As per the study, which has been published in the scientific journal Cell Stem Cell, human-pig chimeric embryos, comprising both human and pig cells, were developed.These embryos were implanted in surrogate pig mothers and grew kidneys containing mostlyhuman cells that had a normal structure after 28 days of development. As per the lead researcher, there were also pig cells in the humanized kidney but human cells dominated and comprised 60 to 70% of the total cells.
“Rat organs have been produced in mice, and mouse organs have been produced in rats, but previous attempts to grow human organs in pigs have not succeeded,” the senior author Liangxue Lai, of the Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences and Wuyi University told The Guardian. “Our approach improves the integration of human cells into recipient tissues and allows us to grow human organs in pigs.”Pigs are a highly attractive target for growing human organs given their similarities with humans in physiology and organ size, as well as in embryonic development. The human kidney is one of the most transplanted solid organs worldwide and also one of the earliest appearing during embryogenesis. As per the US Organ Procurement and Transplantation Network, currently 88,500 people are waiting for a transplant in the US.
“It took us five years”
“It took us five years,” senior study author Miguel Esteban, principal investigator at the Guangzhou Institute of Biomedicine and Health, Chinese Academy of Sciences told CNN. “We modified the pig genetically to create a space for the human cells to grow with less competition from pig cells, and we also modified the human cells to make them survive in an environment that was not their natural one,” Esteban told the media via email.
“The results indicate that it might be possible to generate a functional human kidney inside newborn pigs, offering an attractive alternative to overcome the shortage of human organs for transplantation,” the researchers have said.
However, this study has several limitations. First, the overall ratio of degenerating pig embryos is high, and it will be necessary to assess whether this is partly related to the chimerism or any other aspects of the injection procedure. Second, contribution to other lineages, including the brain and germ cells, raises serious ethical concerns if the pigs were brought to term. Third, it is important to consider that organs are composed of multiple cell types including vascular cells that are essential for normal function and could cause rejection if any are of porcine origin.
Apart from the kidneys, other cells of central nervous system were mostly pig cells. Previous attempts of creating such hybrids had failed because the pig cells used to outcompete the human cells. However, in the new study the embryo was genetically engineered to create a niche within the embryo which could be filld by human embryonic stem cells.
“Our findings demonstrate proof of principle of the possibility of generating a humanized primordial organ in organogenesis-disabled pigs, opening an exciting avenue for regenerative medicine and an artificial window for studying human kidney development,” the researchers have said.