CELLS TO ORGANS 

Transplant surgeons will one day 
use organs grown in labs, writes Biplab Das 

Kidneys and hearts growing inside glass jars may sound like science fiction, but scientists in Japan are on the way to achieving the impossible. Researchers at the University of Tokyo have succeeded in growing amphibian organs in vitro from embryonic cells. 

Their experiments have thrown up the possibility of organ-producing factories being set up sometime in the future. When that happens, organ transplants will become much easier than they are today. Surgeons will be able to perform transplant operations without harvesting organs from human or animal donors. 

The development of a fully grown foetus from a zygote is a complicated process, made possible by the teamwork of cells, which work like a highly trained orchestra. Every cell in the zygote has its own genetic score but has to wait for cues from cells in its surroundings. Each cell plays its role in accordance with the signals it receives. 

Having learned the process of intercellular communication, developmental biologist Makota Asashima and his colleagues at the University of Tokyo administered specific cues to undifferentiated cells from newt and frog embryos. This enabled the cells to grow into complete organs like liver and even a beating heart. The research was reported in Science last August. 

The scientists used cells taken from a part of the early amphibian embryo called the animal cap, a region that later develops into the embryo's mesodermal (middle) tissues such as muscle and internal organs. 

Some years ago, the researchers made an interesting observation in their lab. A low concentration of actinin - a protein known to be instrumental during organ formation in the embryo - in the culture fluid (the medium in which cells are cultured) caused the animal cap cells to develop into red or white blood cells. In higher concentrations, the protein induced formation of muscle tissue. Once initiated, these tissues' developmental programs seemed to operate without external stimuli. 

"This led me to wonder whether it would be possible to create a complete functional organ in vitro," says Asashimo. He was right. Upon administering 50 nanogram (1nanogram= .00000001gram) actinin per mililitre of culture fluid, the cells formed into notochord - a rod of cells along the embryo's dorsal surface that develops into the nervous system. A dose of about 75 nanogram / ml led to the development of a beating heart while 100 nanogram / ml yielded a liver. 

In another experiment, actinin accomplished by retinoic acid and an insulin-like growth factor produced a pronephros - a precursor to the kidneys, and rudimentary eyes and ears. 

"The question of what purified factors can do, exemplified by the work of Asashima and colleagues, is very interesting," comments Hazel Sive, a molecular biologist at the Whitehead Institute for Biomedical Research at Cambridge, Massachusetts. 

Of course, Asashima's research will have to be extended to the domain of human organs before it becomes clinically useful. Successful experiments will help create an alternative to donated organs, and also do away with prickly ethical debates like the one on xenotransplantation.