Alzheimer's, Parkinson's, multiple sclerosis. These and other diseases will be cured in the future by transplanting embryonic stem cells, which are capable of developing into all types of cells in the body. But the USA and some European countries are not ready to fund research that requires the use of embryos
In the cardiology department, a patient with heart failure is waiting for treatment that will save his life. In the nearby laboratory, a scientist collects embryonic cells that he has grown in a test tube and by means of chemical substances directed their development into heart muscle cells. These cells are intended for transplantation into the patient's heart, where they will function in place of the damaged heart muscle. In another laboratory, they direct the development of embryonic cells into nerve cells that will be implanted in the brain of a Parkinson's patient, in an area whose functional capacity has been lost.
These two scenarios are not taken from science fiction. They are very close to reality and reflect only a hint of the possibilities inherent in the embryonic stem cells - cells that store within them the potential to produce almost every cell of the cell types found in the body. Stem cells are one of the current research areas in biology. The journal "Science" called them "the cells that preserve their youth" and crowned them as the breakthrough of 1999.
The ability to direct the development of embryonic stem cells to all types of cells in the body will open almost unlimited possibilities of use, such as the creation of new tissues in the laboratory as a replacement for tissues damaged with age due to disease or trauma, the restoration of tissues destroyed by chemotherapy treatments and even the use of cells instead of organ transplants. Scientists predict that the embryonic stem cells will be used to cure diseases such as diabetes, Alzheimer's, Parkinson's and multiple sclerosis, to restore a damaged spine and more.
However, despite the enormous potential inherent in them, the research of embryonic stem cells encounters political and ethical barriers. The cells are produced from an embryo a few days old, usually from fertilized eggs that have not been used, or from young embryos after an abortion. This is not compatible with the anti-abortion movement in the US, nor with the American law prohibiting federal funding for research in which human fetuses are used. That is why the research is funded by biotechnology companies, and most of the field is in commercial hands.
Scientists have been studying mouse embryonic stem cells for two decades. But the turning point happened at the end of 1998, when two independent research groups - one led by James Thomson from the University of Wisconsin in Madison, and the other led by John Gerhart from Johns Hopkins University in Baltimore - announced that they had succeeded in growing human embryonic stem cells in the laboratory and preserving their potential The rare - the possibility to develop into all types of cells found in the body. The researchers used embryonic cells less than a week old, which are still in their initial state, before they began to differentiate into tissues and organs. After growing them in tissue cultures, they found that the cells are able to divide endlessly and stay alive for many years. This opens up a new and promising field of research, centered on the aspiration to direct the stem cells to the various tissues in the body.
Since the discovery, research has accelerated. In '99, researchers managed to direct embryonic stem cells in mice and rats to develop in tissue cultures into several tissue types. Research teams from the USA and Germany have succeeded in directing mouse embryonic stem cells to develop into cells that produce the sheath of nerve fibers called myelin. The myelin sheath is damaged in multiple sclerosis, and the consequences are clear. When these cells were injected into the brains of mice lacking myelin, the cells began to produce normal myelin tissue in the mice's brains. Another group from St. Louis University, Missouri, directed the developmental pathway of mouse embryonic stem cells into neurons. When they implanted these nerve cells in rats with spinal cord injuries, they were able to partially restore their mobility. Although no one has shown that embryonic stem cells of human origin also behave this way, Gerhart is already examining the ability of the human cells he developed to restore a damaged spine and fight degenerative diseases of the nervous system.
At the same time, researchers are trying to examine what can be done with stem cells derived from adults. In our body, various tissues contain stem cells that serve as a source for the various types of cells found in the tissue. In the bone marrow, for example, blood cells and immune system cells develop. In the nervous system, the different types of nerve cells develop from stem cells, and so in the other tissues. Until recently, it was believed that once a cell was programmed to be part of a certain tissue, its destiny was determined forever and there was no way to change it. But in the last year, scientists were surprised to find out that this statement is not accurate. Researchers took stem cells from the brains of rats, and when they transferred them to the bone marrow, the cells changed their purpose and started producing blood cells. Stem cells from a mouse's muscle, transferred to the bone marrow, turned into blood cells and managed to save mice whose bone marrow was destroyed following chemotherapy treatment. Bone marrow cells show even greater flexibility - they can be turned into brain cells, liver cells and muscle cells, including heart muscle.
The results of the studies amazed the biologists. They found that the role a certain cell received during embryonic development is not final - stem cells belonging to a certain tissue can change their purpose. The tissue cells that absorbed the stem cells guide them in the direction of their development through biological signals that they transmit. These signals, the biologists assume, are growth factors (proteins that stimulate growth and differentiation) and proteins located on the surface of the cells, which transmit the signals through contact.
The treatment of Parkinson's disease will most likely be the first use of embryonic stem cells. For more than ten years, Anders Bjorkland and his team from Land University in Sweden have been implanting nerve cells taken from embryos into the brains of Parkinson's patients to restore the damaged area of the brain. In many cases the transplanted cells reduce the symptoms of the disease. But the treatment does not solve the problem, since there is no way to obtain cells for all those who need them (one million people suffer from Parkinson's in the US alone), what is more, only 5% of them are absorbed by the brain. The solution is the use of embryonic stem cells that have been allowed to develop into nerve cells in the brain. Researchers believe that transplanting the cells in the appropriate area of the brain will guide the cells to develop in the desired direction and the cells will function instead of those affected by the disease. Preliminary animal experiments confirm this.
Although the transplantation of embryonic stem cells could help millions of patients, there is still no agreement on the public funding of the research. The US government, and some European countries, are not prepared to allocate public funds for research that requires the use of human embryos. The biotechnology companies are jumping on the bandwagon and conducting intensive research to develop medical products from the new technologies. "When the funding is in private hands, all research results, patents and intellectual property belong to the funders. The commercial companies are the ones who will dictate the schedule for the implementation of the technology, and the considerations will not necessarily be in the best interest of the public and the patients," says Prof. Yosef Itzkovich, director of the Women's and Maternity Department at Rambam Hospital, who was a partner in the discovery of human stem cells in Thomson's group. In his opinion, if the knowledge and technology are available to everyone, more forces will join the race and the results will be better.
"We invested huge sums in the field expecting to receive sophisticated and exclusive products," says Thomas Okrama, president of the "Giron" company that researches embryonic stem cells. In 99, her scientists succeeded in producing different types of heart muscle cells and nerve cells from the embryonic stem cells, and now they are trying to inject the stem cells with different genes that will allow them to direct their differentiation.
More than a dozen other companies are developing products from human stem cells extracted from adult tissue on the assumption that they will be easier to use because they are not taken from embryos. Biotechnology companies bet on the technologies they develop and their stock indices on the stock exchange. The tough competition quickly pushes the research from the laboratory to the application stages. Several companies have already begun clinical trials to test products they have developed to treat Parkinson's disease and osteoarthritis (degenerative joint disease). Other companies focus on growing and multiplying the stem cells of the bone marrow responsible for creating blood cells and immune system cells. The company's scientists are developing systems that make it possible to grow these cells in large quantities and use them to restore the immune system of cancer patients, which was damaged by the chemotherapy treatments.
The Osiris company from Baltimore isolated stem cells from the tissue surrounding the bone marrow. Her scientists noticed that these cells differentiate into cartilage and muscle cells, and now they are exploring the possibility of using them to restore cartilage and repair damaged tendons. Stem cells originating from the nervous system were a "hot product" already last year, after the potential inherent in them for the treatment of head injuries became clear.
Hundreds of millions of people in the world suffer from diseases that can be treated with stem cell transplantation. Many more millions will be able to enjoy healthy aging made possible by stem cells. "We are still far from routine use of stem cells," says Prof. Itzkovich. "There is still a need to develop technologies that will provide mature stem cells that have undergone normal differentiation, so that we know with confidence that they will develop in the desired directions and not into malignant tumors, but there is no doubt that we have come a long way."
