Cell sources used to rebuild damaged tissues are the major issue in the development of regenerative medicine. Three sources of cells can be tapped for transplant: differentiated tissues (refers to a technique developed at Harvard and posted here in August 2008, a better approach to the production of Induced Pluripotent Stem Cells), adult stem cells (ASCs) and derivatives of embryonic stem cells (ESCs). Adult stem cells regenerate epithelia, brain tissue, muscle, blood and bone. They have also been found in other tissues that normally scar after injury, such as myocardium, spinal cord and retinal tissues.
"Adult stem cell therapy has real potential to regenerate at least muscle and bone damaged by injury or genetic disease, and cardiac stem cells may be a way to regenerate new cardiomyocytes after myocardial infarction," says David L. Stocum, Indiana University-Purdue University Indianapolis professor. Progress is also being made toward the use of ESCs to derive functional cells for treatment of diabetes and muscular dystrophy.
Regeneration is a regulative developmental process ubiquitous across all species. It functions throughout the life cycle to maintain or restore the normal form and function of cells, tissues and, in some cases organs, appendages and whole organisms. The roots, stems and leaves of plants, for example, have extensive regenerative capacity, and entire plants can grow from single cells or small cuttings.
The regenerative capability of most vertebrate animals, however, is restricted to certain tissues. In the absence of injury, many cell types such as epithelia and blood cells turn over rapidly, while others such as hepatocytes, myofibers, osteocytes, and most neurons, have low turnover rates or do not turn over at all. In organisms that grow throughout life, such as fish, the total number of cells in various tissues increases continuously, indicating that the number of new cells produced is higher than the number of cells lost.
The ability to reprogram adult somatic cells to ESCs in culture has led the authors to the concept that it may be possible to use natural or synthetic molecules to reprogram adult somatic cells in vivo to adult stem cells that will recapitulate the development of a tissue, organ or appendage, or to stimulate resident adult stem cells to do so. They argue that strong regenerators, such as fish and amphibians know how to do this naturally, and should be studied to learn what molecules are required for such stimulation or reprogramming. The counterparts of these molecules, or synthetic small molecules that mimic their action, could then be applied to regeneration-deficient mammalian tissues.
Adapted from the IUPUI announcement through EurekAlert.
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