What’s new with stem cells? : The Latest Research
Parkinson’s Disease
Various trials are being conducted around the globe in which Multipotent stem cells are used to migrate to areas of damaged or dead nerve cells and replace them with brand new healthy cells.
Experiments performed at the National Institutes of Health have confirmed that embryonic rat nerve cells that are grown in culture and transplanted into rats with a type of disorder likened to human Parkinson’s disease will morph into healthy, mature brain cells. Significant neurologic recovery was examined.
Britain researchers have recently been performing studies where human stem cells are grown and cultured, and then transplanted into the brains of Parkinson’s-like rats. At autopsies of these rats, approximately twenty weeks later, the human cells have been found far from the original transplant sites, and have been noted to have differentiated into several types of rat brain cells.
Xenotransplant experiments are also being performed currently. Researchers at the Medical School of Harvard University planted fetal pig neural tissue into the brain of a human with Parkinson’s disease in late 2003. The patient unfortunately did die, however the autopsy revealed that the pig cells had matured into cells that would produce dopamine, the missing chemical transmitter in Parkinson’s disease.
In January of 2002, Harvard Medical School also tested the efficacy of undifferentiated mouse stem cells into the brains of rats with a Parkinson’s-like disorder. This study is continuing currently, and results show that the cells from the mice differentiate into fully mature neurons that produce dopamine. The animals have shown, and continue to show functional improvement.
Spinal Cord Injury
In one of the latest studies, conducted at Washington University in St. Louis, chemicals were used to dissolve the myelin in laboratory rats. After a period of three days, rat embryonic stem cells were transplanted into the spinal columns of the injured rats. After autopsy, mature myelin-producing cells were identified at the site of the transplants. Another study at this facility induced rats with spinal cord injuries, and after nine days of injury, transplanted stem cells into the rats’ spinal cords. After five weeks, the laboratory rats showed improvement in weight bearing and coordination.
Research has also been done with human brain cells. Recently, a 2004 study indicated that the white matter of the human adult brain, made mostly of myelin, seems to harbor stem cells that can become glia or neurons (white or grey matter, respectively). In fetal rat brains, these cells differentiated both in vitro and after they were transplanted. This could potentially lead to future repair in both white and grey matter of the human brain.
Researchers at Emory University in Atlanta are currently working on a trial to test if stem cells can be used to improve or cure the negative effects of Multiple Sclerosis. The researchers have used cells from the CNS of dogs with a demyelinating disease which mirrors human MS. Larg
e areas of repair of the demyelinated areas have been reported.
Bone Marrow
Mesenchymal stem cells, which are found in the bone marrow of adult humans, have been identified as having the potential to develop into mature cells that produce fat, cartilage, muscle, and tendons. Various trials have shown that these cells can be isolated and transplanted.
A recent report from the Children’s Hospital in Philadelphia indicated that human Mesenchymal cells have been transplanted into sheep were they grew, matured and differentiated. They were identified in sheep tissue up to thirteen months after the initial operation, and found to have matured into cardiomyocytes (makers of heart muscle). This study confirms that these Mesenchymal cells not only maintain their multipotent status after transplantation, they have the ability to withstand immune system rejection.
Reprogramming of Stem Cells
In the early stages of stem cell research, it was believed that only embryonic stem cells could morph into any cell in the body, and that once these cells were transplanted into a certain organ, they could only differentiate into cells for that specific organ site. However, new examinations reveal that adult stem cells that would have once been assumed to be committed to becoming a certain type of mature cell can be reprogrammed to mature into an entirely different cell line.
In September of 2001 at the University of Wisconsin, laboratory experimenters treated embryonic stem cells with serum, the liquid component of blood. They found that blood stem cells were then produced. This method could lead to further understanding of human blood formation and future methods of obtaining blood cells for transfusion.
Scientists at Yale University School of Medicine have done studies with mice to demonstrate the potential of blood stem cells. They irradiated female mice, killing off their own blood stem cells and then transplanted male stem cells into them. The scientists found, by tracking the presence of the Y chromosome, that the transplanted male cells had not only become bone marrow and blood cells, but also morphed into cells of the lung, digestive system, liver and skin.
In November of 2001, a study was begun by Dr. Lorraine Iacovetti, who uncovered new information about stem cells in her laboratory at Thomas Jefferson Hospital. She and her team investigated how stem cells could switch from one type to another. After using various growth factors and nutrients, they managed to convert human blood stem cells into human neuron stem cells. After lack of stimulation for three days, these cells reverted back to their original state. Now, Iacovetti and her tram are working on other types of transformations.
Gene Therapy
Johns Hopkins University published an article in late 2002 in an issue of Blood which discussed a method of using stem cells for gene therapy and repair. Mice were bred to have poor immunity. The mice were then injected with blood stem cells that carried a specific gene which was activated only inside a specific immune cell, the antigen-presenting cell. Close monitoring of these cells indicated that the cells ultimately developed into the same antigen-presenting cell. Among potential uses for this type of therapy would be implantation of genes into stem cells that would improve the immune system.
At the Goldyne Savad Institute of Gene Therapy in Jerusalem, studies recently conducted (2004) showed that a lentiviral vector, (a modified virus) could be used to alter the gene expression of human embryonic stem cells. This demonstrates the possible use of stem cells for various cell therapies.
The Heart
New investigation suggests that stem cells can regenerate heart muscle. In August of 2001 a group of investigators working with animals with induced hear attacks, introduced stem cells of bone marrow into the damaged hearts. After approximately thirty days, the hearts of the animals were scrutinized and the group noticed that mortality had dropped by 68% and the amount of damaged muscle in the heart decreased by 40%.
At the University of Udine in Italy in 2002, the same researchers studied male patients who had died after having received heart transplants from female donors. What they found was that about 10% of the patients’ heart muscle cells and heart blood vessel cells had Y chromosomes. This indicates chimerism as a result of the stem cell migration into the transplanted hearts. This evidence implies that stem cells began to populate some part of the transplanted heart, indicating that humans carry stem cells for various heart cells and that these stem cells can migrate and probably oftentimes do migrate into damaged hearts.
Cancer
Current studies are being done at the Thomas Jefferson University Hospital that compare various stem cells to cancer cells. In a recent publication in Nature,(2005) the researchers claim the possibility of at least one form of cancer being the result of damaged stem cells.
These same researchers are working on the latest cancer study involving stem cells. They have been investigating colon cancer and a gene called APC, which when mutated is related to the increased risk of colon cancer. In a computer analysis model designed to show the effects of mutant APC on the crypts or valleys of the colon, it was noted that APC mutations increased the number of stem cells in the bottoms of the crypts of the colon, and this could indeed be an underlying cause of colon cancer. This group plans to release more test results in the latter part of 2005. |
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