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Exploitation and control of women's reproductive bodies
Published in Wendy A. Rogers, Jackie Leach Scully, Stacy M. Carter, Vikki A. Entwistle, Catherine Mills, The Routledge Handbook of Feminist Bioethics, 2022
Therapeutic cloning involves producing stem cells which can repair and replace damaged human tissue, and it depends on a suitable supply of human eggs. Biologists have observed that the mammalian egg can remodel and replicate chromosomes not only from a sperm head but also from a variety of other cells (Kiessling 2004). This property has been exploited in the process of somatic cell nuclear transfer (SCNT), which involves removing the nucleus from an egg and replacing it with the nucleus of a somatic cell. The egg is then stimulated with a shock to develop into an embryo, either for transfer to a uterus for further development (reproductive cloning), or for culture in vitro (therapeutic cloning).
Reproduction
Published in Gary Chan Kok Yew, Health Law and Medical Ethics in Singapore, 2020
Cloning is the reproduction of genetic material of an ancestor-organism without sex.116 The process is known as somatic cell nuclear transfer where the nucleus of an adult cell is taken from an existing organism and implanted or fused into the egg. The egg still contributes the mitochondrial DNA albeit not a significant amount of genetic material. Nonetheless, the clone would still be genetically different from the ancestor.
Human Genetic Engineering
Published in Gary Seay, Susana Nuccetelli, Engaging Bioethics, 2017
More than 100 years ago, scientists first demonstrated that simple organisms could be replicated by embryo-twinning at early stages of development. 3 In 1958, John Gurdon performed the first successful transfer of a tadpole’s intestinal cell nucleus into an enucleated frog egg, creating a clone or genetic replica of that tadpole. Known as ‘somatic cell nuclear transfer,’ this cloning technique proceeds by injecting the DNA of a donor cell, or fusing the entire cell, into an enucleated egg. Any resulting embryo is immediately implanted into a gestational carrier, in the hope that it will result in a live-born clone. In 1996, UK scientists Ian Wilmut and Keith Campbell transferred the nucleus of an adult sheep’s udder cell to an empty egg to produce the first mammal cloned from an adult somatic cell. After 277 attempts that led to the creation of 27 sheep embryos and only 13 implantations, Dolly the Sheep was the only clone to survive. Success rates in animal cloning are disappointing, with primates posing the greatest technical challenges. But in 2013 scientists created human embryonic stem cells from a baby for the purpose of studying its rare genetic disorder. The difficulties facing such therapeutic cloning became evident during the 2004–05 scandal involving a South Korean scientist suspected of faking his data.
What to Expect When Expecting CRISPR Baby Number Four
Published in The American Journal of Bioethics, 2019
Christopher Thomas Scott, Cynthia Selin
Hwang’s ersatz experiment, which he dropped at the 2004 International Stem Cell Society annual meeting, was a bolt from the blue. Technical hurdles, including overcoming the species barrier, had for years flummoxed researchers attempting to use somatic cell nuclear transfer (SCNT) to clone primate embryonic stem cell lines. Yet He’s CRISPR babies hardly came as a surprise. Telltales were apparent as early as 2013 when a Chinese team reported generating rats using the technology (Li et al. 2013). In January 2014, a different group in China reported twin cynomolgus monkeys born with mutations made with CRISPR/Cas9 (Niu et al. 2014).1 These experiments foreordained the eventual application of the technology in human embryos. Although it wasn’t until 2016 that two essays by scientists, inventors, and bioethicists in the journals Nature and Science detailed recommendations for how future human germline research should proceed (Baltimore et al. 2015; Lanphier et al. 2015), the future had rushed ever closer: Chinese experiments using human embryos were reported on the heels of the essays. Using CRISPR in nonviable human embryos, one research team knocked out the human gene HBB, while another introduced CCR5, an HIV-resistance allele (Kang et al. 2016; Liang et al. 2015). A third experiment in the United States successfully corrected a mutation causing heart disease in viable human embryos, which were later destroyed as part of the protocol (Ma et al. 2017).
Challenges and ethical considerations for using cloned primates for human brain discovery
Published in Expert Opinion on Drug Discovery, 2018
Alan O. Trounson, Andrew J. French
Ethical discussion on cloning has mainly been confined to human reproductive cloning and somatic cell nuclear transfer or therapeutic cloning [15]. There were some concerns about cloning farm animals and their entry into the human food chain but these have disappeared with regulatory approval for their use. Cloning NHP is a technical step closer to the cloning of humans and this might be an ethical concern to some people. Regulatory authorities do not require data from NHP models in preclinical medical research unless the therapeutic risks and efficacy cannot be demonstrated adequately in rodents or other large animals, or in vitro. It is difficult to completely avoid the use of NHP in neurological research because of the need to find models that represent closely human neuronal conditions. NHP research attracts increased opposition from animal activists but the degree of concern varies in different cultures. There is also a general trend by research ethics committees for reducing the number of animals used in experiments in medical research and cloned animals may be considered as supporting this trend because of their genetic homogeneity. However, other practical factors such as cost and availability will also impact on the use of cloned NHP.
Spermatogonial stem cell transplantation and male infertility: Current status and future directions
Published in Arab Journal of Urology, 2018
Connor M. Forbes, Ryan Flannigan, Peter N. Schlegel
Pluripotent stem cells can be obtained through multiple mechanisms. Several often-studied mechanisms are harvesting of embryonal stem cells, reprogramming adult somatic cells to make induced pluripotent stem cells, or from somatic cell nuclear transfer (SCNT) where a nucleus is inserted into an oocyte [61]. In humans, of course, the initial embryonic development is guided by centrioles from male-derived germ cells, limiting the potential success of using nuclear transfer alone (or male germ cells that have not yet initiated tail development.) The traditional pathway suggests that pluripotent stem cells must be differentiated into primordial germ cells (PGCs) prior to SSCs [61]. A review of the mechanisms for this differentiation can be found by Nikolic et al. [62].