Stem Cells in Regeneration and Aging
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Questions and Answers

What role do neoblasts play in the regeneration of planarians?

  • They function as specialized cells for nerve signaling.
  • They inhibit the regeneration process.
  • They serve as undifferentiated stem cells for tissue regeneration. (correct)
  • They are responsible for producing muscle fibers.

    • Which factor is responsible for decreasing neurogenesis in young mice when exposed to old mouse blood?

  • Circulating stem cells from old mice.
  • The systemic environment of old blood. (correct)
  • Neurogenic factors from young blood.
  • The muscle regeneration factors from old mice.

    • What percentage of cells in a planarian are neoblasts?

  • 5%
  • 50%
  • 20% (correct)
  • 10%

    • Which statement best describes the regeneration abilities of mammals compared to planarians?

    <p>Mammals have some ability to regenerate, though not as effectively as planarians.</p> Signup and view all the answers

    What is currently unknown about mammalian limb regeneration?

    <p>Reasons for the inability to regenerate limbs.</p> Signup and view all the answers

    What cellular mechanism allows olfactory neurons to be continuously replaced?

    <p>Migration of progenitor cells</p> Signup and view all the answers

    What is the approximate percentage of neuronal turnover in the hippocampus of adult mice and humans per year?

    <p>1.75%</p> Signup and view all the answers

    What dramatic change occurs in the brains of certain songbirds annually?

    <p>Neurons are lost and replaced</p> Signup and view all the answers

    Which type of cells can be differentiated into neurons and glial cells through a change of medium?

    <p>Neural stem cells</p> Signup and view all the answers

    What factor enhances the ability of grafted neural stem cells to adapt to a new environment in the brain?

    <p>Behavior adjustment to match location</p> Signup and view all the answers

    Which clinical application has been tried using stem cells for treating central nervous system conditions?

    <p>Stroke damage recovery</p> Signup and view all the answers

    What is a characteristic property of embryonic stem (ES) cells once cultured?

    <p>Potential for genetic manipulation</p> Signup and view all the answers

    What occurs when neural stem cells from the mouse hippocampus are implanted into a different part of the brain?

    <p>They generate corrective neurons</p> Signup and view all the answers

    What is the primary role of ES-derived cells in the formation of chimeric animals?

    <p>To differentiate into any cell type and integrate into the inner cell mass.</p> Signup and view all the answers

    Which set of factors is responsible for reprogramming fibroblasts into induced pluripotent stem cells (iPS)?

    <p>Oct4, Sox2, Myc, and Klf4.</p> Signup and view all the answers

    What mechanism helps maintain cells in an embryonic stem cell-like state during iPS cell generation?

    <p>A self-sustaining feedback loop among OSKM factors.</p> Signup and view all the answers

    How can researchers select for successfully converted iPS cells from fibroblasts?

    <p>Using a promoter active only in embryonic stem cells.</p> Signup and view all the answers

    Which of the following statements is true regarding the conversion of fibroblasts to iPS cells?

    <p>Only a small percentage converts to pluripotent stem cells.</p> Signup and view all the answers

    What is G418 used for in the context of iPS cell research?

    <p>To selectively kill eukaryotic cells that do not express the G418 resistance gene.</p> Signup and view all the answers

    Which factors are most noted for enhancing the conversion efficiency of fibroblasts to iPS cells?

    <p>Chromatin state-altering factors with the most direct effects.</p> Signup and view all the answers

    What is the ultimate significance of generating non-chimeric mice from ES-derived germ cells?

    <p>They provide a simpler model for studying gene function without chimerism.</p> Signup and view all the answers

    What characterizes asymmetric stem-cell division?

    <p>One daughter cell inherits the determinant while the other does not.</p> Signup and view all the answers

    During symmetric stem-cell division, what happens to both daughter cells?

    <p>They both retain stem cell identity.</p> Signup and view all the answers

    What happens when ES or iPS cells are introduced to later stage embryos or adult tissues?

    <p>They fail to receive appropriate cues and may form teratomas.</p> Signup and view all the answers

    What is a consequence of daughters making differentiation choices stochastically?

    <p>Clones may completely disappear if both commit to differentiation.</p> Signup and view all the answers

    How does aging affect hematopoietic stem cells?

    <p>They gradually lose the ability to repopulate the system.</p> Signup and view all the answers

    What are embryoid bodies?

    <p>Aggregates formed by detached cultured stem cells that begin to specialize.</p> Signup and view all the answers

    What does the term 'cell-autonomous factors' refer to in the context of aging stem cells?

    <p>Intrinsic factors within the stem cells that affect their function.</p> Signup and view all the answers

    Which structure can be produced by cultured human ES cells that resembles the organization of a retina?

    <p>Optic cup.</p> Signup and view all the answers

    What components are present in the three-dimensional optic cup structure?

    <p>Layers of neural cells and pigmented epithelium.</p> Signup and view all the answers

    Which statement about the influence of niche on stem cell behavior is correct?

    <p>A young niche cannot support aged hematopoietic stem cells effectively.</p> Signup and view all the answers

    What factor might determine whether a daughter cell differentiates or remains a stem cell?

    <p>The local environment the daughter cell encounters.</p> Signup and view all the answers

    How can iPS cells derived from a patient with a genetic disease be utilized?

    <p>They can help in disease mechanism analysis and drug discovery.</p> Signup and view all the answers

    In which situation is the choice to differentiate made randomly?

    <p>During the first division of stem cells with identical determinants.</p> Signup and view all the answers

    What is a primary risk when grafting differentiated cells back into an individual?

    <p>Immune rejection.</p> Signup and view all the answers

    What is required for stem cells to differentiate into specific adult cell types?

    <p>An environment rich in growth factors and specific cues.</p> Signup and view all the answers

    What visual indicator is used to identify layers within the developing retina of an optic cup?

    <p>Blue staining shows all nuclei.</p> Signup and view all the answers

    Study Notes

    Stem Cells in Tissue Homeostasis and Regeneration

    • Asymmetric Stem Cell Division:

      • A cell-fate determinant (red) localizes to one side of the cell.
      • When the cell divides, one daughter inherits the determinant and remains a stem cell.
      • The other daughter commits to differentiation.

    • Symmetric Stem Cell Division:

      • Both daughter cells inherit determinants.
      • Both remain stem cells.

    • Drosophila Testis Germ-Line Stem Cell Division:

      • Division plane is determined by the central hub of somatic niche cells.
      • Cell junctions provide spindle-orienting cues.
      • Daughter cell that maintains contact with the niche remains a stem cell.

    • Independent-Choice Mechanism:

      • Stem cell division fates can be determined by the environment or stochastically (randomly).
      • Environmental factors influence cell fate.
      • Random choice gives a 25% chance of both daughters committing to differentiation.

    • Stem Cells and Aging:

      • Hematopoetic stem cells lose repopulation ability with age.
      • Stem cell niche does not rescue old hematopoetic stem cells
      • Age of the cells is more important than the niche

    • Parabiosis:

      • Joining animals to share a circulatory system allows for testing effects of blood and cells with age.
      • Blood from old mice decreases neurogenesis in young mice.
      • Blood from young mice restores skeletal muscle stem cell function in old mice.

    • Planarian Regeneration:

      • Planarian worms have neoblasts (stem cells) that are small, undifferentiated dividng cells.
      • Neoblasts are totipotent, able to create all cell types
      • Planarians can regenerate entire body from a small chunk of tissue

    • Newt Limb Regeneration:

      • Newts regrow lost limbs.
      • Early blastema forms with epidermis, nerve, bone, and dermis.
      • Newly activated stem cells and progenitor cells form in the wound epidermis.

    • Continuing Neuron Production in Adult Brains:

      • Neural stem cells in the forebrain continually produce neurons, primarily in the olfactory bulb.
      • Olfactory neurons are continuously replaced
      • Adult mice and humans have neuronal turnover (about 1.75% per year) in the hippocampus.

    • Songbird Neuronal Turnover:

      • Songbirds have high neuronal turnover each breeding season for song refinement

    • Neural Stem Cells Cultured Stages Shown:

      • Fetal brain or embryonic stem cells are first dissociated and cultured in suspension in media
      • Cells next form neurospheres (A)
      • Followed by pure culture (B) of the neural stem cells
      • Finally, differentiation (C) in a new medium

    • Neural Stem Cells Grafting:

      • Grafted into adult brains, demonstrating adaptability to new locations
      • Example: Mouse hippocampus stem cells in the olfactory bulb pathway
      • Has broad therapeutic potential for treating CNS diseases

    • ES Cell Production and Pluripotency:

      • ES cells can be harvested and re-introduced into a blastocyst (a very early embryo).
      • ES-derived cells can differentiate into any cell type.
      • Generating a chimeric mouse is possible

    • Reprogramming Fibroblasts to iPS Cells:

      • The OSKM factors (Oct4, Sox2, Myc, and Klf4) induce self-sustaining feedback (gray shading) to help maintain fibroblasts in an ES-like state.
      • Forced expression in mice fibroblasts converts some into pluripotent stem cells that can be induced into blastocysts.

    • Strategy for Selecting iPS Cells:

      • G418 antibiotic kills non-iPS cells
      • Only iP cells (with active Fbx15 promoter from stem cells) survive
      • Successful conversion to iPS cells is thereby selected

    • Events During Reprogramming Fibroblasts to iPS:

      • Downregulation of somatic markers, and activation of pluripotency genes are not observed

    • Factors Enhancing iPS Conversion Efficiency:

      • Various factors, including chromatin remodeling, histone modification, histone variants, and DNA/RNA modification may enhance the efficiency of conversion with direct effects in the top 3 rows.

    • Generating Specific Adult Cell Types and Organoids:

      • ES and iPS cells can generate specific adult cell types, and even organoids.
      • Early exposure into a later stage embryo or adult tissue leads to differentiation issues and potentially teratoma formation.

    • Production of Differentiated Cells from Stem Cells:

      • Embryoid bodies (aggregates) drive differentiation by specializing
      • Cultured in media with factors for various cell development

    • Cultured Human ES Cell Organoids:

      • Self-assembly into three-dimensional eye-like structures (optic cup).
      • Including a retina similar to those formed during normal eye development in vivo.
      • Includes developing retina layers (neural cells) and pigmented epithelium.

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    Description

    This quiz explores the mechanisms of stem cell division, including asymmetric and symmetric division, and their roles in tissue homeostasis and regeneration. It also delves into the impact of environmental factors and aging on stem cell functionality. Test your knowledge on the fascinating biology of stem cells!

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