What are adult stem cells?

What are adult stem cells?
An adult stem cell is thought to be an undifferentiated cell, found among differentiated cells in a tissue or organ that can renew itself and can differentiate to yield some or all of the major specialized cell types of the tissue or organ. The primary roles of adult stem cells in a living organism are to maintain and repair the tissue in which they are found. Scientists also use the term somatic stem cell instead of adult stem cell, where somatic refers to cells of the body (not the germ cells, sperm or eggs). Unlike embryonic stem cells, which are defined by their origin (the inner cell mass of the blastocyst), the origin of adult stem cells in some mature tissues is still under investigation.Research on adult stem cells has generated a great deal of excitement. Scientists have found adult stem cells in many more tissues than they once thought possible. This finding has led researchers and clinicians to ask whether adult stem cells could be used for transplants. In fact, adult hematopoietic, or blood-forming, stem cells from bone marrow have been used in transplants for 40 years. Scientists now have evidence that stem cells exist in the brain and the heart. If the differentiation of adult stem cells can be controlled in the laboratory, these cells may become the basis of transplantation-based therapies.The history of research on adult stem cells began about 50 years ago. In the 1950s, researchers discovered that the bone marrow contains at least two kinds of stem cells. One population, called hematopoietic stem cells, forms all the types of blood cells in the body. A second population, called bone marrow stromal stem cells (also called mesenchymal stem cells, or skeletal stem cells by some), were discovered a few years later. These non-hematopoietic stem cells make up a small proportion of the stromal cell population in the bone marrow, and can generate bone, cartilage, fat, cells that support the formation of blood, and fibrous connective tissue.In the 1960s, scientists who were studying rats discovered two regions of the brain that contained dividing cells that ultimately become nerve cells. Despite these reports, most scientists believed that the adult brain could not generate new nerve cells. It was not until the 1990s that scientists agreed that the adult brain does contain stem cells that are able to generate the brain's three major cell types—astrocytes and oligodendrocytes, which are non-neuronal cells, and neurons, or nerve cells.A. Where are adult stem cells found, and what do they normally do?Adult stem cells have been identified in many organs and tissues, including brain, bone marrow, peripheral blood, blood vessels, skeletal muscle, skin, teeth, heart, gut, liver, ovarian epithelium, and testis. They are thought to reside in a specific area of each tissue (called a "stem cell niche"). In many tissues, current evidence suggests that some types of stem cells are pericytes, cells that compose the outermost layer of small blood vessels. Stem cells may remain quiescent (non-dividing) for long periods of time until they are activated by a normal need for more cells to maintain tissues, or by disease or tissue injury.Typically, there is a very small number of stem cells in each tissue, and once removed from the body, their capacity to divide is limited, making generation of large quantities of stem cells difficult. Scientists in many laboratories are trying to find better ways to grow large quantities of adult stem cells in cell culture and to manipulate them to generate specific cell types so they can be used to treat injury or disease. Some examples of potential treatments include regenerating bone using cells derived from bone marrow stroma, developing insulin-producing cells for type 1 diabetes, and repairing damaged heart muscle following a heart attack with cardiac muscle cells.B. What tests are used for identifying adult stem cells?Scientists often use one or more of the following methods to identify adult stem cells: (1) label the cells in a living tissue with molecular markers and then determine the specialized cell types they generate; (2) remove the cells from a living animal, label them in cell culture, and transplant them back into another animal to determine whether the cells replace (or "repopulate") their tissue of origin.Importantly, it must be demonstrated that a single adult stem cell can generate a line of genetically identical cells that then gives rise to all the appropriate differentiated cell types of the tissue. To confirm experimentally that a putative adult stem cell is indeed a stem cell, scientists tend to show either that the cell can give rise to these genetically identical cells in culture, and/or that a purified population of these candidate stem cells can repopulate or reform the tissue after transplant into an animal.

Can Stem Cells Mend a Broken Heart?: Stem Cells for the Future Treatment of Heart Disease ?

Can Stem Cells Mend a Broken Heart?: Stem Cells for the Future Treatment of Heart Disease
Cardiovascular disease (CVD), which includes hypertension, coronary heart disease, stroke, and congestive heart failure, has ranked as the number one cause of death in the United States every year since 1900 except 1918, when the nation struggled with an influenza epidemic. Nearly 2600 Americans die of CVD each day, roughly one person every 34 seconds. Given the aging of the population and the relatively dramatic recent increases in the prevalence of cardiovascular risk factors such as obesity and type 2 diabetes, CVD will be a significant health concern well into the 21st century.Cardiovascular disease can deprive heart tissue of oxygen, thereby killing cardiac muscle cells (cardiomyocytes). This loss triggers a cascade of detrimental events, including formation of scar tissue, an overload of blood flow and pressure capacity, the overstretching of viable cardiac cells attempting to sustain cardiac output, leading to heart failure, and eventual death. Restoring damaged heart muscle tissue, through repair or regeneration, is therefore a potentially new strategy to treat heart failure.The use of embryonic and adult-derived stem cells for cardiac repair is an active area of research. A number of stem cell types, including embryonic stem (ES) cells, cardiac stem cells that naturally reside within the heart, myoblasts (muscle stem cells), adult bone marrow-derived cells including mesenchymal cells (bone marrow-derived cells that give rise to tissues such as muscle, bone, tendons, ligaments, and adipose tissue), endothelial progenitor cells (cells that give rise to the endothelium, the interior lining of blood vessels), and umbilical cord blood cells, have been investigated as possible sources for regenerating damaged heart tissue. All have been explored in mouse or rat models, and some have been tested in larger animal models, such as pigs.
A few small studies have also been carried out in humans, usually in patients who are undergoing open-heart surgery. Several of these have demonstrated that stem cells that are injected into the circulation or directly into the injured heart tissue appear to improve cardiac function and/or induce the formation of new capillaries. The mechanism for this repair remains controversial, and the stem cells likely regenerate heart tissue through several pathways. However, the stem cell populations that have been tested in these experiments vary widely, as do the conditions of their purification and application. Although much more research is needed to assess the safety and improve the efficacy of this approach, these preliminary clinical experiments show how stem cells may one day be used to repair damaged heart tissue, thereby reducing the burden of cardiovascular disease.

What are the potential uses of human stem cells and the obstacles that must be overcome before these potential uses will be realized?

What are the potential uses of human stem cells and the obstacles that must be overcome before these potential uses will be realized?
There are many ways in which human stem cells can be used in research and the clinic. Studies of human embryonic stem cells will yield information about the complex events that occur during human development. A primary goal of this work is to identify how undifferentiated stem cells become the differentiated cells that form the tissues and organs. Scientists know that turning genes on and off is central to this process. Some of the most serious medical conditions, such as cancer and birth defects, are due to abnormal cell division and differentiation. A more complete understanding of the genetic and molecular controls of these processes may yield information about how such diseases arise and suggest new strategies for therapy. Predictably controlling cell proliferation and differentiation requires additional basic research on the molecular and genetic signals that regulate cell division and specialization. While recent developments with iPS cells suggest some of the specific factors that may be involved, techniques must be devised to introduce these factors safely into the cells and control the processes that are induced by these factors.Human stem cells could also be used to test new drugs. For example, new medications could be tested for safety on differentiated cells generated from human pluripotent cell lines. Other kinds of cell lines are already used in this way. Cancer cell lines, for example, are used to screen potential anti-tumor drugs. The availability of pluripotent stem cells would allow drug testing in a wider range of cell types. However, to screen drugs effectively, the conditions must be identical when comparing different drugs. Therefore, scientists will have to be able to precisely control the differentiation of stem cells into the specific cell type on which drugs will be tested. Current knowledge of the signals controlling differentiation falls short of being able to mimic these conditions precisely to generate pure populations of differentiated cells for each drug being tested.Perhaps the most important potential application of human stem cells is the generation of cells and tissues that could be used for cell-based therapies. Today, donated organs and tissues are often used to replace ailing or destroyed tissue, but the need for transplantable tissues and organs far outweighs the available supply. Stem cells, directed to differentiate into specific cell types, offer the possibility of a renewable source of replacement cells and tissues to treat diseases including Alzheimer's diseases, spinal cord injury, stroke, burns, heart disease, diabetes, osteoarthritis, and rheumatoid arthritis.

What are induced pluripotent stem cells?

What are induced pluripotent stem cells?
Induced pluripotent stem cells (iPSCs) are adult cells that have been genetically reprogrammed to an embryonic stem cell–like state by being forced to express genes and factors important for maintaining the defining properties of embryonic stem cells. Although these cells meet the defining criteria for pluripotent stem cells, it is not known if iPSCs and embryonic stem cells differ in clinically significant ways. Mouse iPSCs were first reported in 2006, and human iPSCs were first reported in late 2007. Mouse iPSCs demonstrate important characteristics of pluripotent stem cells, including expressing stem cell markers, forming tumors containing cells from all three germ layers, and being able to contribute to many different tissues when injected into mouse embryos at a very early stage in development. Human iPSCs also express stem cell markers and are capable of generating cells characteristic of all three germ layers.Although additional research is needed, iPSCs are already useful tools for drug development and modeling of diseases, and scientists hope to use them in transplantation medicine. Viruses are currently used to introduce the reprogramming factors into adult cells, and this process must be carefully controlled and tested before the technique can lead to useful treatments for humans. In animal studies, the virus used to introduce the stem cell factors sometimes causes cancers. Researchers are currently investigating non-viral delivery strategies. In any case, this breakthrough discovery has created a powerful new way to "de-differentiate" cells whose developmental fates had been previously assumed to be determined. In addition, tissues derived from iPSCs will be a nearly identical match to the cell donor and thus probably avoid rejection by the immune system. The iPSC strategy creates pluripotent stem cells that, together with studies of other types of pluripotent stem cells, will help researchers learn how to reprogram cells to repair damaged tissues in the human body.

What are the similarities and differences between embryonic and adult stem cells?

What are the similarities and differences between embryonic and adult stem cells?

Human embryonic and adult stem cells each have advantages and disadvantages regarding potential use for cell-based regenerative therapies. One major difference between adult and embryonic stem cells is their different abilities in the number and type of differentiated cell types they can become. Embryonic stem cells can become all cell types of the body because they are pluripotent. Adult stem cells are thought to be limited to differentiating into different cell types of their tissue of origin.

Embryonic stem cells can be grown relatively easily in culture. Adult stem cells are rare in mature tissues, so isolating these cells from an adult tissue is challenging, and methods to expand their numbers in cell culture have not yet been worked out. This is an important distinction, as large numbers of cells are needed for stem cell replacement therapies.
Scientists believe that tissues derived from embryonic and adult stem cells may differ in the likelihood of being rejected after transplantation. We don't yet know whether tissues derived from embryonic stem cells would cause transplant rejection, since the first phase 1 clinical trial testing the safety of cells derived from hESCS has only recently been approved by the United States Food and Drug Administration (FDA).
Adult stem cells, and tissues derived from them, are currently believed less likely to initiate rejection after transplantation. This is because a patient's own cells could be expanded in culture, coaxed into assuming a specific cell type (differentiation), and then reintroduced into the patient. The use of adult stem cells and tissues derived from the patient's own adult stem cells would mean that the cells are less likely to be rejected by the immune system. This represents a significant advantage, as immune rejection can be circumvented only by continuous administration of immunosuppressive drugs, and the drugs themselves may cause deleterious side effects

What are induced pluripotent stem cells?

What are induced pluripotent stem cells?

Induced pluripotent stem cells (iPSCs) are adult cells that have been genetically reprogrammed to an embryonic stem cell–like state by being forced to express genes and factors important for maintaining the defining properties of embryonic stem cells. Although these cells meet the defining criteria for pluripotent stem cells, it is not known if iPSCs and embryonic stem cells differ in clinically significant ways. Mouse iPSCs were first reported in 2006, and human iPSCs were first reported in late 2007. Mouse iPSCs demonstrate important characteristics of pluripotent stem cells, including expressing stem cell markers, forming tumors containing cells from all three germ layers, and being able to contribute to many different tissues when injected into mouse embryos at a very early stage in development. Human iPSCs also express stem cell markers and are capable of generating cells characteristic of all three germ layers.
Although additional research is needed, iPSCs are already useful tools for drug development and modeling of diseases, and scientists hope to use them in transplantation medicine. Viruses are currently used to introduce the reprogramming factors into adult cells, and this process must be carefully controlled and tested before the technique can lead to useful treatments for humans. In animal studies, the virus used to introduce the stem cell factors sometimes causes cancers. Researchers are currently investigating non-viral delivery strategies. In any case, this breakthrough discovery has created a powerful new way to "de-differentiate" cells whose developmental fates had been previously assumed to be determined. In addition, tissues derived from iPSCs will be a nearly identical match to the cell donor and thus probably avoid rejection by the immune system. The iPSC strategy creates pluripotent stem cells that, together with studies of other types of pluripotent stem cells, will help researchers learn how to reprogram cells to repair damaged tissues in the human body.

What are the potential uses of human stem cells and the obstacles that must be overcome before these potential uses will be realized?

What are the potential uses of human stem cells and the obstacles that must be overcome before these potential uses will be realized?

There are many ways in which human stem cells can be used in research and the clinic. Studies of human embryonic stem cells will yield information about the complex events that occur during human development. A primary goal of this work is to identify how undifferentiated stem cells become the differentiated cells that form the tissues and organs. Scientists know that turning genes on and off is central to this process. Some of the most serious medical conditions, such as cancer and birth defects, are due to abnormal cell division and differentiation. A more complete understanding of the genetic and molecular controls of these processes may yield information about how such diseases arise and suggest new strategies for therapy. Predictably controlling cell proliferation and differentiation requires additional basic research on the molecular and genetic signals that regulate cell division and specialization. While recent developments with iPS cells suggest some of the specific factors that may be involved, techniques must be devised to introduce these factors safely into the cells and control the processes that are induced by these factors.
Human stem cells could also be used to test new drugs. For example, new medications could be tested for safety on differentiated cells generated from human pluripotent cell lines. Other kinds of cell lines are already used in this way. Cancer cell lines, for example, are used to screen potential anti-tumor drugs. The availability of pluripotent stem cells would allow drug testing in a wider range of cell types. However, to screen drugs effectively, the conditions must be identical when comparing different drugs. Therefore, scientists will have to be able to precisely control the differentiation of stem cells into the specific cell type on which drugs will be tested. Current knowledge of the signals controlling differentiation falls short of being able to mimic these conditions precisely to generate pure populations of differentiated cells for each drug being tested.
Perhaps the most important potential application of human stem cells is the generation of cells and tissues that could be used for cell-based therapies. Today, donated organs and tissues are often used to replace ailing or destroyed tissue, but the need for transplantable tissues and organs far outweighs the available supply. Stem cells, directed to differentiate into specific cell types, offer the possibility of a renewable source of replacement cells and tissues to treat diseases including Alzheimer's diseases, spinal cord injury, stroke, burns, heart disease, diabetes, osteoarthritis, and rheumatoid arthritis.

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Can Stem Cells Mend a Broken Heart?: Stem Cells for the Future Treatment of Heart Disease

Can Stem Cells Mend a Broken Heart?: Stem Cells for the Future Treatment of Heart Disease

Cardiovascular disease (CVD), which includes hypertension, coronary heart disease, stroke, and congestive heart failure, has ranked as the number one cause of death in the United States every year since 1900 except 1918, when the nation struggled with an influenza epidemic. Nearly 2600 Americans die of CVD each day, roughly one person every 34 seconds. Given the aging of the population and the relatively dramatic recent increases in the prevalence of cardiovascular risk factors such as obesity and type 2 diabetes, CVD will be a significant health concern well into the 21st century.
Cardiovascular disease can deprive heart tissue of oxygen, thereby killing cardiac muscle cells (cardiomyocytes). This loss triggers a cascade of detrimental events, including formation of scar tissue, an overload of blood flow and pressure capacity, the overstretching of viable cardiac cells attempting to sustain cardiac output, leading to heart failure, and eventual death. Restoring damaged heart muscle tissue, through repair or regeneration, is therefore a potentially new strategy to treat heart failure.
The use of embryonic and adult-derived stem cells for cardiac repair is an active area of research. A number of stem cell types, including embryonic stem (ES) cells, cardiac stem cells that naturally reside within the heart, myoblasts (muscle stem cells), adult bone marrow-derived cells including mesenchymal cells (bone marrow-derived cells that give rise to tissues such as muscle, bone, tendons, ligaments, and adipose tissue), endothelial progenitor cells (cells that give rise to the endothelium, the interior lining of blood vessels), and umbilical cord blood cells, have been investigated as possible sources for regenerating damaged heart tissue. All have been explored in mouse or rat models, and some have been tested in larger animal models, such as pigs.

A few small studies have also been carried out in humans, usually in patients who are undergoing open-heart surgery. Several of these have demonstrated that stem cells that are injected into the circulation or directly into the injured heart tissue appear to improve cardiac function and/or induce the formation of new capillaries. The mechanism for this repair remains controversial, and the stem cells likely regenerate heart tissue through several pathways. However, the stem cell populations that have been tested in these experiments vary widely, as do the conditions of their purification and application. Although much more research is needed to assess the safety and improve the efficacy of this approach, these preliminary clinical experiments show how stem cells may one day be used to repair damaged heart tissue, thereby reducing the burden of cardiovascular disease.

DNA Footprinting

DNA Footprinting

DNA Footprinting was developed in 1977 and is an analytical procedure in molecular biology for identifying the specific sequence of DNA (the binding site) that binds to a particular protein. DNA Footprinting is most commonly performed on proteins that are thought to play some significant functional role such as gene regulation. This method can be performed on proteins which bind both double and single-stranded DNA. Additionally, DNA-binding proteins can be split into two groups, namely site-specific DNA-binding proteins and non-specific DNA–binding proteins.

DNA Footprinting uses a damaging agent such as a chemical reagent, radical or a nuclease that can cut or modify DNA at every base pair. However, where the ligand binds to DNA, the cleavage is restrained. DNA Footprinting discovers which specific parts of a DNA molecule have sites for specific proteins to attach to them. Using this technique, DNA that has first been in the presence of DNA-binding proteins and then exposed to a damaging agent, can be compared to DNA that was never exposed to the binding protein (and thus not protected against the damaging agent). The DNA sequence that is protected from cleaving can then be identified as the binding site.

DNA Footprinting can provide information that is, conceptually, much like fingerprinting in the sense that it can be used to identify a unique individual. DNA Footprinting can extract a banding pattern, or electropherogram, much like a bar code, that can identify a species or individual (some genes will be vary at the species level and others at the individual level)

Altered Genes

Altered Genes
Each of us carries about half a dozen defective genes. We remain blissfully unaware of this fact unless we, or one of our close relatives, are amongst the many millions who suffer from a genetic disease. About one in ten people has, or will develop at some later stage, an inherited genetic disorder, and approximately 2,800 specific conditions are known to be caused by defects (mutations) in just one of the patient's genes. Some single gene disorders are quite common - cystic fibrosis is found in one out of every 2,500 babies born in the Western World - and in total, diseases that can be traced to single gene defects account for about 5% of all admissions to children's hospitals. In the U.S. and Europe, there are exciting new programs to 'map' the entire human genome - all of our genes. This work will enable scientists and doctors to understand the genes that control all diseases to which the human race is prone, and hopefully develop new therapies to treat and predict diseases.

Diseases of Genetic Origin

Most of us do not suffer any harmful effects from our defective genes because we carry two copies of nearly all genes, one derived from our mother and the other from our father. The only exceptions to this rule are the genes found on the male sex chromosomes. Males have one X and one Y chromosome, the former from the mother and the latter from the father, so each cell has only one copy of the genes on these chromosomes. In the majority of cases, one normal gene is sufficient to avoid all the symptoms of disease. If the potentially harmful gene is recessive, then its normal counterpart will carry out all the tasks assigned to both. Only if we inherit from our parents two copies of the same recessive gene will a disease develop. On the other hand, if the gene is dominant, it alone can produce the disease, even if its counterpart is normal. Clearly only the children of a parent with the disease can be affected, and then on average only half the children will be affected. Huntington's chorea, a severe disease of the nervous system, which becomes apparent only in adulthood, is an example of a dominant genetic disease.
Finally, there are the X chromosome-linked genetic diseases. As males have only one copy of the genes from this chromosome, there are no others available to fulfill the defective gene's function. Examples of such diseases are Duchenne muscular dystrophy and, perhaps most well known of all, hemophilia.
Queen Victoria was a carrier of the defective gene responsible for hemophilia, and through her it was transmitted to the royal families of Russia, Spain, and Prussia. Minor cuts and bruises, which would do little harm to most people, can prove fatal to hemophiliacs, who lack the proteins (Factors VIII and IX) involved in the clotting of blood, which are coded for by the defective genes. Sadly, before these proteins were made available through genetic engineering, hemophiliacs were treated with proteins isolated from human blood. Some of this blood was contaminated with the AIDS virus, and has resulted in tragic consequences for many hemophiliacs. Use of genetically engineered proteins in therapeutic applications, rather than blood products, will avoid these problems in the future.
Not all defective genes necessarily produce detrimental effects, since the environment in which the gene operates is also of importance. A classic example of a genetic disease having a beneficial effect on survival is illustrated by the relationship between sickle-cell anemia and malaria. Only individuals having two copies of the sickle-cell gene, which produces a defective blood protein, suffer from the disease. Those with one sickle-cell gene and one normal gene are unaffected and, more importantly, are able to resist infection by malarial parasites. The clear advantage, in this case, of having one defective gene explains why this gene is common in populations in those areas of the world where malaria is endemic.

Gene Therapy

Much attention has been focused on the so-called genetic metabolic diseases in which a defective gene causes an enzyme to be either absent or ineffective in catalyzing a particular metabolic reaction effectively. A potential approach to the treatment of genetic disorders in man is gene therapy. This is a technique whereby the absent or faulty gene is replaced by a working gene, so that the body can make the correct enzyme or protein and consequently eliminate the root cause of the disease. The most likely candidates for future gene therapy trials will be rare diseases such as Lesch-Nyhan syndrome, a distressing disease in which the patients are unable to manufacture a particular enzyme. This leads to a bizarre impulse for self-mutilation, including very severe biting of the lips and fingers. The normal version of the defective gene in this disease has now been cloned.
If gene therapy does become practicable, the biggest impact would be on the treatment of diseases where the normal gene needs to be introduced into only one organ. One such disease is phenylketonuria (PKU). PKU affects about one in 12,000 white children, and if not treated early can result in severe mental retardation. The disease is caused by a defect in a gene producing a liver enzyme. If detected early enough, the child can be placed on a special diet for their first few years, but this is very unpleasant and can lead to many problems within the family.
The types of gene therapy described thus far all have one factor in common: that is, that the tissues being treated are somatic (somatic cells include all the cells of the body, excluding sperm cells and egg cells). In contrast to this is the replacement of defective genes in the germline cells (which contribute to the genetic heritage of the offspring). Gene therapy in germline cells has the potential to affect not only the individual being treated, but also his or her children as well. Germline therapy would change the genetic pool of the entire human species, and future generations would have to live with that change. In addition to these ethical problems, a number of technical difficulties would make it unlikely that germline therapy would be tried on humans in the near future.
From: IO. "Biotechnology in Perspective." Washington, D.C.: Biotechnology Industry Organization, 1990.

CLONING

CLONING

The words 'cloning' and 'genetic engineering' are often used by people as though they mean the same thing. Well, they have an overlapping meaning that becomes clear when we look through history.

"Genetic engineering, in its broadest definition, means to manipulate a species so that a particular trait is increased in the population. A trait is how an organism looks or acts or what it does. Brown eyes is a trait. Flying in circles is a trait. Climbing trees is a trait.

"The earliest forms of genetic engineering occurred on farms, where most people on earth lived at the time. They managed to do this by selecting seeds from plants that maybe had more fruit production or tastier leaves than other plants of its type.

"They planted those seeds and grew plants that had more of the favorable traits. Then they chose to save the seeds from the best of that lot to sow the next year. So, year by year, the farmers produced better and better crops. This type of activity probably has been going on since mankind first settled in villages and began making a life for themselves in one location, about 12,000 years ago!

"The same sort of thing would have also happened with animals. By eating the animals that didn't have favorable traits, like pulling a large load, and letting the animals with the favorable traits reproduce, herds and flocks would slowly develop more and more traits that humans found useful. It was thousands of years before mankind figured out how plants and animals reproduce themselves. With this knowledge, people could pollinate plants by hand or pen a pair of animals together in order to deliberately cause an increase in a favorable trait.

"It was only in the last 250 years that scientists began figuring out about chromosomes

and genes and the role they play in the way one generation passes its traits on to the next. And its only been in the last 30 years that scientists have been able to cut out specific genes from one organism and put them in another.

"It is this 30 year old technology that is described by the narrow definition of genetic engineering. Mankind has long been able to have a deliberate impact on the world around him. He now possesses the tools to deliberately impact himself. Some people are afraid of what might be done with that power.

"The word 'clone' was first used as a noun to describe a population of cells that reproduced themselves faithfully. A clone produces cells that not only have the same chromosomes, but which turn on the same genes, turn off the same genes, and therefore look identical, act the same, and do the same things.

Stem Cell Technology

Stem Cell Technology

After animal cells differentiate into tissues and organs, some tissues retain a group of undifferentiated cells to replace that tissue’s damaged cells or replenish its supply of certain cells, such as red and white blood cells. When needed, these adult stem cells (ASCs) divide in two. One cell differentiates into the cell type the tissue needs for replenishment or replacement, and the other remains undifferentiated.

Embryonic stem cells (ESCs) have much greater plasticity than ASCs because they can differentiate into any cell type. Mouse embryonic stem cells were discovered and cultured in the late 1950s. The ESCs came from 12-dayold mouse embryo cells that were destined to become egg or sperm (germ cells) when the mouse matured. In 1981, researchers found another source of mouse ESCs with total developmental plasticity—cells taken from a 4-dayold mouse embryo.
In the late 1990s researchers found that human ESCs could be derived from the same two sources in humans:
primordial germ cells and the inner cell mass of 5-day-old embryos. Scientists also have been able to isolate pluripotent stem cells from human placentas donated following
normal, full-term pregnancies. Under certain culture conditions, these cells were transformed into cartilagelike
and fat-like tissue.

Maintaining cultures of ESCs and ASCs can provide answers to critical questions about cell differentiation: What factors determine the ultimate fate of unspecialized stem cells?
How plastic are adult stem cells? Could we convert an ASC into an ESC with the right combination of factors? Why do stem cells retain the potential to replicate indefinitely? Is the factor that allows continual proliferation of ESCs the same factor that causes uncontrolled proliferation of cancer cells?
If so, will transplanted ESCs cause cancer?

The answers to these questions and many more will determine the limits of the therapeutic potential of ESCs and ASCs. Only when we understand the precise mix of factors controlling proliferation and development will we be able to reprogram cells for therapeutic purposes. Using stem cell cultures, researchers have begun to elaborate the intricate and unique combination of environmental factors, molecular signals and internal genetic programming that decides a cell’s fate. Israeli scientists directed ESCs down specific developmental pathways by providing different growth factors. Others discovered that nerve stem cells require a dose of vitamin A to trigger differentiation into one specific type of nerve cell, but not another.

Research Applications Of Biotechnology

Research Applications Of Biotechnology

Researchers use biotechnology to gain insight into the precise details of cell processes: the specific tasks
assigned to various cell types; the mechanics of cell division; the flow of materials in and out of cells; the path by which an undifferentiated cell becomes specialized; and the methods cells use to communicate with each other, coordinate their activities and respond to environmental changes.

Researchers dissect these processes into the smallest possible bits of useful information. This requires identifying the molecular players involved in each facet of the process, elucidating the nature of their interactions and discovering the molecular control mechanisms that govern these interactions. Once they have teased apart details of the process, they must then reassemble the pieces in a way that provides insight into the inner workings of cells and, ultimately, of whole organisms.

Interestingly, the tools of biotechnology have also become important research tools in many branches of science other than cell and molecular biology, such as chemistry, engineering, materials science, ecology, evolution and computer science. The biotech-driven discoveries in these fields help the biotech industry and others discover and develop products, as well as help industries improve their performance in areas such as environmental stewardship
and workplace safety.

Time Line of Biotechnology Developement Uptil 1928

Time Line of Biotechnology Developement Uptil 1928

1911
The first cancer-causing virus is discovered by Rous.

1914
Bacteria are used to treat sewage for the first time in
Manchester, England.

1915
Phages, or bacterial viruses, are discovered.

1919
First use of the word biotechnology in print.

1920
The human growth hormone is discovered by Evans
and Long.

1928
Penicillin discovered as an antibiotic: Alexander Fleming.
A small-scale test of formulated Bacillus thuringiensis
(Bt) for corn borer control begins in Europe. Commercial
production of this biopesticide begins in France in 1938.
n Karpechenko crosses radishes and cabbages, creating
fertile offspring between plants in different genera.
n Laibach first uses embryo rescue to obtain hybrids
from wide crosses in crop plants—known today as
hybridization.

Time Line of Biotechnology Developement Uptil 1890

Time Line of Biotechnology Developement Uptil 1890

1835–1855
Schleiden and Schwann propose that all organisms are
composed of cells, and Virchow declares, “Every cell
arises from a cell.”

1857
Pasteur proposes microbes cause fermentation.

1859
Charles Darwin publishes the theory of evolution by
natural selection. The concept of carefully selecting
parents and culling the variable progeny greatly
influences plant and animal breeders in the late 1800s
despite their ignorance of genetics.

1865
Science of genetics begins: Austrian monk Gregor
Mendel studies garden peas and discovers that genetic
traits are passed from parents to offspring in a predictable
way—the laws of heredity.

1870–1890
Using Darwin’s theory, plant breeders crossbreed cotton,
developing hundreds of varieties with superior
qualities.
Farmers first inoculate fields with nitrogen-fixing
bacteria to improve yields.
William James Beal produces first experimental corn
hybrid in the laboratory.
1877—A technique for staining and identifying bacteria
is developed by Koch.
1878—The first centrifuge is developed by Laval.
1879—Fleming discovers chromatin, the rod-like
structures inside the cell nucleus that later came to be
called chromosomes.

1900
Drosophila (fruit flies) used in early studies of genes.

1902
The term immunology first appears.

1906
The term genetics is introduced.

Time Line of Biotechnology Developement Uptil 1833

Time Line of Biotechnology Developement Uptil 1833

8000 B.C.
Humans domesticate crops and livestock.
Potatoes first cultivated for food.

4000–2000 B.C.
Biotechnology first used to leaven bread and ferment
beer, using yeast (Egypt).
Production of cheese and fermentation of wine (Sumeria,
China and Egypt).
Babylonians control date palm breeding by selectively
pollinating female trees with pollen from certain male
trees.

500 B.C.
n First antibiotic: moldy soybean curds used to treat
boils (China).

A.D. 100
First insecticide: powdered chrysanthemums (China).

1322
An Arab chieftain first uses artificial insemination to
produce superior horses.

1590
Janssen invents the microscope.

1663
Hooke discovers existence of the cell.

1675
Leeuwenhoek discovers bacteria.

1761
Koelreuter reports successful crossbreeding of crop
plants in different species.

1797
Jenner inoculates a child with a viral vaccine to
protect him from smallpox.

1830–1833
1830—Proteins discovered.
1833—First enzyme discovered and isolated.

Biotechnology Industry Facts

Biotechnology Industry Facts

Biotechnology industry originated in the 1970s,
based largely on a new recombinant DNA technique
whose details were published in 1973 by Stanley
Cohen of Stanford University and Herbert Boyer of the
University of California, San Francisco. Recombinant
DNA is a method of making proteins—such as human
insulin and other therapies—in cultured cells under
controlled manufacturing conditions. Boyer went on
to co-found Genentech, which today is biotechnology’s
largest company by market capitalization.

Biotechnology has created more than 200 new therapies
and vaccines, including products to treat cancer,
diabetes, HIV/AIDS and autoimmune disorders.
n There are more than 400 biotech drug products and
vaccines currently in clinical trials targeting more
than 200 diseases, including various cancers, Alzheimer’s
disease, heart disease, diabetes, multiple sclerosis,
AIDS and arthritis.

Biotechnology is responsible for hundreds of medical
diagnostic tests that keep the blood supply safe
from the AIDS virus and detect other conditions early
enough to be successfully treated. Home pregnancy
tests are also biotechnology diagnostic products.

Consumers are enjoying biotechnology foods such as
papaya, soybeans and corn. Biopesticides and other
agricultural products also are being used to improve
our food supply and to reduce our dependence on
conventional chemical pesticides.

Environmental biotechnology products make it possible
to clean up hazardous waste more efficiently by
harnessing pollution-eating microbes without the use
of caustic chemicals.

Industrial biotechnology applications have led to cleaner
processes that produce less waste and use less energy and
water in such industrial sectors as chemicals, pulp and
paper, textiles, food, energy, and metals and minerals. For
example, most laundry detergents produced in the United
States contain biotechnology-based enzymes.

DNA fingerprinting, a biotech process, has dramatically
improved criminal investigation and forensic
medicine, as well as afforded significant advances in
anthropology and wildlife management.

The biotech industry is regulated by the U.S. Food and
Drug Administration (FDA), the Environmental Protection
Agency (EPA) and the Department of Agriculture
(USDA).

As of Dec. 31, 2005, there were 1,415 biotechnology
companies in the United States, of which 329 were
publicly held.

Market capitalization, the total value of publicly traded
biotech companies (U.S.) at market prices, was $410
billion as of Dec. 31, 2005.

The biotechnology industry has mushroomed since
1992, with U.S. health-care biotech revenues increasing
from $8 billion in 1992 to $50.7 billion in 2005.

Biotechnology is one of the most research-intensive
industries in the world. The U.S. biotech industry
spent $19.8 billion on research and development in
2005.
n The top five biotech companies invested an average of
$130,000 per employee in R&D in 2005.
n In 1982, recombinant human insulin became the first
biotech therapy to earn FDA approval. The product
was developed by Genentech and Eli Lilly and Co.

Corporate partnering has been critical to biotech
success. In 2005, biotech companies signed 564 new
agreements with pharmaceutical firms and 354 with
fellow biotechs, according to BioWorld.

Most biotechnology companies are young companies
developing their first products and depend on investor
capital for survival. Biotechnology attracted more than
$20 billion in financing in 2005 and has raised more
than $100 billion since 2000.

The biosciences—including not just biotechnology
but all life sciences activities—employed 1.2 million
people in the United States in 2004 and generated an
additional 5.8 million related jobs.

The average annual wage of U.S. bioscience workers
was $65,775 in 2004, more than $26,000 greater than
the average private sector annual wage.
Bioethanol—made from crop wastes using biotech
enzymes—could meet a quarter of U.S. energy needs
by 2025.

The Biotechnology Industry Organization (BIO) was
founded in 1993 to represent biotechnology companies
at the local, state, federal and international
levels. As of December 2006, BIO’s membership consisted
of more than 1,100 biotechnology companies,
academic centers, state and local associations and
related enterprises.

Cells and Biological Molecules

Cells are the basic building blocks of all living things. The simplest living things, such as yeast, consist of a single, self-sufficient cell. Complex creatures more familiar to us, such as plants, animals and humans, are made of many different cell types, each of which performs a very specific task. In spite of the extraordinary diversity of cell types in living things, what is most striking is their remarkable similarity. This unity of life at the cellular level provides the foundation for biotechnology. All cells have the same basic design, are made of the same construction materials and operate using essentially the same processes. DNA (deoxyribonucleic acid), the genetic material of almost all living things, directs cell construction and operation, while proteins do all the work. Because DNA contains the information for making proteins, it directs cell processes by determining which proteins are produced and when. All cells speak the same genetic language. The DNA information manual of one cell can be read and implemented by cells from other living things. Because a genetic instruction to make a certain protein is understood by many different types of cells, technologies based on cells and biological molecules give us great flexibility in using nature’s diversity. In addition, cells and biological molecules are extraordinarily specific in their interactions. As a result, biotechnology products can often solve specific problems, generate gentler or fewer side effects and have fewer unintended consequences. Specific, precise, predictable. Those are the words that best describe today’s biotechnology.

What Is Biotechnology?

Using biological processes is hardly a noteworthy
event. We began growing crops and raising animals
10,000 years ago to provide a stable supply of food
and clothing. We have used the biological processes of
microorganisms for 6,000 years to make useful food
products, such as bread and cheese, and to preserve
dairy products. Why is biotechnology suddenly receiving
so much attention?
During the 1960s and ’70s our understanding of biology
reached a point where we could begin to use the
smallest parts of organisms—their biological molecules—
in addition to using whole organisms.
A more appropriate definition in the new sense of the
word is this:
“New” Biotechnology—the use of cellular and
biomolecular processes to solve problems or make
useful products.
We can get a better handle on the meaning of the word
biotechnology by simply changing the singular noun
to its plural form, biotechnologies.
Biotechnology is a collection of technologies that capitalize
on the attributes of cells, such as their manufacturing
capabilities, and put biological molecules, such
as DNA and proteins, to work for us.