Recent advances in adult stem cell technology

7 November 2000

Stem cells can be found in most adult tissues

From studies on adult stem cells in the last 30 years it had been clearly shown that many adult tissues contain stem cells, but stem cells capable of producing only cells proper to that tissue. Thus it was not thought that these cells could be reprogrammed. In more recent years, however, pluripotent stem cells were also discovered in various human tissues--in bone marrow, in the brain, in the connective tissues of various organs, and in umbilical cord blood; these are cells capable of producing different types of cells, mostly blood cells, muscle cells and neural (nerve) cells. [Cf. C. S. POTTEN (ed.), Stem Cells, Academic Press, London 1997, p. 474; D. ORLIC, T. A. BOCK, L. KANZ, Hemopoietic Stem Cells: Biology and Transplantation, Ann. N. Y. Acad. Sciences, vol. 872, New York 1999, p. 405; M. F. PITTENGER, A. M. MACKAY, S.C. BECK et al., Multilineage Potential of Adult Human Mesenchymal Stem Cells, Science 1999, 284, 143-147; C. R. R. BJORNSON, R.L. RIETZE, B. A. REYNOLDS et al., Turning Brain into Blood: a Hematopoietic Fate Adopted by Adult Neural Stem Cells in vivo, Science 1999, 283, 534-536; V. OUREDNIK, J. OUREDNIK, K. I. PARK, E. Y. SNYDER, Neural Stem Cells - a Versatile Tool for Cell Replacement and Gene Therapy in the Central Nervous System, Clinical Genetics 1999, 56, 267-278; I. LEMISCHKA, Searching for Stem Cell Regulatory Molecules: Some General Thoughts and Possible Approaches, Ann. N.Y. Acad. Sci. 1999, 872, 274-288; H. H. GAGE, Mammalian Neural Stem Cells, Science 2000, 287, 1433-1438; D. L. CLARKE, C. B. JOHANSSON, J. FRISEN et al., Generalized Potential of Adult Neural Stem Cells, Science 2000, 288, 1660-1663; G. VOGEL, Brain Cells Reveal Surprising Versatility, ibid., 1559-1561.] It seems live neural stem cells can be obtained from adult cadavers even hours or days after death (UniSci [unisci.com], 28 April 1999).

Adult stem cells rival embryonic stem cells in their capacity to provide a wide variety of tissues

Studies in recent years "suggest that stem cells in different adult tissues may be more similar than previously thought and perhaps in some cases have a developmental repertoire close to that of embryonic stem cells" and "demonstrates that an adult neural stem cell has a very broad developmental capacity and may potentially be used to generate a variety of cell types for transplantation in different diseases" [D.L.CLARKE, C.B.JOHANSSON, J.FRISEN et al., Generalized Potential of Adult Stem Cells, Science 2000, 288 1660-1663]
  • Researchers at the University of Pennsylvania in Philadelphia have revealed that cells in human fat have been coaxed to grow into bone cells. This suggests that fat deposits could be an abundant source of adult stem cells from which a range of different cell types could be grown. Dr Louis P Bucky said that fat deposits could provide "a potentially unlimited source of cells to turn into mature cells of different types" unlike stem cells extracted from adult bone marrow. [Reuters Health, 18 October 2000]
  • Italian scientists have revealed that adult neural stem cells have been found to be unexpectedly pliable and have been successfully converted into muscle tissue. Stem cells from the brain of adult mice were re-programmed to behave like muscle cells by being placed in close proximity to mature muscle cells. The same result was then achieved using neuronal stem cells taken from an adult human volunteer. The research, published on 19 September 2000 in the Nature Neuroscience journal, was undertaken by a group of scientists from the National Neurological Institute and the Institute for Stem Cell Research, based in Milan.
  • Scientists in Florida, USA, have disclosed that adult stem cells found in bone marrow can be converted into immature nerve cells. The study, carried out by the University of South Florida's College of Medicine and published in the Experimental Neurology journal, suggests that eventually cells could be taken from a patient's bone marrow and converted into neurones to treat Parkinson's disease, stroke and other brain conditions. [University of South Florida press release, 1 August 2000], thus avoiding any possibility of rejection. It was reported [BBC News] on 20 July 2000 that British scientists [Imperial Cancer Research Fund] had discovered that stem cells in bone marrow could convert into liver cells.

Adult stem cells can be genetically modified to serve important new roles in the body

The progress and results obtained in the field of adult stem cell research show not only their great plasticity but also their many possible uses, in all likelihood no different from those of embryonic stem cells, since plasticity depends in large part upon genetic information which can be reprogrammed. For example, Dr. Micheline Mathews of Harvard Medical School has cured a rare genetic disease in mice by inserting the missing gene into their own stem cells. In April 2000, French researchers reported in Science what was described as the first clear success in human gene therapy, curing severe combined immunodeficiency disease (SCID) in several children by inserting the missing gene into their bone marrow stem cells.

Adult stem cells may be safer for transplantation, as their development into different types of cells is more manageable

Adult stem cells only become different types of cells when they are given new signals to do so. Placed in their usual environment, they seem to produce only the cell types of that particular tissue which is exactly what is needed to repair such tissue safely. Thus, "besides skirting the ethical dilemmas surrounding research on embryonic and fetal stem cells, adult cells... might have another advantage: They may be easier to manage" (G. Vogel, in Science, Feb. 25, 2000).

Adult stem cells can also be "immortalised" and multiplied in culture

In the January 1999 Nature Genetics, University of Texas researchers reported that the enzyme telomerase can " immortalise" adult cell cultures without producing the uncontrolled growth of cancer cells. In the March 28, 2000, Proceedings of the National Academy of Sciences, Dr. Darwin Prockop (now at Tulane University) reported on advances enabling his team to multiply human bone marrow stem cells a billion-fold in six weeks.

Companies are investing in adult stem cell technology

Osiris Therapeutics, Inc. is a private company in Baltimore, USA, focusing on restoration of damaged and diseased tissue. Osiris uses adult bone marrow to isolate, purify and grow human mesenchymal stem cells (hMSCs), the progenitor cells that give rise to connective tissues including bone marrow stroma, bone, cartilage, ligament, tendon and fat, as well as muscle. They believe that hMSC cell therapy will prove effective treatment for damage arising from injury, aging or degenerative diseases.

Some argue that the British biotechnology industry would lose out to European competition if research into human cloning were prohibited. However, Germany has the strongest rules in Europe for the protection of embryos in research, yet it has overtaken the United Kingdom in terms of the number of biotechnology firms locating there.


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