Stem Cells.pptx

Stem Cells.pptx

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  STEM CELLS PRESENTER: ZELEKEENDALEW (MSc) MODERATOR: Dr. Solomon Genet( PHD) 1
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  Objectives  Define whatstem cells are  List the types of stem cells and their properties  List the methods of stem cell culture  List the medical roles of stem cells 9/20/2022 Stem cells 2
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  Outline  Definition  Typesof stem cells  Stem cells and organogenesis  Stem Cell Culture  Medical roles of stem cells  Summary  References 9/20/2022 Stem cells 3
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  What are StemCells? 4  A stem cell is a relatively unspecialized cell that can reproduce itself indefinitely.  able to differentiate into any cell of an organism and have the ability of self-renewal.  exist both in embryos and adult cells.
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  5  They havetwo unique properties that enable them to do this  They can divide over and over again to produce new cells.  As they divide, they can change into the other types of cells that make up the body.
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  6 What factors accountfor the stemness and cell differentiation capability of ES cells?  Expression of high levels of active telomerase.  allows them to escape senescence.  Expression of specific genes.  A gene called Oct4, is exclusively expressed in ES cells.  Codes for a transcription regulator.  A core set of transcription regulators defines and maintains the ES cell state.
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  Types of StemCell 7 There are three main types of stem cell:  Embryonic stem cells  Supply new cells for an embryo as it grows and develops into a baby.  Are said to be pluripotent,  they can change into any cell in the body.
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  8 https://pubmed.ncbi.nlm.nih.gov/16923385/
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  9 Adult stem cells Supply new cells as an organism grows and to replace cells that get damaged.  Are said to be multipotent  they can only change into some cells in the body, not any cell.
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  Adult stem cells… 10 Blood (or 'haematopoietic') stem cells can only replace the various types of cells in the blood.  Skin (or 'epithelial') stem cells provide the different types of cells that make up our skin and hair.
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  11 Induced pluripotent stemcells (iPS cells)  Stem cells that scientists make in the laboratory  Induced’ means that they are made in the lab by taking normal adult cells, like skin or blood cells, and reprogramming them to become stem cells.  Just like embryonic stem cells, they are pluripotent so they can develop into any cell type
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  Stem cell Types…  Stem cells are of many types, specialized for the genesis of different classes of terminally differentiated cells—  intestinal stem cells for intestinal epithelium,  epidermal stem cells for epidermis,  hematopoietic stem cells for blood 9/20/2022 Stem cells 12
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   Tissue RenewalThat Does Not Depend on Stem Cells:  Insulin Secreting Cells in the Pancreas and  Hepatocytes in the Liver  Some types of cells can divide even though fully differentiated  allowing for renewal and regeneration without the use of stem cells. 9/20/2022 Stem cells 13
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   insulin-secreting cells(β cells) of the pancreas  Sequestered in cell clusters called islets of Langerhans  contain no obvious subset of cells specialized to act as stem cells  yet fresh β cells are continually generated within them  Renewal occurs by simple duplication of the existing insulin-expressing cells, not by means of stem cells. 9/20/2022 Stem cells 14
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  Hepatocyte  renew bysimple duplication of fully differentiated cells  normally live for a year or more and renew themselves through cell division at a very slow rate  Within a day or so after either sort of damage, a surge of cell division occurs among the surviving hepatocytes, quickly replacing the lost tissue. 9/20/2022 Stem cells 15
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   If two-thirdsof a rat’s liver is removed, for example, a liver of nearly normal size can regenerate from the remainder by hepatocyte proliferation within about two weeks.  Both the pancreas and the liver contain small populations of stem cells that can be called into play as a backup mechanism for production of the differentiated cell types in more extreme circumstances. 9/20/2022 Stem cells 16
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   Some TissuesLack Stem Cells and Are Not Renewable  the auditory epithelium and the retinal epithelium lack stem cells, and their sensory receptor cells—the sensory hair cells in the ear, the photoreceptors in the retina—are irreplaceable. 9/20/2022 Stem cells 17
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  Fibroblasts  When atissue is injured, the fibroblasts nearby proliferate, migrate into the wound and  produce large amounts of collagenous matrix that helps to isolate and repair the damaged tissue.  are the easiest of cells to grow in culture  a feature that has made them a favorite subject for cell biological studies. 9/20/2022 Stem cells 18
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   Figure: Thefamily of connective tissue cells. 9/20/2022 Stem cells 19
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   Figure :Control of fibroblast differentiation by the physical properties of the extracellular matrix. 9/20/2022 Stem cells 20
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  Myoblasts  Precursors ofskeletal muscle fibers.  after a period of proliferation, they stop dividing,  expression of a muscle-specifc genes required for terminal differentiation  Fuse with one another to form multinucleate skeletal muscle fibers  Once differentiation and cell fusion have occurred, the cells do not divide  The nuclei never again replicate their DNA. 9/20/2022 Stem cells 21
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   Some MyoblastsPersist as Quiescent Stem Cells in the Adult  able of serving as myoblasts are retained  small, flattened, and inactive cells lying in close contact with the mature muscle cell  The process of muscle repair by means of satellite cells is, however, limited.  exhaustion of their regenerative capacity 9/20/2022 Stem cells 22
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  myoSatellite cells  Arethe stem cells of adult skeletal muscle  held in reserve in a quiescent state  available when needed as a self-renewing source of terminally differentiated cells.  If the muscle is damaged or stimulated to grow, these cells are activated to proliferate  their progeny can fuse to repair the damaged muscle or to allow muscle growth. 9/20/2022 Stem cells 23
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  BLOOD CELLS  Areall generated from a common stem cell, located in the bone marrow.  hematopoietic stem cell is thus multipotent  giving rise to all the types of terminally differentiated blood cells as well as some other types of cells, such as the osteoclasts in bone  have limited life-spans and are produced throughout life. 9/20/2022 Stem cells 24
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   Bone MarrowContains Multipotent Hematopoietic Stem Cells, Able to Give Rise to All Classes of Blood Cells  The developing blood cells and their precursors, including the stem cells, are intermingled with one another  The stem cells constitutes a tiny fraction of the bone marrow population  about 1 cell in 50,000–100,000 9/20/2022 Stem cells 25
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  Figure: Depiction ofhematopoiesis cell lines 9/20/2022 Stem cells 26
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  Neural Stem Cells Stem cells capable of generating new neurons are hard to find.  Were thought to be absent many years.  Can be manipulated in culture and used to repopulate the central nervous system.  It is now discovered that neural stem cells that generate both neurons and glial cells do persist in certain parts of the adult human brain.  There is continuing turnover of neurons in the hippocampus. 9/20/2022 Stem cells 27
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   Neural stemcells can be obtained from The hippocampal region or fetal brains  Grown in culture, and then grafted back into other sites in the brain,  generate neurons appropriate to the new location. 9/20/2022 Stem cells 28
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   Neural stemcells from pluripotent stem cells can be grafted into an adult brain. 9/20/2022 Stem cells 29
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   Embryonic Stem(ES) Cells Can Generate Any Part of the Body.  A fertilized egg, or an equivalent cell produced by nuclear transplantation can generate a whole new multicellular individual.  can be taken from an early mouse embryo, at the blastocyst stage.  A class of stem cells called embryonic stem cells through cell culture can be driven from it.  Originate from the inner cell mass of the early embryo. 9/20/2022 Stem cells 30
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   Figure :Production and pluripotency of ES cells. 9/20/2022 Stem cells 31
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   iPS cellsalso be derived from adult human cells and from various other differentiated cell types besides fibroblasts.  ES and iPS cells can be guided to generate specific adult cell types and even whole organs. 9/20/2022 Stem cells 32
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   Cells ofone specialized type can be forced to transdifferentiate directly into another.  Fibroblasts can be made to transdifferentiate directly into heart muscle cells.  By forcing expression of combination of factors: Gata4, Mef2c, and Tbx5 9/20/2022 Stem cells 33
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  34  Reprogramming focuseson the expression of oncogenes such as  octamer-binding transcription factor-4 (Oct4),  Kruppel-like factor-4 (Klf4)  c-myelocytomatosis (c-Myc)  enhanced by a downregulation of genes promoting genome stability, such as p53.
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  Stem Cells andorganogenesis 35  After fertilization, the zygote usually divides rapidly, or cleaves, to form many smaller cells.  during this cleavage, the embryo does not grow.  a blastula—typically a solid or a hollow fluid- filled ball of cells is then formed.
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  Stem Cells and organogenesis… 36 Complex cell rearrangements called gastrulation  transform the blastula into a multilayered structure containing. a rudimentary internal gut.  Some cells of the blastula remain external, constituting the ectoderm, which will give rise to the epidermis and the nervous system.
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  Stem Cells and organogenesis… 37 A blastocyst is formed after the fusion of sperm and ovum fertilization. Its inner wall is lined with short- lived stem cells, namely, embryonic stem cells.  Blastocysts are composed of two distinct cell types:  The inner cell mass (ICM), develops into epiblasts and induces the development of a foetus.  the trophectoderm (TE).
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  38  The trophectodermcontinues to develop  forms the extraembryonic support structures needed for the successful origin of the embryo, such as the placenta  As the TE begins to form a specialized support structure, the ICM cells remain undifferentiated, fully pluripotent and proliferative  allows them to form any cell of the organism
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  39  Human embryonicstem cells (hESCs) are derived from the ICM.  During the process of embryogenesis, cells form aggregations called germ layers  Each germ layers eventually give rise to differentiated cells and tissues of the foetus and, later on, the adult organism.
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  40  After hESCsdifferentiate into one of the germ layers, they become multipotent stem cells,  potency limited to only the cells of the germ layer.  Pluripotent stem cells will then be formed all over the organism as undifferentiated cells  Able to proliferate by the formation of the next generation of stem cells  differentiation into specialized cells under certain physiological conditions.
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  41  Although thederivation of ESCs without separation from the TE is possible, such a combination has growth limits.  proliferating actions are limited, co-culture of these is usually avoided.
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  Stem cell Culturing 42 Cells are placed in a culture dish filled with culture medium.  Passage is inefficient but popular process of sub-culturing cells to other dishes.
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  43  Phenotypic pluripotencyassays  Recognizing undifferentiated cells is crucial in successful stem cell therapy.  Stem cells appear to have a distinct morphology  a prominent nucleolus, high nucleus to cytoplasm ratio  Cells appear to be flat with defined borders, in contrast to differentiating colonies.  appear as loosely located cells with rough borders.
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  44  When stemcells differentiate, the methylation process silences pluripotency genes  reduces differentiation potential, although other genes may undergo demethylation to become expressed.
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  45 hESC derivation andmedia  hESCs can be derived using a variety of methods, from classic culturing to microsurgery.  hESC differentiation must be specified to avoid teratoma formation.  hESCs spontaneously differentiate into embryonic bodies (EBs).
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  46  EBs canbe studied instead of embryos or animals to predict their effects on early human development.
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  47  The essentialpart of these culturing procedures is a separation of inner cell mass to culture future hESCs.  Particular attention must be taken in controlling spontaneous differentiation.  When the colony reaches the appropriate size, cells must be separated.
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  48  Cell passagingis used to form smaller clusters of cells on a new culture surface. There are four important passaging procedures. Enzymatic dissociation  is a cutting action of enzymes on proteins and adhesion domains that bind the colony.  It is crucial to not leave hESCs alone after passaging.  Solitary cells are more sensitive and can easily undergo cell death  collagenase type IV is an example.
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  49 Manual passage  Focuseson using cell scratchers.  The selection of certain cells is not necessary.  This should be done in the early stages of cell line derivation
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  50 Trypsin utilization  allowsa healthy, automated hESC passage.  However, there is a risk of decreasing the pluripotency and viability of stem cells.
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  51 Ethylene diamine tetraaceticacid (EDTA)  indirectly suppresses cell-to-cell connections by chelating divalent cations.  Their suppression promotes cell dissociation.  Prevent joining of cadherins (calcium dependent adhesion) between cells  Prevent clumping of cells  Detaching adherent cells for passaging
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  Stem cell Culturing… 52  Stem cells require a mixture of growth factors and nutrients to differentiate and develop.  The medium should be changed each day.  Traditional culture methods used for hESCs are  mouse embryonic fibroblasts (MEFs) as a feeder layer  bovine serum as a medium.
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  53  First feederlayer-free culture can be supplemented with serum replacement, combined with laminin .  This causes stable karyotypes of stem cells and pluripotency lasting for over a year.  Initial culturing media can be  serum (e.g. foetal calf serum (FCS)  artificial replacement such as  Synthetic serum substitute (SSS),  Knockout Serum Replacement (KOSR), or  StemPro.
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  54  Turning pointin stem cell therapy John B. Gurdon in 1962  Challenged the dogma that the specialized cell is irreversibly committed to its fate.  Successfully cloning frogs by transferring a nucleus from a frog’s somatic cells into an oocyte.  demonstrated that it is possible for a somatic cell to again acquire pluripotency.
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  55
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  56 Davis R.L. in1987  showed that reprogramming cells is possible, and it can even be used to transform cells from one lineage to another  enforced expression of genes that were originally found in myoblasts caused the conversion of fibroblasts into myoblasts.  myogenic differentiation 1 (Myod1)
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  57 Shinya Yamanaka andKazutoshi Takahashi In 2006  discovered that it is possible to reprogram multipotent adult stem cells to the pluripotent state.  avoided endangering the foetus’ life in the process.
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  58  Four transcriptionfactors (Oct-3/4, Sox2, KLF4, and c-Myc).  Are mainly expressed in embryonic stem cells  could induce the fibroblasts to become pluripotent  This new form of stem cells was named iPSCs.  One year later, the experiment also succeeded with human cells.
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  Medical roles ofStem Cells 59  play a large role in developing restorative medicine.  The difference between a stem cell and a differentiated cell is reflected in the cells’ DNA.
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  Medical roles ofStem cells… 60  Many serious medical conditions, such as birth defects or cancer, are caused by improper differentiation or cell division.  Several stem cell therapies are possible, among which are treatments for Heart failure, retinal and macular degeneration, tendon ruptures, and diabetes type 1
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  61 Hematopoietic stem celltransplantation  the most popular stem cell therapy.  the most tissue-specific stem cells  experimentally studied for more than 50 years.  HSCs are responsible for the generation of all functional haematopoietic lineages in blood.
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  62 limitations  There isa limited number of transplantable cells  an efficient way of gathering them has not yet been found.  problem with finding a fitting antigen-matched donor for transplantation.  Viral contamination or any immunoreactions can cause a reduction in efficiency
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  63 Stem cells asa target for pharmacological testing  Stem cells can be used in new drug tests.  Each experiment on living tissue can be performed safely on specific differentiated cells fro pluripotent cells  If any undesirable effect appears, drug formulas can be changed until they reach a sufficient level of effectiveness.
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   Figure: Useof iPS cells for drug discovery and for analysis and treatment of genetic disease. 9/20/2022 Stem cells 64
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  65  Stem cellsas an alternative for arthroplasty. Rejuvenation by cell programming.  using cell reprogramming technology in elder animals and humans to erase marks of ageing without removing the epigenetic marks of cell identity.
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  66  Cells fromaged individuals have  different transcriptional signatures,  high levels of oxidative stress,  dysfunctional mitochondria, and  shorter telomeres than in young cells
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  67  There isa hypothesis that when human or mouse adult somatic cells are reprogrammed to iPSCs, their epigenetic age is virtually reset to zero.
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  68 Cell-based therapies  Stemcells can be induced to become a specific cell type that is required to repair damaged or destroyed tissues.
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  69  It ispossible to generate healthy heart muscle cells and later transplant them to patients with heart disease.  it can be possible to induce stem cells to differentiate into insulin-producing cells
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  70
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  71 Fertility diseases  Scientistsshowed that it is possible to form sperm from iPSCs  Young adults at risk of losing their spermatogonial stem cells (SSC), mostly cancer patients can benefit from it
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  72  Therapy forincurable neurodegenerative diseases  Parkinson’s disease, Alzheimer’s disease (AD), and Huntington disease.
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  73  Brain tissuefrom aborted fetuses was used on patients with Parkinson’s disease  showed that therapies with pure stem cells are an important and achievable therapy.
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  74 Stem cell usein dentistry  There are stem cells in the periodontal ligament  capable of differentiating into osteoblasts or cementoblasts  their functions were also assessed in neural cells  Stem cells of the root apical areas are able to recreate periodontal ligament.
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  Medical role… 75  Adultstem cells are currently used to treat some conditions, for example:  Blood stem cells are used to provide a source of healthy blood cells for people with some blood conditions:  Thalassaemia  cancer patients who have lost their own blood stem cells during treatment.
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  Medical roles… 76  Age-relatedmacular degeneration (AMD)  a condition in which cells in the retina of the eye called retinal pigment epithelium (RPE) cells stop working.  stem cells could be used as a new form of treatment in the future:  using iPSCs to produce new RPE cells in the lab that can then be put into a patient’s eye to replace the damaged cells.
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  77 An illustration showinghow stem cells can be used to produce retinal pigment epithelium (RPE) cells that can be used to treat patients with age-related macular degeneration (AMD). Image credit: Genome Research Limited
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  Medical roles 78  Stemcells could be used to generate new organs for use in transplants:  damaged organs can be replaced by obtaining healthy organs from a donor  donated organs may be 'rejected' by the body as the immune system sees it as something that is foreign.
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  Summary 79  A stemcell is a relatively unspecialized cell that can reproduce itself indefinitely and act as internal repair systems of the body.  The three types of Stem cells are ESCs, Adult stem cells and iPSC  Stem cells can be isolated and be cultured under appropriate conditions.  Stem cells may be one way of generating new cells that can then be transplanted into the body to replace those that are damaged or lost.
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  80  Differentiated stemcells can be reprogrammed to give undifferentiated cells capable of differentiation into different lineage.  Stem cells when specialized gives the genesis of different classes of terminally differentiated cell.  Stem cells have immense medical role including the cure for neurodegenerative diseases.
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  References 81  Takahashi, K.and Yamanaka, S. (2006) ‘Induction of Pluripotent Stem Cells from Mouse Embryonic and Adult Fibroblast Cultures by Defined Factors’, Cell, 126(4), pp. 663–676. doi: 10.1016/j.cell.2006.07.024.  Albert, B., Johnson, A. and Lewis, J., 2015. Molecular Biology of The Cell. New York: Garland Science.  Khan, F. A. et al. (2018) ‘Isolation, Culture, and Functional Characterization of Human Embryonic Stem Cells: Current Trends and Challenges’, Stem Cells International. Edited by V. Sorrenti, 2018, p. 1429351. doi: 10.1155/2018/1429351.  Campbell’s molecular biology of the cell eleventh edition.  Rahman, M. et al. (2016) ‘STEM CELL AND CANCER STEM CELL: A Tale of Two Cells’, Progress in Stem Cell, 3(02), p. 97. doi: 10.15419/psc.v3i02.124.  Li, Y., Xu, C. and Ma, T. (2014) ‘In vitro organogenesis from pluripotent stem cells’, Organogenesis, 10(2), pp. 159–163. doi: 10.4161/org.28918.