In the 20-27 December 2001 issue of Nature, Peter Aldhous, editor of Nature News and Features, stated that “the idea of `therapeutic cloning` seems to be in decline. Despite the possibility of deriving ES cells with a genetic makeup identical to that of patients, the procedure does not seem feasible in the regular clinic, since it will be exorbitant expensive and time-consuming to put it into practice, there will hardly be enough human eggs left. [47] While there are no federal laws prohibiting human cloning, there are some restrictions on the use of taxpayer dollars for cloning and related research. In December 1994, President Clinton used his executive power to block federal funding for embryos created specifically for research purposes. [40] Congress followed suit the following year with the passage of the Dickey-Wicker Amendment, which prohibited federal funding for “the creation of one or more human embryos for research purposes” or for research “in which embryos are created or destroyed.” [41] The original text of the Dickey Wicker amendment included embryos created by “cloning” in its funding prohibition; In 1997, the wording of the Act was amended to be even more specific about the cloning technique used to manufacture carts. [42] Dolly`s announcement also prompted President Clinton to send a memorandum to the heads of executive departments and agencies ordering that no federal funds “be allocated to human cloning.” [43] In Asia, the situation is quite different. Japan, China, Singapore and South Korea are following the UK`s approach. India welcomes human embryonic stem cell research, as outlined at a recent Indo-British meeting of the Royal Society aimed at generating international cooperation in this field. But until now, it still prohibits therapeutic and reproductive cloning. Advances in biotechnology require an understanding of both scientific principles and ethical implications to be clinically applicable in medicine.
In this regard, therapeutic cloning offers significant potential in regenerative medicine by bypassing immune rejection and curing genetic disorders when used in conjunction with gene therapy. Therapeutic cloning as part of cell replacement therapy has enormous potential for de novo organogenesis and long-term treatment of Parkinson`s disease, Duchenne muscular dystrophy and diabetes mellitus, as shown in vivo studies. Scientific barriers to advances in therapeutic cloning include tumorigenicity, epigenetic reprogramming, mitochondrial heteroplasm, transfer of pathogens between species, and low availability of oocytes. Therapeutic cloning is also often associated with ethical considerations regarding the source, destruction and moral status of IVF embryos on the basis of the potential argument. Legislative and financial issues are also addressed. Future considerations would include a distinction between therapeutic and reproductive cloning in legislative formulations. The procedure for SCNT is no different from that for reproductive cloning (1). The host cell is blocked in metaphase II (2) and immobilized by light aspiration through a pipette tip. A glass needle is used to remove a small piece of the zona pellucida and is reintroduced by this puncture to extract the polar body and egg nuclei. The incorporation of somatic nuclei into the enucleated egg can be done by electrofusion, in which an electrical impulse is applied to incorporate a mammalian cell into the egg (to make a dolly). Alternatively, a somatic nucleus can be injected into the perivitelline space, the fluid-filled region between the zona pellucida and the ooplasm as used for cumulina, the first mouse cloned by SCNT. Mitosis occurs in vitro until the blastocyst, a sphere of hollow cells filled with fluid (40 to 150 cells) to which the embryoblast or inner cell mass from which the NTESC is taken is attached from the inside.
The subsequent addition of cell-type specific markers and growth hormones promotes the differentiation of NTESC into the desired cell line, which is implanted in vivo in the nuclear donor for therapeutic purposes, e.g. in cell replacement therapy. In vitro, ESCs can multiply infinitely and are totipotent, able to differentiate into any cell type in the body, unlike adult stem cells, which are multipotent, i.e. forced to produce any type of cell belonging to a specific line (3). Legal constraints and the resulting lack of funding were major obstacles to the promotion of therapeutic cloning. For example, although therapeutic cloning is not completely banned in the United States, federal funds cannot be used for experiments with the 20 cell lines in the National Institute of Health (NIH) registry (44) that were established before September 9. August 2001. Of these Bush-approved cell lines, 12 are dead and the rest are not useful for research purposes. Researchers are therefore dependent on the scarcity of private funding, although 4 US states, including California with an annual investment of 295 million, have a budget specifically dedicated to stem cell research (44).
Clinton was concerned about the production of chimeras through “experiments of crossing human and non-human species” (58), but paradoxically, all of the cell lines in the NIH registry that received Bush`s approval were grown on layers of animal feed cells and therefore contain traces of animal contaminants. Proponents of a total ban hoped to impose their will on States that advocated some research on therapeutic cloning, and were not deterred by questions about the lack of legitimacy of a possible international treaty if the majority of countries withdrew. “If the Belgian proposal succeeds, the US and other countries would still be free to ban human cloning, but countries that see the promise of therapeutic cloning can still do research,” Lord May suggested. Funding practices also vary considerably from state to state. Five states (Arizona, Indiana, Louisiana, Michigan and Nebraska) prohibit public funding of any form of cloning research. Some states officially approve public funding of cloning for biomedical research, such as California (where a 2004 initiative created a ten-year, $3 billion commitment for stem cell research, including cloning for biomedical research)[63] and New York (where the state government has allocated more than $300 million to fund stem cell research since 2007). [64] In the meantime, other states have not issued funding bans simply because Parliament would hardly allow such spending anyway, so a ban would be considered unnecessary. Missouri does not have a permanent legal ban on funding cloning research, but since 2007, lawmakers have regularly included language in every budget bill limiting funding for human cloning. [65] Legislative attempts in the U.S. Congress were blocked due to a similar division over cloning for research purposes. The field of regenerative medicine is an evolving science with a multidisciplinary approach that applies technical and life science principles to promote the regeneration, healing or replacement of tissues and organs damaged and injured due to age or disease or other factors to restore normal body or organ function. [20] This is one of those areas that can benefit enormously from advances in cloning technology, particularly in the form of therapeutic cloning.
Since the goal of regenerative medicine is to help patients suffering from illness or injury by restoring damaged or injured tissues and organs, therapeutic cloning can be of paramount importance for the advancement of regenerative medicine. After Dolly the cloning of the sheep, there was a flood of legislative activity as members of Congress from both parties tried to restrict the practice of human cloning. None of the proposed bills were passed. The controversies surrounding cloning policy at the federal and state levels have focused on three main issues: first, whether different types of cloning should be regulated differently; secondly, should taxpayers` money be used to fund cloning-related research; and, finally, whether women can be paid by scientists for the supply of eggs, and other issues related to the regulation of egg supply.
Recent Comments