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Stem Cells and the Maintenance of Adult Tissues


Title: The Cell, 5e Author: Betz, Joan Last modified by: l-admin Created Date: 10/16/2000 7:08:56 PM Document presentation format: On-screen Show (4:3) – PowerPoint PPT presentation

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Title: Stem Cells and the Maintenance of Adult Tissues

Stem Cells and the Maintenance of Adult Tissues
  • Chapt 17 2. Stem cells have great potential
  • Adult stem cells
  • Embryonic stem cells
  • In early development, cells proliferate rapidly,
    then differentiate to form specialized cells of
    adult tissues
  • Most differentiated cells in adult animals are no
    longer capable of proliferation.
  • If cells are lost, replace by proliferation of
    cells derived from self-renewing stem cells.

Stem Cells,Maintenance of Adult Tissues
  • 1. Some differentiated cells can
  • proliferate to repair damaged tissues
  • Fibroblasts in connective tissue
  • proliferate in response to platelet-derived
  • growth factor (PDGF) released at wound
  • Endothelial cells lining blood vessels
  • proliferate to form new blood vessels
  • (repair and regrowth of damaged tissue)
  • Triggered by vascular endothelial growth
  • factor (VEGF), from cells that lack oxygen

Fig. 17.13,14, 15
Stem Cells and the Maintenance of Adult Tissues
  • 2. Adult Stem cells
  • Less differentiated, self-renewing cells in most
    adult tissues.
  • Retain capacity to proliferate, replace
    differentiated cells throughout lifetime of
  • Divide to produce one daughter cell that
    remains stem cell and one that divides,
  • Ex. blood cells, sperm,
  • epithelial cells skin, intestine

Fig. 17.17
Fig 17.18 Formation of blood cells
  • Hematopoietic (blood-forming) stem cells were the
    first identified (1961)
  • distinct types
  • specialized functions
  • Short life span
  • from bone marrow

Stem Cells and Maintenance of Adult Tissues
  • Epithelial cells that line intestines live only a
    few days before they die

Fig. 17.19
Stem Cells and the Maintenance of Adult Tissues
  • Adult stem cells potential utility in medicine.
  • Hematopoietic stem cell transplantation
  • (or bone marrow transplantation)
  • important role in treatment of cancers.

Fig. 17.22
Cord blood is source of hematopoietic stem
cells Epithelial stem cells - skin grafts for
burns, wounds, and ulcers.
Embryonic Stem Cells and Therapeutic Cloning
  • Embryonic stem cells (ES)
  • Grow indefinitely as pure stem cell populations
  • Pluripotency capacity to develop into all of
    different types of cells in adult tissues.
  • Enormous interest -
  • basic science and clinical applications.
  • Distinction cloning cells versus cloning organisms

Embryonic Stem Cells and Therapeutic Cloning
  • ES cells first cultured from mouse embryos in
  • Mouse ES cells important experimental tool
  • Can introduce altered genes into mice.
  • Model system to study molecular basis of cell

Fig. 17.23 ES cells can differentiate Martin
Expt neuron-like, endodermal, cartilage
Embryonic Stem Cells and Therapeutic Cloning
  • Mouse ES cells need growth factor LIF, to
    maintain undifferentiated state (leukemia
    inhibitory factor)
  • LIF signals through JAK/STAT path
  • If LIF is removed, cells
  • aggregate and differentiate.
  • Different growth factors direct
  • differentiation along specific paths
  • Model for future human therapeutics
  • Diseases like Parkinsons, diabetes
  • Human ES cell lines exist

Fig. 17.24
Embryonic Stem Cells and Therapeutic Cloning
  • 1997 Dolly the sheep cloned
  • Somatic cell nuclear transfer process
  • This cloning in mammals is difficult and
  • Possible therapeutic cloning

Fig. 17.25
Embryonic Stem Cells and Therapeutic Cloning
  • Therapeutic cloning
  • Nucleus from adult human cell transferred to
    enucleated egg
  • Resulting embryo cells used to produce
    differentiated cells for transplantation therapy.
  • Bypasses problem of tissue rejection
  • Problems with therapeutic cloning
  • Low efficiency of generating embryos by somatic
    cell nuclear transfer.
  • Ethical concerns
  • Possible cloning of humans (reproductive
  • destruction of embryos

Fig. 17.26 therapeutic cloning for personalized
tissue transplants
Embryonic Stem Cells and Therapeutic Cloning
  • Induced pluripotent stem cells
  • Very recent procedures
  • may overcome technical,
  • ethical difficulties
  • Reprogram somatic cells to
  • resemble embryonic stem cells.
  • Only 4 key transcription factors
  • reprogram adult mouse somatic cells
  • Oct4, Sox2, Klf4, c-Myc)
  • Also adult human fibroblasts

Fig. 17.27