Science / Medicine : Cellular Factors in Healing

A sensitive new technique for detecting which genes are active has been developed by cell biologists at UC San Francisco and Cetus Corp. of Emeryville. The researchers reported last week in Science magazine that they had used the technique to show conclusively that macrophages, the scavenger cells of the immune system, produce several growth factors that stimulate healing in human wounds.

The researchers detected genetic activity by studying messenger ribonucleic acid (mRNA), which carries information from deoxyribonucleic acid, the cell’s master blueprint, to sites where cellular proteins are synthesized. The presence of mRNA from a gene indicates that the gene is active, but the amount of mRNA present is extremely small. Scientists have thus had to grow large numbers of cells in the laboratory to obtain enough mRNA for analysis, a process that can take months or years. And growing cells in this manner can alter genetic activity within the cells.

In the new work, the biologists used recombinant DNA techniques developed at Cetus to produce billions of copies of the mRNA. The technique allows the researchers to analyze all the mRNA in a cell in as little as 24 hours. The UCSF researchers had been trying to identify the important growth factors in wound healing for more than a decade. The new assay allowed them to identify one--called transforming growth factor alpha.