Any term that includes the word “cloning” might send a shiver down your spine, conjuring up visions of a world populated with copies of people who blur the definition of identity. However, the professionals studying this process are far from crazy scientists attempting to wreak havoc; in fact, they’re working to better society by researching methods to ease tissue transplants, treating degenerative diseases, and slow senescence. Therapeutic cloning, also known as somatic cell nuclear transfer, refers to the process of removing a nucleus from a somatic cell and placing it in an enucleated egg cell, which will eventually provide useful embryonic stem cells. Not intended for reproductive purposes, SCNT shows great promise for utilization in medicine, despite moral and ethical quandaries surrounding the process.
How Does Therapeutic Cloning Work?
SCNT is a complicated process. In her article “Therapeutic Cloning: Promises and Issues,” Charlotte Kfoury explains that it begins with delicately extracting the nucleus of an egg cell, or oocyte, with a glass needle. Next, the nucleus of a somatic cell is integrated into the (now enucleated) oocyte via electrofusion. This cell with a new nucleus then divides in vitro to create a blastocyst, which provides embryonic stem cells.
These embryonic stem cells are valuable and unique because they are totipotent, meaning that they have the capability to develop into a wide variety of body cells. This quality opens doors for regenerative medicine, enhancing gene therapy and further elucidating the development of cells.
The implications of therapeutic cloning for medicine are vast and exciting, from expanding the possibilities of regenerative medicine to providing potential cures for diseases such as Parkinson’s. Although challenges and controversy slow the progress of stem-cell-related treatments, researchers around the globe are working to apply SCNT in a variety of contexts.
Perhaps the most obvious notion that comes to mind, regenerative medicine has much to gain from SCNT. Major issues that arise with organ and tissue transplants are immune rejection and intense side effects of immunosuppressive drugs. Kfoury notes that immune rejection can be addressed by utilizing the patient’s own cells in SCNT, introducing healthy cells that won’t trigger an immune response in the patient’s body. This also removes the need for immunosuppressive drugs, thereby combating the problem of uncomfortable side effects.
Going even further, many are hopeful that therapeutic cloning could eventually pave the way for personalized organogenesis. Using SCNT to produce organs for those in need would alleviate organ shortage, which is another great issue in transplants today. While synthesizing entirely new organs is still a distant possibility, Kfoury reports that the creation of skin grafts for burn patients and blood vessels for atherosclerosis patients exhibits the great potential for SCNT to improve regenerative medicine.
Another pro of therapeutic cloning is the possible application for diabetes mellitus, which, according to the NIH, affects approximately 30.3 million people in the United States today. Those who suffer from diabetes mellitus don’t produce enough insulin and can require insulin therapy or, in extreme cases, a pancreas transplant. D’Amour et al. illustrated the potential for this application in 2006 by differentiating embryonic stem cells into endocrine cells. The development and introduction of insulin-producing endocrine cells using embryonic stem cells from SCNT could prove to be a more effective treatment than insulin therapy, and the potential for organogenesis would address the shortage of pancreases available for transplant.
The application of SCNT for paralysis is equally exhilarating. Experiments by Deshpande et al. in 2006 illustrated that embryonic stem cells could differentiate into motor neurons and restore mobility in paralyzed rats. This astonishing development will hopefully pave the way for healing those affected by paralysis.
One of the most intriguing pros of SCNT is its potential to cure Parkinson’s Disease, as well as other neurodegenerative diseases. Barberi et al. utilized SCNT in treating mice afflicted with Parkinson’s by injecting them with embryonic stem cells that were differentiated into different types of neurons. This improved their overall function, blazing a trail of hope for human patients in the future.
Therapeutic cloning could also benefit patients indirectly through animal models. Researchers hope to take somatic cells from patients and use SCNT to transfer the disease to an animal model. This way, treatments could be tested for effectiveness before putting the patient through any undue strain. This would be quite an accomplishment in the medical world because it would be highly individualized and circumvent ineffective treatments.
Despite the plethora of potential clinical applications, therapeutic cloning has its cons. Moral and ethical issues arise in response to the process and oocyte availability, and several practical challenges halt the progress of SCNT.
Oocyte Usage and Availability
Although the advanced procedure of SCNT is something to be celebrated in the scientific world, it remains a relatively inefficient process. One oocyte can provide many embryonic stem cells, but it takes a staggering 280 oocytes to achieve an ideal line of embryonic stem cells, according to Kfoury. This lack of efficiency inevitably creates an ethical conundrum when it comes to oocyte availability. There are plenty who are happy to donate eggs, but authorities often limit financial incentives so as not to disproportionately impact poorer classes. For instance, the UK’s government-backed Human Fertility and Embryo Authority limits the number of eggs a woman can donate for research to two. In addition, the HFEA limits the amount a donor can be paid as reimbursement of the medical costs for donation.
The donation of oocytes is also controversial because the procedure is invasive, and complications can negatively impact donors. The National Gamete Trust in the UK explains that the process takes several months and requires extensive screening; some clinics will bar a donor for an unhealthy BMI or other medical concerns. Hormonal injections are often utilized to increase the amount of eggs a woman produces for donation, and this method can lead to ovarian hyperstimulation syndrome, which has negative impacts such as abdominal pain and nausea.
Beyond the practical obstacles faced by those who have made the choice to donate, an even larger issue with obtaining oocytes for therapeutic cloning is that few women are motivated to donate eggs to science at all. The thought of helping to create a life, to assist a couple in becoming a family, appears more attractive to donors than the thought of eggs sequestered in a petri dish and poked at with glass needles. The implicit discomfort surrounding reproductive cloning serves as a deterrent as well. Therapeutic cloning has a markedly different goal than reproductive cloning but does employ the same process. This incites nervousness among donors, as many people are not properly aware of the difference between the two and the potential benefits of research involving SCNT.
The question of whether payment is appropriate for those donating eggs to research has fired up a moral debate as well. Some argue against putting a price tag on a part of the body that is not involved in the propagation of life. Others contend that donating oocytes for SCNT research is an insult to the human capacity to generate life. Such opinions inevitably influence legislation and thereby impact the donation community, and this can slow the progress of SCNT research greatly because it limits the amount of eggs available. And because SCNT requires 280 oocytes to produce a single desired result, putting a cap on the pool of potential donors through moral and ethical disagreements is especially detrimental.
Another layer to the moral concerns which limit therapeutic cloning is the destruction of embryos. As the seed of human life, the sentience of human embryos is hotly debated, with some equating their destruction to murder and others claiming that a mere cluster of cells is incapable of consciousness and feeling. This being the case, embryos older than two weeks are usually not allowed to be used for research, further limiting the number of oocytes available for SCNT. According to Kfoury, 60 percent of embryos come from IVF treatments, because there are irregular embryos that form and would be unsuitable for implantation. Yet, despite the fact that these embryos would not develop properly into people, it is the principle of destruction that continually generates aversion and stimulates controversy around therapeutic cloning.