Stem Cells

Published on March 2017 | Categories: Documents | Downloads: 43 | Comments: 0 | Views: 383
of 4
Download PDF   Embed   Report

Comments

Content

Stem cells
Stem cells are stirring great excitement in medical research. But, what are stem cells? Why are scientists so intrigued by them? And, what are some of the concerns about stem cell research? When an egg is fertilised by a sperm to make a human embryo, the single fertilised egg cell divides millions of times to form the six billion or more cells that make up our bodies. Most of these cells have undergone a process called differentiation, which leads to them becoming specialised for a certain function. For example, neurons (nerve cells) are specialised to convey electrical messages around the body. Stem cells play a critical role in normal growth and development by providing new cells for growth and for replacing and repairing used and damaged tissues. Stem cells differ from other cells in the body in three main ways. 1. Stem cells are unspecialised. They have not developed into cells that perform a specific function (differentiation). 2. Stem cells are capable of self-renewal. Once a cell has become specialised, it has a very limited capacity to produce new cells, and then only cells of the same type. Thus, if a muscle or blood cell is damaged, it cannot replace itself. Stem cells, however, are able to divide and produce copies of themselves and lead to self-renewal. 3. Stem cells can differentiate. They can divide and produce cells that have the potential to become other more specialised cell types. These new cells and tissues are used to repair or replace damaged or diseased cells in the body. Stem cells from different tissues and from different stages of development can give rise to varying numbers and types of cells.

Types of stem cells
Three main types of stem cells are being investigated for their potential use in research and medicine. The cell types differ in their degree of differentiation and ability to self-renew. In humans: a. Embryonic stem cells come from a five to six-day-old embryo. They have the ability to form virtually any type of cell found in the human body. b. Embryonic germ cells are derived from the part of a human embryo or foetus that will ultimately produce gametes (eggs or sperm). c. Adult stem cells are undifferentiated cells found among specialised (differentiated) cells in a tissue or organ after birth. Based on current research, adult stem cells appear to have a more restricted ability to produce different cell types and to self-renew than embryonic stem cells. d. Umbilical cord blood stem cells are used to treat a range of blood disorders and immune system conditions.

Stem cells growing in culture Stem cells that have the potential to develop into any of the cell types found in an adult organism are called pluripotent. Embryonic stem cells are pluripotent. Stems cells that only have the potential to make a few cell types in the body are called multipotent. Adult stem cells appear to be multipotent. Cells that are capable of forming a completely new embryo that can develop into a new organism are called totipotent. A fertilised egg is totipotent. None of the stem cells used in research appear to have this capacity. More basic research is required to find out how stem cells can be:
   

located and extracted kept alive in the laboratory multiplied for extended periods of time Directed to form specific types of specialized cells.

Potential uses of stem cells
Stem cells have potential uses in many different areas of research and medicine, as described below. However, these applications are all likely to be 10-20 years away.
Replacing damaged tissue

Human stem cells could be used in the generation of cells and tissues for cell-based therapies. This involves treating patients by transplanting specialized cells that have been grown from stem cells in the laboratory. Due to their ability to replace damaged cells in the body, stem cells could be used to treat a range of conditions including heart failure, spinal injuries, diabetes and Parkinson disease. Scientists hope that transplantation and growth of appropriate stem cells in damaged tissue will regenerate the various cell types of that tissue. For example, haematopoietic stem cells (stem cells found in bone marrow) could be transplanted into patients with leukaemia to generate new blood cells. Or, neural stem cells may be able to regenerate nerve tissue damaged by spinal injury.
Studying human development

Stem cells could be used to study early events in human development and find out more about how cells differentiate and function. This may help researchers find out why some cells become cancerous and how some genetic diseases develop. This knowledge may lead to clues about how these diseases may be prevented.

Testing new drugs

Stem cells grown in the laboratory may be useful for testing drugs and chemicals before they are trialled in people. The cells could be directed to differentiate into the cell types that are important for screening that drug. These cells may be more likely to mimic the response of human tissue to the drug being tested than animal models do. This may make drug testing safer, cheaper and more ethically acceptable to those who oppose the use of animals in pharmaceutical testing.
Screening toxins

Stem cells may be useful for screening potential toxins in substances such as pesticides before they are used in the environment.
Testing gene therapy methods

Stem cells may prove useful during the development of new methods for gene therapy that may help people suffering from genetic illnesses.

Ethics of stem cell research
The overwhelming objection to stem cell research is that it involves the destruction of an embryo or foetus. For many, this constitutes destruction of a potential human, and conflicts with religious and moral views held in our society. For others, the potential for this research to provide treatments and possibly cures for debilitating illnesses that have no cure and significantly impact on our way of life overrides this concern. Central to any argument on this is what actually constitutes the beginning of life for a human. Opinions on this vary from the moment of conception to a 14 day embryo and a living baby at birth. This issue is highly emotive, and it will always be necessary to consider all opinions and to balance the harm that might be done against the potential good this research may provide for those suffering from debilitating diseases

Advantages of Stem Cell Research

 

  









It provides medical benefits in the fields of therapeutic cloning and regenerative medicine. It provides great potential for discovering treatments and cures to a plethora of diseases including Parkinson’s disease, schizophrenia, Alzheimer’s disease, Cancer, spinal cord injuries, diabetes and many more. Limbs and organs could be grown in a lab from stem cells and then used in transplants or to help treat illnesses. It will help scientists to learn about human growth and cell development. Scientists and doctors will be able to test millions of potential drugs and medicine, without the use of animals or human testers. This necessitates a process of simulating the effect the drug has on a specific population of cells. This would tell if the drug is useful or has any problems. Stem cell research also benefits the study of development stages that cannot be studied directly in a human embryo, which sometimes are linked with major clinical consequences such as birth defects, pregnancy loss and infertility. A more comprehensive understanding of normal development will ultimately allow the prevention or treatment of abnormal human development. Another advantage of stem cell research is that it holds the key to reversing the effects of aging and prolonging our lives. Stem cell research has already found many treatments that help slow the aging process, and a bonus of further stem cell research is a possible ‘cure’ for aging altogether. An advantage of the usage of adult stem cells to treat disease is that a patient’s own cells could be used to treat a patient. Risks would be quite reduced because patients’ bodies would not reject their own cells. An advantage of using embryonic stem cells is that they can develop into any cell types of the body, and may then be more versatile than adult stem cells.

Disadvantages of Stem Cell Research


    

The use of embryonic stem cells for research involves the destruction of blastocysts formed from laboratory-fertilized human eggs. For those people who believe that life begins at conception, the blastocyst is a human life and to destroy it is immoral and unacceptable. Like any other new technology, it is also completely unknown what the long term effects of such an interference with nature could materialize. Embryonic stem cells amy not be the solution for all ailments. According to a new research stem cell therapy was used on heart disease patients. It was found that it can make their coronary arteries become narrower. A disadvantage of most adult stem cells is that they are pre-specialized, for instance, blood stem cells make only blood, and brain stem cells make only brain cells. A disadvantage of embryonic stem cells is that they are derived from embryos that are not a patient’s own and the patient’s body may reject them.

Sponsor Documents

Or use your account on DocShare.tips

Hide

Forgot your password?

Or register your new account on DocShare.tips

Hide

Lost your password? Please enter your email address. You will receive a link to create a new password.

Back to log-in

Close