Welcome Everyone

Welcome EveryoneWelcome Everyone

To know “transdifferentiation”

Sun, Luguo

2013.03.25

What is transdifferentiation?

CONTENTS

Phenomenon of transdifferentiation

Studies of transdifferentiation

Significance of transdifferentiation studies

What? Differentiation

Trans-differentiation

De-differentiation



De-differentiation-- the process by which a less specialized cell becomes a more specialized cell type

differentiation

Pluripotent SC

multipotent SC

Unipotent SC

Progenitor cells

Mature and differentiated cells

Differentiation

Adult SC

What?

SC: stem cell



De-differentiation

--refers to a reduction in the molecular and/or functional properties of a differentiated cell type

differentiation

iPSC

De-differentiation

What?

Pluripotent SC

Multipotent SC

Unipotent SC

Progenitor cells

Mature and differentiated cells

Shinya Yamanaka John Gurdon

2012 Nobel Prize in Physiology or Medicine

"for the discovery that mature cells can be reprogrammed to grow new cells."



De-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

differentiation



Differentiated cells

What?

Another type of Differentiated cells

Stem cells

Differentiated C. of different lineage

Differentiated cells

De-Differentiated cells

Another type of Differ. cells

De-D

Trans-D

Molecular Basis:

Differential gene expression in different cell type

Every cell has a complete and identical set of genes

“Master switch genes” are fate determining

What?

--expressed in one cell type but not another--are responsible for the formation of different

tissues.--are transcription factors


CONTENTS




--Naturally occurring

For repairing

Len cells(keratinocytes)

Iris pigment epithelial cells

e.g: newts, chick repair of damaged or removed lens

Animals:

De-differentiated

--The concept of “transdifferentiation” was first introduced in 1974

Eguchi and Okada, 1973,1977,1991

Phenomena

A major dysfunction and pathologic

Barret’s metaplasia

High risk of tumorigenesis oesophageal squamous epithelium

Intestinal-like tissue

Trans-Diff

•metaplasia

•Liver fibrosis

Hepatic stellate cells( quiescent)

Myofibroblast-like cells(collagen-producing)

fibrosis

in human:

Fibrotic stimulus

Phenomena

•EMT（ Epithelial to mesenchymal transition)

——Required for tissue morphogenesis during embryonic development

——Contributes to increased metastasis and drug resistance in cancer

——includes morphogenetic and gene expression changes

E-cadherin+

ZO-1 +

ECM+

Fibronectin +

vimentin +

Singh,A et al Oncogene, 2010

Phenomena

‘

‘


CONTENTS




Studies——Transdifferentiation experiments have been performed in vivo and in vitro in various systems

Candidate cells

cell types with proximal lineage

Neighboring tissues

Cells with different lineage

Small jump:

Liver cells

Pancreatic exocrine cells

Insulin-producingβcells

Pancreas cells

big jump:

Studies

Fibroblasts: easy -access, more abundant

Methods of transdifferentiation

Addition of specific molecules including chemicals, proteins et al.

Cell-cell co-culture

Transfection of “Master switch” genes

Cell-cellular extract co-culture

Studies

pancreatic cells hepatocytes

Fibroblasts other cells

Studies

•2000-2003： in vitro

C/EBPβ

Pdx-1 pancreatic duodenal homeobox-1

（地塞米松）

+ C/EBPβ

Biochem J , 2003; J Cell Physi, 2006;


hepatocytes pancreatic cells

High glucose

Pancreatic cell extra

ct

Nature, 2000; PNAS, 2002;

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..

•Fibroblasts→skeletal muscle cells

•Fibroblasts→neuronal cells

•Fibroblasts→myocardial cells

•Fibroblasts→blood cells







Mice fetal fibroblasts + MyoD

Skeletal muscle cells

Other types of cells

+ MyoD

MyoD only expresses in skeletal muscle cells and is the “Master switch gene”

cell, 1987; Science,1988,1989;PNAS, 1989,1990;

•Fibroblasts → skeletal muscle cells

•Fibroblasts → neuronal cells

•Fibroblasts → myocardial cells

•Fibroblasts →blood cells


2010年： amazing study Nature, 2010

BAM: Brn2, Ascl1, Myt1I

Hign efficiency :20%

Form synapses and transmit action potentials






PNAS, 2011(2)， Nature 2011（ 2） ,

2011年： followed

human

+Lmx1a,FoxA2

dopamine neuron

MouseHealthy human patients

Ascl 1 Nurr1 Lmx1a

Human Fetal/ postnatal

+ Neuro D1

iN cells(Dies in Parkinson’s dis

ease)






Cell stem cell , 2011.9, Nature,2011

2011年：more closer for clinical application

Mouse, human EFs

+ 4 motor neuron specific TFs

Spinal moter neuron (iMNs)

No dedifferentiatin

Adult human

iN cells

MiR-9 MiR-124(or +Ascl1+Myt1l)

MiR-124+Brn2+Myt1l

iN cells






Cardiac fibroblasts in the infarcted myocardium scar

+ Myocardin Cardiomyocytes

FASEB J, 2007; Cell, 2010; Nature cell biology, 2011

post-natal cardiac or dermal fibroblasts

Gata4, Mef2c,Tbx5 Cardiomyocytes






Mice fetal or adult fibroblasts

PU.1 ,C/EBPalpha/beta macrophages

PNAS, 2008



Studies


CONTENTS




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




-- creating living, functional tissues to repair or replace tissue or organ function lost due to age, disease, damage, or congenital defects

-- To treat

e.g： Neurodegenerative diseases cardiac injury diabetes genetic disorder blood diseases……

--cells

e.g: Natural stem cells iPSC Trans-D cells

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 attackBad: --No self renewal --No genetic modification --may not fully convert




-- creating living, functional tissues to repair or replace tissue or organ function lost due to age, disease, damage, or congenital defects

-- To treate.g： Nerve degenerative diseases cardiac injury diabetes genetic disorder blood diseases

--cells

e.g: Natural stem cells iPSC Trans-D cells


CONTENTS




That is all for today!

Welcome Everyone

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