This is a technique with wider possibilities, too: other US teams are working on a chimera-based treatment, this time for Parkinson’s disease, which will use chimeras to create human neurones. #CHIMERA PEOPLE SKIN#Using this controversial technology, a human skin cell, pre-treated and injected into a genetically edited pig embryo, could grow a new liver, heart, pancreas or lung as required. The human stem cells for the pancreas then make an almost entirely human pancreas in the resulting human-pig chimera, with just the blood vessels remaining porcine. In order to create the desired organ, they use gene editing, or CRISPR, to knock out the embryo’s pig’s genes that produce, for example, the pancreas. They then inject these into a pig embryo to make a human-pig chimera. In this case, the scientists take a skin cell from a human and from this make stem cells capable of producing any cell or tissue in the body, known as ‘induced pluripotent stem cells’. Horses and donkeys are different species with different numbers of chromosomes, but they can breed together. A mule is the offspring of a male donkey (jack) and a female horse (mare). They are like mules that will provide organs that can be transplanted into humans. These chimeras are animals that combine human and pig characteristics. Scientists in the United States are creating so-called ‘human-pig chimeras’ which will be capable of growing the much-needed organs. While politicians wring their hands about sensible solutions to the shortage, including the nudge of opt-out donation, scientists using genetic manipulations have been making significant progress in growing transplantable organs inside pigs. A lucrative trade in organs has grown up, and transplant tourism has become relatively common. For example, 3,000 kidney transplants were made last year in the United Kingdom, but that still left 5,000 people on the waiting list at the end of the period. The term chimera derives from the mythical beast called the Chimera, supposedly a lion with a snake for a tail and a goat’s head protruding from its back.There is a well-documented organ shortage throughout the world. Much of the fruit we eat comes from chimeric plants, because of the widely-used practice of grafting fruit-producing branches onto the roots of another variety or species. Those that produce modified sperm or eggs are then bred to produce animals with the modification in every cell. The resulting animals have a mix of modified and unmodified cells. Stem cells are modified outside the body and injected into early embryos. The aim of this work is to provide organs for transplantation, but the creation of animal-human chimeras is controversial.Ĭhimeric animals are often created during genetic engineering and CRISPR genome editing. Several groups around the world are now trying to grow specific organs in another species, such as a human heart in a pig. For instance, mice with human immune systems have long been used for medical research. When individuals are a mix of male and female cells, there can also be abnormalities in the reproductive organs.įor decades, biologists have also been creating chimeras that are a mix of cells from different species. Sometimes there are visible signs, such as differently coloured eyes or patches of skin of different shades. For this reason, it is not clear how common it is. People with this form of chimerism can appear entirely normal, so it is usually discovered only by accident. Parts of the resulting individual derive from one embryo and parts from another. The most dramatic is when two embryos that would normally develop into non-identical twins fuse in the womb. Biologists are also creating chimeras whose bodies are a mix of cells from different species, such as pigs with a few monkey cells in most of their organs.Īll animals develop from a single fertilised egg, so in theory every single cell in the body should have exactly the same genome. More rarely, a single person can be a fairly equal mix of cells that appear to derive from two different individuals. Many people’s bodies contain at least a few living cells from another person. A chimera is an individual whose body is composed of cells that are genetically distinct, as if they are from different individuals – and sometimes they really are from different individuals.
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