The inhibition of fibroblast proliferation by a novel monokine: an in vitro and in vivo study.

We have identified a product of rabbit macrophages that inhibits fibroblast proliferation. Tested in vitro against several fibroblast populations, this monokine inhibited rabbit conjunctival fibroblast proliferation by 85% (p = 0.005), human conjunctival fibroblast proliferation by 88% (p = 0.005), human hypertrophic scar fibroblast proliferation by 85% (p = 0.005), and human keloid fibroblast proliferation by 79% (p = 0.005). Additionally (in an in vivo model), this monokine was injected into healing rabbit wounds and inhibited fibroblast proliferation by 33% after 7 days (p = 0.0001) and by 27% after 2 weeks (p < 0.0001). Preliminary analysis of the active factor demonstrates that it is not species-specific, has a molecular weight less than 3000 d, is resistant to degradation by trypsin and carboxypeptidase A, is heat-stable, and is produced by macrophages largely in the first 3 days of culture.