Differences in cell division and thymidine incorporation with rat and primate fibroblasts in collagen lattices

Human and gorilla dermal fibroblasts, primate cells, suspended in a collagen lattice, do not divide for the first 3 days. In contrast, rat fibroblasts divide within 24 hr. In this study, the proliferation of rat fibroblasts were compared to primate fibroblasts. Rat fibroblasts in monolayer culture increase from 100,000 to 355,000 in 2 days, and human cells increase from 100,000 to 436,000 in the same period. An initial seeding of 100,000 rat fibroblasts suspended in collagen increased to 163,000 cells in 2 days. An initial 100,000 human fibroblasts seeded in collagen decreased to 80,000 cells in 2 days. Retarded proliferation of human and gorilla fibroblasts in collagen is unrelated to a defect in DNA synthesis. By autoradiography human fibroblasts suspended in collagen incorporate labelled thymidine. By flow cytometry analysis, the DNA concentrations of human fibroblasts suspended in collagen exhibited 41% in a 4N chromosome state, compared to 14% in monolayer culture. Nuclei of gorilla fibroblasts from collagen displayed 42% in a 4N state, compared to 19% in monolayer culture. With nuclei of rat fibroblasts from collagen, 14% were in a 4N state, compared to 9% in monolayer culture. Primate fibroblasts show a three-fold increase in the number of nuclei in a 4N state compared to rat fibroblasts suspended in collagen. After replating fibroblasts released from collagen in monolayer culture in the presence of 1 mM hydroxyurea (an inhibitor of DNA synthesis) primate fibroblasts doubled in 24 hr. Under identical conditions, rat fibroblasts showed no cell division.(ABSTRACT TRUNCATED AT 250 WORDS)