Last week was a big one for the future of kidney transplants – specifically, kidneys grown in pigs.
At the Guangzhou Institute of Biomedicine and Health, scientists reported that they have used human pluripotent stem cells to grown part-human, part-porcine kidneys in pig embryos. About half of the cells making up the kidneys were human, while the vasculature was composed of pig cells. The engineered embryos were removed from surrogate sows about one month after transplantation, and the small fraction that were of high enough quality to analyze were found to be developing normally. While this is an encouraging result, especially considering that there are many more patients in need of kidney transplants than there are available organs, ethical and practical concerns remain. For instance, to help the cells grow into kidneys, the Guangzhou team had to overexpress two genes, one of which is related to the cells’ ability to proliferate and may have implications for tumor formation.
Meanwhile in New York, a two-month study centered on a patient who received an experimental pig kidney transplant came to an end. In July, surgeons at the NYU Langone Transplant Institute performed the procedure, known as xenotransplantation, on a brain-dead man who was being kept alive with a ventilator. The transplanted kidney functioned well for at least a month (and possibly longer – the status of renal function at the end of the predetermined two-month study period was not clear from the NYU press release at the time of writing this blog post). Unlike the part-human kidneys described above, the donor kidney in this case was fully porcine, albeit sourced from a pig that had a single gene knocked out in order to prevent the formation of the carbohydrate alpha-gal. Alpha-gal is responsible for rapid rejection of normal pig organs by the human body, as well as a rare “meat allergy” spread by tick bites.
Hopefully, further developments in both research directions can bring hope to those in need of kidney transplants. If you’d like to learn more, check out this article about the hybrid human-pig kidneys or this press release about the xenotransplantation study.