Fibroblast behavior on gels of type I, III, and IV human placental collagens

Various collagens were extracted and purified from human placenta after partial pepsin digestion. We prepared type III+I (57:43), enriched type I, type III, and type IV collagens on an industrial level, and studied their biological properties with MRC5 fibroblast cells. Using the process of contraction of a hydrated collagen lattice described by Bell [1], we found that the contraction rate was dependent on collagen type composition. The contraction was faster and more pronounced with pepsinized type I collagen than with pepsinized type III+I (57:43) collagen; the lowest rate was obtained with the pepsinized type III collagen. Using a new technique of collagen cross-linking, a gel was made with type IV collagen. This cross-linking procedure, based on partial oxidation of sugar residues and hydroxylysine by periodic acid, followed by neutralization, resulted in an increased number of natural cross-link bridges between oxidized and nonoxidized collagen molecules, without internal toxic residues. The fibroblasts were unable to contract type IV/IVox collagen gels. The type IV/IVox collagen gel was transparent and its amorphous ultrastructure lacked any visible striated fibrils. Fibroblast cells exhibited atypical behavior in these type IV/IVox collagen gels as evidenced by optical and electron microscopy. The penetration of fibroblasts could be measured. Fibroblasts penetrated faster in type IV/IVox collagen gels than in untreated type III+I collagen gels. The lowest rate of penetration was obtained with cross-linked type III+I gels. Fibroblast proliferation was similar on untreated or cross-linked type III+I collagen gels and slightly increased on type IV/ IVox collagen gels, suggesting that this cross-linking procedure was not toxic.