATA-1

CMP

HSC

CLP

Notch1IkarosHoxB4GATA-2

Bcl-2

p21

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Transcriptional regulation of myeloid differentiation

Monocyte

Neutrophil

Eosinophil

Erythrocyte

Megakaryocyte

GMP

CMPHSC

EMP

PU.1 & GATA-1

PU.1

GATA-1/FOG

ICSBP, PU.1

C/EBP, GATA-1

GATA-1

GATA-1, 2

C/EBP

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Transcriptional regulation of lymphoid differentiation

CLP

Pro-T

PU.1IL-7R

GM-CSFR

Notch1

Pu.1, E2A

PU.1

Pax5?EBF Pax5

Early pro-B Late pro-B

Pre-pro-B V-D-JHD-JH

B cell

MonocyteHSC

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HSCHSC

HSCHSC

EndothelFibroblast

Osteoblast

G-CSF, GM-CSF TPOTGF

Steady-state and activated haemopoiesis

EPO

EPO

IL-1TNF

Macrophage

Bacterialinfection

Inflammation

AnemiaHypoxia

HSCHSC

HSCHSC

SCF, FLT-3I, TPOEndothel

G-CSF, GM-CSF

Fibroblast

Osteoblast

Blood vessel

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Human hemopoietic potentialIntraembryonic sources and potential:• D19: HPP in embryo in the absence of

detectable CD34+ hematopoietic cells, and spanned both lymphoid and myeloid lineages

• D24: in the splanchnopleural mesoderm• D27: aorta with CD34+ progenitorsYolk sac: only myelopoiesis starting at around

the 3rd week

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Other potential uses of hemopoietic stem cells• Regenerative medicine in parenchymal

tissues: muscle, neural tissues, liver, etc.• Sources: adult or embryonic (umbilical vein

mononuclear cells)• Experimental settings: use of genetically

marked cells or inducible Cre-Lox transgenic animals, and their detection in damaged/regenerating tissues

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Summary

• Hemopoiesis is established in successive waves at various anatomical locations, where hemopoietic activities at different host tissues result in diverse cellular progeny.

• The hemopoietic committment is under the combined effects of endogenous programing and external signals, where latter elements may alter the steady-state hemopoiesis.

• Hemopoietic stem cells may promote the regeneration of non-hemopoietic tissues by (a) promoting vascular repair, (b) tissue repair and (c) possible transdifferentiation.