Cloning and Stem Cells

Single nucleotide polymorphisms (SNPs) are DNA sequence variations among individuals. Research is under way to hnd out about specihc SNPs (or sets of SNPs) that are associated with various medical conditions and to study the differences in SNP patterns among various human populations. It is hoped that knowledge of SNPs will improve medical treatment by enabling prediction of disease risk and response to therapies. 

Source Coronini R, et al. Decoding the literature on genetic variation, Nature Biotechnology 21 21-29 (2003). 

In one study, researchers from Vanderbilt University in Nashville, Tennessee (USA), compared responses to a jS-blocker called atenolol among 34 patients. All patients had genetic variations affecting one of the building blocks of the receptor that binds to jS-blocker drugs, which affected the way the receptor responded to the binding of the drug. 

Thirteen had one type of genetic variation, Gly389, and 21 had another variation, called Arg389. 

Source Sofowora GG, et al. A common ft-adrenergic receptor polymorphism (Arg389Gly) affects blood pressure response to /J-blockade, Clinical Pharmacology Therapeutics 73 366-371 (2003). 

Exhibit 11.7 describes a recent gene therapy trial that resulted in unexpected outcomes, which the regulatory authorities have to consider. A recent report of gene therapy for treatment of Alzheimer s disease is also included. 

As discussed in Section 4.7, stem cells have the potential to treat medical conditions beyond the scope that can be offered by drugs alone. However, there are many scientific and ethical hurdles to overcome. On the scientific 

Infants with severe combined immunodeficiency disease (SCID, bubble boy syndrome) have a gene defect that leads to a complete lack of white blood cells. Without treatment, these infants die from complications of infectious diseases during the first few years of life. The only treatment currently approved for this condition is a bone marrow transplant. 

Gene therapy offers another potential avenue to fix the defective gene. The therapy itself is by no means straightforward. In a French gene therapy trial, two children with SCID were successfully treated. However, both these children unexpectedly developed a leukemia-like condition. On this news, the FDA put a temporary clinical hold on the gene therapy trial until further investigations are carried out. 

In a recent gene therapy study, a gene for the expression of a protein called neprilysin was introduced into transgenic mice. Neprilysin regulates amyloid levels, which are implicated in Alzheimer s disease (Exhibit 11.9). The results showed a 50% reduction in the levels of amyloid. 

---

Thompson, B., and B. Harrub. 2001. Human cloning and stem-cell research—Science s slippery slope. Montgomery, AL Apologetics Press. 

In 2001, President George W. Bush created the Presidential Council on Bioethics and appointed Leon Kass, a respected bioethicist, as chair. The task was to recommend action on cloning and stem cell research. In July 2002 the committee gave the president a report in... 

Shostak, Stanley. Becoming Immortal Combining Cloning and Stem-Cell Therapy. Albany State University of New York Press, 2002. Examines the question of whether human beings are equipped for potential immortality. 

Reverence for life, in one sense or another, is reflected in societal and political problems. In the United States at this time, vigorous debate, and sometimes violence, is elicited by concerns about birth control, abortion, the cloning of stem cells, and the death penalty. 

The ethical issues discussed above are, in most countries, codified in legal form. Treatment of human beings and human samples depends on the legal environment. Research objectives may also be subject to legal issues, like in cloning or stem cell research. 

Simon Of course there is lateral division. There is also circumferential growth of the plant later on. I don t know how much. When I said that there were three or four stem cells in each individual layer, this was done by classical clone analysis, marking cells during development and then looking for the maximum sized sector that can be found. The maximum sector comprised one-third to one-quarter of the entire circumference of the plant, indicating that there are three or four stem cells. 

Stem cells and cell therapy is the use of pluripotent and multipotent cells to generate healthy cells and tissues to replace the faulty ones in disease conditions. The main ethical questions are the source of the cells and the possibility of cloning humans. 

We can divide cloning into therapeutic cloning and reproductive cloning. Therapeutic cloning is synonymous with stem cell research. Under proper control and environment, embryonic stem cells can potentially be directed to grow and develop into different tissues that are invaluable for replacing... 

As discussed in Section 4.7, stem cells have the potential to treat medical conditions beyond the scope that can be offered by drugs alone. However, there are many scientific and ethical hurdles to overcome. On the scientific front, stem cell research activities will intensify over the next decade. These challenges can broadly be divided into (1) determining how to develop stem cells into specific tissues and (2) implanting these tissues into the body without rejection by the recipient s immune system. On the ethical front, it is expected that there will be more debates on the ethical issues of stem cell research. Most scientists consent to therapeutic cloning (stem cell research) but not reproductive cloning. The ethical issue of stem cell research concerns harvesting cells from embryos that are a few days old. This action destroys the embryos. Some questions are ... 

In November 2003, the members of the Europe Parliament voted to approve embryonic stem cell research, using techniques similar to that adopted for cloning Dolly the sheep, although severe restrictions were put in place. For US scientists, however, the US legislation meant that they were only allowed to performed research using 12 existing sources of the embryonic stem cells and were not allowed to create any new sources. 

Figure 6. Proliferation of the murine Myl-D7 stem cell line is stimulated efficiendy only by membrane-bound CSF-1. 2-10 Myl-D7 cells were cultured on MMCE cells expressing the different CSF-1 isoforms in 48-well plates. Cloning efficiencies were determined weekly and Myl-D7 clones (>10 cells) were transferred onto new MMCE cells. Values of Myl-D7/MS5 cocultures were set to 100% at each time point (data not shown). Results are expresses as percentage of control Myl-D7/MS5 cultures and are mean values +SD (four experiments). After 3 weeks in coculture a) no difference was found in the proliferation rates of cells stimulated by either wildtype- or soluble CSF-1 (P>.05) b) mean values for populations stimulated by membrane-bound- or soluble CSF-1 were significantly different (P<.001).

Itoh K, Friel J, Kluge N, Kina T, Kondo-Takaori A, Kawamata S, Uchiyama T, Ostertag W, 1996. A novel hemopoietic multi-lineage clone, Myl-D-7, is stromal cell dependent and supported by an alternative mechanism(s) independent of stem cell factor/c kit interaction. Blood 87 3218... 

---