Stem Cell Research

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Stem Cell Research

Stem Cells
Stem cell research focuses on utilizing stem cells to generate specific cell types for the treatment of disease. Image Credit: Public Domain Images

Stem Cell Research

Stem cell research has become increasingly important as these cells can be used to treat a variety of diseases. Stem cells are unspecialized cells of the body that have the ability to develop into specialized cells for specific organs or to develop into tissues. Unlike specialized cells, stem cells have the ability to replicate through cell cycle many times, for long periods of time. Stem cells are derived from several sources in the body. They are found in mature body tissues, umbilical cord blood, fetal tissue, the placenta, and within embryos.

Stem Cell Function

Stem cells develop into tissues and organs in the body. In some cell types, such as skin tissue and brain tissue, they can also regenerate to aid in the replacement of damaged cells. Mesenchymal stem cells, for example, play a vital role in healing and protecting damaged tissue. Mesenchymal stem cells are derived from bone marrow and give rise to cells that form specialized connective tissues, as well as cells that support the formation of blood. These stem cells are associated with our blood vessels and move into action when vessels become damaged. Stem cell function is controlled by two important pathways. One pathway signals cell repair, while the other inhibits cell repair. When cells get worn out or damaged, certain biochemical signals trigger adult stem cells to start working to repair tissue. As we grow older, the stem cells in the older tissue are inhibited by certain chemical signals from reacting as they normally would. Studies have shown, however, that when placed in the proper environment and exposed to the appropriate signals, older tissue can repair itself once again.

How do stem cells know what type of tissue to become? Stem cells have the ability to differentiate or transform into specialized cells. This differentiation is regulated by internal and external signals. A cell's genes control the internal signals responsible for differentiation. External signals that control differentiation include biochemicals secreted by other cells, the presence of molecules in the environment, and contact with nearby cells. Stem cell mechanics, the forces cells exert on the substances to which they are in contact with, play a crucial role in stem cell differentiation. Studies have shown that adult human mesenchymal stem cells develop into bone cells when cultured on a stiffer stem cell scaffold or matrix. When grown on a more flexible matrix, these cells develop into fat cells.

Stem Cell Production

Although stem cell research has shown much promise in the treatment of human disease, it is not without controversy. Much of the stem cell research controversy centers around the use of embryonic stem cells. This is because human embryos are destroyed in the process of obtaining embryonic stem cells. Advances in stem cell studies however, have produced methods for inducing other stem cell types into taking on the characteristics of embryonic stem cells. Embryonic stem cells are pluripotent, meaning that they can develop into almost any type of cell. Researchers have developed methods for converting adult stem cells into induced pluripotent stem cells (iPSCs). These genetically altered adult stem cells are prompted to function as embryonic stem cells. Scientists are constantly developing new methods to generate stem cells without destroying human embryos. Examples of these methods include:

  • Somatic Cell Nuclear Transfer

    Researchers have successfully produced human embryonic stem cells using a technique called somatic cell nuclear transfer (SCNT). This process involves removing the nucleus from an unfertilized egg cell and replacing it with the nucleus of another cell. In this study, human skin cell nuclei were transplanted into unfertilized enucleated (removed genetic material) egg cells. These cells went on to develop and produce embryonic stem cells. The stem cells had no chromosomal abnormalities and normal gene function.
    Human Skin Cells Converted Into Embryonic Stem Cells
     
  • Genetic Reprogramming

    Researchers from Lund University in Sweden have developed a technique for creating various kinds of nerve cells from adult skin tissue. By activating specific skin cell genes, connective tissue cells called fibroblasts can be reprogrammed into developing into neurons. Unlike other reprogramming techniques, which require adult skin cells be converted to induced pluripotent stem cells (iPSCs) prior to becoming nerve cells, this technique allows skin cells to be directly converted to nerve cells.
    New Genetic Technique Converts Skin Cells Into Brain Cells
     
  • MicroRNA Method

    Researchers have discovered a more efficient method for creating reprogrammed stem cells. Using the microRNA method, about 10,000 induced pluripotent stem cells (iPSCs) can be produced from every 100,000 adult human cells used. The current method for producing iPSCs only yields less than 20 of these reprogrammed cells from every 100,000 adult human cells used. The microRNA method could lead to the development of a cellular "storehouse" of iPSCs that could be used in tissue regeneration.
    New Highly Efficient Way to Make Reprogrammed Stem Cells

Stem Cell Therapy

Stem cell research is needed to develop stem cell therapy treatments for disease. This type of therapy involves prompting stem cells to develop into specific types of cells to repair or regenerate tissue. Stem cell therapies could be used to treat individuals with a number of conditions including multiple sclerosis, spinal cord injuries, nervous system diseases, cardiac disease, baldness, diabetes, and Parkinson's disease. Stem cell therapy may even be a potential means of helping to preserve endangered species. A Monash University study indicates that researchers have discovered a way to help the endangered snow leopard by producing iPSCs from ear tissue cells of adult snow leopards. The researchers hope to be able to coax the iPSCs cells into forming gametes for the future reproduction of these animals through cloning or other methods.

Source:

  • Stem Cell Basics: Introduction. In Stem Cell Information [World Wide Web site]. Bethesda, MD: National Institutes of Health, U.S. Department of Health and Human Services, 2002 [cited Thursday, June 26, 2014] Available at (http://stemcells.nih.gov/info/basics/pages/basics1.aspx)