Stem cell treatments
From Wikipedia, the free encyclopedia
Medical researchers believe that stem cell treatments have the potential to change the face of human disease and alleviate suffering. A number of current stem cell treatments already exist, although they are not commonly used because they tend to be experimental and not very cost-effective. In the future, medical researchers anticipate being able to use technologies derived from stem cell research to treat cancer, spinal cord injuries, and muscle damage, amongst a number of other diseases and impairments.
However, there still exists a great deal of social and scientific uncertainty surrounding stem cell research, which will only be overcome through years of intensive research and by gaining the acceptance of the public.
Furthermore, many technical difficulties remain which hinder the ultimate goals in stem cell therapeutics. Expanding stem cell populations extracted from patients remains a large problem. Also, even once these populations are expanded, implanted stem cells may not expand or grow efficiently enough to add enough corrective factor to be beneficial for treatment. These and other technical problems remain to be solved.
Contents |
[edit] Current treatments
For over 30 years, bone marrow (adult) stem cells have been used to treat cancer patients with conditions such as leukemia and lymphoma. During chemotherapy, most growing cells are killed by the cytotoxic agents. These agents not only kill the leukemia or neoplastic cells, but also those which release the stem cells from the bone marrow. These are therefore removed before chemotherapy, and are re-injected afterwards.
[edit] Potential treatments
[edit] Brain Damage
Stroke and traumatic brain injury lead to cell death characterized by a loss of neurons and oligodendrocytes within the brain. Healthy adult brains contain neural stem cells that divide, and act to maintain stem cells numbers or become progenitor cells. In healthy adult animals, progenitor cells migrate within the brain and function primarily to maintain neuron populations for olfaction (the sense of smell). Interestingly, in pregnancy and after injury this system appears to be regulated by growth factors and can increase the rate at which new brain matter is formed. In the case of brain injury although the reparative process appears to initiate substantial recovery is rarely observed in adults suggesting a lack of robustness. Recently, results from research conducted in rats subjected to stroke suggested that administration of drugs to increase the stem cell division rate and direct the survival and differentiation of newly formed cells could be successful. In the study referenced below, biological drugs were administerd after stroke to activate two key steps in the reparative process. Findings from this study seem to support a new strategy for the treatment of stroke using a simple elegant approach aimed at directing recovery from stroke by potentially protecting and/or regenerating new tissue. The authors found that, within weeks, recovery of brain structure is accompanied by recovery of lost limb function suggesting the potential for development of a new class of stroke therapy or brain injury therapy in man.
[edit] Cancer
Research injecting neural (adult) stem cells into the brains of dogs can be very successful in treating cancerous tumors. With traditional techniques brain cancer is almost impossible to treat because it spreads so rapidly. Researchers at the Harvard Medical School caused intracranial tumours in rodents. Then, they injected human neural stem cells. Within days the cells had migrated into the cancerous area and produced cytosine deaminase, an enzyme that converts a non-toxic pro-drug into a chemotheraputic agent. As a result, the injected substance was able to reduce tumor mass by 80 percent. The stem cells neither differentiated nor turned tumorigenic.[1]
[edit] Spinal cord injury
A team of Korean researchers reported on November 25, 2004, that they had transplanted multipotent adult stem cells from umbilical cord blood to a patient suffering from a spinal cord injury and she can now walk on her own, without difficulty. The patient had not even been able stand up for the last 19 years. The team was co-headed by researchers at Chosun University, Seoul National University and the Seoul Cord Blood Bank (SCB). For the unprecedented clinical test, the scientists isolated adult stem cells from umbilical cord blood and then injected them into the damaged part of the spinal cord. [1] [2] [3] [4]
The Korean researchers have followed up on their original work. The original treatment was conducted in November 2004. On April 18, 2005, the researchers announced that they will be conducting a second treatment on the woman. [5] The researchers have followed up with a case study write-up on their work. It is located in the journal Cytotherapy. [6]
According to the October 7, 2005 issue of The Week, University of California researchers injected human embryonic stem cells into paralyzed mice, which resulted in the mice regaining the ability to move and walk four months later. The researchers discovered upon dissecting the mice that the stem cells regenerated not only the neurons, but also the cells of the myelin sheath, a layer of cells with which nerve fibers communicate with the brain (damage to which is often the cause of neurological injury in humans). [7]
In January 2005, researchers at the University of Wisconsin-Madison differentiated human blastocyst stem cells into neural stem cells, then into the beginnings of motor neurons, and finally into spinal motor neuron cells, the cell type that, in the human body, transmits messages from the brain to the spinal cord. The newly generated motor neurons exhibited electrical activity, the signature action of neurons. Lead researcher Su-Chun Zhang described the process as "you need to teach the blastocyst stem cells to change step by step, where each step has different conditions and a strict window of time."
Transforming blastocyst stem cells into motor neurons had eluded researchers for decades. The next step will be to test if the newly generated neurons can communicate with other cells when transplanted into a living animal; the first test will be in chicken embryos. Su-Chun said their trial-and-error study helped them learn how motor neuron cells, which are key to the nervous system, develop in the first place.
The new cells could be used to treat diseases like Lou Gehrig's disease, muscular dystrophy, and spinal cord injuries.
[edit] Muscle damage
Adult stem cells are also apparently able to repair muscle damaged after heart attacks. Heart attacks are due to the coronary artery being blocked, starving tissue of oxygen and nutrients. Days after the attack is over, the cells try to remodel themselves in order to become able to pump harder. However, because of the decreased blood flow this attempt is futile and results in even more muscle cells weakening and dying. Researchers at Columbia-Presbyterian found that injecting bone-marrow stem cells, a form of adult stem cells, into mice which had had heart attacks induced resulted in an improvement of 33 percent in the functioning of the heart. The damaged tissue had regrown by 68 percent.
[edit] Heart damage
Several types of heart disease have been treated in clinical trials and therapy is commercially available. Patients such as Jeannine Lewis[8] and legendary Hawaiian crooner Don Ho[9]have traveled to Thailand to receive stem cell therapy for their heart disease.
Using the patient's own bone marrow derived stem cells or more recently, peripheral blood-derived stem cells, Dr. Amit Patel at the University of Pittsburgh, McGowan Institute of Regenerative Medicine has shown a dramatic increase in ejection fraction for patients with congestive heart failure. He works with many other countries such as Argentina, Uruguay, Ecuador, Greece, Japan, and Thailand where he has taught minimally invasive techniques for the treatment of non-ischemic (idiopathic) and ischemic heart failure.
In Malaysia as well, Stem Cell Therapy for the heart is well established (www.stemlife1.blogspot.com). Results are inline with results published in research papers.
[edit] Low blood supply
In December 2004, a team of researchers led by Dr. Luc Douay at the University of Paris developed a method to produce large numbers of red blood cells. The Nature Biotechnology paper, entitled Ex vivo generation of fully mature human red blood cells, describes the process: precursor red blood cells, called hematopoietic stem cells, are grown together with stromal cells, creating an environment that mimics the conditions of bone marrow, the natural site of red blood cell growth. Erythropoietin, a growth factor, is added, coaxing the stem cells to complete terminal differentiation into red blood cells.
Further research into this technique will have potential benefits to gene therapy, blood transfusion, and topical medicine.
[edit] Baldness
Hair follicles also contain stem cells, and some researchers predict research on these follicle stem cells may lead to successes in treating baldness through "hair multiplication," also known as "hair cloning," as early as 2008. This treatment is expected to work through taking stem cells from existing follicles, multiplying them in cultures, and implanting the new follicles into the scalp. Later treatments may be able to simply signal follicle stem cells to give off chemical signals to nearby follicle cells which have shrunk during the aging process, which in turn respond to these signals by regenerating and once again making healthy hair. Hair Cloning Nears Reality as Baldness Cure (WebMD Nov. 2004)
[edit] Missing teeth
In 2004, scientists at King's College London discovered a way to cultivate a complete tooth in mice [10] and were able to grow them stand-alone in the laboratory. Researchers are confident that this technology can be used to grow live teeth in human patients.
In theory, stem cells taken from the patient could be coaxed in the lab into turning into a tooth bud which, when implanted in the gums, will give rise to a new tooth, which would be expected to take two months to grow. [11] It will fuse with the jawbone and release chemicals that encourage nerves and blood vessels to connect with it. The process is similar to what happens when humans grow their original adult teeth.
Its estimated that it may take until 2009 before the technology is widely available to the general public, but the genetic research scientist behind the technique, Professor Paul Sharpe of King's College, estimates the method could be ready to test on patients by 2007 [12]. His startup company, Odontis, fully expects to offer tooth replacement therapy by the end of the decade.
[edit] Deafness
There has been success in regrowing cochlea hair cells with the use of stem cells. [13]
[edit] Blindness and Vision Impairment
Since 2003, researchers have successfully transplanted retinal stem cells into damaged eyes to restore vision. Using embryonic stem cells, scientists are able to grow a thin sheet of totipotent stem cells in the laboratory. When these sheets are transplanted over the damaged retina, the stem cells stimulate renewed repair, eventually restoring vision [14]. The latest such development was in June of 2005, when researchers at the Queen Victoria Hospital of Sussex, England were able to restore the sight of forty patients using the same technique. The group, led by Dr. Sheraz Daya, was able to successfully use adult stem cells obtained from the patient, a relative, or even a cadaver. Further rounds of trials are ongoing [15].
In April 2005, doctors in the UK transplanted corneal stem cells from an organ donor to the cornea of Deborah Catlyn, a woman who was blinded in one eye when an acid was thrown in her eye at a nightclub. The cornea, which is the transparent window of the eye, is a particularly suitable site for transplants. In fact, the first successful human transplant. The transplant carried out in 1905 by Dr. Eduard Zirm. The recipient was Alois Gloger, a labourer who had been blinded in an accident. The cornea has the remarkable property that it does not contain any blood vessels, making it relatively easy to transplant. The majority of corneal transplants carried out today are due to a degenerative disease called keratoconus which causes vision imapairment and has no known cure even after corneal transplant. It is hoped that stem cell research will one day provide a cure to such debilitating corneal disorders.
As more research yields increasingly precise techniques, stem cell transplantation to restore vision may become viable on a large. The success rate of the procedure is currently from 20 to 70 percent [16], and further stem cell research is required.
[edit] ALS (Lou Gehrig's Disease)
In the April 4th, 2001 edition of JAMA (Vol. 285, 1691-1693) [17], Drs. Gearhart and Kerr of Johns Hopkins University used stem cells to cure rats of an ALS-like disease. The rats were injected with a virus to kill the spinal cord motor nerves related to leg movement. Dr. Gearhart and Dr. Kerr then injected the spinal cords of the rats with stem cells. These migrated to the sites of injury where they were able to regenerate the dead nerve cells restoring the rats which were once again able to walk.
[edit] Some scientists see shift in stem cell hopes
It was reported in the New York Times (14th August 2006), by Nicholas Wade, that some scientists see a shift in stem cell hopes. Several mentioned that the main role of stem cells was in research. Many no longer see cell therapy as the first goal of the research, parting company with those whose near-term expectations for cell therapy remain high. [18]
Thomas M. Jessell, a neurobiologist at Columbia University said that:
"Many of us feel that for the next few years the most rational way forward is not to push stem cell therapies". [19]
[edit] Controversy
There is wide spread controversy over the use of embryonic stem cells. This controversy is over the technique used to create new embryonic stem cell lines, which often requires the destruction of the blastocyst. While the American government does not fund embyronic stem cell research that uses new lines, it does fund embryonic stem cell research that uses existing stem cell lines. The argument for this is that creating embryonic stem cells with existing lines does not require the destruction nor the use of a human embryo. Nevertheless, the lack of harsher regulations from the federal government has led states to further restrict the use of embryonic stem cells in research and medicine.
[edit] Stem cell use in animals
[edit] Horses
Stem cell treatment has begun on horses, mainly to treat injuries to the tendons, ligaments, and joints of sport horses or racehorses. Fat is harvested from the tail head and processed, and an animal may receive treatment within three days after the sample is taken. Injuries that may be treated include Degenerative Joint Disease, soft-tissue injuries, Osteochondrosis, fractures, and sub-chonral bone cysts. Currently, research is also being preformed on stem cell application in laminitis and COPD.[20]
[edit] Dogs
There is currently research being preformed on the usefulness of stem cells in canine muscular distrophy, if successful this could provide a means of treating MD in humans.
[edit] External links
[edit] References
| Stem cells |
|---|
| Sources: Embryonic stem cells | Adult stem cells | Cancer stem cells |
| Related articles: Stem cell treatments | Stem cell controversy | Stem cell line | Progenitor cell | Cell differentiation |
![[7]](http://img227.imageshack.us/img227/7954/stemcellbreakthru052wl.jpg){kind=link}