Creation of iPS pig cells could bring on humanized porkers
Posted for David Cyranoski; Cross-posted from The Great Beyond
Researchers in China have made pluripotent stem cells from a pig. The cells could be useful for making humanized pig organs for transplant to humans, pig models of human disease useful for testing drugs, and for improving pig farming productivity and nutritional value.
Lei Xiao, head of the research group at the Shanghai Institutes for Biological Sciences where the research was done, admits that none of these will happen for the next several years. But his creation in pigs of induced pluripotent stem (iPS)-cells which share with embryonic stem cells the ability to differentiate into any cell type in the body-is still a huge accomplishment. (Paper).
The isolation and culture of embryonic stem (ES) cells from mice in 1981 revolutionized the use of mice as a developmental and biomedical research model. But it is a difficult process. It took 17 years to culture human iPS
cells. Even now there are ES cells for only four mammals: mice, humans, monkeys, and rats. Pig ES cells, despite many attempts, still do not exist.
Stable iPS cell lines could be an easier alternative. iPS cell lines, which are made by using defined genes, proteins or small molecules to "reprogram" adult cells to an embryonic-like state, have been created in the same 4 species as those listed above for ES cells. Xiao's research make pigs the fifth.
Xiao's four iPS cell lines appear to match the key properties of ES cells, notably pluripotency. They express all the right markers, they form cancerous growths known as teratomas that show all the major cell types when injected into immune-deficient mice, and they have been able to maintain this pluripotency for more than 20 passages into new cell cultures.
The cells will still need to be compared with pig ES cells. Xiao says that his recipe for culturing the cells might work with ES cells. But he might already be scooped on that-the research group of once lionized now scandalized cloner Woo Suk Hwang in Korea has been promising in the Korean press a publication showing pig ES cells within a couple months. (Korean Times).
Pig iPS cells and ES cells will then have to prove their usefulness. Xiao will use the cells to either "knock in" genes (by introducing genetic material) or "knock out" genes (by interrupting some genes' functions).
For example, immunity-related genes can be knocked out to make the pig's organs compatible with humans. But transgenic manipulation of pigs has been going on now-albeit with a more time-consuming, less efficient, more difficult method using cloning procedures-for years now. Still there are no pig-based transplants ready. And some argue that using transgenics to solve problems in agriculture, like the creation of transgenic pigs with healthy meat rich in Omega-3 fatty acid, is a completely over- the-top, using a hammer to squash a flea, solution.
(Nature Biotechnology - 24, 1472 - 1473 (2006) doi:10.1038/nbt1206-1472)
Image: by johnmuk from Flickr under Creative Commons
