Silkworm spins skin

A silkworm that spins a protein from human skin has been created in Japan. The technology could introduce biotechnology to silk-manufacturing countries.

The genetically engineered worms spool out thread that contains a form of the human protein collagen and weave it into their cocoons1. The insects carry sections of the human collagen gene.

Because silk threads are made from a pure natural protein, extracting the human addition should be relatively simple, hopes Katsutoshi Yoshizato of Hiroshima University in Japan, one of the research team. To make silk, cocoons are heated to kill the pupas inside and the silk filament is unwound. The team then extract the collagen by chemical means.

"It's an amazing technology," says biotech consultant Florian Wurm of the Swiss Federal Institute of Technology in Lausanne, Switzerland. Pharmaceutical companies hope to harvest human collagen for many applications including artificial skin and wound dressings.

The silk is the first that has been genetically modified to contain a medically useful molecule. But some human proteins may not be processed correctly in insect cells, Wurm points out.

Japan, China, India and other countries that already manufacture silk could convert workshops almost overnight to the lucrative production of collagen or other biomedical proteins, says Wurm: "This is something they should jump on right away."

Currently some human therapeutic proteins, such as insulin for diabetics and the clotting factor thrombin, are reaped from mammalian cells grown in expensive bioreactors. Proteins in human plasma are extracted from blood donations. Both techniques are expensive and laborious.

Silkworms, on the other hand, are cheap, quick and easy to farm. Fed on mulberry leaves, the pre-pubescent moths spin themselves cocoons within 3 days. Worldwide, they produce some 60,000 tons of silk per year.

The worms could be a boon to biotechnologists looking to scale up recombinant protein production. With the same aim, some have already created transgenic cows that could secrete proteins into their milk, or fruit and rice plants that make them in edible crops.

References

1. Tomita, M. et al. Transgenic silkworms produce recombinant human type III procollagen in cocoons. Nature Biotechnology, published online, doi.10.1038/nbt771 (2002). |Article|