Stem Cell Cloning
The cloning procedure works by combining a patient's
body cell with an unfertilized egg cell from a donor. The
patient's skin cell is inserted into the outer membrane of the
egg cell and chemically induced to begin developing into a
blastocyst. In the blastocyst, embryonic cells divide,
producing a mass of stem cells.
body cell with an unfertilized egg cell from a donor. The
patient's skin cell is inserted into the outer membrane of the
egg cell and chemically induced to begin developing into a
blastocyst. In the blastocyst, embryonic cells divide,
producing a mass of stem cells.
Cloning/Embryonic Stem Cells
The term cloning is used by scientists to describe many different processes that involve making duplicates of biological material. In most cases, isolated genes or cells are duplicated for scientific study, and no new animal results. The experiment that led to the cloning of Dolly the sheep in 1997 was different: It used a cloning technique called somatic cell nuclear transfer and resulted in an animal that was a genetic twin -- although delayed in time -- of an adult sheep. This technique can also be used to produce an embryo from which cells called embryonic stem (ES) cells could be extracted to use in research into potential therapies for a wide variety of diseases.
Thus, in the past five years, much of the scientific and ethical debate about somatic cell nuclear transfer has focused on its two potential applications: 1) for reproductive purposes, i.e., to produce a child, or 2) for producing a source of ES cells for research.
Cloning for Reproductive Purposes
The technique of transferring a nucleus from a somatic cell into an egg that produced Dolly was an extension of experiments that had been ongoing for over 40 years. In the simplest terms, the technique used to produce Dolly the sheep - somatic cell nuclear transplantation cloning - involves removing the nucleus of an egg and replacing it with the diploid nucleus of a somatic cell. Unlike sexual reproduction, during which a new organism is formed when the genetic material of the egg and sperm fuse, in nuclear transplantation cloning there is a single genetic "parent." This technique also differs from previous cloning techniques because it does not involve an existing embryo. Dolly is different because she is not genetically unique; when born she was genetically identical to an existing six-year-old ewe. Although the birth of Dolly was lauded as a success, in fact, the procedure has not been perfected and it is not yet clear whether Dolly will remain healthy or whether she is already experiencing subtle problems that might lead to serious diseases. Thus, the prospect of applying this technique in humans is troubling for scientific and safety reasons in addition to a variety of ethical reasons related to our ideas about the natural ordering of family and successive generations.
Scientific Uncertainties
Several important concerns remain about the science and safety of nuclear transfer cloning using adult cells as the source of nuclei. To date, five mammalian species -- sheep, cattle, pigs, goats, and mice -- have been used extensively in reproductive cloning studies. Data from these experiments illustrate the problems involved. Typically, very few cloning attempts are successful. Many cloned animals die in utero, even at late stages or soon after birth, and those that survive frequently exhibit severe birth defects. In addition, female animals carrying cloned fetuses may face serious risks, including death from cloning-related complications.
An additional concern focuses on whether cellular aging will affect the ability of somatic cell nuclei to program normal development. As somatic cells divide they progressively age, and there is normally a defined number of cell divisions that can occur before senescence. Thus, the health effects for the resulting liveborn, having been created with an "aged" nucleus, are unknown. Recently it was reported that Dolly has arthritis, although it is not yet clear whether the five-and-a-half-year-old sheep is suffering from the condition as a result of the cloning process. And, scientists in Tokyo have shown that cloned mice die significantly earlier than those that are naturally conceived, raising an additional concern that the mutations that accumulate in somatic cells might affect nuclear transfer efficiency and lead to cancer and other diseases in offspring. Researchers working with clones of a Holstein cow say genetic programming errors may explain why so many cloned animals die, either as fetuses or newborns.
History
Stem cells are the cellular putty from which all tissues of the body are made. Ever since human embryonic stem cells were first grown in the lab, researchers have dreamed of using them to repair damaged tissue or create new organs, but such medical uses have also attracted controversy. Yesterday, the potential of stem cells to revolutionise medicine got a huge boost with news of an ultra-versatile kind of stem cell from adult mouse cells using a remarkably simple method. This timeline takes you through the ups and downs of the stem cell rollercoaster.
1981, Mouse beginnings
Martin Evans of Cardiff University, UK, then at the University of Cambridge, is first to identify embryonic stem cells – in mice.
Martin Evans of Cardiff University, UK, then at the University of Cambridge, is first to identify embryonic stem cells – in mice.
1997, Dolly the sheep
Ian Wilmut and his colleagues at the Roslin Institute, Edinburgh unveil Dolly the sheep, the first artificial animal clone. The process involves fusing a sheep egg with an udder cell and implanting the resulting hybrids into a surrogate mother sheep. Researchers speculate that similar hybrids made by fusing human embryonic stem cells with adult cells from a particular person could be used to create genetically matched tissue and organs.
Ian Wilmut and his colleagues at the Roslin Institute, Edinburgh unveil Dolly the sheep, the first artificial animal clone. The process involves fusing a sheep egg with an udder cell and implanting the resulting hybrids into a surrogate mother sheep. Researchers speculate that similar hybrids made by fusing human embryonic stem cells with adult cells from a particular person could be used to create genetically matched tissue and organs.
1998, Stem cells go human
James Thomson of the University of Wisconsin in Madison and John Gearhart of Johns Hopkins University in Baltimore, respectively, isolate human embryonic stem cells and grow them in the lab.
James Thomson of the University of Wisconsin in Madison and John Gearhart of Johns Hopkins University in Baltimore, respectively, isolate human embryonic stem cells and grow them in the lab.
2001, Bush controversy
US president George W. Bush limits federal funding of research on human embryonic stem cells because a human embryo is destroyed in the process. But Bush does allow continued research on human embryonic stem cells linesthat were created before the restrictions were announced.
US president George W. Bush limits federal funding of research on human embryonic stem cells because a human embryo is destroyed in the process. But Bush does allow continued research on human embryonic stem cells linesthat were created before the restrictions were announced.
2005, Fraudulent clones
Woo Suk Hwang of Seoul National University in South Korea reports that his team has used therapeutic cloning – a technique inspired by the one used to create Dolly – to create human embryonic stem cells genetically matched to specific people. Later that year, his claims turn out to be false.
Woo Suk Hwang of Seoul National University in South Korea reports that his team has used therapeutic cloning – a technique inspired by the one used to create Dolly – to create human embryonic stem cells genetically matched to specific people. Later that year, his claims turn out to be false.
2006, Cells reprogrammed
Shinya Yamanaka of Kyoto University in Japan reveals a way of making embryonic-like cells from adult cells – avoiding the need to destroy an embryo. His team reprograms ordinary adult cells by inserting four key genes – forming “induced pluripotent stem cells”.
Shinya Yamanaka of Kyoto University in Japan reveals a way of making embryonic-like cells from adult cells – avoiding the need to destroy an embryo. His team reprograms ordinary adult cells by inserting four key genes – forming “induced pluripotent stem cells”.
2007, Nobel prize
Evans shares the Nobel prize for medicine with Mario Capecchi and Oliver Smithies for work on genetics and embryonic stem cells.
Evans shares the Nobel prize for medicine with Mario Capecchi and Oliver Smithies for work on genetics and embryonic stem cells.
2009, Obama-power
President Barack Obama lifts 2001 restrictions on federal funding for human embryonic stem cell research.
President Barack Obama lifts 2001 restrictions on federal funding for human embryonic stem cell research.
2010, Spinal injury
A person with spinal injury becomes the first to receive a medical treatment derived from human embryonic stem cells as part of a trial by Geron of Menlo Park, California, a pioneering company for human embryonic stem cell therapies.
A person with spinal injury becomes the first to receive a medical treatment derived from human embryonic stem cells as part of a trial by Geron of Menlo Park, California, a pioneering company for human embryonic stem cell therapies.
2012, Blindness treated
Human embryonic stem cells show medical promise in a treatment that eases blindness.
Human embryonic stem cells show medical promise in a treatment that eases blindness.
2012, Another Nobel
Yamanaka wins a Nobel prize for creating induced pluripotent stem cells, which he shares with John Gurdon of the University of Cambridge.
Yamanaka wins a Nobel prize for creating induced pluripotent stem cells, which he shares with John Gurdon of the University of Cambridge.
2013, Therapeutic cloning
Shoukhrat Mitalipov at the Oregon National Primate Research Center in Beaverton and his colleagues produce human embryonic stem cells from fetal cells using therapeutic cloning – the breakthrough falsely claimed in 2005.
Shoukhrat Mitalipov at the Oregon National Primate Research Center in Beaverton and his colleagues produce human embryonic stem cells from fetal cells using therapeutic cloning – the breakthrough falsely claimed in 2005.
2014, Pre-embryonic state
Charles Vacanti of Harvard Medical School together with Haruko Obokata at the Riken Center for Developmental Biology in Kobe, Japan, and colleagues announced a revolutionary discovery that any cell can potentially be rewound to a pre-embryonic state – using a simple, 30-minute technique.
Charles Vacanti of Harvard Medical School together with Haruko Obokata at the Riken Center for Developmental Biology in Kobe, Japan, and colleagues announced a revolutionary discovery that any cell can potentially be rewound to a pre-embryonic state – using a simple, 30-minute technique.
2014, Therapeutic cloning – with adult cells
Teams led by Dieter Egli of the New York Stem Cell Foundation and Young Gie Chung from CHA University in Seoul, South Korea, independently produce human embryonic stem cells from adult cells, using therapeutic cloning. Egli’s team use skin cells from a woman with diabetes and demonstrate that the resulting stem cells can be turned into insulin-producing beta cells. In theory, the cells could be used to replace those lost to the disease.
Teams led by Dieter Egli of the New York Stem Cell Foundation and Young Gie Chung from CHA University in Seoul, South Korea, independently produce human embryonic stem cells from adult cells, using therapeutic cloning. Egli’s team use skin cells from a woman with diabetes and demonstrate that the resulting stem cells can be turned into insulin-producing beta cells. In theory, the cells could be used to replace those lost to the disease.
2014, Human trials
Masayo Takahashi at the same Riken centre is due to select patients for what promises to be the world’s first trial of a therapy based on induced pluripotent stem cells, to treat a form of age-related blindness.
Masayo Takahashi at the same Riken centre is due to select patients for what promises to be the world’s first trial of a therapy based on induced pluripotent stem cells, to treat a form of age-related blindness.
https://www.newscientist.com/article/dn24970-stem-cell-timeline-the-history-of-a-medical-sensation/
Opinion
In my own opinion the stem cell cloning is very omportant in
our health because it can help or cure a harmful deases
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