For the first time, a new type of stem cell, derived from virgin births, has been tested in people. The cells have been injected into the brains of people with Parkinsons disease, and will soon be tried out as a way of fixing physical brain injuries. Like embryonic stem cells, these cells could be a powerful treatment for a range of diseases, but importantly, their origins mean they are free of many of the ethical concerns relating to the use of cells from embryos. Embryonic stem cells can theoretically be used to make or heal any part of the body, but they come from fertilised and discarded human embryos, which some people believe is unethical. But the virgin birth stem cells come from unfertilised eggs, so no life is created or ended. The virgin-birth stem cells could be seen as morally equivalent to cells made from sperm, according to Daniel Brison at the University of Manchester, UK, who wasnt involved in the work. An unfertilised egg doesnt have any potential for human life. Virgin births occur in a range of animals, from aphids to worms, and occasionally in larger species such as sharks and Komodo dragons. Through a process called parthenogenesis, females in these species are able to make embryos from unfertilised eggs, which divide to form an embryo without needing sperm. But this doesnt happen in mammals. If unfertilised human eggs are coaxed into dividing in the lab, they die after a few days. However, stem cells extracted from these balls of cells before they die seem, like stem cells taken from embryos made using fertilised eggs, to be able to become any of the bodys cell types.
People with Parkinsons disease have previously shown improvements when given transplants of foetal nerve cells that release the chemical dopamine. This probably helps because the condition is caused by the death of cells in the brain that normally make dopamine, leading to symptoms like tremors. But these transplants come from aborted foetuses, meaning the supply is very limited. Now, instead, Russell Kern of US firm International Stem Cell Corporation (ISCO) and his team are giving people with Parkinsons transplants of parthenogenetic stem cells. The cells were transformed into neural stem cells before transplant. Work in animals suggests that they will develop into neurons that release dopamine several months after injection. So far, preliminary results show that, of the six-people treated so far, there have seen some improvements in symptoms, such as being unable to move for fewer periods of time, the team announced at the Society for Neuroscience meeting in Washington DC, this month. However, it will take a larger, placebo-controlled trial to know for sure if the cells are effective, partly because Parkinsons disease seems particularly susceptible to the placebo effect.
Because the brain is relatively shut off from the immune system by the blood-brain barrier, the parthenogenetic cells dont need to be immunologically matched to each person for the treatment of Parkinsons disease and brain injuries. Patients are taking a modest, one-year course of immune-suppressing medicines, though, to be on the safe side, says Kern. Long-term immunosuppression would be needed if the cells are implanted elsewhere in the body. Parthenogenetic stem cells arent tailored for their individual recipients. One advantage of not creating personalised stem cells for each patient is that they can be created years in advance and given extensive safety testing, says Kern. This means the cells might avoid the risks of induced pluripotent stem cells, which can be personalised by making them made from a patients skin cells, but which are created in such a way that can induce potentially cancer-causing mutations. On the other hand, it is still unknown if the virgin birth stem cells really have the same capacity for regeneration as embryonic stem cells. Sperm and egg cells have different patterns of chemical imprinting that affect the activity of different genes, so stem cells derived solely from eggs may have unusual imprinting patterns. Kern says tests show that this doesnt affect their ability to turn into dopamine-making neurons, however.
New Scientist, 27 November 2017 ; http://www.newscientist.com/