Stem cell Basics

1. What are stem cells, and why are they important ? 1) Two important characteristics : Cell division, Plasticity 2) Two kinds of stem cells from animals and humans : Embryonic stem cell, Somatic or adult stem cell 3) Discovery of stem cell : 1981- mouse embryonic stem cell 1998- derivation of human embryonic stem cells 2006- iPSCs

4) Regenerative abilities of stem cells offer new potentials for treating diseases “ regenerative medicine” 5) Stem cell research continues to advance knowledge about how an organism develops from a single cell and how healthy cells replace damaged cells in adult organisms. 6) However, research on stem cells raises scientific questions as rapidly as it generates new discoveries.

2. What are the unique properties of all stem cells? 1) Three general properties They are capable of dividing (proliferation) and renewing themselves for long periods (long-term self-renewal) They are unspecialized They can give rise to specialized cell types

2) Research concerns about their long-term self- renewal Why can ES cells proliferate for a years or more in the Lab w/O differentiation, but most non-Es cell (adult stem cells) cannot What factors in living organisms normally regulate stem cell proliferation and self-renewal

Stem cells are unspecialized, but can give rise to specialized cells Differentiation is processed by signals Internal signals are controlled by a cell’s gene/ outside signals trigger each step of the differentiation process (microenvironment) Hence, interaction of signals during differentiation causes the cell’s DNA to acquire epigenetic markers

7) Many questions about stem cell differentiation Are the interanl and external signals for cell differentiation similar for all kinds of stem cells? Can specific sets of signals be identified that promote differentiation into specific cell types? Adult stem cells show the tissue-restricted differentiation ability?

3. What are embryonic stem cells? What stages of early embryonic development are important for generating embryonic stem cells? How are ES cells grown in the lab?

3) What Laboratory tests are used to identify ES Cells? Growing and subculturing the stem cells for many months Determine the presence of TFs that are typically produced by undifferentiated cells. Check the specific markers which are expressed by undifferentiated cells Examining the chromosome Determining the viability after re-plating Testing whether the humans EX cells are pluripotent

4) How are ES cells stimulated to differentiate? Recipes: http://stemcells.nih.gov/info/2006report/

4. What are adult stem cells? An undifferentiated cell, found among differentiated cells in a tissue or organ that can renew itself and can differentiated to yield some or all of the major specialized cell types of the tissue or organ. Primary role: maintain and repair the tissue in which they are found Called as somatic stem cell Research on adult stem cells has led researcher and clinicians to as whether those cells could be used for transplants History of research on adult stem cell 1950s: hematopoietic stem cells, bone marrow stromal stem cell (mesenchymal stem cell) 1960s: discovery of brain stem cell in rat 1990s: agreement of differentiation ability of brain stem cells

1) Where are adult stem cells found, and what do they normally do? Identified in many organs and tissues Reside in a specific area of each tissue (stem cell niche) Very small number of stem cells in each tissue Relatively low proliferating capacity

2) What tests are used to identify adult stem cells? Label the cells in a living tissue with molecular markers and then determine the specialized cell types they generate Remove the cells from a living animal, label them in cell culture, and transplant them back into another animal to determine whether the cells replace their tissue of origin

3) What is known about adult stem cell differentiation?

Differentiation HSC: all types of blood cells Mesenchymal stem cell: bone cell, cartilage cell, fat cells, stromal cell Neural stem cell: astrocyte, oligodendrocytes, neurons Epithelial stem cells Skin stem cells: keratinocyte, hair follicle, epidermis Transdifferentiation / reprogramming

4) What are the key question about adult stem cells? How many kinds of adult stem cell exist, and in which tissues do they exist? How do adult stem cells evolve during development and how are they maintained in the adult? Why do stem cells remain in an undifferentiated state when all the cell around them have differentiated? What are the characteristics of their “niche” that controls their behavior? Do adult stem cell have the capacity to transdifferentiate, and is it possible to control this process to improve its reliability and efficiency?

5. What are similarities and differences between ES and adult stem cells? Abilities in the number and type of differentiated cell types they can become Availability in cell-based therapies Different immune rejection after transplantation (?)

6. What are induced pluripotent stem cells? Adult cells that have been genetically reprogrammed to an ES cells It is not known if iPSCs and ES cell differ in clinically significant ways Mouse iPSC 2006/ human iPSC 2007 Expressing stem cell markers, teratoma formation, pluripotency Powerful tools for drug development and modeling of Dxs. However, the virus used to introduce the stem cell factors sometimes causes cancers