Urine may be better than milk for ‘biopharming’

Scientists in the United States have produced mice that can produce urine rich in human growth hormone.

The scientists, from the Department of Agriculture in Maryland, have produced the mice by replacing the protein coding region of a gene that is expressed only in the epithelial cells lining the bladder with the genetic sequence that codes for human growth hormone (Nature BioTechnology 1997;16:75-9).

The next step will be to see if larger farm animals can be similarly modified to produce human proteins. If such technology is developed, the commercial production of biologically useful proteins from the urine of genetically modified farm animals could become a viable option.

Three body fluids-milk, blood, and urine-have been suggested as potentially suitable media for protein production in genetically modified animals. So far, proteins have been produced from both milk and blood. The most recent example of this was Polly, the genetically cloned sheep that has been designed to produce human factor IX in her milk.

However, only female animals can be used for protein production in milk, and the process also depends on lactation taking place. Protein production in urine should therefore confer several advantages over production in milk: not only could the whole herd be used, but production …