High cell density alters the ratio of type III to I collagen synthesis by fibroblasts

Abstract

HUMAN fibroblasts in culture synthesise both type I and type III collagen¹, with type I accounting for 70–90% of the total². In culture, the rates at which these proteins are synthesised is constant and apparently rather rigidly controlled³. However, the proportions of these collagens differs in cells cultured with increased amounts of serum (increased type III/I)⁴ as well as in cells obtained from patients with certain diseases. Cells from patients with the Ehlers-Danlos type IV syndrome make little or no type III collagen^5,6, whereas cells from patients with osteogenesis imperfecta have an increased type III/I (refs 7, 8). We have found that cells from some patients with systemic sclerosis (scleroderma), have a reduced type III/I ratio. However, as previously reported, these cells grew to a lower density than control cells⁹. We report here that normal fibroblasts from human and guinea pig skin produce proportionally more type III collagen at high cell density, probably because of a reduction in the synthesis of type I collagen.