Biochemical characterization of collagens synthesized by fibroblasts derived from normal and diseased human gingiva

Fibroblasts obtained from healthy and diseased human gingiva were labeled with radioactive amino acids and the collagenous proteins synthesized were studied. Sodium dodecyl sulfate polyacrylamide gel electrophoresis of untreated, reduced, and pepsin-treated proteins of the medium and cell extract showed that the collagenous proteins synthesized by these cells exist in the precursor form. Type I collagen was the chief constituent. In addition, cells from normal tissue synthesized type III collagen in amounts varying from 5 to 30%. Type III collagen was not detected in the cultures of fibroblasts from diseased tissue; however, an additional collagen fractionated between 2.5 to 5.0 M NaCl and accounted for 22 to 29% of the total. This collagen had an alpha1/alpha2 ratio of 8.6 and hydroxylysine/lysine ratio and cyanogen bromide peptide pattern were similar to that of alpha1[I]. It is concluded that the fibroblasts derived from disease gingiva synthesize a collagen of composition (alpha1)3, probably of type I.