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STEM CELLS (TYPES (embryonic stem cells (derived from inner cell mass…

- - - - during zygotic stage of development
  - - - part of blastocyst (early embryo)
      - cells form entire fetus
      - cannot form placenta or extra embryonic membranes
    - - reproduce indefintely (but in a controlled manner)
        
        divide in an undifferentiated state
        
        useful to remove and culture for medicinal and research purposes
  - - - only produces specialised cell types of tissue
      - divides through lifetime of organism
      - eg: blood (haematopoietic) stem cells
        
        found in adult bone marrow and umbilical cord blood
        
        bone marrow
        
        produces blood cells
        
        arises from haematopoietic stem cells
        
        undergo asymmetric division
        
        differentiation regulated by cytokines (protein in cell signalling) and hormones
        
        umbilical cord blood
        
        blood from placenta and umbilical cord
        
        rich in haematopoietic stem cells
        
        advantages of using it in stem cell transplants
        
        less prone to rejection than bone marrow
        
        no foreign antigens on cell membrane
        
        1 more item...
        
        differentiates into blood cells and immune cells
        
        treats blood disorders and immune system conditions
        
        leukaemia
        
        sickle cell anaemia
    - - replenish dying cells
      - regenerate damaged tissues
- - - - by somatic cell nuclear transfer (SCNT)
        
        nucleus removed from somatic cell (non-sex cell) and implanted into a donor egg with a removed nucleus
        
        egg cell thinks it is fertilised
        
        after stimulation, divides as a normally fertilised egg would
        
        forms embryo
        
        inner cell mass extracted and culture to provide embryonic tem cells
      - to get pluripotent cells in the inner cell mass
    - - premise: adult stem cells can generate cell types of different tissue in right condition
        
        inducing pluripotency in multipotent stem cells
        
        by plasticity (trans-differentiation)
        
        mature somatic cells have genes introduced
        
        regulates function of other genes important in early steps of embryonic development
      - overcomes ethical implications
        
        doesn't need to destroy human embryo
        
        less invasive skin biopsy to obtain adult stem cells
        
        less health risks to donors
        
        made in patient-matched manner
        
        each individual has own pluripotent stem cell line
        
        patient-specific basis of diseases (personalised drugs)
        
        transplants have no risk of immune rejection
  - - - cell based therapy
        
        specialised cells grown from stem cells in lab are transplanted into patient
        
        regenerates cell types in that tissue
    - - stem cells differentiated into cell types the drug works on
        
        mimics human tissue responses
        
        replaces animal testing
        
        safer, cheaper, more ethically acceptable
    - - to help people with genetic illenesses
    - - see what makes cells cancerous and development of genetic diseases
    - - unlimited supply of primary human cells that are difficult to obtain
        
        eg. neurons
        
        determines how much a substance damages organisms
        
        screen toxins before used in environment
  - - - some believe embryo has same moral status as adult/ born child
        
        believe that human life begins at conctraception
        
        deserves rights
        
        removing inner cell mass is like murder
      - some believe embryo is only a person at later stage of development
        
        respect as potential human being
        
        can be used for research with scientific justification, careful oversight, informed consent in donating embryo
    - - embryos used in research from in-vitro fertilisation
        
        oocytes fail to fertilise or embryos failed to develop to be implanted are discarded
        
        infertility patients discard frozen embryos after treatment
        
        may not have consent from gamete donors
        
        is consent necessary when they ceded their right to use gametes?
    - - medical complications or health risks to donors form oocyte donation
        
        fully informed consent?
      - appropriate usage
        
        not iinfluening people to serve as donors
    - - stem cell technology is time consuming and expensive
        
        high cost means only rich can access
        
        widen social divisions and enhances class division
- - - - expression of genes of specific proteins giving specific functions
        
        forms tissue-specific structures
      - triggered by cell signalling
        
        chemicals secreted by other cells
        
        physical contact
        
        molecules in environment
  - - - adult stem cells divide throughout the life of the organism
    - - makes multiple identical copies of itself (proliferation)
    - - symmetric division
        
        forms 2 identical unspecialised daughter cells
        
        both cells can self-renew
        
        pool of stem cells is continuously replenished
      - asymmetric division
        
        forms 1 identical unspecialised daughter cell and 1 differentiated specialised cell
        
        only unspecialised daughter cell can undergo self-renewal
        
        differentiated specialised cell in G0 phase
        
        can only undergo cell division to replace damaged or diseased cells
- - - - cell can differentiate into any cell type
        
        forms whole organism
      - includes lower potency levels
        
        totipotency includes pluripotent includes multi potency includes unipotency
    - - cell differentiates into almost any cell type
        
        forms organs or types of cells
    - - cell gives rise to limited range of cells
        
        limited amount of tissues appropriate to location
    - - cell only differentiates into one type of cell