Brent Cornell

    
Stem cells can be used to replace damaged or diseased cells with healthy, functioning ones

This process requires:

• The use of biochemical solutions to trigger the differentiation of stem cells into the desired cell type
• Surgical implantation of cells into the patient’s own tissue
• Suppression of host immune system to prevent rejection of cells (if stem cells are from foreign source)
• Careful monitoring of new cells to ensure they do not become cancerous

Examples of Stem Cell Therapy

1.  Stargardt’s Disease

• An inherited form of juvenile macular degeneration that causes progressive vision loss to the point of blindness
• Caused by a gene mutation that impairs energy transport in retinal photoreceptor cells, causing them to degenerate
• Treated by replacing dead cells in the retina with functioning ones derived from stem cells
  
  

2.  Parkinson’s Disease

• A degenerative disorder of the central nervous system caused by the death of dopamine-secreting cells in the midbrain
• Dopamine is a neurotransmitter responsible for transmitting signals involved in the production of smooth, purposeful movements
• Consequently, individuals with Parkinson’s disease typically exhibit tremors, rigidity, slowness of movement and postural instability
• Treated by replacing dead nerve cells with living, dopamine-producing ones
  
  

3.  Other Therapeutic Examples

• Leukemia:  Bone marrow transplants for cancer patients who are immunocompromised as a result of chemotherapy
• Paraplegia:  Repair damage caused by spinal injuries to enable paralysed victims to regain movement
• Diabetes:  Replace non-functioning islet cells with those capable of producing insulin in type I diabetics
• Burn victims:  Graft new skin cells to replace damaged tissue

Examples of Therapeutic Stem Cell Use

    
Stem cells can be derived from one of three sources:

• Embryos (may be specially created by therapeutic cloning)
• Umbilical cord blood or placenta of a new-born baby
• Certain adult tissues like the bone marrow (cells are not pluripotent) 

The ethical considerations associated with the therapeutic use of stem cells will depend on the source

• Using multipotent adult tissue may be effective for certain conditions, but is limited in its scope of application
• Stem cells derived from umbilical cord blood need to be stored and preserved at cost, raising issues of availability and access
• The greatest yield of pluripotent stem cells comes from embryos, but requires the destruction of a potential living organism

Artificial Stem Cell Techniques

Stem cells can be artificially generated via nuclear transfer or nuclear reprogramming, with distinct benefits and disadvantages

• Somatic cell nuclear transfer (SCNT): 
  • Involves the creation of embryonic clones by fusing a diploid nucleus with an enucleated egg cell (therapeutic cloning)
  • More embryos are created by this process than needed, raising ethical concerns about the exigency of excess embryos

• Nuclear reprogramming:
  • Induce a change in the gene expression profile of a cell in order to transform it into a different cell type (transdifferentiation) 
  • Involves the use of oncogenic retroviruses and transgenes, increasing the risk of health consequences (i.e. cancer)