Manifestation of Novel Social Challenges of the
European Union
in the Teaching Material of
Medical Biotechnology Master’s Programmes
at the University of Pécs and at the University
of Debrecen
Identification number: TÁMOP-4.1.2-08/1/A-2009-0011
Manifestation of Novel Social Challenges of the
European Union
in the Teaching Material of
Medical Biotechnology Master’s Programmes
at the University of Pécs and at the University
of Debrecen
Identification number: TÁMOP-4.1.2-08/1/A-2009-0011
Dr. Péter Balogh and Dr. Péter Engelmann
Transdifferentiation and regenerative medicine –
Lecture 2
STEM CELL TYPES,
THEIR
MAINTENANCE AND
HOMEOSTASIS
Sources and types of stem
cells: different origins and
developmental spectra
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ES:
• Embryonic stem cells from the ICM (inner cell
mass)
• Primordial Germ Cells (PGCs) → Embryonic Germ
(EG) cells
iPS: non-embryonic somatic cells developed by the
introduction of specific key transcription
factors: Oct4, Sox2, c-myc, Klf4
MSC: mesenchymal stem cells present in bone
marrow, adipose tissue, umbilical cord blood,
amniotic fluid, placenta, dental pulp, tendons,
synovial membrane and skeletal muscle, capable of
self-renewal and differentiation in vitro into a
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Sources of embryonic stem
cells (ESCs)
Morula
Oct3/4
Early blastocyst
Inner cell mass
(ICM)
Late blastocyst Egg cylinder stage
Nanog
Epiblast
Primitive
ectoderm
Germ cell line
Somatic cell lineag
Ectoderm
Mesoderm
Endoderm
Blastocyst cavity
Visceral
endoderm
Primitive
Gata6 endoderm
Cdx2
Trophectoderm
Parietal
endoderm
Proamniotic
cavity
Extraembryonic ectoderm
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Stem cell sources in the
mouse embryo
• Preimplantation embryo: inner cell
mass (ICM) of the blastocyst (early
blastocyst stage).
• Late blastocyst stage: formation of
epiblast
• Postimplantation embryo: formation of
primitive ectoderm with restricted
pluripotency → the germ cell lineage
and somatic lineages of the embryo.
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Characteristics of ES cells
• Derivation from the preimplantation or periimplantation
embryo
• Prolonged undifferentiated proliferation,
• Stable developmental potential to form derivatives of all
three embryonic germ layers even after prolonged culture
• EC cells: teratocarcinoma-derived pluripotent embryonal
carcinoma cells generating cells of all three germ layers
Cartilage
(mesodermal)
Epidermis
(ectodermal)
Intestinal glands
(endodermal)
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Cell membrane markers for
ESCs
PSA-NCAM
Glc
Gal
Lewis X
CD34
Tra 1-60 (KSPG)
NG2 and 473HD (CSPG)
SSEA-3
SSEA-4
Man
GlcNAc
GalNAc
GlcA
IdoA
Xyl
Fuc
Sia
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Structure of glycoantigens
characteristic for ES cells
• SSEA-3 and SSEA-4: 5–6 monosaccharides
attached to a ceramide lipid tail,
forming the globoseries
glycosphingolipids GL-5 and GL-7,
their expression is reduced upon
differentiation.
• The TRA (tumor rejection antigens)
TRA-1–60 and TRA-1–81 keratan sulfated
proteoglycan (KSPG) epitopes ,
probably associated with podocalyxin,
a heavily sialylated membrane protein
structurally similar to CD34.
Characteristics of CDdefined antigens for ES
cells
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• CD34: HSC/endothelial shared antigen
expressed hemopoietic stem
cells/progenitors
• CD133: Five transmembrane domain cellsurface glycoprotein, expressed by
neural stem cells
Main regulatory mechanisms
of stem cells – external and
internal effects
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External
Interactions with the matrix
proteins, soluble factors and
other cell types in stem cell
niches, direct interactions with
ECM proteins, complex signaling
feedback from adjacent ESC niche
cells (stromal/differentiated).
Internal
TF network regulating pluripotency
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Stem cell niches in various
organs
Germarium of the ovary
Inner sheath
cell
SSC
Cap cell BL
Terminal
filament
The apex of the testis The subventricular zone (SVZ)
of the brain
BLSpermatogonia
GSC
Hub cells
SSC
Egg
chamber
Neuroblast BV
Astrocyte
Transitamplifying
Meiosis
Gonialblast
Cyst cell
Spermatocytes
GSC
Cystoblast
Ependymal cells
Lateral ventricle
Follicle
16-cell
cyst cells
The bone marrow
BL
The crypt of an intestinal The
villus
bulge of the hair follicl
Hair shaft
Stromal cell
Enteroendocrine cells
Multipotent SC
Bone marrow
Villus
Muscle
Goblet cells
HSC
BL
Bulge
MyeloidLymphoid
Osteoblast
Crypt
BL
Sebaceou
s
SC gland
Transit amplifying
Stem cells
Paneth cells
Matrix
Dermal papilla
Hair
bulb
Stem cell environment –
examples for stem cell
niche
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• Germanium region of the ovary and the
apex of the testis (germ-line stem
cell and somatic stem cell)
• Subventricular zone in the brain
(neural stem cell)
• Bulge of hair follicle (epithelial
stem cell)
• Crypt of intestinal villi (endodermal
stem cell)
• Bone marrow (hemopoietic stem cell)
Multiple interactions
involved in stem cell
homeostasis
Nanog
Oct4
Nanog
Tbx3
ESC regulators
Tcf3
Tle1
Fzd5
Wnt signaling
Nanog
Oct4
Jarid2
Tcf3
Phc1
N-myc
Dppa5
Sox2
LRH1
GCNF
Tcf3
Oct4
Oct4
Pluripotency
Rif1
Trp53bp1
Tumor
Epigenetic regulators RNA binding Telomere
protein associatedsuppressor
Sall4
Oct4
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Differentation
Antagonistic regulatory
circuits between
differentiation and
pluripotency
• ESC/iPS regulation – hierarchic
transcription factors
• Wnt signaling
• Epigenetic regulators
• RNA binding
• Telomere associated effectors
• Tumor suppression
• Cell cycle regulation
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mRNA regulation of stem
cell gene expression
Sox2
Oct4
Nanog
Other factors
AAAAA
AAAAA
mRNAs
miRNAs
AAAAA
AAAAA
Alternatively spliced mRNAs
Antisense transcripts
AAAAA
AAAAA
Intergenic spliced mRNAs
Other RNAs?
siRNAs?
Intergenic transcripts
TF regulation for
selfrenewal/differentiation
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• Oct3/4, Nanog, Sox2, Stat3: maintenance of
proliferation
• Cdx2: Inhibitory cross-interaction with
Oct3/4
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Reprogramming: Induction of
pluripotency in iPS cells
Oct3/4
Klf4
Sox2
Transcription factors
Target genes
c-Myc
Epigenetic modifiers
Reprogramming: Lineage
shift in differentiated
cells
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• Reprogramming of B-cell lineage into
macrophages – role of C/EBPa
• Induction of neuronal commitment from
fibroblasts – Ascl1, Brn2 and Mytl1
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Sequential maturation and
regeneration of pluripotency
Ectoderm
progenitor
Pluripotent cell
Pluripotent cell
Neuronal
progenitor
Mature neuron
Endoderm
Mesoderm Ectoderm
Pluripotent cell
Differentiation-associated
commitment and
reversibility
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Differentiation is coupled with
• commitment and loss of
pluripotency/transdifferentiation capacity
BETWEEN lineages
• Requirement for continuous stimulation for
promoting specification WITHIN a lineage.
Reversal: Introduction of iPS-associated
multilineage differentiation is associated
with LOWERING of pleiotropic induction
requirement and ELEVATION of differentiation
signal threshold
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Summary
• Depending on their origin and developmental
spectra, stem cells are quite heterogeneous,
where their homeostasis is determined by
their (a) endogenous programming with
various levels of regulating gene
expression and (b) external factors,
including cytokines and adhesion proteins
binding to extacellular matrix an other cell
comprising the stem cell niche.
• Stem cell commitment and differentiation are
not irreversible, as differentiated cell can
be modulated to regain multipotency.