Charlotte Merrill

Collagen Biosynthesis by Cells in a Tissue Equivalent Matrix In Vitro

Collagen biosynthesis by fibroblasts and subsequent processing and polymerization have been studied in conventional monolayer cultures and in a new model system in vitro in which cells organize into a tissue like structure. While the bulk of the newly made collagen becomes tightly and selectively bound to the matrix of the tissue equivalent model, in monolayer cultures most of the collagen passes into the culture medium. Collagen biosynthesis appears to be regulated differently in cells of the tissue equivalent model as compared with monolayered cells. In the former there is a 6- to 8-fold decrease in collagen output even though overall protein synthesis per unit of DNA is twice as great as in monolayered cells. Cells grown in tissue lattices exhibit much higher collagenolytic activity than cells in monolayer suggesting the model may also be of special use for studying collagen turnover and matrix remodeling.

Regulation of proliferation of fibroblasts of low and high population doubling levels grown in collagen lattices

While IMR 90 and AG 1519 fibroblasts of low and high population doubling levels grow to confluency when plated on plastic surfaces, they cease to divide within four days when incorporated into collagen lattices. Growth inhibition in the lattices is not due to exhaustion of the medium or isotope, or to contact inhibition; nor is it due to impermeability of the lattice to the materials in the medium. While cells in a lattice arrest in G0, this state is reversible when cells are permitted to leave the lattice and populate a plastic substrate. We conclude that fibroblasts in tissue-like lattices may be responsive to some of the same controls as cells in connective tissues.

Do diploid fibroblasts in culture age

Publisher Summary In the intact organism, fibroblasts may be called upon to participate in wound healing and connective tissue restructuring. Fibroblasts are connective tissue parenchymal cells, which retain the capacity to divide when the need to do so arises. Although they subserve a repair function, they cannot be considered stem cells in the sense that basal epithelial cells or bone marrow cells are stem cells, because stem cells are programmed to divide on a more or less regular basis. When a fibroblast participates in wound healing and becomes part of a scar, it may be stimulated to divide, to undergo maturation or differentiation, and eventually to withdraw from the cell cycle. Fibroblasts that participate in wound healing acquire characteristics that clearly distinguish them from fibroblasts of normal tissues. Among the changes that occur are an increase in the number and diameter of intracellular fibrillar elements and change from a nucleus with a smooth membrane to one that has multiple indentations or deep folds.

The collagen lattice: a model for studying the physiology, biosynthetic function and pharmacology of the skin

Until recently, changes in cell physiology following application of pharmacological agents have been studied in vivo or in vitro using monolayered cells. Although both approaches have unique advantages, both have shortcomings. Now the development of a skin-equivalent model has provided a system for studying cell responses at the tissue and organ levels in vitro (Bell, Ivarsson & Merrill, 1979; Bell et al., 1981a, b). The in vitro tissue model can be made simple or complex with respect to eel! type heterogeneity and matrix constitution; ideally, however, it should resemble skin as closely as possible. It has the special advantage, unlike skin, of being able to survive for long periods in vitro. In this paper we compare the model morphologically with skin and review some aspects of the biosynthetic output of cells in the tissue equivalent with that of monoiayered cells. Finally we illustrate in a pharmacological study that the model can be used to provide new information that in vivo studies or monolayer cell studies cannot yield.

An Interactive Computer System for the Analysis of Cell Lineages

We have developed an interactive computer system for analysing cell lineage data. It can be utilized in studies of cell motility, cell division, cell differentiation, and cell aging. It has enabled us to document the heterogeneity of human foreskin fibroblasts in culture and to propose that loss of proliferative potential may mean that cells enter a state of differentiation which makes them unable to respond to mitotic stimulation. Our method, which enables us to apply immunological and cytochemical probes after recording the history of a cell lineage, should allow us to define precisely features which uniquely distinguish cycling from noncycling cells on an individual cell basis.

Effects of ageing and long-term subcultivation on collagen lattice contraction and intra-lattice proliferation in three rat cell types

Many cells can contract a hydrated collagen lattice when seeded within one, reorganizing the collagen fibrils into a compact structure by tractional forces exerted during cell movement and translocation. The effects of ageing on this tractional-motility property of cells was examined for three cell types from adult Fischer 344 male rats: skin fibroblasts, aortic smooth muscle cells, and dedifferentiated chondrocytes. All cell types at low population doubling levels (PDL less than 10) contracted collagen lattices, though with different proficiencies (smooth muscle cells greater than dedifferentiated chondrocytes greater than skin fibroblasts). There was no significant difference in contraction ability of cell isolates of the same type obtained from 4-month and 24-30-month animals. Cells that had been subcultivated extensively (PDLs of 50-110) retained contractional ability. The cell types proliferated within lattices to varying extents, and there was no correlation between a cell types extent of proliferation in a lattice and its proliferation in monolayer culture. That lattice contraction ability is preserved intact with ageing in three cell types suggests that the tractional forces exerted by cells on a collagen matrix in vitro may have a significant role in adult life in vivo.