Welcome
Everyone
To know
“transdifferentiation”
Sun, Luguo
2013.03.25
CONTENTS

What is transdifferentiation?

Phenomenon of transdifferentiation

Studies of transdifferentiation

Significance of transdifferentiation
studies
What?

Differentiation

De-differentiation

Trans-differentiation
What?

Differentiation

-- the process by which a less specialized
cell becomes a more specialized cell type
De-differentiation

Trans-differentiation
What?

Differentiation
Pluripotent SC
multipotent SC
Adult SC
Progenitor cells
Mature and
differentiated cells
SC: stem cell
differentiation
Unipotent SC
What?

Differentiation

De-differentiation

--refers to a reduction in the molecular
and/or functional properties of a
differentiated cell type
Trans-differentiation
What?

De-differentiation
Pluripotent SC
Multipotent SC
Progenitor cells
Mature and
differentiated cells
iPSC
differentiation
Unipotent SC
2012 Nobel Prize in Physiology or Medicine
"for the discovery that mature
cells can be reprogrammed to
grow new cells."
Shinya Yamanaka
John Gurdon
What?

Differentiation

De-differentiation

Trans-differentiation
--Broadly, it refers to converting one sort of cell
into another
--Strictly, it refers to the switch between one
differentiated cell type to another
What?

Trans-differentiation
Differentiated cells
Another type of Differentiated cells
differentiation
Stem cells
Differentiated C. of different lineage
Trans-differentiation
What?
Differentiated
cells
Another type of Differ. cells
De-Differentiated cells

Molecular Basis:
 Every cell has a complete and identical set of genes
Differential gene expression in different cell type
 “Master switch genes” are fate determining
--expressed in one cell type but not another
--are responsible for the formation of different
tissues.
--are transcription factors
CONTENTS

What is transdifferentiation?

Phenomenon of transdifferentiation

Studies of transdifferentiation

Significance of transdifferentiation
studies
Phenomena
--Naturally occurring
--The concept of “transdifferentiation” was first
introduced in 1974
Animals: For repairing
e.g: newts, chick repair of damaged or removed lens
Iris pigment epithelial De-differentiated
cells
Len cells
(keratinocytes)
Eguchi and Okada, 1973,1977,1991
Phenomena
in human:
A major dysfunction and pathologic
•metaplasia
Barret’s metaplasia
oesophageal
Trans-Diff Intestinal-like
squamous epithelium
tissue
High risk of tumorigenesis
•Liver fibrosis
Hepatic stellate cells
( quiescent)
Fibrotic
stimulus
Myofibroblast-like cells
(collagen-producing)
fibrosis
Phenomena
‘
•EMT（Epithelial to mesenchymal
transition)
ECM+
E-cadherin+
ZO-1 +
Fibronectin +
vimentin +
Singh,A et al Oncogene, 2010
——Required for tissue morphogenesis during embryonic development
‘
——Contributes to increased metastasis
and drug resistance in cancer
——includes morphogenetic and gene expression changes
CONTENTS

What is transdifferentiation?

Phenomenon of transdifferentiation

Studies of transdifferentiation

Significance of transdifferentiation
studies
Studies
——Transdifferentiation experiments have been
performed in vivo and in vitro in various systems
Studies

Candidate cells
Small jump:
 cell types with proximal lineage
Liver cells
Pancreas cells
 Neighboring tissues
Pancreatic
exocrine cells
Insulinproducingβcells
big jump:
 Cells with different lineage
Fibroblasts: easy -access, more abundant
Studies

Methods of transdifferentiation
 Transfection of “Master switch” genes
 Addition of specific molecules including chemicals, proteins
et al.
 Cell-cellular extract co-culture
 Cell-cell co-culture
Studies
pancreatic cells
Fibroblasts
hepatocytes
other cells
pancreatic cells
hepatocytes
•2000-2003：in vitro
（地塞米松）
+ C/EBPβ
C/EBPβ
Pdx-1
pancreatic duodenal
homeobox-1
Biochem J , 2003; J Cell Physi, 2006;
hepatocytes
pancreatic cells
Transplantation of the induced pancreatic cells
into diabete mice could alleviate the symptom
with the elevated level of blood insulin.
Transdifferentiation of liver cells to pancreatic cells has considerable
clinical significance since it could be a potential therapy for diabetes..
Nature, 2000; PNAS, 2002;
Fibroblasts
•Fibroblasts→skeletal muscle cells
•Fibroblasts→neuronal cells
•Fibroblasts→myocardial cells
•Fibroblasts→blood cells
other cells
Fibroblasts
other cells
•Fibroblasts→skeletal muscle cells
•Fibroblasts→neuronal cells
Mice fetal
fibroblasts
•Fibroblasts→myocardial cells
Skeletal muscle cells
+ MyoD
Other types of
•Fibroblasts→blood cells
cells
MyoD only expresses in skeletal
muscle cells and is the “Master
switch gene”
cell, 1987; Science,1988,1989;PNAS, 1989,1990;
Fibroblasts
other cells
•Fibroblasts → skeletal muscle cells
•Fibroblasts → neuronal cells
2010年：amazing study
Nature, 2010
•Fibroblasts → myocardial cells
•Fibroblasts →blood cells
BAM: Brn2, Ascl1, Myt1I
Hign efficiency :20%
Form synapses and transmit action potentials
Fibroblasts
other cells
•Fibroblasts→skeletal muscle cells
•Fibroblasts→neuronal cells
2011年：followed
•Fibroblasts→myocardial cells
•Fibroblasts→blood cells
Human Fetal/
postnatal
human
+
Neuro D1
+Lmx1a
,FoxA2
iN cells
Mouse
Healthy human
patients
Ascl 1
Nurr1
Lmx1a
dopamine neuron
(Dies in Parkinson’s
disease)
PNAS, 2011(2)，Nature 2011（2）,
Fibroblasts
other cells
•Fibroblasts→skeletal muscle cells
•Fibroblasts→neuronal cells
2011年：more closer for clinical application
•Fibroblasts→myocardial cells
Adult human
•Fibroblasts→blood cells
MiR-9
MiR-124
MiR-124 +Brn2
(or
+Myt1l
+Ascl1
+Myt1l)
Mouse, human EFs
+ 4 motor
neuron
specific TFs
No
dedifferentiatin
iN cells iN cells
Spinal moter
neuron (iMNs)
Cell stem cell , 2011.9, Nature,2011
Fibroblasts
other cells
•Fibroblasts→skeletal muscle cells
•Fibroblasts→neuronal cells
Cardiac fibroblasts in
thecells
infarcted
•Fibroblasts→myocardial
myocardium scar
•Fibroblasts→blood cellspost-natal cardiac or
dermal fibroblasts
+ Myocardin
Gata4, Mef2c,Tbx5
Cardiomyocytes
Cardiomyocytes
FASEB J, 2007; Cell, 2010; Nature cell biology, 2011
Fibroblasts
other cells
•Fibroblasts→skeletal muscle cells
•Fibroblasts→neuronal cells
•Fibroblasts→myocardial cells
•Fibroblasts→blood cells
Mice fetal or
adult
fibroblasts
PU.1 ,C/EBPalpha/beta
macrophages
PNAS, 2008
Studies
pancreatic cells
Fibroblasts
hepatocytes
other cells
CONTENTS

What is transdifferentiation?

Phenomenon of transdifferentiation

Studies of transdifferentiation

Significance of transdifferentiation
studies
Significance

As a new approach in regenerative medicine

Helpful to improve our understanding of
normal developmental biology

Helpful to identify transcription factors that
induce cells to differentiate
Significance


As a new approach in regenerative medicine
-- creating living, functional tissues to repair or
replace tissue or organ function lost due to
to improve
our
understanding
of
age, disease,
damage,
or congenital defects
Helpful
normal developmental
biology
-- To treat
e.g：Neurodegenerative diseases
cardiac injury
 Helpful to identify transcription factors
diabetes
induce cells to genetic
differentiate
disorder
blood diseases……
--cells
e.g: Natural stem cells
iPSC
Trans-D cells
that
Good :-- self renewal
--pluripotency
--can be genetically modified
--No immune attack
Bad : --Time-consuming
--Expensive
--Low induction efficiency
--risk of tumor forming
Good : -- easier and faster
-- Low cost
-- Less likely to form tumors
-- High efficiency
-- No immune attack
Bad: --No self renewal
--No genetic modification
--may not fully convert
Significance

As a new approach in regenerative medicine
-- creating living, functional tissues to repair or

replace tissue or organ function lost due to age,
improve
ourorunderstanding
of
disease, damage,
congenital defects
Helpful to
normal developmental
biology
-- To treat
e.g：Nerve degenerative diseases
cardiac injury
 Helpful to identify transcription factors
diabetes
disorder
induce cells togenetic
differentiate
blood diseases
--cells
e.g: Natural stem cells
iPSC
Trans-D cells
that
Significance

As a new approach in regenerative medicine

Helpful to improve our understanding of
normal developmental biology

Helpful to identify transcription factors that
induce cells to differentiate
CONTENTS

What is transdifferentiation?

Phenomenon of transdifferentiation

Studies of transdifferentiation

Significance of transdifferentiation
studies
That is all for today!