Stem Cell:The Promise and The Challenge

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Edgar Elvin Cox
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1 Stem Cell:The Promise and The Challenge Chia-Cheng Cheng Chang, Ph.D. Department of Pediatrics and Human Development Michigan State University

2 Stem cells are undifferentiated cells with the capacity for unlimited or prolonged self-renewal and the ability to give rise to differentiated cells.

3 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 Carcinogenesis 21: , 2000

4 New Excitement About Stem Cells Successful cultivation of Human embryonic stem cell lines. Adult stem cells can differentiate into developmentally unrelated cell types.

6 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) Developed teratomas in immune-deficient mice

developmental potential to form trophoblasts and gut epithelium (endoderm), cartilage, bone, smooth and

7 Advantage and Drawbacks of Embryonic Stem Cells and Stem Cells from the Adult ES 1. High malleability 2. Potential for undesired development (teratomas( teratomas) 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

High ethical burden Uncertain legal status Adult Stem Cells Limited developmental potential Better behaved,

8 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 Science 287:1418,2000

9 Adult Stem Cells Can Differentiate into Developmentally Unrelated Cell Types 1. Neural stem cells produced myeloid and lymphoid cells as well as early hematopoietic cells. 2. Stem cells from mouse muscle could repopulate the blood stream and rescue lethally irradiated mice. 3. Bone marrow stem cells can become brain cells and liver cell precursors, plus heart skeletal and smooth muscle.

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

10 Location of Adult Stem Cells Hematopoietic yolk sac blood island, fetal liver and spleen, bone marrow, circulating umbilical cord Blood Liver portal zone near bile duct Intestine crypt Epidermal basal layer Retinal pigmented cilliary margin Breast epithelial end buds(cap cells) and basal layer of mammary gland Pancreas pancreatic islats and ducts Mesenchymal bone marrow stroma,, adipose tissue

Epidermal basal layer Retinal pigmented cilliary margin Breast epithelial end buds(cap cells) and

12 Retinal Stem Cell Localized to ciliary margin Can differentiate into retinal-specific neuronal and glial progeny ( rod photo- receptors, bipolar neurons and muller glia).

17 Clonogenic stem cells in small and large intestine Roberts et al., Radiation Res. 141: , 1995

18 Mouse Endbuds and Budding Structures Formed by Two Types of HBEC In Vivo In Vitro

19 Lobule Type 1 and Organoid Formed in Matrigel In Vivo In Vitro

20 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).

21 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. 6. Specific gene expression.

25 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 Liver stem cells--afp,ggt

26 Methods for Isolating Stem Cells from Adult Tissue 1. Flow cytometry Hematopoietic stem cells-- --CD34 +, HLA-DR - Neural crest stem cells-- --p75 + Epidermal stem cells-- --β1 integrin 2. Microdissection/colony /colony-forming assay Retinal stem cells Hair follicle stem cells

27 Methods for Isolating Stem Cells from Adult Tissue 3. Cell adhesion or lack of adhesion --Human epidermal stem cells adhered most rapidly to Type IV collagen, fibronectin or keratinocytes ECM. --Late attachment of human breast epithelial stem cells on plastic. 4. Contact insensitive growth on cell mat Putative human kidney epithelial stem cells.

28 Alternative Models for Stem Cell Deployment 1. Invariant Asymmetry 2. Populational Asymmetry

31 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 Highly expressed in ES cells and adult stem cells

32 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 ). bcl-2 Transgenic expression increased HSC in BM.

33 Regulation of Stem Cell Proliferation/Differentiation CDK2 A CDK2 inhibitor prevented hair loss caused by chemotherapy (etopside( etopside) ) in mice. Oxidative stress Lowered oxygen and antioxidant (N-acetyl acetyl- L-cysteine) ) promote growth of CNS and glial precursors respectively.

34 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 Cancer Res. 59: , 1999.

35 Clinical Applications of Stem Cells 1. Hematopoiesis as a model of stem and progenitor cell transplantation. Fanconi Anemia an autosomal recessive disorder characterized by progressive bone marrow failure leading to aplastic anemia. Bone marrow ablative doses of chemotherapy and radiotherapy to eliminate endogenous cancer leukemia (CML), lymphoma (Hodgkin s), multiple myeloma,, breast cancer.

36 Clinical Applications of Stem Cells 2. Transplantation therapy for acute and chronic degenerative disease Epidermal-- --skin graft for patients with severe burns Neuronal-- --Parkinson s s disease, multiple sclerosis and other neurodegenerative disease (brain gangliosidosis, demyelinating disease). Liver-- --For Liver damage by drugs, toxins or viral infection. Islet-for insulin non --producing pancreas Skeletal muscle satellite-- --muscular dystrophies or muscle loss;heart disease Mesenchymal tissue engineering in plastic reconstructive surgery 3. Gene therapy

38 Stem Cell Therapy for Parkinson's Disease 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 --Conventional treatments have had limited success. --Grafting immature neurons from aborted human fetuses have had up to 50% reduction in patients' symptoms and the effects appear to last.

39 Stem Cell Therapy for Parkinson's Disease Promise of ES cells --Potential to provide large quantity of nigral (dopamine) neurons with better quality control. Challenge of ES cell application --Ethical concern (better with adult stem cells). --Developing techniques to grow and to differentiate ES cells into dopamine neurons and their supportive cells.

40 Caplan, A.I. And Bruder,S.P. Trends in Mol.Medicine 7 : 259~264, 2001

41 Bianco,P.& Robey, P.G.Nature 414:118~121, 2001

42 Bianco,P.& Robey, P.G.Nature 414:118~121, 2001

43 Stem Cell Research and Ethics Millions of patients may benefit from the applications of stem cells. Ethics of embryo destruction are not addressed. A time for restraint to develop a national policy and ethical framework. Stem Cell Research Applications: : A society leaving the original Garden of Eden, or A great promise not only for unexpected insight into biology but ultimately for the alleviation of human suffering.

Stem Cell Quick Guide: Stem Cell Basics

Stem Cell Quick Guide: Stem Cell Basics What is a Stem Cell? Stem cells are the starting point from which the rest of the body grows. The adult human body is made up of hundreds of millions of different