Scientists Grow Human/Pig Chimeric Cells to Study Early Embryonic Development

Researchers from the Salk Institute of Biological Studies were able to combine pig cells and human cells to create chimeric cells. The edited cells are helping scientists understand early embryonic development and stem cell differentiation. The details are in a paper that was just published in the journal Cell.

Stem cells can develop into any kind of cell, making them very useful in medical research and medicine. Most stem cells are found in embryos but there are also adult stem cells that are capable of dividing indefinitely. Scientists can induce stem cells to grow into different kinds of cells but the technology is limited in scope. Currently, there’s no way to grow functional transplantable organs from stem cells. The ability to grow organs in a laboratory would save many lives; an estimated 22 Americans die every day while waiting for an organ donor.

Studying early embryonic processes is key to improving stem cell technology and chimeric cells can help. Chimeras are organisms that contain sets of cells with completely separate genomes. Chimeric cells can contain material from two different animal species. Gene editing tools, such as CRISPR, can be used to delete critical genes from one set of cells. Since animals often have overlapping developmental genes, the other set of cells can fill the niche, allowing the chimeric cells to stabilize and grow. The first chimeric cells were derived from a mixture of rat and mouse cells. Interestingly, the mouse/rat chimeras grew gallbladders—an organ that doesn’t naturally develop in rats but develops in mice. The research team built on this study and attempted to mix humans cells with a non-rodent animal. They chose pigs because they have organs that are about the same size as human organs.

After running into a number of challenges and roadblocks, the research team was successful in creating human/pig chimeric cells. The cells could be implanted into pigs to study early embryonic development. The chimeric cells were only allowed to develop for a few weeks and the human cells contributed very little to development. This helps avoid the problem of cells ending up too humanlike, which would raise ethical concerns.

The research team’s study shows that it’s possible to create human/pig chimeric cells, a cell line that could be very useful in medicine. By implanting the cells into living pigs, the team can study early embryonic development. The findings will also help scientists better understand how stem cells differentiate. This could lead to breakthroughs in growing transplantable organs.


Wu et al. Interspecies Chimerism with Mammalian Pluripotent Stem Cells. Cell (2017).

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