Stem cells are fascinating and stem cell research is one of the most promising areas in medicine. In recent years they have gone from being a hot topic talked about at conferences to an audience of scientists, to a household term.
In brief, a stem cell is an extraordinary, very early stage, unspecialised cell that has the potential to develop into a number of specialised cell types, generating the cells that compose all the tissues and organs in the body. For example a stem cell could turn into skin cells, liver cells, nerve cells etc. Stem cells from foetuses or embryos can develop into any type of cell, while those found in mature tissues are more specialised and develop only into specific cell types. In adults, stem cells act as an internal repair system, constantly replacing and regenerating cells in order to maintain proper and efficient function of tissues and organs.
The term stem cell appears in the scientific literature as early as 1868, in book titled Natürliche Schöpfungsgeschichte(translated into English as The History of Creation), written by the eminent German biologist Ernst Haeckel. He used the phrase stem cell to describe the fertilized egg that becomes an organism.
Adult stem cells, derived mostly from bone marrow and umbilical cord blood, have been used in research since the 1960s, with applications focused primarily on treatments for cancer. In 1998, James Thomson (University of Wisconsin-Madison) created the first embryonic stem cell line by isolating cells from human embryonic blastocysts, (the inner cell mass of the early embryo formed by division of a fertilised egg). Cell lines are a family of constantly dividing cells which can replicate for long periods of time in an artificial environment in the lab and can be used for research.
As previously mentioned embryonic stem cells are ‘pluripotent’, that is they have not yet been programmed and can develop into many different cell types when given the specific simulation necessary. Often, embryonic stem cells are derived from blastocysts generated for IVF donated for research by couples who have undergone in vitro fertilisation (IVF) to become
pregnant and have more embryos than they need.
At the blastocyst stage, five to 10 days after fertilisation, the embryo is a cluster of 100-200 cells. Often blastocysts are judged to be of insufficient quality to use in IVF and would otherwise be discarded. Once embryonic stem cells have been isolated, the blastocyst is no longer able to develop into a foetus.
The use of stem cells derived from human embryos continues to cause ethical concerns and is prohibited by law in many countries. In the United States, a ban on federal funding of embryonic stem cell research was overturned in April 2011. In the UK, the use of embryos in stem cell research is permitted but tightly regulated.
However researchers from Advanced Cell Technology (ACT) reported in November 2006 that they generated stem cell lines by plucking single cells from embryos and in February 2008 the same group reported the derivation of five stem cell lines without
embryo destruction. The ability to create new stem cell lines without destroying embryos would address the ethical concerns of many, and allow the generation of matched tissue for children and siblings born from embryos generated by IVF and genetically screened before implantation.
In my opinion the use of stem cells is instrumental to advancing science and medicine and improving human life. However, this research must be tightly regulated and monitored and there must be sufficient evidence to support scientific claims before their use in therapy.
Much has been learnt about stem cells and their potential uses. They have potential for many different areas of health and medical research and studying them can help us understand how they transform into the astonishing range of specialised cells that make us what we are. Stem cells can potentially be used to replace tissue damaged or destroyed by disease or injury. Stem cells, directed to develop into specific cell types, offer the possibility of a renewable source of replacement cells and tissues to treat Alzheimer’s and Parkinson’s disease, multiple sclerosis, spinal cord injury, stroke, burns, heart disease, diabetes, osteoarthritis and rheumatoid arthritis as well as to test new drugs in a wide range of cell types.
There is still much more of the stem cell puzzle to solve and a better understanding of normal cell development will allow us to understand and perhaps correct the errors that cause these medical conditions
Developments that have featured in the news in the past month or so include:
Muscles that make up the human heart have been made from embryonic stem cells for the first time. http://www.nature.com/nature/journal/v453/n7194/abs/nature06894.html
Ones to watch:
US doctors began the first official trial of using human embryonic stem cells in patients in October 2010. A pilot trial is being carried out by a biotech company called Geron, based in San Francisco. The trial aims to assess the safety of cells developed from human embryonic stem cells in patients who have had a recent spinal cord injury and to see whether there is any return of movement or feeling in the patient’s lower body in the year after injection with the stem cells (http://www.geron.com/).
Advanced Cell Technology (ACT), a company in Massachusetts have begun a clinical trial using retinal cells derived from human embryonic stem cells to treat patients with Macular Dystrophy, a disease that causes progressive vision loss usually to the point of blindness (http://www.advancedcell.com)
The London Project to Cure Blindness, directed by Professor Pete Coffey of University College London Institute of Ophthalmology is a 5 year research project that aims to develop a cell therapy for Age-related Macular Degeneration (http://www.thelondonproject.org).