1. Can you find an article explaining more about stem cells? How does the article compare and contrast different types of stem cells?

Possible student response: The Science News for Students article “Explainer: What is a stem cell?” published 6/27/2013, describes the basic properties of stem cells. According to the article, naturally occurring stem cells may be divided into two categories: pluripotent stem cells that can give rise to any cell type in the body, and adult stem cells that can give rise to any cell type within a certain category of cells. The article also lists an artificially created, third stem-cell type called induced pluripotent stem cells (iPS cells). Researchers have developed methods to convert any cell type — even ones that aren’t stem cells — into iPS cells. Researchers are attempting to find ways to use iPS cells to produce any desired cell type to aid patients.

2. Can you find an article that discusses the potential medical applications of induced pluripotent stem (iPS) cells? How do in vitro applications (outside the patient, in the lab) and in vivo applications (in a patient) compare?  

Possible student response: The Science News for Students article “Stem cells: The secret to change,” published 4/10/2013, gives several examples of medical applications of iPS cells. One early application is producing a variety of cell types for in vitro screening of new drugs to measure how effective they might be in a person. An example of an in vivo application is the possibility of treating patients with Pearson syndrome who cannot make their own red blood cells; other cells from the patient might be turned into iPS cells and then into red blood cells. Other examples of in vivo applications that have already been tested in nonhuman animals include using iPS cells to replace cells in a damaged retina to treat blindness and using iPS cells to replace neurons in a damaged spinal cord to treat paralysis. In general, in vitro applications require less safety testing and can be implemented sooner, but in vivo applications might have a more dramatic payoff for human health.

3. Can you find an article about using gene therapy to restore hearing? How does gene therapy compare with stem cell therapy?

Possible student response: The article “Gene therapy restores hearing in mice,” published 7/8/2015, discusses how scientists successfully demonstrated a viral gene therapy vector in mice. The mice had a genetic mutation that caused their sound-sensing cells to die off, and the viral gene therapy vector contained a healthy copy of that gene. Injecting mice with the viral gene therapy vector caused the mice to have more sound-sensing cells and to be more responsive to noises than similar untreated mice. In general, gene therapy methods would add to or otherwise alter the genes in a patient’s existing cells. If this type of gene therapy were to one day be used in people, researchers and doctors would have to be very careful that the patient’s immune system does not attack the virus or the virus-infected cells, or that the virus does not create undesirable effects. Stem cell therapies, which also add cells to the patient, are most effective if those cells were originally derived from the patient, so that the patient’s immune system will not attack them. These two methods are not mutually exclusive, so they can be combined, as they were in “Gene therapy fixes rare skin disease.”