Stem cells have been dogged by political and ethical controversies because some are derived from discarded human embryos, and because of fear and confusion about links with human reproductive cloning.
The future of stem cell therapies was thrown deeper into doubt in late 2005, when a leader of the field – Woo Suk Hwang, South Korea’s stem cell king” – was found to have forged key discoveries and flouted ethical protocols. So has the stem cell miracle been postponed? No.
There exists a widespread controversy over stem cell research that emanates from the techniques used in the creation and usage of stem cells. Embryonic stem cell research is particularly controversial because, with the present state of technology, starting a stem cell line requires the destruction of a human embryo and/or therapeutic cloning.
Opponents of the research argue that this practice is a slippery slope to reproductive cloning and tantamount to the instrumentalisation of a human being. Contrarily, some medical researchers in the field argue that it is necessary to pursue embryonic stem cell research because the resultant technologies are expected to have significant medical potential, and that the embryos used for research are only those meant for destruction anyway (as a product of invitro fertilisation).
This, in turn, conflicts with opponents in the pro-life movement, who argue that an embryo is a human being and therefore entitled to dignity even if legally slated for destruction. The ensuing debate has prompted authorities around the world to seek regulatory frameworks and highlighted the fact that stem cell research represents a social and ethical challenge. However, there still exists a great deal of social and scientific uncertainty surrounding stem cell research, which could possibly be overcome through public debate and future research.
Medical researchers however believe that stem cell therapy has the potential to radically change the treatment of human diseases. A number of adult stem cell therapies already exist, particularly bone marrow transplants that are used to treat leukemia. In the future, medical researchers anticipate being able to use technologies derived from stem cell research to treat a wider variety of diseases including cancer, Parkinson’s disease, spinal cord injuries, and muscle damage, amongst a number of other impairments and conditions.
Many achievements of stem cell research no doubt will help overcome the uncertainty around these researches , including the replacement teeth that was grown from scratch and implanted into the mouths of adult mice. A similar technique to this might one day help to replace missing teeth in humans. Takashi Tsuji at the Tokyo University of Science in Japan and his colleagues extracted single tooth mesenchymal and epithelial cells – the two cell types that develop into a tooth – from mouse embryos. They persuaded these cells to multiply and injected them into a drop of collagen gel. Within days, the cells formed tooth buds, the early stage of normal tooth formation.
The team extracted teeth from adult mice and transplanted the tooth buds into the cavities, where they developed into teeth with a normal structure and composition. The engineered teeth also developed a healthy blood supply and nerve connections. Other researchers have previously grown intact teeth from engineered tooth buds implanted in the kidneys of mice. They stopped short of showing that engineered buds could develop into teeth in the jaw. Adult stem cells can be made to turn into blood or any of the body’s tissues, too. Doubts have grown, but now a prominent skeptic has shown that the claim seems to be true. They formed all the cell types found in blood.
Catherine Verfaillie of the University of Minnesota in Minneapolis demonstrated the existence of Multipotent Adult Progenitor Cells (MAPCs) in 2002, isolated from bone marrow, a class of stem cells that normally form muscle and bone. Insulin-secreting cells created from human embryonic stem cells for the first time is also raising hopes of a limitless supply of cells that could be transplanted into people with type 1 diabetes. Emmanuel Baetge and his colleagues at Novocell in San Diego, California, used a cocktail of chemicals to coax the stem cells to form pancreatic. The cells produce as much insulin as normal pancreatic islet cells, but unlike adult islet cells, these do not appear to be regulated by sugar levels. Baetge is confident they can overcome this problem.
If they succeed, the company has also developed a way to coat the cells in a polymer called polyethylene glycol, which would prevent them from being rejected by the recipient’s immune system, thus allowing sugar, insulin and other signaling molecules to filter in and out. A leading cause of blindness could one day be treatable using stem cell therapy. Rats with a degenerative eye disease similar to macular degeneration, the most common cause of blindness in older people, have had their vision rescued by implants derived from human embryonic stem cells.
A team led by Robert Lanza of Advanced Cell Technology in Worcester, Massachusetts, was able to persuade human embryonic stem cells to grow into cells resembling retinal pigment epithelial cells. These are the cells which support the photoreceptors in the retina, and without them the photoreceptors do not survive. When injected into rats with failing vision, the cells boosted the thickness of their degraded retinas. The visual acuity of the treated rats seemed to be around 70 per cent of normal – about twice as good as if they had not been treated.
The promise by stem cell to combat childhood brain disease, the first clinical safety trial of a purified human fetal stem cell product, was tried out. The trial could pave the way for neural stem cell transplants to treat a range of brain and spinal cord disorders. A team from the Oregon Health and Science University Doernbecher Children’s Hospital actually treated six children suffering from the inherited neurodegenerative condition, Batten’s disease – also known as neuronal ceroid lipofuscinosis (NCL)with this neural stem cell transplant technology. The children had injections of neural stem cells that have been purified – isolated from other cell types – and grown from donated human fetal tissue. The stem cell product and isolation technique was developed by Stem Cells Inc, of Palo Alto, California, which is sponsoring the trial.
Could stem cells help heal damaged livers? This was the result that a pioneering treatment that used bone marrow cells from bodies of nine Japanese patients with cirrhosis is saying is really possible. The procedure could potentially ease the symptoms of cirrhosis and make a liver transplant unnecessary. “None of the patients was cured, but evidence from blood samples and liver scans suggested that their organs were functioning better six months after treatment,” said Isao Sakaida, head of the team at Yamaguchi University in western Japan that developed the treatment. “Another six patients show similar results, but haven’t been followed up yet for six months, and so weren’t included in our report,” he says.
Spinal cord damage promises to benefit from stem cells, a study carried out in injured rats with spinal cord damage suggested.
The team, led by Michael Fehlings at the Toronto Western Research Institute, Canada, used stem cells taken from mice brains. They injected a finely tuned cocktail of growth hormones, anti-inflammatory drugs and the cells into rats with crushed spines.
Although those rats not given the stem cell treatment naturally regained some of their hind limb function two weeks after the injury, they were however extremely uncoordinated. The stem cell treatment improved limb function, although it did not completely restore it.
Fehlings and his teammate found that while 30 per cent of the transplanted cells survived if the procedure took place two to three weeks after the rats suffered spinal cord damage, this number plummeted to five per cent transplantation that occurred between six and eight weeks after the injury.
No doubt stem cell is of immense importance to man’s existence, but the ethical issues must be resolved just as the several disreputes associated with the research need to be attended to properly.Will medical care be tranformed by this technology, time will tell.
By Sade Oguntola