2. Cell's Potency

• Types of Cell's Potency

  1. Totipotent
  2. Multipotent
  3. Oligopotent
  4. Unipotent
• Stem Cells (Properties & Potency)

  1. Embryonic Stem Cell
  2. Adult Stem cell
• Types of Stem Cell

  1. Embryonic Stem Cell
  2. Adult Stem Cell
  3. Fetal Stem Cell
  4. Amniotic Stem Cell
• TOTIPOTENT STEM CELLS

  • Differentiates to all types of cells
  • Examples: Blastocyst’s inner cell mass, outer trophoblast, zygote, spore, 16-cell stage morula
• PLURIPOTENT STEM CELLS

  • Gastrula
  • Differentiate in any 3 germ layers
  • Ectoderm, mesoderm, endoderm; embryonic stem cell, callus, 32-cell stage morula
• MULTIPOTENT PROGENITOR CELLS

  • Differentiates into selected types of tissue
  • Hematopoietic stem cells
  • Endothelia stem cell
  • Mesenchymal stem cell
  • Migrate into different locations from embryo
  • Neural stem cells
  • Part of the nervous system
• OLIGOPOTENT PRECURSOR CELLS

  • develop into few cell types 
  • Lymphoid or myeloid stem cells develop into B and T cells; 
  • Vascular stem cells develop into (1) endothelial and (2) smooth muscle cells 
• UNIPOTENT PRECURSOR CELLS

  • Differentiate into 1 cell type only.
  • Hepatoblasts to hepatocytes
  • Chondroblasts to chondrocytes
  • Fibroblasts to fibrocytes
  • Osteoblasts to osteocytes
• Hepatoblasts to hepatocytes

  • Blasts: young cells, mature and cell proper: cytes
  • liver
• • Chondroblasts to chondrocytes
  • “chondro” refers to cartilage, the young cartilage cells
• • Fibroblasts to fibrocytes
  • Fibers in connective tissues
• • Osteoblasts to osteocytes
  • Young bone cells to bone cell proper
• Totipotent

  • Able to make all the cells in the human body and the placenta
  • Occurrence: Before 3 days
  • Origin: From cells of first few cell divisions
  • Referred to: Early embryonic cells (blastomeres)
• Pluripotent

  • Able to make most of the cells in the human body, with the exception of placental tissues
  • Occurrence: 3-14 days (before ‘gastrulation’, the development of three germ layers in the embryo
  • Origin: From inner cell mass of blastula
  • Referred to: Embryonic stem cells (if cultured in vitro) Pluripotent stem cells (cells within the inner cell mass)
• Multipotent

  • Able to make a range of cells within a particular tissue type (such as blood)
  • Occurrence: After 14 days
  • Origin: From cells of the developing individual as well as adult
  • Referred to: Cord blood stem cells, Adult stem cells
• Zygote

  
• Morula

  
• Blastula/Blastocyst

  
• Gastrula

  
• Totipotent Stem Cells

  • zygote
  • morula
  • cell division: before 3 days
  • approx. no. of cells: 1-16 cells
• Pluripotent Stem Cells

  • Blastula/Blastocyst
  • cell division: 3-14 days
  • approx. no. of cells: up to several hundred cells
• Multipotent Stem Cells

  • Gastrula
  • cell division: after 14 days
  • approx. no. of cells: several hundred and more cells
• TOTIPOTENT

  • Zygote - single cell where sperm fertilizes egg
  • Morula - 16 cell stage
  • For pre-implantation, genetic diagnosis
• PLURIPOTENT

  • Pluripotent - can become anything except placenta
  • Blastula - hollow ball stage where the pre placental cells form the ball with the early embryo inside (known as the blastocyst stage)
  • Embryonic stem cell - taken from blastocyst or earlier stages; inner cell mass of the blastocyst stage
  • Embryonic stem cell line - cultured under in vitro conditions that allow proliferation without differentiation for months to years
  • From the inner cell mass are used to make embryonic stem cell lines
• MULTIPOTENT

  • Gastrula - develops into cell 3 layers; limited to form tissues only from that layer
  • Adult stem cell - any stem cells taken after the 3 cell layers have formed; taken from umbilical cord or after birth
  • Multipotent (adult) cells are already committed to a certain tissue layer
• TOTIPOTENT

  • Relative potency: High
  • Examples: Zygote, early morula
  • Found: Early cells of fertilized egg
  • Expression of pluripotency genes: +++
  • Expression of lineage specific genes: +
  • Pros: Easy to isolate and grow
  • Cons: Ethical issues
• PLURIPOTENT

  • Relative potency: Medium
  • Examples: Embryonic stem cells, Induced pluripotent stem cells
  • Found: Inner mass cells of the blastocyst
  • Expression of pluripotency genes: ++
  • Expression of lineage specific genes: ++
  • Pros: Easy to isolate and grow
  • Cons: Ethical issues, teratoma formation
• MULTIPOTENT

  • Relative potency: Low
  • Examples: Haematopoietic stem cells, neural stem cells, mesenchymal stem cells
  • Found: In many tissues
  • Expression of pluripotency genes: +
  • Expression of lineage specific genes: +++
  • Pros: Less ethical issues, less chance of immune rejection if taken from same patient
  • Cons: Hard to isolate, limited differentiation, scarce
• TOTIPOTENT

  • Fate/differentiation: All cells in the human body and placenta
  • Occurrence/Cell division: Before 3 days
  • Origin/source: 1-16 cells of cell division
  • Term: Early embryonic cells of blastomeres
  • No. of Cells: 1-16 cells
  • Uses: Implantation, genetic diagnosis
• PLURIPOTENT

  • Fate/differentiation: Most of the cells in the human body except placenta
  • Occurrence/Cell division: 3-14 days
  • Origin/source: Inner cell mass of blastula
  • Term: In vitro embryonic stem cells or pluripotent stem cells of inner cell mass
  • No. of Cells: 32-hundred cells
  • Uses: Used to make embryonic stem cell lines
• Progenitor cell

  • has a tendency to differentiate into a specific type of cell, pushed to differentiate into its "target" cell.
  • can divide only a limited number of times
• Progenitor Cells

  • Oligopotent
  • stage of cell differentiation
  • in the “center” between stem cells and fully differentiated cells
  • can move through the body and migrate towards the tissue where they are needed
  • found in adult organisms and they act as a repair system for the body
  • replenish special cells, but also maintain the blood, skin and intestinal tissues
  • in embryonic pancreatic tissue
• Stem Cell vs. Progenitor Cell

  Stem Cell - self-renewal in vitro is unlimited

  Progenitor Cell - self-renewal in vitro is limited
• Stem Cell vs. Progenitor Cell

  Stem Cell - potentiality is multipotent

  Progenitor Cell - potentiality is unipotent, sometimes oligopotent
• Stem Cell vs. Progenitor Cell

  • Stem Cell - Maintenance of self-renewal
  • Progenitor Cell - No maintenance of self-renewal
• Stem Cell vs. Progenitor Cell

  • Stem Cell - Population reaches maximum number of cells before differentiating
  • Progenitor Cell - Population does not reach maximum population
• Functions of Progenitor Cells

  • lie dormant or possess little activity in the tissue in which they reside.
  • To replace cells lost by normal attrition.
  • Growth factors or cytokines are two substances that trigger the progenitors to mobilize toward the damaged tissue. At the same time, they start to differentiate into the target cells.
  • situated near the tissue of their target differentiation.
  • When the cytokines, growth factors and other cell division enhancing stimulators take on the progenitors, a higher rate of cell division is introduced. It leads to the recovery of the tissue.
• Growth factors and cytokines are two substances that trigger the progenitors to mobilize toward the damaged tissue. At the same time, they start to differentiate into the target cells.
• Examples of Progenitor Cells

  1. Satellite cells
• Examples of Progenitor Cells

  1. Satellite Cells
  2. Neural progenitors
  3. Radial glial cells
  4. Bone marrow stromal cells
  5. (Periosteum) progenitor cells
  6. Pancreatic progenitor cells
  7. Angioblasts or endothelial progenitor cells (EPC)
  8. Blast cells
  9. Boundary cap cells