Issue 61 / January - February 2008
The Cell Bank of Our Body: Stem Cells
Injuries, illnesses and aging are inevitable parts of our lives. The human body can deal with basic injuries and illnesses in daily life by cell regeneration. However, aging and certain injuries have no cure since the tissues cannot be fully restored. This is related to the function of stem cells, the unique cells that are responsible for refreshing tissues and compensating for cellular losses.
Because stem cells are rare in the tissues (one out of ten thousand) and we are constantly losing them, our body cannot grow, maintain, and repair itself continuously. This is the main reason for the wear and tear on our bodies as we get older. Nevertheless, assuming that there should be a cure for any illness except death, the clinical research on stem cells is quite promising with respect to many diseases. The One Who has placed stem cells in our body as a source of auto-regeneration, has also given us the idea that we can possibly discover the laws of stem cell production for use in medical treatment. Stem cells are the cells that all cells stem from. What makes them different from other cell types is their capacity to divide infinitely, their ability to differentiate when they are subjected to biochemical and environmental signals. Stem cells can form other cell types with specific biological functions. They can give rise to all the mature cells for the heart, the skin, the nerves, the cornea, and so on.
The potential of stem cells for new therapeutic approaches is highly encouraging and stem cell studies have become one of the most active areas of research in biomedical sciences. Researchers are attempting to identify the unique features of stem cells which can be used in medical applications. It is believed that the correct use of stem cells will enable doctors to heal and regenerate damaged tissues and organs, and cure many genetic disorders. In the near future, stem cell studies are expected to provide direct solutions for conditions caused by other cells‚Äô lacking the ability to divide and self-renew. These conditions include Parkinson‚Äôs, Alzheimer‚Äôs, spinal cord injuries, heart attacks and heart disease as well as blood cancer, diabetes, and bone loss.
Moreover, the potential of stem cells to reduce the effects of aging make it seem likely that in future there may be seventy-five-year-olds with the healthy bodies of teenagers. Stem cells as an alternative to organ transplants The most straightforward application of stem cell research has been as a new source for tissue and organ transplants. This is a great alternative for patients who are waiting for a donor organ. It is known that in the case of organ transplant from a donor, even from the closest of relatives, the body rejects any foreign tissue and special drugs are needed to suppress attack by the immune system and to lower the rate of rejection. Since stem cells are genetically the patient‚Äôs own cell, rejection is not an issue in stem cell transplants. One of the best studied areas of stem cell research is the treatment of heart failure. Cardiac muscle cells are complex and unable to generate new cells. Cell death in cardiac muscle causes serious heart failure due to ineffective muscle contraction in the heart. In addition, when a patient has successive heart attacks and myocardial infarctions (death of cardiac muscle resulting from interruption of the blood supply), the number of dead cells increases because of the decreased level of oxygen reaching the heart tissue. This usually leads to the death of the patient after the third heart attack. The conventional therapy uses the insertion of a small tube, a stent, to fix the artery and to increase the level of oxygen reaching the muscle cells.
However, this method cannot effectively compensate for the dead cells. To recover cellular losses, potential stem cells from bone marrow were collected and then processed to prepare cardiac muscle stem cells. They were then injected into the damaged area which led to the production of new healthy muscle tissue. The size of the dead area decreased notably and the performance of the heart improved. In one study performed at the University of Wisconsin, initial trials resulted in patients feeling better with less chest pain and improved exercise capacity. Skin production for severe burns Severe burns to the skin require long and painful treatments and usually result in scarring and disability. Although current treatments, such as skin grafting and the use of artificial skin technologies, suffice to re-cover the injured area, they are not adequate for the regeneration of functional skin following burns. Scientists aim to produce skin cells in the laboratory by using the patient‚Äôs own stem cells. This would lead to replacing the damaged area of skin with fully functional tissue readily, without pain or long-lasting treatment procedures. Type I diabetes and stem cell therapy In type I diabetes, cells that produce the insulin hormone are destroyed by white blood cells. So, the body can no longer produce insulin to balance the sugar level in the blood.
People with type I diabetes need to take insulin injections daily. However, in one recent study, a team of American and Brazilian scientists used stem cells obtained from patients‚Äô own blood to regenerate insulin-producing cells in their bodies. According to the study leader, Dr. Julio Voltarelli of the University of Sao Paolo, results are very encouraging. For example, one patient has been free from insulin injections for 35 months. Fourteen out of fifteen patients were cured. Although some still have different level of insulin dependence, they no longer need a daily insulin intake.Ethical concerns about stem cells Stem cells can be produced from various sources. The human embryo is probably the best source to obtain stem cells, since embryonic stem cells (ESC) have a higher ability to divide and readily undergo cell differentiation during early development. The embryos that are used for research are generally obtained from the remnants of in vitro fertilizations or from abortions (premature termination of a pregnancy). However, the use of human embryos for stem cell research is very controversial. Objections to embryonic studies arise because the studies involve interference with human life at the early stages and uncertainties about when life begins. Ethical and legal disputes have resulted in the prohibition of ESC research in several countries. Embryos are not the sole source of stem cells. They can also be obtained from many adult tissues, especially bone marrow, the placenta, and umbilical cord. These sources are not considered ethically problematic, but stem cells obtained from adult tissues have less ability to differentiate into various cell types. In addition, adult stem cells cannot be isolated easily from tissues, and the growth of these cells in culture takes more time than that of embryonic stem cells. The challenge is to find the balance between hope for cure and respect for life. The question when life starts or a fetus has been given a soul is a subject for religion and philosophy. According to Catholics, for instance, the human embryo is valuable and one must consider the zygote (a single cell that is the result of fertilization) a human being. Thus, embryos or zygotes cannot be killed, stored, or used for any purpose. However, the Catholic Church allows that research on adult stem cells can be carried out for medical research. In contrast, Jewish religious leaders do not consider the zygote or blastocyst a complete human being. They hold that embryonic stem cell research can be done if it is beneficial for humans and if it does not cause any problem for human life. Islam favors all studies beneficial for humanity and society if they do not raise ethical or spiritual issues. Islam especially supports the use of adult stem cells for stem cell studies. It also allows studies on blastocysts remaining after in vitro fertilization if there is no cure available by other means and there is no economic gain from the donation of blastocysts for research and stem cell therapies. Consequently, ethical issues related to ESCs have resulted in a search for alternative sources for stem cells that has the utmost importance for the scientific, religious and social sphere.
Placental and umbilical cord blood stem cells
Even though intensive care units for new born babies are developed with the most recent technology, they are yet way too primitive and insufficient, compared to a several-kilogram organ in mother‚Äôs womb. This organ, which is also featured as the real hero of birth by scientists, is called placenta. The placenta is an organ whose main role in pregnancy is the exchange of any material required for embryonic growth such as gases, nutrients and hormones from the mother‚Äôs blood and the removal of toxins and biological waste from the fetus. It also functions as a barrier against any immunologic attack on the embryo by the mother‚Äôs immune system so that a foreign body (a baby) can survive in the mother‚Äôs womb. In addition, it has important metabolic and hormonal functions. Fifteen years ago, researchers discovered that the placenta has a large number of high quality stem cells. These cells could be extremely important for the baby in the case of any genetic or metabolic problem causing tissue loss or damage later in life. The placenta can be stored just after birth. In addition, it is very probable that these stem cells will be a good source for cell therapies for relatives. Who could have thought that the remnants of birth would have such importance in medicine fifty years ago? The One Who, with the highest wisdom, creates every single thing with many purposes has made placenta and cord blood a useful source of stem cells.
The advantages of stem cells from cord blood
Stem cells isolated from cord blood are the youngest after ESCs. They have a higher ability to divide than commonly used adult stem cells from bone marrow. In contrast to bone marrow, stem cells isolated from cord blood can be used for family members because they do not interact with the immune system and they do not cause any negative response. Moreover, they are more durable than adult stem cells and can be stored for a long time by freezing the placenta and umbilical cord. They also do not contain tumors or viruses. These juvenile stem cells can easily transform into many cell types and tissues if they are sent the correct biological and genetic signals in the culture environment. Nowadays, stem cells isolated from cord blood are most commonly used to support the blood and immune systems in patients with cancer who are being treated with chemotherapy and/or radiotherapy. Recently, some clinical studies have shown that they can also be useful for treating blood cancer. The flexibility of stem cells obtained from cord blood offers hope that stem cell studies will increase the prospects of treatment of these diseases.
Restoring vital body functions: What does the future promise?
Discoveries are emerging every day about stem cells. As we have shown, stem cells might be the key to the replacement of lost cells in many devastating diseases. Some day, diseases like Parkinson‚Äôs, diabetes, chronic heart failure, and liver failure may be history because of stem cell technologies. The aging process might be slowed by compensating for the effect of tissue loss with stem cells. There is also great hope of finding an alternative to organ transplantation, for which currently there is a lack of sufficient and suitable donor organs. For instance, in the case of liver failure, healthy cells produced from stem cells can be injected into the patient. Moreover, by using a liver-like environment, it may be possible to produce a complete or partial liver for transplant. Another fascinating potential benefit of stem cells lies in the possibility of regenerating nerve cells in the spinal cord after injury. There is always hope of a cure. The scriptures contain many examples of miraculous treatments of disease at the hands of the Prophets.
These miracles are not only proof of their prophethood, but also indicate the upper limits that humans can reach by means of knowledge. For instance, recently a scientist in London was able to cure some patients of blindness using their own cells. In this case, age-related degeneration of retinal cells was causing the blindness. Professor Peter Coffee, from the Institute of Ophthalmology, reported that they reversed the condition by transplanting cells taken from the side of the patient‚Äôs eye and embryonic stem cells into retina to replace the dead cells. This kind of study reminds us of the miracle of Prophet Muhammad peace be upon him who healed the eyesight of a blind person simply by his touch.
Thanks to the Human Genome Project, we now have tools to manipulate the deciphered sequence of our DNA. The combination of our knowledge about the genome with stem cell technology may allow us to approach the limits defined by the miracles of these perfect examples of humanity. In the meantime, future research should be carried out with due regard for its effects on society, humanity and environment and keeping in mind all the possible ethical issues and consequences of our actions.
Fatih Kocabas is a PhD candidate at Southwestern Medical Center, Texas University.
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