Stem Cell:The Promise and The Challenge

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Stem Cell：The Promise and The Challenge

Chia

Chia-Cheng Chang, Ph.D.-Cheng Chang, Ph.D. Department of Pediatrics Department of Pediatrics and Human Development and Human Development Michigan State University Michigan State University

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Stem cells are undifferentiated cells

with the capacity for unlimited or

prolonged self

-

renewal and the ability

to give rise to differentiated cells.

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Differentiation

can be defined as qualitative

changes in the cellular phenotype that are a

consequence of the onset of synthesis of

new gene products, i.e. the non-cyclic

changes in gene expression that ultimately

lead to functional competence.

Bach, Renehan and Potten

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New Excitement About Stem Cells

Successful cultivation of Human embryonic

stem cell lines.

Adult stem cells can differentiate into

developmentally unrelated cell types.

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Characteristics of Human ES Cells

•Normal Karyotypes

•Express high telomerase activity

•Express cell surface markers of primate embryonic stem cells •Maintained undifferentiated proliferation for 4-5 months and

developmental potential to form trophoblasts and gut epithelium (endoderm), cartilage, bone, smooth and striated muscle (mesoderm), neural epithelium, stratified squamous epithelium (ectoderm)

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ES

1. High malleability

2. Potential for undesired

development (

development (teratomasteratomas)) 3. Infinite lifespan,

3. Infinite lifespan,

unlimited supply

4. High ethical burden

Uncertain legal status

Adult Stem Cells

Limited developmental potential

Better behaved, easier to manage

Lose their ability to proliferate/

differentiate after a time in culture

Less moral ambiguity

Less legal controversy

Advantage and Drawbacks of Embryonic

Stem Cells and Stem Cells from the Adult

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Can Old Cells Learn New Tricks?

Stem cells found in adults show

surprising versatility, but it’s

not yet clear whether they can

match the power of cells from

embryos.

G. Vogel

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Adult Stem Cells Can Differentiate into

Developmentally Unrelated Cell Types

1.

1. Neural stem cells produced myeloid and lymphoid cells as Neural stem cells produced myeloid and lymphoid cells as well as early

well as early hematopoietichematopoieticcells.cells. 2.

2. Stem cells from mouse muscle could repopulate the blood Stem cells from mouse muscle could repopulate the blood stream and rescue lethally irradiated mice.

stream and rescue lethally irradiated mice. 3.

3. Bone marrow stem cells can become brain cells and liver Bone marrow stem cells can become brain cells and liver cell precursors, plus heart skeletal and smooth muscle. cell precursors, plus heart skeletal and smooth muscle.

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Location of Adult Stem Cells

Hematopoietic

Hematopoietic—— yolk sac blood island, fetal liveryolk sac blood island, fetal liver and spleen, bone marrow, circulating umbilical cord

and spleen, bone marrow, circulating umbilical cord

Blood

Liver

Liver ——portal zone near bile ductportal zone near bile duct Intestine

Intestine ——cryptcrypt Epidermal

Epidermal ——basal layerbasal layer

Retinal

Retinal ——pigmented pigmented cilliary cilliary marginmargin

Breast epithelial

Breast epithelial ——end buds(Cap cells) and basal layer of end buds(Cap cells) and basal layer of mammary gland

mammary gland

Pancreas

Pancreas ——pancreatic pancreatic islats islats and ductsand ducts Mesenchymal

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Retinal Stem Cell

•

• Localized to ciliary

Localized to

ciliary

margin

•

• Can differentiate into retinal

Can differentiate into retinal

-

specific

neuronal and

neuronal and glial

glial

progeny ( rod photo-

progeny ( rod photo

-receptors, bipolar neurons and

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Clonogenic stem cells in small and large intestine

Roberts et al.,

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Mouse Endbuds and Budding Structures Formed by Two Types of HBEC

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Lobule Type 1 and Organoid Formed in Matrigel

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Some Characteristics of Stem Cells

1. Undifferentiated cells with the capacity for

unlimited or prolonged self-renewal that can give rise to differentiated cells.

2. Unipotent and multipotent

e.g. Intestinal stem cells produce one or more of the 4 classes of mature differentiated cells (absorptive, goblet, Paneth and enteroendocrine cells).

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Some Characteristics of Stem Cells

3. Metaplasia-The formation of one differentiated cell type from another.

e.g. Patches of intestinal epithelium in the stomach; foci of hepatocytes in the regenerating pancreas. 4. Slow cycling in cell division.

5. Contact-insensitive;deficient in gap-junctional intercellular communication.

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Specific Gene Expression in Stem Cells

• Human hematopoietic stem cells--CD34, Thy-1

• Epidermal stem cells--β1integrin (α2β1, α3β1) • Small intestinal stem cells--β-catenin

• Hair follicle stem cells--cytokeratin-15

• Retinal stem cells--CHX10, Nestin

• Neural crest stem cells--p75

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Methods for Isolating Stem Cells from

Adult Tissue

1. Flow

1. Flow cytometrycytometry Hematopoietic

Hematopoietic stem cellsstem cells----CD34CD34++_{, HLA}_{, HLA}_-_-_DR_DR-

-Neural crest stem cells

Neural crest stem cells----p75p75++

Epidermal stem cells

Epidermal stem cells----ββ1 1 integrinintegrin 2.

2. MicrodissectionMicrodissection/colony/colony--forming assayforming assay Retinal stem cells

Retinal stem cells

Hair follicle stem cells

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Methods for Isolating Stem Cells from

Adult Tissue

3. Cell adhesion or lack of adhesion

----Human epidermal stem cells adhered most rapidly to Human epidermal stem cells adhered most rapidly to Type IV collagen,

Type IV collagen, fibronectinfibronectinor or keratinocyteskeratinocytesECM.ECM.

----Late attachment of human breast epithelial stem cellsLate attachment of human breast epithelial stem cells on plastic.

on plastic.

4. Contact insensitive growth on cell mat

Putative human kidney epithelial stem cells.

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Alternative Models for Stem Cell

Deployment

1.

1. Invariant Asymmetry

Invariant Asymmetry

2.

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Regulation of Stem Cell roliferation/Differentiation

β-integrin/ECM ----epidermal

Required for cell survival and Keratinocyte differentiation through MAP Kinase.

β-catenin(Tcf/Lef)----intestine

-Tcf-null mice lack stem cells in the small intestine -Overexpression of β-catenin increases the proportion of stem cells in vitro and in vivo.

Telomerase

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Regulation of Stem Cell Proliferation/Differentiation

P21 cip1/waf1_{(cell cycle inhibitor)}

Hematopoietic stem cell quiescence maintained by p21;bone marrow transplant from p21-1-_{mice leads to}

hematopoietic failure.

MAP kinase signaling

The growth of undifferentiated ES cells was enhanced by culture in MAP kinase (MEK) inhibitor (PD 098059).

bcl-2

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Regulation of Stem Cell Proliferation/Differentiation

CDK2

A CDK2 inhibitor prevented hair loss

caused by chemotherapy (

caused by chemotherapy (etopside

etopside) in mice.

) in mice.

Oxidative stress

Lowered oxygen and antioxidant (N

Lowered oxygen and antioxidant (N-

-acetyl

acetyl-

-L

L

-cysteine

-

cysteine) promote growth of CNS and

) promote growth of CNS and

glial

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High Susceptibility of a Human Breast

Epithelial Cell Type with Stem Cell

Characteristics to Telomerase

Activation and Immortalization.

Sun, W., K.S. Kang, I. Morita, J.E. Trosko and C.C. Chang

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Clinical Applications of Stem Cells

1.

1. HematopoiesisHematopoiesisas a model of stem and progenitor cell as a model of stem and progenitor cell transplantation.

transplantation.

■

■Fanconi Fanconi Anemia Anemia ——an an autosomal autosomal recessive disorder recessive disorder characterized by progressive bone marrow failure leading

characterized by progressive bone marrow failure leading

to

to aplastic aplastic anemia.anemia.

■

■Bone marrow ablative doses of chemotherapy and Bone marrow ablative doses of chemotherapy and radiotherapy to eliminate endogenous cancer

radiotherapy to eliminate endogenous cancer

〔

〔leukemia (CML), lymphoma (Hodgkinleukemia (CML), lymphoma (Hodgkin’’s), multiple s), multiple

myeloma

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Clinical Applications of Stem Cells

2.

2. Transplantation therapy for acute and chronic degenerative diseaTransplantation therapy for acute and chronic degenerative diseasese

EpidermalEpidermal----skin graft for patients with severe burnsskin graft for patients with severe burns

Neuronal--Neuronal--ParkinsonParkinson’’s disease, multiple sclerosis and other s disease, multiple sclerosis and other

neurodegenerative disease (brain

neurodegenerative disease (brain gangliosidosisgangliosidosis, , demyelinatingdemyelinating disease).

disease).

Liver--Liver--For Liver damage by drugs, toxins or viral infection.For Liver damage by drugs, toxins or viral infection.

Islet-Islet-for insulin non for insulin non ----producing pancreasproducing pancreas

Skeletal muscle satellite--Skeletal muscle satellite--muscular dystrophies or muscle loss;heart muscular dystrophies or muscle loss;heart

disease disease

Mesenchymal—Mesenchymal—tissue engineering in plastic reconstructive surgerytissue engineering in plastic reconstructive surgery

3. Gene therapy 3. Gene therapy

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Stem Cell Therapy for Parkinson's

Disease

•

• Parkinson's disease: slow, rigid or uncontrollable Parkinson's disease: slow, rigid or uncontrollable

movement caused by the death of a particular group of

brain neurons that produce dopamine.

•

• Logical candidate for cell replacement therapy Logical candidate for cell replacement therapy

----Conventional treatments have had limited success.Conventional treatments have had limited success.

----Grafting immature neurons from aborted human Grafting immature neurons from aborted human fetuses have had up to 50% reduction in patients'

fetuses have had up to 50% reduction in patients'

symptoms and the effects appear to last.

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Stem Cell Therapy for

Parkinson's Disease

•

• Promise of ES cellsPromise of ES cells

----Potential to provide large quantity of Potential to provide large quantity of nigralnigral (dopamine) neurons with better quality control. (dopamine) neurons with better quality control. •

• Challenge of ES cell applicationChallenge of ES cell application

----EEthical concern (better with adult stem cells)._{thical concern (better with adult stem cells).}

----Developing techniques to grow and to Developing techniques to grow and to differentiate ES cells into dopamine neurons differentiate ES cells into dopamine neurons and their supportive cells.

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Stem Cell Research and Ethics

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• Millions of patients may benefit from the Millions of patients may benefit from the applications of stem cells.

applications of stem cells.

•

• Ethics of embryo destruction are not addressed. A Ethics of embryo destruction are not addressed. A time for restraint to develop a national policy and

time for restraint to develop a national policy and

ethical framework.

Stem Cell Research Applications

Stem Cell Research Applications: A society leaving : A society leaving the original Garden of Eden, or A great promise

the original Garden of Eden, or A great promise

not only for unexpected insight into biology but

ultimately for the alleviation of human suffering.