Human-pig chimeric embryos could transform organ transplant future
Scientists from the US are injecting pig embryos with human stem cells to produce human-pig embryos called chimera. This is part of the research aimed at solving the worldwide shortage of transplant organs.
The University of California, Davis team says they expect the pigs to look and behave like their normal counterparts. The only difference would be one organ is composed of human cells. The chimeric embryos are being allowed to develop in the sows for 28 days before the pregnancies are terminated and the tissue removed for analysis.
The chimeric embryo is created in two stages. First, scientists use a technique called CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) gene editing to remove the pig embryo’s DNA responsible for the growth of the pancreas. This creates a genetic “niche” or void. Then, they inject the embryo with human induced pluripotent (iPS) stem cells. The iPS cells were derived from adult cells and “dialed back” to become stem cells capable of developing into any tissue in the body.
The UC Davis team hopes that the human stem cells will take advantage of the genetic niche in the pig embryo so that the resulting fetus will grow a human pancreas.
According to Walter Low, a professor in the department of neurosurgery, University of Minnesota, pigs are ideal “biological incubators” for growing human organs. They could even be potentially used to create other organs including hearts, livers, kidneys, lungs and corneas.
He said that taking iPS cells from a patient who needs a transplant would produce an organ that is an exact genetic copy of the patient’s, but a much younger and healthier version. Plus, the patient will not need to take immunosuppressive drugs which carry side-effects.
Low also stressed that research using another form of gene editing called TALENs was still at the preliminary stages, trying to identify the target genes which must be removed in order to prevent the pig from developing a particular organ.
His team is also trying to use the chimeric embryos to create dopamine-producing human neurons to treat patients with Parkinson’s disease. These embryos were allowed to develop for up to 62 days – the normal gestation period is around 114 days.
Like the California team, Low said they were also monitoring the effects on the pig’s brain and if they find that it’s too human, they will not allow for that fetus’ birth.
